Controlled phase and structure engineering-driven unique dielectric behavior enabling tailored electromagnetic attenuation

Controlled phase and structure engineering-driven unique dielectric behavior enabling tailored electromagnetic attenuation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Controlled phase and structure engineering-driven unique dielectric behavior enabling tailored electromagnetic attenuation Sihao Dou, Yunfei He, Yuxiang Zheng, Yuefeng Yan, Zhiyuan Dan, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7308006/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 10 Nov, 2025 Read the published version in Advanced Composites and Hybrid Materials → Version 1 posted 8 You are reading this latest preprint version Abstract Modulating the phase composition and microstructural geometry in polymetallic metal-organic framework (MOF) derivatives represents a promising approach for achieving tunable electromagnetic response. However, deciphering the intrinsic phase-structure-property correlations in complex systems remains challenging. Herein, a competitive coordination and directed reduction strategy is employed to fabricate ternary Fe/Co/Zn (FCZ) composites with precisely controlled composition and architecture. Specifically, the topological structure progressively evolves from the inheritance of leaf-like precursors to hierarchical self-assembly and to final reconfiguration. Introducing Fe into the original Co/Zn bimetallic system progressively suppresses the Co3ZnC phase, while promoting the formation of the Fe-Co solid solution and amorphous ZnO. The construction of multiple heterointerfaces and high-density defects within nitrogen-doped carbon substrates facilitates the coupling effect of multiple polarization loss mechanisms. This synergistic effect induces an anomalous dielectric behavior, characterized by attenuated polarization relaxation peaks concurrent with enhanced polarization response. Consequently, the optimized FCZ4 demonstrates exceptional electromagnetic wave absorption performance, featuring an ultra-low reflection loss of −84.41 dB and an ultra-broad bandwidth of 6.08 GHz. Gradient regulation of Fe content enables the realization of tunable frequency response characteristics spanning the low-to-high frequency range. This work establishes a generalized phase-structure-dielectric correlation model, offering new insights into tailorable electromagnetic attenuation in multi-metallic systems. Phase-structure modulation Trimetallic coordination competition Crystal-amorphous synergy Polarization relaxation peak Electromagnetic wave absorption Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 1. Introduction The exponential surge in electromagnetic (EM) pollution, propelled by the ubiquitous deployment of 5G/6G networks and high-precision radar systems, has heightened the demand for advanced electromagnetic wave (EMW) absorbers with tailorable attenuation characteristics [1-3]. Next-generation absorbers must simultaneously satisfy multidimensional performance metrics: ultra-low reflection loss (5 GHz), sub-2.5 mm thickness, and lightweight flexibility [4-6]. Metal-organic framework (MOF)-derived carbon composites have emerged as frontier candidates owing to their designable architectures, atomic-level compositional tunability, and multiscale dielectric mechanisms [7-9]. Since monometallic MOFs are constrained by their structural and compositional homogeneity, which impede the simultaneous achievement of high-efficiency absorption and broadband coverage, bimetallic systems have been developed as a promising solution [10-12]. Nevertheless, conventional bimetallic MOF derivatives often suffer from uncontrollable phase segregation, rigid topological configuration, and disordered spatial dispersion of metallic constituents, resulting in compromised electromagnetic compatibility [13-15]. Most critically, the inherent trade-off between phase heterogeneity and structural inflexibility obstructs the establishment of precise dielectric response modulation, thereby hindering the rational design of high-performance EMW absorbers [16, 17]. The intrinsic limitations of bimetallic systems have catalyzed innovative efforts toward ternary heterometallic architectures [18-20]. Central to this strategy is leveraging the third heterogeneous metal to regulate the compositional distribution, induce high-density lattice defects, and construct multilevel heterogeneous interfaces, thereby enhancing electromagnetic attenuation. Huang et al. [18] prepared flower-like magnetic-carbon microspheres by incorporating a third metal (Cu, Zn, Fe, and Mn) into CoNi bimetallic MOF precursors. By modulating the composition of the ternary alloy, it optimized the intrinsic EM parameters and impedance matching characteristics, achieving a 5.8 GHz absorption bandwidth at 2.0 mm. Liu et al. [19] synthesized a CoNiMn trimetallic MOF by simultaneously introducing Co and Ni into Mn-MOF, which significantly enhanced the oxygen vacancy concentration compared to the bimetallic system. The resulting dielectric polarization dominated EMW loss, realizing a wide absorption bandwidth of 8.0 GHz with a thickness of only 2.1 mm. Ning et al. [20] reported defect-rich NiFe 2 O 4 /MoNi 4 -NC composites via Fe 3+ ion exchange into NiMo-MOFs followed by template-assisted pyrolysis. Non-homogeneous doping-induced lattice distortion, which amplifies dipole polarization, is coupled with strong interfacial polarization triggered by the multi-heterogeneous interfaces, contributing to the excellent EMW absorption property with a 5.76 GHz bandwidth. Despite these advances, fundamental barriers persist. The inevitable phase separation within the polymetallic matrix complicates efforts to regulate the spatial arrangement of metallic components and promote the development of advantageous phase configurations [21]. Incorporating a third metallic component fails to alter the original bimetallic system's topological architecture, limiting the scope for structural optimization to achieve targeted impedance engineering and enhance EMW multiple scattering for improved energy dissipation [18]. Crucially, fine-grained manipulation of the dielectric response via precise phase and structure modulation remains elusive, obstructing the establishment of deterministic phase-structure-performance correlations [22]. These barriers are rooted in uncontrollable coordination microenvironments and constrained thermal decomposition pathways. Consequently, accurate control over the metal-ligand coordination nodes during precursor crystallization and the sequential reduction of metallic species during subsequent pyrolysis is necessary to achieve tailored electromagnetic attenuation [23]. Herein, through the gradient incorporation of Fe 3+ ions, which exhibit superior ligand affinity and the lowest reduction potentials, into the Co/Zn bimetallic MOF system, we realize precision modulation of crystalline phases and nanostructures in the trimetallic MOFs, thereby enabling tunable electromagnetic responses. Specifically, by regulating the introduced Fe 3+ content, a progressive geometrical optimization of the topological structure is achieved, encompassing leaf-like precursor inheritance to multistage self-assembly to final reconfiguration. The Fe 3+ -mediated stepwise phase transformation facilitates the development of a Fe-Co solid solution and amorphous ZnO while suppressing the nucleation pathway of the Co 3 ZnC phase, permitting controlled phase separation. The resultant coupling intensification of the multi-polarization mechanism elicits distinctive dielectric behaviors characterized by the gradual attenuation of the relaxation peak and a concomitant augmentation in polarization loss. As a result, the optimized composites exhibit superior EMW absorption performance, featuring an ultra-low reflection loss of −84.41 [email protected] GHz and attaining a broad EAB spanning 6.08 GHz at a thickness of 2.03 mm. This work offers novel design strategies for polymetallic MOF derivatives, providing deep insights into polarization mechanisms within amorphous-crystalline heterosystems for advanced EMW absorption materials. 2. Results and Discussion 2.1 Structural evolution Bimetallic MOF and its derivatives were synthesized through co-precipitation, followed by pyrolysis [24]. The observed structure of the leaf-like Co/Zn-ZIF (expressed as CZ-Z; sample names are listed in Table S1 ) can be attributed to the asymmetric coordination behaviors induced by the distinct ligand characteristics of nitrate versus acetate anions ( Fig. 1a and Fig. S1 ). Nevertheless, the CZ-Z-derived composites (labeled as CZ) display structural collapse into stacked circular-like sheets ( Fig. 1d and Fig. S2 ). The abnormal structural disinheritance might stem from the asymmetric coordination environment within the MOF precursor, triggering crystallographic lattice distortions and architectural destabilization [25]. Meanwhile, the Co 3 ZnC intermetallic compound (PDF#29-0524) and metallic Co (PDF#15-0806), as identified by X-ray diffraction (XRD), inherently possess high surface energy characteristics that promote Ostwald ripening processes ( Fig. 1c and Note S1 ) [26, 27]. This results in particle migration and agglomeration, ultimately leading to the catastrophic failure of the carbon scaffold's load-bearing architecture. Hence, to suppress the metallic particle aggregation while preserving the structural integrity of the precursor, the strategic incorporation of a third metallic Fe element through targeted inducing to achieve precise modulation of the phase and structure proves essential. XRD patterns of FCZ-Z x precursors demonstrate almost identical peak positions and intensities compared to CZ-Z ( Fig. S3 ). However, the gradual lightening of the powder coloration observed in macroscopic samples confirms the successful integration of Fe 3+ into the framework and reveals alterations in the coordination environment within the system ( Fig. S4a ). As presented in Fig. 1e , introducing 0.6 mmol Fe 3+ into the bimetallic MOF precursor results in the partial retention of leaf-like morphological features (called FCZ1), indicating that Fe 3+ incorporation effectively alleviates structural collapse. Specifically, Fe 3+ with inherently higher charge density competitively coordinates with 2-methylimidazole against Co 2+ /Zn 2+ counterparts, establishing a reinforced Fe-Co-Zn hybrid coordination node [28]. Additionally, Fe nanoparticles (NPs) embedded within the carbon matrix can mitigate the migration and aggregation of metallic particles. These synergistic effects drive a topological transformation in the bimetallic MOF. Notably, the diffraction peak intensity corresponding to the Co 3 ZnC phase exhibits marked attenuation, suggesting that Fe 3+ incorporation suppresses the formation of the Co 3 ZnC phase ( Fig. S4b ). This phenomenon may be rationalized by the inherently superior standard reduction potential ( E °) of Fe 3+ (Fe 3+ /Fe 0 = −0.037 V) compared to Co 2+ (Co 2+ /Co 0 = −0.277 V) and Zn 2+ (Zn 2+ /Zn 0 = −0.762 V) [29-31]. The preferential reduction of Fe 3+ to metallic Fe dominates the initial reduction sequence, rapidly depleting available reducing agents within the system. This competitive consumption consequently imposes kinetic limitations for subsequent reduction processes of Co 2+ and Zn 2+ , hindering the Co-Zn alloying pathway. Besides, the E ° of Co 2+ is higher than that of Zn 2+ , and the establishment of this directional reduction gradient contributes to the preferential generation of Fe-Co solid solutions ( Fig. 1b ). Conversely, the Zn reduction reaction is significantly inhibited, leading to the growth of amorphous ZnO. The pyrolyzed composites fully inherit the precursor framework after increasing the Fe 3+ concentration to 1.2 mmol (marked as FCZ2), as depicted in Fig. 1f . Moreover, the overall structure displays a self-assembly behavioral tendency, forming a three-dimensional interconnected network through oriented growth along two orthogonal axes of the leaf-like architecture. The observed morphology may originate from magnetic interactions and anisotropic stress effects, collectively driving the spontaneous cross-assembly phenomena [32]. With a further elevation of the Fe 3+ level (labeled as FCZ3), the magnetic properties demonstrate a corresponding enhancement, accompanied by a self-assembly process initiated among multiple adjacent leaf-like architectures. Ultimately, this leads to the formation of thermodynamically favorable configurations through multistage structural integration ( Fig. 1g ). Concurrently, the Co 3 ZnC content progressively diminishes, signifying the efficacy of Fe 3+ incorporation in modulating the phase distribution within the bimetallic system. Interestingly, when introduced Fe 3+ reaches 2.4 mmol (denoted as FCZ4), a well-defined morphological evolution is observed ( Fig. 1h and Fig. S5 ). The self-assembled leaf-like architectures initially undergo mutual crop and segmentation processes, splitting into triangular boomerang-shaped units. Afterward, epitaxial growth occurs preferentially at the junction points of these units, driving further structural reorganization until a developed triangular-like architecture is achieved. The separation procedure may be attributed to the supersaturated doping of Fe 3+ , leading to the precipitation of excess metallic Fe nanoparticles, which catalyze the oxidative etching of the carbon substrate through high-temperature metal-carbon interfacial reactions [33]. This process could induce localized dissolution at the leaf-like edges of the carbon framework, generating triangular-like notch defects. Then, Fe NPs mediate the anisotropic carbon deposition, which is preferentially localized at triangular notches, facilitating the nucleation of branching substructures that propagate the development of pseudo-triangular architectures [34]. Eventually, the reduced interfacial energy at triangular edges activates a "self-healing" mechanism that thermodynamically stabilizes the system, enabling structural optimization toward geometrically regular configurations. Notably, XRD analysis reveals no detectable diffraction peaks related to Co 3 ZnC, only featuring characteristics of amorphous carbon and broadened metallic Co diffraction peaks. The result firmly suggests that the reduction of Fe 3+ fully consumes the available reductant within the system, thereby effectively obstructing the formation pathway of Co 3 ZnC. Incorporating 3.0 mmol Fe 3+ induces enhanced magnetic interaction (recorded as FCZ5), combined with carbon-mediated bridging effects, collectively motivate the stacking and reconfiguring of the triangular-like architecture ( Fig. 1i ). The emergence of a novel Fe 3 ZnC 0.5 (PDF#29-0741) phase is identified in the XRD patterns, accompanied by distinct diffraction peaks corresponding to the metallic Fe (PDF#06-0696) phase [14, 35]. This phenomenon could be explained by the saturation of Fe dissolution within the Fe-Co solid solution matrix. Once the solubility limit is exceeded, excess Fe atoms facilitate localized Fe-Zn alloying pathways. Therefore, a Fe 3+ concentration of 2.4 mmol represents the critical threshold for phase transition within the system. When the Fe 3+ concentration exceeds 3.0 mmol (noted as FCZ6), the diffraction peak intensities related to Fe 3 ZnC 0.5 and Fe phases display a pronounced enhancement ( Fig. S6 ). Simultaneously, the FCZ6 evolves and integrates at the structural articulation, ultimately attaining a coherent quasi-octahedral configuration ( Fig. S7 ). Furthermore, systematic investigations into the effects of adding Fe 3+ to monometallic MOF systems were also conducted ( Fig. S8-S13 and Note S2 ). These results indicate that the Fe 3+ -dominated ternary coordination competition model and directed reduction hierarchy realize a precise regulation of the phase and structure of bimetallic MOF-derived materials ( Fig. 1j ). This Fe 3+ -driven modulation operates through targeted tuning of kinetic pathways and thermodynamic equilibria, demonstrating broad applicability across polymetallic MOF systems, thus offering the potential to attain customizable MOF-derived EMW absorbers. Transmission electron microscopy (TEM) characterization further illustrates the structural evolution governed by the gradient Fe 3+ content ( Fig. 1k and Fig. S14 ). The magnified TEM images unlock more explicit morphological information, showing that metal NPs of varying sizes are randomly dispersed across the amorphous carbon matrix ( Fig. S15 ). The high-resolution transmission electron microscopy (HRTEM) images confirm the existence of metal NPs anchored on amorphous carbon ( Fig. S16 ). Meanwhile, localized regions featuring metal particles encapsulated by amorphous/graphitic carbon are also observed. HRTEM analysis reveals distinct lattice fringes with interplanar spacings of 0.204 nm and 0.202 nm, characteristic of the (111) and (110) crystallographic planes in metallic Co and Fe phases, respectively. Additionally, observed spacings of 0.216 nm and 0.219 nm are unambiguously assigned to the (111) plane family of the Co 3 ZnC phase and the newly formed Fe 3 ZnC 0.5 phase. These crystal signatures provide conclusive evidence for the effective substitution of Fe 3+ into the crystal lattice and the subsequent phase transition. The elements C, N, O, Co, Zn, and Fe are uniformly distributed throughout the composites, as illustrated by the results of the energy dispersive spectrometer (EDS) elemental mapping ( Fig. 1l and Fig. S17-S23 ). 2.2 Phase transition To elucidate the underlying mechanisms governing phase transition following Fe 3+ incorporation, X-ray photoelectron spectroscopy (XPS) was employed to investigate the elemental composition and chemical states. The survey XPS spectra of CZ exhibit the presence of C, N, O, Co, and Zn elements, while the FCZ x displays an extra Fe element ( Fig. S24 ). The high-resolution C 1s spectrum can be deconvoluted into C-C/C=C (284.8 eV), C-N (286.1 eV), C-O (287.9 eV), and C=O (289.5 eV), respectively ( Fig. 2a ) [36]. Three characteristic peaks located at 398.7 eV, 400.8 eV, and 403.0 eV are also identified in the high-resolution N 1s spectrum, which are ascribed to pyridinic N, pyrrolic N, and graphitic N, respectively ( Fig. 2b ) [37]. These findings collectively indicate the successful doping of heteroatom N into the carbon lattice [38]. Notably, the high-resolution Zn 2p spectrum of CZ and FCZ x can be distinctly separated into two peaks at 1022.1 eV and 1045.1 eV, which correspond to Zn 2p 3/2 and Zn 2p 1/2 , respectively ( Fig. 2d ) [24]. Quantitative analysis of elemental composition via inductively coupled plasma optical emission spectrometry (ICP-OES) reveals that the Zn species concentration remained at dynamic equilibrium ( Fig. 2g and Table S2-S3 ). This observation, along with the persistent absence of characteristic Zn-related diffraction peaks in XRD patterns and undetectable crystallographic signatures assigned to ZnO in HRTEM, strongly reveals that Zn predominantly exists as amorphous ZnO within the composites. Concurrently, the ZnO content increases with elevated Fe 3+ introduction levels, directly correlated with the progressive diminishment of the Co 3 ZnC phase. The crystal structures and electronic properties of monometallic MZ and FZ materials provide additional evidence to corroborate this proposed argument ( Fig. S25 ). The high-resolution O 1s spectrum demonstrates the presence of lattice oxygen (533.5 eV) and surface-adsorbed oxygen (535.8 eV) species, as well as prominent spectral features of oxygen vacancies (531.6 eV), occupying approximately 80% of the integrated oxygen signal ( Fig. 2c and Fig. S24f ) [39]. These are likely to trigger enhanced dipole polarization originating from a high density of lattice defects, thus promoting further dissipation of EMW. The Co 0 (778.5 eV) species and multivalent Co are recognized in the high-resolution Co 2p spectrum ( Fig. 2e ) [38]. Similarly, the high-resolution Fe 2p spectra of FCZ x upon introducing Fe 3+ exhibit Fe 0 (707.5 eV) species and multivalent Fe ( Fig. 2f ) [40]. The surface-sensitive nature of XPS analysis suggests that the observed higher oxidation states of Co or Fe are primarily attributed to surface oxidation or atmospheric exposure effects. The bulk phase mainly retains its metallic state and solid solution characteristics. Consistent findings are further validated in the monometallic MC and FC systems ( Fig. S26 ). ICP research also illustrates a progressive enrichment of Fe species within the composites, offering solid proof for successfully incorporating Fe 3+ into the bimetallic MOF system. The abundant metallic Co creates favorable conditions for Fe 3+ to substitute its lattice sites, ultimately resulting in the generation of Fe-Co solid solution through atomic-scale substitutional doping. The following results confirm the formation of Fe-Co solid solution: i) The slight angular shift of the Co phase observed at 44.2°, ascribed to the (111) crystal plane, combined with the pronounced diffraction peak broadening characteristic, provides proof of Fe atomic incorporation into the Co lattice ( Fig. 1c ). ii) HRTEM analysis reveals multiple indistinguishable interplanar spacing values intermediate between pure Co (0.204 nm) and pure Fe (0.202 nm), offering direct crystallographic evidence for the generation of a disordered solid solution ( Fig. S16 ). iii) Thermal field modulation studies demonstrate that the ordered Co 7 Fe 3 (PDF#50-0795) intermetallic phase formation initiates at temperatures exceeding 900 °C, which corroborates the growth of the Fe-Co solid solution at low temperatures ( Fig. S27 and Note S3 ) [41]. iv) The saturation magnetization ( M s ) tested via a vibrating sample magnetometer (VSM) gradually enhances from an initial value of 13.33 emu g -1 to 20.48 emu g -1 at maximum Fe addition concentration, indicating a magnetic behavior that aligns with the fundamental principle of magnetic moment superposition in Fe-Co solid solution ( Fig. 2h , Fig. S28 , and Table S4 ) [42]. v) Density functional theory (DFT) calculations show that the Fe-Co solid solution exhibits improved thermodynamic stability relative to Co 3 ZnC and Fe 3 ZnC 0.5 , as evidenced by its minimum formation energy ( Fig. 2j , Fig. S29-S35 , Table S5 , and Note S4 ). Besides, the hybridization between Fe 3 d and Co 3 d orbitals induces intensified spin polarization and enhanced exchange interactions, resulting in an increased population of unoccupied states in the spin-down channel. This configuration results in progressive improvement of energy band density with elevated Fe incorporation concentrations ( Fig. 2k, l ). Concurrently, the orbital hybridization shifts the spin-down-dominated antibonding states closer to the Fermi level, significantly raising the projected density of states (PDOS) of Fe. In contrast, the partial transfer of Co's d -orbital electrons into the Fe-Co hybridized states slightly reduces the PDOS contribution from Co ( Fig. 2m, n ). Interfacial charge density gradients at Fe-Co hybrid interfaces generate strong local dipoles, facilitating polarization relaxation and promoting dielectric loss capacity. Electron paramagnetic resonance (EPR) spectroscopy was employed to qualitatively characterize the spatial distribution of unpaired electron density (paramagnetic substance). The high signal-to-noise ratio peaks observed in the narrow spectral region fail to provide discernible information ( Fig. S36 ). Nevertheless, the change in the intensity of these signals likely reflects the concentration variation of paramagnetic centers and unpaired electrons. The broad EPR signals centered at g ≈ 2.15 suggest the presence of paramagnetic centers, probably attributed to high-spin Fe 3+ species or unpaired electrons in Fe-Co solid solutions, instead of high-spin Co 2+ (g ≈ 2.3~2.5) or metal vacancies (g ≈ 1.96) [43, 44]. The signal intensity initially increases with the Fe 3+ content, reaching its peak at 2.4 mmol. This growth suggests a rising concentration of paramagnetic Fe 3+ or Fe-Co solid solutions. However, a decline occurs at FCZ5, probably due to a partial Fe 3+ reduction to metallic Fe 0 or a decrease in Fe-Co solid solution content caused by the generation of Fe 3 ZnC 0.5 and Fe phases. The thermal stability of the composites was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The decomposition of CZ in an air atmosphere begins at approximately 327 °C, with a sharp mass reduction above 548 °C, culminating in a loss of roughly 40.89% of its mass at 950 °C ( Fig. S37 ). In comparison, FCZ4 exhibits an elevated decomposition temperature of 345 °C and a final mass loss of about 38.30%. This implies that multiple phases raise the temperature at which carbon decomposes by facilitating the generation of a highly eutectic mixture [45]. N 2 adsorption-desorption isotherms were utilized to assess the specific surface area and pore size distribution of the composites. All samples demonstrate type IV isotherms with a distinct hysteresis loop, signifying the existence of mesoporous features ( Fig. S38 ) [46]. The specific surface area of the composites progressively reduces with the incorporation of Fe 3+ , varying from an initial value of 223.3 m 2 g -1 to 47.4 m 2 g -1 . At the same time, the average pore size continuously rises, ranging from 3.62 nm to 18.60 nm ( Fig. 2i ). The hierarchical self-assembly process and subsequent structural reconfiguration of the leaf-like architectures lead to a decrease in specific surface area while promoting the generation of a higher density of mesoporous structures. These mesopores are conducive to multiple internal reflections of incident EMW within the material matrix, extending their propagation pathway and favoring enhanced attenuation efficiency of EMW. 2.3 Outstanding EMW Absorption Performances The composites with tunable phases and structures were ingeniously applied to absorb EMW at gigahertz frequencies. The reflection loss (RL) intensity and effective absorption bandwidth (EAB, the frequency range for RL ≤−10 dB) were employed to assess the EMW capacity of the composites with a mass filler loading of 50%. As illustrated in Fig. 3a and Fig. S39-S40 , CZ exhibits relatively general absorption properties at high frequency, achieving a minimum RL (RL min ) of −50.99 dB at a thickness of 2.97 mm and a maximum EAB of 0.48 GHz at a thickness of 1.50 mm. Nevertheless, CZ demonstrates remarkable EMW attenuation performance in the low-to-mid frequency range, showing an absorption bandwidth of 4.32 GHz spanning from 5.60 to 9.92 GHz. It is noteworthy that the remarkably enhanced comprehensive performance of the bimetallic MOF-derived composites compared to their monometallic counterparts may be ascribed to the multicomponent competitive synergies ( Fig. S41 ). As the leaf-like morphology gradually occurs, FCZ1 presents an improvement in RL and EAB, with RL min of −61.67 [email protected] mm and a 5.20 [email protected] mm wide EAB, covering 12.80-18.00 GHz ( Fig. 3b ). Then, despite the reduction in RL min (−22.26 dB) of the FCZ2, its EAB elevates to 5.60 GHz at a matched thickness of 1.83 mm ( Fig. 3c ). The absorption band progressively shifts from the low-to-mid frequency range toward the higher frequency region. Consequently, the effective bandwidth in the low-to-mid frequency range gradually narrows, while the EAB in the high-frequency range demonstrates continuous broadening. When increasing the level of Fe 3+ , the absorption capacity of FCZ3 is ameliorated with an EAB of 5.84 [email protected] mm ( Fig. 3d ). This suggests that the hierarchical self-assembly architecture is critical in facilitating enhanced geometric scattering and optimized interfacial charge polarization mechanisms, thereby boosting the electromagnetic response. Among all the synthesized absorbers, FCZ4 with diverse microstructures possesses the most exceptional EMW absorption performance, featuring an ultra-wide EAB of up to 6.08 GHz only at 2.03 mm thickness, completely covering the Ku-band ( Fig. 3e ). At this moment, the geometric scattering effects and electromagnetic component compatibility achieve an optimal equilibrium, thus realizing maximum EMW efficiency. Nevertheless, the structural reconfiguration and ordered rearrangement of FCZ5 induce simplified geometric scattering pathways and compromised impedance matching, resulting in a substantial decline of its EMW absorption capabilities, with an EAB of 5.60 [email protected] mm ( Fig. 3f ). As the Fe 3+ concentration is promoted further and architectural features fade, this diminishing tendency becomes more prominent. Hence, the FCZ6 demonstrates an RL min of −17.71 dB and an EAB of 5.20 GHz ( Fig. S42 ). Moreover, the monometallic MOF system reveals enhanced performance upon introduction of Fe 3+ , validating the efficacy and broad applicability of this strategic Fe 3+ incorporation approach in advanced absorber design engineering ( Fig. S43 ). Notably, optimizing the FCZ4 filler loading enables a prominently strengthened reflection loss capability, with RL min values reaching −84.41 dB and −66.96 dB, as depicted in Fig. 3g, h and Fig. S44 . To explicitly reflect the excellent EMW absorption property exhibited by FCZ4, the performance of other recently reported MOF-derived absorbers is summarized for comparison. As displayed in Fig. 3i, j and Table S6 , the minimum RL and maximum EAB of FCZ4 exceed those of other absorbers, along with its advantages in controlled structure and modifiable component, FCZ4 emerges as a promising candidate for customizable high-performance MOF-derived absorbers. 2.4 Distinctive Electromagnetic Response Behaviors The exceptionally high-frequency EMW absorption property is linked to its distinct electromagnetic parameters. Thus, the related complex permittivity ( εʹ , εʹʹ ) and complex permeability ( μʹ , μʹʹ ) are first analyzed. The real parts of the complex permittivity and complex permeability, which stand for the storage abilities for electrical polarization and magnetic polarization, respectively, are denoted by the terms εʹ and μʹ [47]. Conversely, the imaginary parts of the complex permittivity ( εʹʹ ) and complex permeability ( μʹʹ ) express the capability of electric dipole and magnetic dipole moments to dissipate EMW as they realign within an alternating electromagnetic field [27]. Besides, the tangent values of complex permittivity (tan δ ε = εʹʹ / εʹ ) and complex permeability (tan δ μ = μʹʹ / μʹ ) represent the relationship between the ratio of loss and stored energy [48]. As illustrated in Fig. 4a, b , the εʹ and εʹʹ values of CZ exhibit marked fluctuations within the ranges of 6.81 to 12.96 and 1.65 to 6.63, respectively. Meanwhile, FCZ1 enhances both parameters following the incorporation of Fe 3+ . Then, despite the continued increase in Fe 3+ concentration leading to a decrease in the εʹ value (from 7.19 to 14.05), FCZ2 displays a significant improvement in εʹʹ value (from 5.13 to 8.62). As the Fe 3+ level progressively rises, the composites show a gradual enhancement in both εʹ and εʹʹ values alongside reduced curve fluctuations, with FCZ5 achieving the highest εʹ (from 7.41 to 16.20) and εʹʹ (from 3.71 to 9.84) values among all samples. However, the μʹ and μʹʹ values fluctuate around 1 and 0, respectively ( Fig. S45 ). This behavior may also be attributed to the intrinsic resonance frequency shift caused by nanoscale magnetic metallic particles, insufficient magnetic coupling interactions, and negligible eddy current generation resulting from the amorphous carbon encapsulation layer. These factors prevent the establishment of frequency-specific magnetically responsive characteristics within the system [49]. The considerably higher tan δ ε values than tan δ μ values in the composites reveal that the EMW dissipation capability originates primarily from dielectric loss rather than magnetic loss contributions ( Fig. 4c ). Additionally, FCZ4 demonstrates the highest tan δ ε value throughout the frequency band, which accounts for its exceptional EMW absorption performance among all samples. Instead, despite possessing the highest values of εʹ and εʹʹ , the formation of new phases elevates electrical conductivity ( σ ), which induces impedance mismatch and compromises EMW attenuation efficiency, thereby reducing the tan δ ε value of FCZ5 ( Fig. 4d and Fig. S46 ). The Co 3 ZnC and metallic Co phases, with superb electrical properties, are responsible for the highest σ of the CZ sample. Nevertheless, the gradual reduction in σ of the composites with the rise in Fe 3+ amount reaches a minimum at FCZ3. The result is primarily driven by the synergistic effects of Fe-Co solid solution formation with enhanced electrical resistivity relative to metallic Co and the progressive depletion of Co 3 ZnC phase content. Subsequently, the highly conductive Fe 3 ZnC 0.5 and Fe phases progressively nucleate and grow, while the structural evolution involving reorganization facilitates a partial restoration of the conductive network, thereby contributing to the recovery of the electrical conductivity. Therefore, the conductivity loss ( ε c ʹʹ ), which is directly proportional to the material conductivity ( ε c ʹʹ = σ / ω ε 0 ), also exhibits a sharp initial decline followed by a slow climb ( Fig. 4e-g ) [38]. The polarization loss ( ε p ʹʹ ), which additionally contributes to the dielectric loss ( ε p ʹʹ = εʹʹ-ε c ʹʹ ), shows an opposite trend. In brief, introducing Fe 3+ induces a substantial alteration in the dielectric response by shifting the primary energy dissipation mechanism from conductive loss to polarization-controlled processes. Intriguingly, two prominent polarization relaxation peaks are observed in the εʹʹ -curve for the CZ. These characteristic peaks demonstrate a continuous reduction in intensity with increasing Fe 3+ concentration. The relaxation feature eventually diminished to baseline levels upon reaching the FCZ3. The Cole-Cole plots, based on the Debye theory, were utilized to elaborate on this unique polarization behavior. Individual semicircles correspond to specific relaxation processes induced by interfacial polarization or dipole reorientation in the Cole-Cole plots, and the trailing straight lines signify electronic conduction losses arising from charge carrier migration [50]. The CZ plot presents two conspicuous semicircles accompanied by linear tails, indicating the concurrent presence of multiple polarization processes coupled with conduction loss ( Fig. 4i ) [51]. The semicircular features progressively decline in prominence as Fe 3+ levels rise, while the linear components reveal enhanced definition, which seems to imply a gradual transition from polarization-dominated to conductivity-dominated dielectric response. The result, however, contradicts the conclusions from the quantitative studies mentioned above. Consequently, we posit that the anomalous dielectric behavior is inextricably linked to the compositional variations. Specifically, in the bimetallic CZ system before Fe 3+ incorporation, dipole polarization mainly originates from lattice defects in amorphous ZnO, while interfacial polarization is predominantly governed by the heterointerfaces at Co 3 ZnC/C and Co/C boundaries. These independent polarization mechanisms collectively give rise to the formation of two well-separated relaxation peaks. Upon adding Fe 3+ , the progressive increase of Fe-Co solid solution content facilitates the generation of extensive and sophisticated heterogeneous interfacial structures, considerably amplifying the interfacial polarization response. The incremental raising of the amorphous ZnO level also induces higher concentrations of lattice defects, thereby boosting the defect-induced polarization effect and further enhancing dipole polarization relaxation. Hence, the intensified synergistic coupling within the multipolarization mechanism may lead to the progressive overlap of relaxation peaks into a single, broad dielectric response, culminating in the gradual smoothing of the curve. The polarization relaxation parameters could be obtained from fitting analysis using a modified Havriliak-Negami model, thus quantitatively accounting for the observed concurrent reduction in relaxation peak intensity and elevation of polarization loss ( Fig. S47 and Table S7 ) [52]. As depicted in Fig. 4q , the parameter α , which governs the breadth of the relaxation time distribution, demonstrates a consistent downward trend. This suggests broadening the relaxation time distribution, thus diminishing the distinct peak shape in the εʹʹ curve. Besides, the gradual increase of the relaxation time ( τ ) results in the characteristic relaxation frequency shift to a lower frequency. When this frequency progressively falls outside the detectable frequency range (i.e., less than 2.0 GHz), it manifests as the "disappearance" of the relaxation peak phenomenon. Notably, even in the vanishing of the relaxation peak, the substantial enhancement in dielectric strength (Δ ε = ε s - ε ∞ ) sustains the overall polarization loss at elevated levels, which corroborates the earlier findings derived from experimental conductivity measurements. These results deviate from the expected behavior of the classical relaxation model, implying the presence of intricate multiscale polarization coupling mechanisms within the material. In summary, the anomalous dielectric characteristics can be ascribed to the coupling effect of multi-polarization mechanisms primarily governed by the Fe-Co solid solution and amorphous ZnO phases. The D and G bands are critical features for characterizing carbon-based materials in Raman spectroscopy [37]. The D band, appearing near 1350 cm -1 , is associated with structural defects and arises from the breathing mode of sp 3 -hybridized carbon atoms [14]. The G band, typically observed around 1580 cm -1 , corresponds to the in-plane vibrational mode of sp 2 -hybridized carbon atoms and reflects the crystallinity of the graphitic structure [53]. The intensity ratio of these bands (I D /I G ) is a quantitative indicator of defect density within the material. As depicted in Fig. 4h , the I D /I G ratio exhibits a progressive increase with incremental Fe 3+ concentration, reaching peak values at FCZ3 and FCZ4 before demonstrating a subsequent decline. This trend suggests that the defect density within the system initially rises and then decreases, causing corresponding variations in the defect-induced polarization loss. Moreover, photoluminescence (PL) spectroscopy was employed to characterize the concentration of defects within the materials, including vacancies, interstitials, and dislocations. These crystal defects act as nonradiative recombination centers, dissipating excitation energy through phonon interactions, which results in the intensity of the PL spectra being inversely proportional to the level of the defects [36]. The observed tendency of spectral intensity displays an initial reduction followed by an elevation with gradual Fe 3+ incorporation ( Fig. S48 ). This provides compelling evidence that polarization relaxation triggered by high-concentration defects progressively emerges as a key factor governing the system's dielectric behavior. HRTEM analysis of FCZ4 reveals the existence of multiple homogeneous interfaces composed of the Co phase, along with heterogeneous interfaces consisting of both Fe and Co phases embedded within an amorphous carbon matrix ( Fig. 4j, k ). These interfaces promote substantial electron aggregation at interfacial boundaries, generating robust interfacial polarization phenomena [54]. Meanwhile, several stress concentration points are intuitively observed, derived from geometrical phase analysis (GPA), and this inhomogeneous stress fraction, due to an unbalanced charge distribution at the interface, could be a defect-induced polarization center ( Fig. 4n, o ) [18]. Similarly, through inverse fast Fourier transform (IFFT) research, well-defined grain boundaries and lattice stacking are resolved, with these lattice deficiencies demonstrating the capacity to act as polarization-active centers owing to their localized structural distortions ( Fig. 4p ) [55]. In conjunction with N atoms doped into the carbon lattice, which can also serve as polarization-triggered centers, these substantial polarization centers generate pronounced polarization relaxation phenomena, thereby amplifying the dielectric response under alternating electromagnetic fields [38]. Furthermore, the high density of oxygen vacancies, point defects, lattice discontinuities, and dislocations induces local electric field distortions, which yield a dipole polarization response that effectively lowers the polarization relaxation energy barrier, thereby significantly enhancing polarization relaxation loss ( Fig. 4l, m ) [53]. The synergistic interface and dipole polarization interaction facilitate a distinctive and efficient dielectric response for reinforced EMW attenuation. Impedance matching ( Z ) and attenuation constant ( AC ) constitute two vital performance metrics for evaluating EMW absorption efficiency. The Z ensures minimal interfacial reflection to maximize EMW penetration into the material's interior, while the AC governs the rapid energy conversion of incident waves into thermal or other forms of energy for dissipation. The impedance matching region is defined when the input impedance ( Z in ) approaches the free space impedance ( Z 0 ) with a normalized magnitude ratio | Z in / Z 0 | ranging between 0.8 and 1.2, as this specific impedance range allows near-complete penetration of EMW into the material's interior [50]. As illustrated in Fig. S49 , the impedance characteristics demonstrate progressive deviation from the ideal matching area, with the FCZ4 also failing to attain optimal impedance matching performance. Although the impedance matching declines in FCZ4, the enhanced attenuation capability resulting from the elevated εʹʹ partially compensates for reflection losses, thereby substantially broadening the EAB. By adjusting the FCZ4 filler loading in the composites to modulate the complex permittivity, optimal impedance matching can be realized. This leads to an improved reflection loss intensity while simultaneously narrowing the EAB due to the constraints imposed by the quarter-wavelength matching mechanism ( Fig. S50-S52 ) [56]. Besides, the variation trend of the AC is observed in Fig. S53 . The progressive degradation of impedance characteristics prevents FCZ5 from attaining satisfactory absorption performance despite exhibiting the maximum AC value among the investigated materials [57]. Thus, the low doping ratio fulfills excellent impedance matching and strong reflection loss, but is unable to achieve the best EAB. In contrast, the high doping ratio enhances dielectric loss and broadband attenuation capability, thereby boosting EAB at the expense of impedance mismatch, which weakens the absorption peak intensity and induces a high-frequency shift. This requires balanced optimization between these competing mechanisms for optimal EMW performance. Moreover, the thermal field modulation results demonstrate that controlled annealing temperature not only dominates the phase evolution path of the composites but also enables effective regulation of the electromagnetic response, rendering the synthesized materials potential for multifunctional EMW management ( Fig. S54-S55 ). The ingeniously designed gradient Fe 3+ introduction achieves the tailoring of dielectric response characteristics through precise phase modulation engineering. This combines hierarchical architectures that enhance electromagnetic impedance compatibility, collectively establishing an intelligent platform for developing high-performance EMW absorbers with tunable electromagnetic properties. 2.5 EMW Absorption Mechanisms To assess the effectiveness of the synthesized composites in absorbing EMW for practical applications, computational simulations of the far-field radar scattering cross section (RCS) were implemented using the CST electromagnetic simulation platform [53]. As displayed in Fig. 5a and Fig. S56-S57 , FCZ4 demonstrates the lowest RCS signals. The analysis of the specific functional relationship between the RCS value and the incident angle exhibits that the FCZ4 is capable of reducing RCS signal strength by up to 10.7 dB m 2 compared to the PEC ( Fig. 5b ) [36]. This indicates that the FCZ4 reveals good environmental adaptability to complex far-field conditions while fulfilling practical application requirements. The electromagnetic power loss density (EPLD) analysis of composites simulated using COMSOL Multiphysics software suggests that progressive geometric structural optimization effectively enhances the scattering effect toward EMW, enabling the FCZ4 to possess superior EMW consumption efficiency ( Fig. 5c ) [38]. The main loss mechanisms responsible for the extraordinary absorption performance of FCZ4 are summarized as follows: i) The morphological evolution and configuration optimization within FCZ4 synergistically enhance EMW interactions through intensified multiple reflections and scattering [58]. ii) Rational modulation of intrinsic conductivity effectively reduces the reflection loss of EMW on the material surface. The three-dimensional conductive network, composed of metal and carbon components, facilitates the directional migration of free charge carriers in response to alternating electromagnetic fields. This microcurrent generation mechanism promotes efficient electromagnetic energy dissipation via conduction loss through thermal conversion [59]. iii) The dispersed heterogeneous structural units within the N-doped carbon matrix, particularly the Fe-Co solid solution, effectively modulate the carrier migration and separation behavior by constructing a high-density phase boundary/heterogeneous interface network [60]. This multiscale interface engineering induces the accumulation of directional spatial charge, forming a pronounced non-equilibrium charge distribution gradient that generates a strong built-in electric field via interfacial dielectric relaxation mechanisms and amplifies the effects of interfacial polarization [61]. iv) The competitive coordination interactions among ternary transition metal ions, coupled with the concurrent presence of multi-ligand configurations, trigger the development of lattice distortions and defect architectures generated during the pyrolysis of MOF materials. These topological defects, coupled with amorphous ZnO, function as localized polarization centers that induce relaxation losses associated with dipole orientation polarization by establishing asymmetric charge distributions [62]. The synergistic interaction among multifaceted dissipation mechanisms, including geometric scattering effects, conductive losses, interfacial polarization relaxation, and dipole relaxation processes, collectively contributes to the high-efficiency EMW attenuation characteristics in FCZ4 composites ( Fig. 5d ). 3. Conclusion This work successfully fabricates high-performance and customizable polymetallic MOF-derived EMW absorbers through an ingeniously designed gradient Fe 3+ incorporation strategy, synergizing ligand competition kinetics and reduction potential thermodynamics. By adjusting the Fe 3+ content, precise phase and structural regulation are achieved, thereby enabling controlled tuning of the dielectric response. The coupling effect between interfacial and dipole polarization induces anomalous dielectric behavior that breaks the perceived boundaries of the traditional polarization loss adjustment. Eventually, the optimized composites exhibit outstanding EMW absorption properties characterized by a strong RL min of −84.41 dB and a broad EAB spanning 6.08 GHz. Furthermore, investigating the thermal field modulation that governs electromagnetic parameters reveals the potential and benefits of the synthesized materials in multifunctional applications. This work opens new avenues for designing customizable MOF-derived absorbers, providing fresh insights into the dielectric polarization mechanism in amorphous-crystalline heterosystems. Declarations Author Contribution Sihao Dou: Writing - original draft, Validation, Methodology, Investigation, Conceptualization. Yunfei He: Writing - review & editing, Data curation, Validation, Software. Yuxiang Zheng, Yuefeng Yan, and Zhiyuan Dan: Writing - review & editing, Data curation. Long Ma and Minghao Yang: Validation, Software. Dongdong Liu, Xiaoxiao Huang, and Bo Zhong: Funding acquisition, Validation, Supervision, Project administration. All authors reviewed and approved the manuscript. Funding This work was supported by the National Natural Science Foundation of China (NSFC 51872058), the Supporting Program for Innovation Team of Outstanding Youth in Colleges and Universities of Shandong Province (2020KJA005), the Natural Science Foundation of Shandong Province (ZR2022QB156), and the Foundation of State Key Laboratory of Precision Welding & Joining of Materials and Structures. Data Availability No datasets were generated or analysed during the current study. Competing interests The authors declare no competing interests. References Zhou X, Min P, Liu Y, Jin M, Yu Z, Zhang H (2024) Insulating electromagnetic-shielding silicone compound enables direct potting electronics. 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Supplementary Files SupplementaryInformation.pdf Cite Share Download PDF Status: Published Journal Publication published 10 Nov, 2025 Read the published version in Advanced Composites and Hybrid Materials → Version 1 posted Editorial decision: Accepted 09 Oct, 2025 Reviews received at journal 09 Oct, 2025 Reviews received at journal 09 Oct, 2025 Reviewers agreed at journal 08 Oct, 2025 Reviewers agreed at journal 08 Oct, 2025 Reviewers invited by journal 08 Oct, 2025 Submission checks completed at journal 08 Oct, 2025 First submitted to journal 07 Oct, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7308006","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":525871527,"identity":"be52a93d-1ded-44d8-956c-f86accb999e8","order_by":0,"name":"Sihao Dou","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Sihao","middleName":"","lastName":"Dou","suffix":""},{"id":525871528,"identity":"4ee3e87a-91bc-436f-997e-1123e2bc967f","order_by":1,"name":"Yunfei He","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yunfei","middleName":"","lastName":"He","suffix":""},{"id":525871529,"identity":"937be544-7725-4bca-b9a5-1431f852c444","order_by":2,"name":"Yuxiang Zheng","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yuxiang","middleName":"","lastName":"Zheng","suffix":""},{"id":525871530,"identity":"ad8d0c43-d04c-4a80-be96-ae472461d695","order_by":3,"name":"Yuefeng Yan","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yuefeng","middleName":"","lastName":"Yan","suffix":""},{"id":525871531,"identity":"54345ffe-2b77-4cdb-a5b2-c37e092ca49f","order_by":4,"name":"Zhiyuan Dan","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Zhiyuan","middleName":"","lastName":"Dan","suffix":""},{"id":525871532,"identity":"4c9dccda-f49f-43be-908f-f65b7d717753","order_by":5,"name":"Long Ma","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Long","middleName":"","lastName":"Ma","suffix":""},{"id":525871533,"identity":"18779a38-e0ad-41cd-99fd-968eaf5a3fc0","order_by":6,"name":"Minghao Yang","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Minghao","middleName":"","lastName":"Yang","suffix":""},{"id":525871534,"identity":"df1c4dc0-a18a-4755-93f3-282761e33645","order_by":7,"name":"Dongdong Liu","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Dongdong","middleName":"","lastName":"Liu","suffix":""},{"id":525871535,"identity":"1b49fb34-2ddb-42fd-837a-0d0bc300c418","order_by":8,"name":"Xiaoxiao Huang","email":"","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Xiaoxiao","middleName":"","lastName":"Huang","suffix":""},{"id":525871536,"identity":"025113df-14f3-4103-8523-17759e4fe5c9","order_by":9,"name":"Bo Zhong","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA0UlEQVRIiWNgGAWjYDACCSBmbGCQM2AG8dhI0GJswMxMopbEDQzEapGf3Xzs4dcdNunb2fkPMHwoO8zAP7sBvxbGOcfSjWXPpOXubGZmYJxx7jCDxJ0D+LUwS+SYSUu2Hc7dcJiZgZm37TCDgUQCfi1sUC3pBiAtf4nRwgPUIvmx7XACWAsjMVokJNLSpBnPpBkCHWZwsOdcOo/EDQJa5GckH5P8ucNG3uD8wYcPfpRZy/HPIKAFBJh5oIwDIJcSVg8EjD+IUjYKRsEoGAUjFgAAzsw9ytqj1DsAAAAASUVORK5CYII=","orcid":"","institution":"Harbin Institute of Technology","correspondingAuthor":true,"prefix":"","firstName":"Bo","middleName":"","lastName":"Zhong","suffix":""}],"badges":[],"createdAt":"2025-08-06 09:23:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7308006/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7308006/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s42114-025-01506-8","type":"published","date":"2025-11-10T15:58:42+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":93071281,"identity":"67f6eaf3-2a93-4e0d-9e50-8dd0852b738e","added_by":"auto","created_at":"2025-10-08 17:55:50","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":488678,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e Schematic diagram of the preparation process of CZ and FCZ\u003cem\u003ex\u003c/em\u003e. \u003cstrong\u003eb\u003c/strong\u003e Schematic illustration of the phase variation. \u003cstrong\u003ec\u003c/strong\u003e XRD patterns. SEM images of \u003cstrong\u003ed\u003c/strong\u003e CZ, \u003cstrong\u003ee\u003c/strong\u003e FCZ1, \u003cstrong\u003ef\u003c/strong\u003e FCZ2, \u003cstrong\u003eg\u003c/strong\u003e FCZ3, \u003cstrong\u003eh\u003c/strong\u003e FCZ4, and \u003cstrong\u003ei\u003c/strong\u003e FCZ5 (all images are on a one μm scaled bar). \u003cstrong\u003ej\u003c/strong\u003e Schematic description of the morphological evolution. \u003cstrong\u003ek\u003c/strong\u003e TEM image of FCZ5. \u003cstrong\u003el\u003c/strong\u003e EDS elemental mapping of FCZ5.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/d24b99e2ad0b097c8efb2607.png"},{"id":93071294,"identity":"b5ec302d-831a-4e52-92f1-982ef686a114","added_by":"auto","created_at":"2025-10-08 17:55:53","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":330464,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e C 1s spectrum, \u003cstrong\u003eb\u003c/strong\u003e N 1s spectrum, \u003cstrong\u003ec\u003c/strong\u003e O 1s spectrum, and \u003cstrong\u003ed\u003c/strong\u003e Zn 2p spectrum of FCZ4. \u003cstrong\u003ee\u003c/strong\u003e Co 2p spectrum. \u003cstrong\u003ef\u003c/strong\u003e Fe 2p spectrum. \u003cstrong\u003eg\u003c/strong\u003e Mass proportion of Fe, Co, and Zn elements obtained from ICP-OES. \u003cstrong\u003eh\u003c/strong\u003e Summary of saturation magnetization and coercivity. \u003cstrong\u003ei\u003c/strong\u003e Summary of specific surface area and average pore diameter (where the pore width is enlarged by a factor of 10). \u003cstrong\u003ej\u003c/strong\u003e Normalized per-atom formation energies of different models (the inset is the optimized model of the Fe\u003csub\u003e12\u003c/sub\u003eCo\u003csub\u003e20\u003c/sub\u003e structure). The spin-down channel of the band structure for \u003cstrong\u003ek\u003c/strong\u003e Co and \u003cstrong\u003el\u003c/strong\u003e Fe\u003csub\u003e12\u003c/sub\u003eCo\u003csub\u003e20\u003c/sub\u003e. The PDOS of \u003cstrong\u003em\u003c/strong\u003e Fe and \u003cstrong\u003en\u003c/strong\u003e Co atoms.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/78063e11ac6ff1ddb21aaee8.png"},{"id":93071273,"identity":"0b3e6c70-9b29-4159-95c4-7acada5abf38","added_by":"auto","created_at":"2025-10-08 17:55:50","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":357953,"visible":true,"origin":"","legend":"\u003cp\u003eThe 2D RL mapping and RL curves of \u003cstrong\u003ea\u003c/strong\u003e CZ, \u003cstrong\u003eb\u003c/strong\u003e FCZ1, \u003cstrong\u003ec\u003c/strong\u003e FCZ2, \u003cstrong\u003ed\u003c/strong\u003e FCZ3, \u003cstrong\u003ee\u003c/strong\u003e FCZ4, and \u003cstrong\u003ef\u003c/strong\u003e FCZ5 (50% mass filler loading). The RL curves of FCZ4 at mass filler loading of \u003cstrong\u003eg\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e 40%, \u003cstrong\u003eg\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e 45%, and \u003cstrong\u003eg\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e 55%. \u003cstrong\u003eh\u003c/strong\u003e Summary of RL\u003csub\u003emin\u003c/sub\u003e and EAB for FCZ4 at different mass filler loading. Comparison of \u003cstrong\u003ei\u003c/strong\u003e RL\u003csub\u003emin\u003c/sub\u003e and \u003cstrong\u003ej\u003c/strong\u003e EAB of FCZ4 with reported MOF-based absorbers.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/574fc2395faa279bd161741b.png"},{"id":93072238,"identity":"083150ba-6891-4c78-a84f-563657df06ce","added_by":"auto","created_at":"2025-10-08 18:03:50","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":612329,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ea\u003c/strong\u003e The real part and \u003cstrong\u003eb\u003c/strong\u003e the imaginary part of the complex permittivity. \u003cstrong\u003ec \u003c/strong\u003eThe dielectric loss tangent values. \u003cstrong\u003ed\u003c/strong\u003e Electrical conductivity. \u003cstrong\u003ee\u003c/strong\u003e \u003cem\u003eε\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e\u003cem\u003eʹʹ\u003c/em\u003e and \u003cem\u003eε\u003c/em\u003e\u003csub\u003ep\u003c/sub\u003e\u003cem\u003eʹʹ\u003c/em\u003e. The proportion of \u003cstrong\u003ef\u003c/strong\u003e \u003cem\u003eε\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e\u003cem\u003eʹʹ \u003c/em\u003eand \u003cstrong\u003eg\u003c/strong\u003e \u003cem\u003eε\u003c/em\u003e\u003csub\u003ep\u003c/sub\u003e\u003cem\u003eʹʹ \u003c/em\u003eto \u003cem\u003eεʹʹ\u003c/em\u003e. \u003cstrong\u003eh\u003c/strong\u003e Raman spectra. \u003cstrong\u003ei\u003c/strong\u003e Cole-Cole plots. \u003cstrong\u003ej-m\u003c/strong\u003e HRTEM images of FCZ4. \u003cstrong\u003en, o\u003c/strong\u003e Strain field micrographs along the Exx directions in j and k. \u003cstrong\u003ep\u003c/strong\u003e IFFT image of k. \u003cstrong\u003eq\u003c/strong\u003e Δ\u003cem\u003eε, τ, \u003c/em\u003eand\u003cem\u003e α \u003c/em\u003eparameters (the values of Δ\u003cem\u003eε \u003c/em\u003ereduced by a factor of 100 and the values of \u003cem\u003eτ \u003c/em\u003ereduced by a factor of 10).\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/7e031242e935cd89a0de531a.png"},{"id":93071283,"identity":"fb6fae0b-ac27-4661-96d6-ad54051b0eb5","added_by":"auto","created_at":"2025-10-08 17:55:50","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":488018,"visible":true,"origin":"","legend":"\u003cp\u003eSimulated 3D radar wave scattering signal of \u003cstrong\u003ea\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e1\u003c/strong\u003e\u003c/sub\u003e PEC, \u003cstrong\u003ea\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e2\u003c/strong\u003e\u003c/sub\u003e CZ, and \u003cstrong\u003ea\u003c/strong\u003e\u003csub\u003e\u003cstrong\u003e3\u003c/strong\u003e\u003c/sub\u003e FCZ4. \u003cstrong\u003eb\u003c/strong\u003e Simulated RCS curves of PEC, CZ, and FCZ4. \u003cstrong\u003ec\u003c/strong\u003e Simulated electromagnetic power loss density. \u003cstrong\u003ed\u003c/strong\u003e Schematic illustration of EMW absorption mechanisms.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/e93461e9da599c59c2989bf2.png"},{"id":96105284,"identity":"3161ab70-0309-4fc7-a38e-c34598f80853","added_by":"auto","created_at":"2025-11-17 16:10:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3172050,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/eadb95ad-60da-4d5b-885e-0e73aa2fdde4.pdf"},{"id":93071243,"identity":"fe5ef5ae-96c9-480a-9f23-fc0947259043","added_by":"auto","created_at":"2025-10-08 17:55:49","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":11098791,"visible":true,"origin":"","legend":"","description":"","filename":"SupplementaryInformation.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7308006/v1/775d207e5f4d8cd0e263c9b8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Controlled phase and structure engineering-driven unique dielectric behavior enabling tailored electromagnetic attenuation","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe exponential surge in electromagnetic (EM) pollution, propelled by the ubiquitous deployment of 5G/6G networks and high-precision radar systems, has heightened the demand for advanced electromagnetic wave (EMW) absorbers with tailorable attenuation characteristics [1-3]. Next-generation absorbers must simultaneously satisfy multidimensional performance metrics: ultra-low reflection loss (\u0026lt;\u0026minus;50 dB), ultra-broad bandwidth (\u0026gt;5 GHz), sub-2.5 mm thickness, and lightweight flexibility [4-6]. Metal-organic framework (MOF)-derived carbon composites have emerged as frontier candidates owing to their designable architectures, atomic-level compositional tunability, and multiscale dielectric mechanisms [7-9]. Since monometallic MOFs are constrained by their structural and compositional homogeneity, which impede the simultaneous achievement of high-efficiency absorption and broadband coverage, bimetallic systems have been developed as a promising solution [10-12]. Nevertheless, conventional bimetallic MOF derivatives often suffer from uncontrollable phase segregation, rigid topological configuration, and disordered spatial dispersion of metallic constituents, resulting in compromised electromagnetic compatibility [13-15]. Most critically, the inherent trade-off between phase heterogeneity and structural inflexibility obstructs the establishment of precise dielectric response modulation, thereby hindering the rational design of high-performance EMW absorbers [16, 17].\u003c/p\u003e\n\u003cp\u003eThe intrinsic limitations of bimetallic systems have catalyzed innovative efforts toward ternary heterometallic architectures [18-20]. Central to this strategy is leveraging the third heterogeneous metal to regulate the compositional distribution, induce high-density lattice defects, and construct multilevel heterogeneous interfaces, thereby enhancing electromagnetic attenuation. Huang et al. [18] prepared\u0026nbsp;flower-like magnetic-carbon microspheres by incorporating a third metal (Cu, Zn, Fe, and Mn) into CoNi bimetallic MOF precursors. By modulating the composition of the ternary alloy, it optimized the intrinsic EM parameters and impedance matching characteristics, achieving a 5.8 GHz absorption bandwidth at 2.0 mm. Liu et al.\u0026nbsp;[19]\u0026nbsp;synthesized a CoNiMn trimetallic MOF by simultaneously introducing Co and Ni into Mn-MOF, which significantly enhanced the oxygen vacancy concentration compared to the bimetallic system. The resulting dielectric polarization dominated EMW loss, realizing a wide absorption bandwidth of 8.0 GHz with a thickness of only 2.1 mm. Ning et al.\u0026nbsp;[20]\u0026nbsp;reported defect-rich NiFe\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e/MoNi\u003csub\u003e4\u003c/sub\u003e-NC composites via Fe\u003csup\u003e3+\u003c/sup\u003e ion exchange into NiMo-MOFs followed by template-assisted pyrolysis. Non-homogeneous doping-induced lattice distortion, which amplifies dipole polarization, is coupled with strong interfacial polarization triggered by the multi-heterogeneous interfaces, contributing to the excellent EMW absorption property with a 5.76 GHz bandwidth. Despite these advances, fundamental barriers persist. The inevitable phase separation within the polymetallic matrix complicates efforts to regulate the spatial arrangement of metallic components and promote the development of advantageous phase configurations\u0026nbsp;[21]. Incorporating a third metallic component fails to alter the original bimetallic system\u0026apos;s topological architecture, limiting the scope for structural optimization to achieve targeted impedance engineering and enhance EMW multiple scattering for improved energy dissipation\u0026nbsp;[18]. Crucially, fine-grained manipulation of the dielectric response via precise phase and structure modulation remains\u0026nbsp;elusive, obstructing the establishment of deterministic phase-structure-performance correlations\u0026nbsp;[22]. These barriers are rooted in uncontrollable coordination microenvironments and constrained thermal decomposition pathways. Consequently, accurate control over the metal-ligand coordination nodes during precursor crystallization and the sequential reduction of metallic species during subsequent pyrolysis is necessary to achieve tailored electromagnetic attenuation\u0026nbsp;[23].\u003c/p\u003e\n\u003cp\u003eHerein, through the gradient incorporation of Fe\u003csup\u003e3+\u003c/sup\u003e ions, which exhibit superior ligand affinity and the lowest reduction potentials, into the Co/Zn bimetallic MOF system, we realize precision modulation of crystalline phases and nanostructures in the trimetallic MOFs, thereby enabling tunable electromagnetic responses. Specifically, by regulating the introduced Fe\u003csup\u003e3+\u003c/sup\u003e content, a progressive geometrical optimization of the topological structure is achieved, encompassing leaf-like precursor inheritance to multistage self-assembly to final reconfiguration. The Fe\u003csup\u003e3+\u003c/sup\u003e-mediated stepwise phase transformation facilitates the development of a Fe-Co solid solution and amorphous ZnO while suppressing the nucleation pathway of the Co\u003csub\u003e3\u003c/sub\u003eZnC phase, permitting controlled phase separation. The resultant coupling intensification of the multi-polarization mechanism elicits distinctive dielectric behaviors characterized by the gradual attenuation of the relaxation peak and a concomitant augmentation in polarization loss. As a result, the optimized composites exhibit superior EMW absorption performance, featuring an ultra-low reflection loss of \u0026minus;84.41 [email protected] GHz and attaining a broad EAB spanning 6.08 GHz at a thickness of 2.03 mm. This work offers novel design strategies for polymetallic MOF derivatives, providing deep insights into polarization mechanisms within amorphous-crystalline heterosystems for advanced EMW absorption materials.\u003c/p\u003e"},{"header":"2. Results and Discussion","content":"\u003cp\u003e\u003cstrong\u003e2.1 Structural evolution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBimetallic MOF and its derivatives were synthesized through co-precipitation, followed by pyrolysis [24]. The observed structure of the leaf-like Co/Zn-ZIF (expressed as CZ-Z; sample names are listed in \u003cstrong\u003eTable S1\u003c/strong\u003e) can be attributed to the asymmetric coordination behaviors induced by the distinct ligand characteristics of nitrate versus acetate anions (\u003cstrong\u003eFig. 1a\u0026nbsp;\u003c/strong\u003eand \u003cstrong\u003eFig. S1\u003c/strong\u003e). Nevertheless, the CZ-Z-derived composites (labeled as CZ) display structural collapse into stacked circular-like sheets (\u003cstrong\u003eFig. 1d\u003c/strong\u003e and \u003cstrong\u003eFig. S2\u003c/strong\u003e). The abnormal structural disinheritance might stem from the asymmetric coordination environment within the MOF precursor, triggering crystallographic lattice distortions and architectural destabilization [25]. Meanwhile, the Co\u003csub\u003e3\u003c/sub\u003eZnC intermetallic compound (PDF#29-0524) and metallic Co (PDF#15-0806), as identified by X-ray diffraction (XRD), inherently possess high surface energy characteristics that promote Ostwald ripening processes (\u003cstrong\u003eFig. 1c\u0026nbsp;\u003c/strong\u003eand \u003cstrong\u003eNote S1\u003c/strong\u003e) [26, 27]. This results in particle migration and agglomeration, ultimately leading to the catastrophic failure of the carbon scaffold\u0026apos;s load-bearing architecture. Hence, to suppress the metallic particle aggregation while preserving the structural integrity of the precursor, the strategic incorporation of a third metallic Fe element through targeted inducing to achieve precise modulation of the phase and structure proves essential.\u003c/p\u003e\n\u003cp\u003eXRD patterns of FCZ-Z\u003cem\u003ex\u003c/em\u003e precursors demonstrate almost identical peak positions and intensities compared to CZ-Z (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS3\u003c/strong\u003e). However, the gradual lightening of the powder coloration observed in macroscopic samples confirms the successful integration of Fe\u003csup\u003e3+\u003c/sup\u003e into the framework and reveals alterations in the coordination environment within the system (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS4a\u003c/strong\u003e). As presented in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1e\u003c/strong\u003e, introducing 0.6 mmol Fe\u003csup\u003e3+\u003c/sup\u003e into the bimetallic MOF precursor results in the partial retention of leaf-like morphological features (called FCZ1), indicating that Fe\u003csup\u003e3+\u003c/sup\u003e incorporation effectively alleviates structural collapse. Specifically, Fe\u003csup\u003e3+\u003c/sup\u003e with inherently higher charge density competitively coordinates with 2-methylimidazole against Co\u003csup\u003e2+\u003c/sup\u003e/Zn\u003csup\u003e2+\u003c/sup\u003e counterparts, establishing a reinforced Fe-Co-Zn hybrid coordination node [28]. Additionally, Fe nanoparticles (NPs) embedded within the carbon matrix can mitigate the migration and aggregation of metallic particles. These synergistic effects drive a topological transformation in the bimetallic MOF.\u003c/p\u003e\n\u003cp\u003eNotably, the diffraction peak intensity corresponding to the Co\u003csub\u003e3\u003c/sub\u003eZnC phase exhibits marked attenuation, suggesting that Fe\u003csup\u003e3+\u003c/sup\u003e incorporation suppresses the formation of the Co\u003csub\u003e3\u003c/sub\u003eZnC phase (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS4b\u003c/strong\u003e). This phenomenon may be rationalized by the inherently superior standard reduction potential (\u003cem\u003eE\u003c/em\u003e\u0026deg;) of Fe\u003csup\u003e3+\u003c/sup\u003e (Fe\u003csup\u003e3+\u003c/sup\u003e/Fe\u003csup\u003e0\u003c/sup\u003e = \u0026minus;0.037 V) compared to Co\u003csup\u003e2+\u003c/sup\u003e (Co\u003csup\u003e2+\u003c/sup\u003e/Co\u003csup\u003e0\u003c/sup\u003e = \u0026minus;0.277 V) and Zn\u003csup\u003e2+\u003c/sup\u003e (Zn\u003csup\u003e2+\u003c/sup\u003e/Zn\u003csup\u003e0\u003c/sup\u003e = \u0026minus;0.762 V) [29-31]. The preferential reduction of Fe\u003csup\u003e3+\u003c/sup\u003e to metallic Fe dominates the initial reduction sequence, rapidly depleting available reducing agents within the system. This competitive consumption consequently imposes kinetic limitations for subsequent reduction processes of Co\u003csup\u003e2+\u003c/sup\u003e and Zn\u003csup\u003e2+\u003c/sup\u003e, hindering the Co-Zn alloying pathway. Besides, the \u003cem\u003eE\u003c/em\u003e\u0026deg; of Co\u003csup\u003e2+\u003c/sup\u003e is higher than that of Zn\u003csup\u003e2+\u003c/sup\u003e, and the establishment of this directional reduction gradient contributes to the preferential generation of Fe-Co solid solutions (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1b\u003c/strong\u003e). Conversely, the Zn reduction reaction is significantly\u0026nbsp;inhibited, leading to the growth of amorphous ZnO.\u003c/p\u003e\n\u003cp\u003eThe pyrolyzed composites fully inherit the precursor framework after increasing the Fe\u003csup\u003e3+\u003c/sup\u003e concentration to 1.2 mmol (marked as FCZ2), as depicted in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1f\u003c/strong\u003e. Moreover, the overall structure displays a self-assembly behavioral tendency, forming a three-dimensional interconnected network through oriented growth along two orthogonal axes of the leaf-like architecture. The observed morphology may originate from magnetic interactions and anisotropic stress effects, collectively driving the spontaneous cross-assembly phenomena [32]. With a further elevation of the Fe\u003csup\u003e3+\u003c/sup\u003e level (labeled as FCZ3), the magnetic properties demonstrate a corresponding enhancement, accompanied by a self-assembly process initiated among multiple adjacent leaf-like architectures. Ultimately, this leads to the formation of thermodynamically favorable configurations through multistage structural integration (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1g\u003c/strong\u003e). Concurrently, the Co\u003csub\u003e3\u003c/sub\u003eZnC content progressively diminishes, signifying the efficacy of Fe\u003csup\u003e3+\u003c/sup\u003e incorporation in modulating the phase distribution within the bimetallic system.\u003c/p\u003e\n\u003cp\u003eInterestingly, when introduced Fe\u003csup\u003e3+\u003c/sup\u003e reaches 2.4 mmol (denoted as FCZ4), a well-defined morphological evolution is observed (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1h\u0026nbsp;\u003c/strong\u003eand \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS5\u003c/strong\u003e). The self-assembled leaf-like architectures initially undergo mutual crop and segmentation processes, splitting into triangular boomerang-shaped units. Afterward, epitaxial growth occurs preferentially at the junction points of these units, driving further structural reorganization until a developed triangular-like architecture is achieved. The separation procedure may be attributed to the supersaturated doping of Fe\u003csup\u003e3+\u003c/sup\u003e, leading to the precipitation of excess metallic Fe nanoparticles, which catalyze the oxidative etching of the carbon substrate through high-temperature metal-carbon interfacial reactions [33]. This process could induce localized dissolution at the leaf-like edges of the carbon framework, generating triangular-like notch defects. Then, Fe NPs mediate the anisotropic carbon deposition, which is preferentially localized at triangular notches, facilitating the nucleation of branching substructures that propagate the development of pseudo-triangular architectures [34]. Eventually, the reduced interfacial energy at triangular edges activates a \u0026quot;self-healing\u0026quot; mechanism that thermodynamically stabilizes the system, enabling structural optimization toward geometrically regular configurations. Notably, XRD analysis reveals no detectable diffraction peaks related to Co\u003csub\u003e3\u003c/sub\u003eZnC, only featuring characteristics of amorphous carbon and broadened metallic Co diffraction peaks. The result firmly suggests that the reduction of Fe\u003csup\u003e3+\u003c/sup\u003e fully consumes the available reductant within the system, thereby effectively obstructing the formation pathway of Co\u003csub\u003e3\u003c/sub\u003eZnC.\u003c/p\u003e\n\u003cp\u003eIncorporating 3.0 mmol Fe\u003csup\u003e3+\u003c/sup\u003e induces enhanced magnetic interaction (recorded as FCZ5), combined with carbon-mediated bridging effects, collectively motivate the stacking and reconfiguring of the triangular-like architecture (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1i\u003c/strong\u003e). The emergence of a novel Fe\u003csub\u003e3\u003c/sub\u003eZnC\u003csub\u003e0.5\u003c/sub\u003e (PDF#29-0741) phase is identified in the XRD patterns, accompanied by distinct diffraction peaks corresponding to the metallic Fe (PDF#06-0696) phase [14, 35]. This phenomenon could be explained by the saturation of Fe dissolution within the Fe-Co solid solution matrix. Once the solubility limit is exceeded, excess Fe atoms facilitate localized Fe-Zn alloying pathways. Therefore, a Fe\u003csup\u003e3+\u003c/sup\u003e concentration of 2.4 mmol represents the critical threshold for phase transition within the system. When the Fe\u003csup\u003e3+\u003c/sup\u003e concentration exceeds 3.0 mmol (noted as FCZ6), the diffraction peak intensities related to Fe\u003csub\u003e3\u003c/sub\u003eZnC\u003csub\u003e0.5\u003c/sub\u003e and Fe phases display a pronounced enhancement (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS6\u003c/strong\u003e). Simultaneously, the FCZ6 evolves and integrates at the structural articulation, ultimately attaining a coherent quasi-octahedral configuration (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS7\u003c/strong\u003e). Furthermore, systematic investigations into the effects of adding Fe\u003csup\u003e3+\u003c/sup\u003e to monometallic MOF systems were also conducted (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS8-S13\u003c/strong\u003e and \u003cstrong\u003eNote S2\u003c/strong\u003e). These results indicate that the Fe\u003csup\u003e3+\u003c/sup\u003e-dominated ternary coordination competition model and directed reduction hierarchy realize a precise regulation of the phase and structure of bimetallic MOF-derived materials (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1j\u003c/strong\u003e). This Fe\u003csup\u003e3+\u003c/sup\u003e-driven modulation operates through targeted tuning of kinetic pathways and thermodynamic equilibria, demonstrating broad applicability across polymetallic MOF systems, thus offering the potential to attain customizable MOF-derived EMW absorbers.\u003c/p\u003e\n\u003cp\u003eTransmission electron microscopy (TEM) characterization further illustrates the structural evolution governed by the gradient Fe\u003csup\u003e3+\u003c/sup\u003e content (\u003cstrong\u003eFig. 1k\u003c/strong\u003e and \u003cstrong\u003eFig.\u0026nbsp;S14\u003c/strong\u003e). The magnified TEM images unlock more explicit morphological information, showing that metal\u0026nbsp;NPs of varying sizes are randomly dispersed across the amorphous carbon matrix (\u003cstrong\u003eFig.\u0026nbsp;S15\u003c/strong\u003e). The high-resolution transmission electron microscopy (HRTEM) images confirm the existence of metal NPs anchored on amorphous carbon (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS16\u003c/strong\u003e). Meanwhile, localized regions featuring metal particles encapsulated by amorphous/graphitic carbon are also observed. HRTEM analysis reveals distinct lattice fringes with interplanar spacings of 0.204 nm and 0.202 nm, characteristic of the (111) and (110) crystallographic planes in metallic Co and Fe phases, respectively. Additionally, observed spacings of 0.216 nm and 0.219 nm are unambiguously assigned to the (111) plane family of the Co\u003csub\u003e3\u003c/sub\u003eZnC phase and the newly formed Fe\u003csub\u003e3\u003c/sub\u003eZnC\u003csub\u003e0.5\u003c/sub\u003e phase. These crystal signatures provide conclusive evidence for the effective substitution of Fe\u003csup\u003e3+\u003c/sup\u003e into the crystal lattice and the subsequent phase transition. The elements C, N, O, Co, Zn, and Fe are uniformly distributed throughout the composites, as illustrated by the results of the energy dispersive spectrometer (EDS) elemental mapping (\u003cstrong\u003eFig. 1l\u003c/strong\u003e and\u003cstrong\u003e\u0026nbsp;Fig.\u003c/strong\u003e \u003cstrong\u003eS17-S23\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.2 Phase transition\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo elucidate the underlying mechanisms governing phase transition following Fe\u003csup\u003e3+\u003c/sup\u003e incorporation, X-ray photoelectron spectroscopy (XPS) was employed to investigate the elemental composition and chemical states. The survey XPS spectra of CZ exhibit the presence of C, N, O, Co, and Zn elements, while the FCZ\u003cem\u003ex\u003c/em\u003e displays an extra Fe element (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS24\u003c/strong\u003e). The high-resolution C 1s spectrum can be deconvoluted into C-C/C=C (284.8 eV), C-N (286.1 eV), C-O (287.9 eV), and C=O (289.5 eV), respectively (\u003cstrong\u003eFig. 2a\u003c/strong\u003e) [36]. Three characteristic peaks located at 398.7 eV, 400.8 eV, and 403.0 eV are also identified in the high-resolution N 1s spectrum, which are ascribed to pyridinic N, pyrrolic N, and graphitic N, respectively (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2b\u003c/strong\u003e) [37]. These findings collectively indicate the successful doping of heteroatom N into the carbon lattice [38].\u003c/p\u003e\n\u003cp\u003eNotably, the high-resolution Zn 2p spectrum of CZ and FCZ\u003cem\u003ex\u003c/em\u003e can be distinctly separated into two peaks at 1022.1 eV and 1045.1 eV, which correspond to Zn 2p\u003csub\u003e3/2\u003c/sub\u003e and Zn 2p\u003csub\u003e1/2\u003c/sub\u003e, respectively (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2d\u003c/strong\u003e) [24]. Quantitative analysis of elemental composition via inductively coupled plasma optical emission spectrometry (ICP-OES) reveals that the Zn species concentration remained at dynamic equilibrium (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2g\u003c/strong\u003e and\u003cstrong\u003e\u0026nbsp;Table S2-S3\u003c/strong\u003e). This observation, along with the persistent absence of characteristic Zn-related diffraction peaks in XRD patterns and undetectable crystallographic signatures assigned to ZnO in HRTEM, strongly reveals that Zn predominantly exists as amorphous ZnO within the composites. Concurrently, the ZnO content increases with elevated Fe\u003csup\u003e3+\u003c/sup\u003e introduction levels, directly correlated with the progressive diminishment of the Co\u003csub\u003e3\u003c/sub\u003eZnC phase. The crystal structures and electronic properties of monometallic MZ and FZ materials provide additional evidence to corroborate this proposed argument (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS25\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eThe high-resolution O 1s spectrum demonstrates the presence of lattice oxygen (533.5 eV) and surface-adsorbed oxygen (535.8 eV) species, as well as prominent spectral features of oxygen vacancies (531.6 eV), occupying approximately 80% of the integrated oxygen signal (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2c\u0026nbsp;\u003c/strong\u003eand\u003cstrong\u003e\u0026nbsp;Fig. S24f\u003c/strong\u003e) [39]. These are likely to trigger enhanced dipole polarization originating from a high density of lattice defects, thus promoting further dissipation of EMW. The Co\u003csup\u003e0\u003c/sup\u003e (778.5 eV) species and multivalent Co are recognized in the high-resolution Co 2p spectrum (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2e\u003c/strong\u003e) [38]. Similarly, the high-resolution Fe 2p spectra of FCZ\u003cem\u003ex\u003c/em\u003e upon introducing Fe\u003csup\u003e3+\u003c/sup\u003e exhibit Fe\u003csup\u003e0\u003c/sup\u003e (707.5 eV) species and multivalent Fe (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2f\u003c/strong\u003e) [40]. The surface-sensitive nature of XPS analysis suggests that the observed higher oxidation states of Co or Fe are primarily attributed to surface oxidation or atmospheric exposure effects.\u0026nbsp;The bulk phase mainly retains its metallic state and solid solution characteristics. Consistent findings are further validated in the monometallic MC and FC systems (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS26\u003c/strong\u003e). ICP research also illustrates a progressive enrichment of Fe species within the composites, offering solid proof for successfully incorporating Fe\u003csup\u003e3+\u003c/sup\u003e into the bimetallic MOF system.\u003c/p\u003e\n\u003cp\u003eThe abundant metallic Co creates favorable conditions for Fe\u003csup\u003e3+\u003c/sup\u003e to substitute its lattice sites, ultimately resulting in the generation of Fe-Co solid solution through atomic-scale substitutional doping. The following results confirm the formation of Fe-Co solid solution: i) The slight angular shift of the Co phase observed at 44.2\u0026deg;, ascribed to the (111) crystal plane, combined with the pronounced diffraction peak broadening characteristic, provides proof of Fe atomic incorporation into the Co lattice (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e1c\u003c/strong\u003e). ii) HRTEM analysis reveals multiple indistinguishable interplanar spacing values intermediate between pure Co (0.204 nm) and pure Fe (0.202 nm), offering direct crystallographic evidence for the generation of a disordered solid solution (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS16\u003c/strong\u003e). iii) Thermal field modulation studies demonstrate that the ordered Co\u003csub\u003e7\u003c/sub\u003eFe\u003csub\u003e3\u003c/sub\u003e (PDF#50-0795) intermetallic phase formation initiates at temperatures exceeding 900 \u0026deg;C, which corroborates the growth of the Fe-Co solid solution at low temperatures (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS27\u0026nbsp;\u003c/strong\u003eand \u003cstrong\u003eNote S3\u003c/strong\u003e) [41]. iv) The saturation magnetization (\u003cem\u003eM\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e) tested via a vibrating sample magnetometer (VSM) gradually enhances from an initial value of 13.33 emu g\u003csup\u003e-1\u003c/sup\u003e to 20.48 emu g\u003csup\u003e-1\u003c/sup\u003e at maximum Fe addition concentration, indicating a magnetic behavior that aligns with the fundamental principle of magnetic moment superposition in Fe-Co solid solution (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2h\u003c/strong\u003e, \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS28\u003c/strong\u003e, and \u003cstrong\u003eTable S4\u003c/strong\u003e) [42]. v) Density functional theory (DFT) calculations show that the Fe-Co solid solution exhibits improved thermodynamic stability relative to Co\u003csub\u003e3\u003c/sub\u003eZnC and Fe\u003csub\u003e3\u003c/sub\u003eZnC\u003csub\u003e0.5\u003c/sub\u003e, as evidenced by its minimum formation energy (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2j\u003c/strong\u003e, \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS29-S35\u003c/strong\u003e, \u003cstrong\u003eTable S5\u003c/strong\u003e, and \u003cstrong\u003eNote S4\u003c/strong\u003e).\u0026nbsp;Besides, the hybridization between Fe 3\u003cem\u003ed\u003c/em\u003e and Co 3\u003cem\u003ed\u003c/em\u003e orbitals induces intensified spin polarization and enhanced exchange interactions, resulting in an increased population of unoccupied states in the spin-down channel. This configuration results in progressive improvement of energy band density with elevated Fe incorporation concentrations (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2k, l\u003c/strong\u003e). Concurrently, the orbital hybridization shifts the spin-down-dominated antibonding states closer to the Fermi level, significantly raising the projected density of states (PDOS) of Fe. In contrast, the partial transfer of Co\u0026apos;s \u003cem\u003ed\u003c/em\u003e-orbital electrons into the Fe-Co hybridized states slightly reduces the PDOS contribution from Co (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2m, n\u003c/strong\u003e). Interfacial charge density gradients at Fe-Co hybrid interfaces generate strong local dipoles, facilitating polarization relaxation and promoting dielectric loss capacity.\u003c/p\u003e\n\u003cp\u003eElectron paramagnetic resonance (EPR) spectroscopy was employed to qualitatively characterize the spatial distribution of unpaired electron density (paramagnetic substance). The high signal-to-noise ratio peaks observed in the narrow spectral region fail to provide discernible information (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS36\u003c/strong\u003e). Nevertheless, the change in the intensity of these signals likely reflects the concentration variation of paramagnetic centers and unpaired electrons. The broad EPR signals centered at g \u0026asymp; 2.15 suggest the presence of paramagnetic centers, probably attributed to high-spin Fe\u003csup\u003e3+\u003c/sup\u003e species or unpaired electrons in Fe-Co solid solutions, instead of high-spin Co\u003csup\u003e2+\u003c/sup\u003e (g \u0026asymp; 2.3~2.5) or metal vacancies (g \u0026asymp; 1.96) [43, 44]. The signal intensity initially increases with the Fe\u003csup\u003e3+\u003c/sup\u003e content, reaching its peak at 2.4 mmol. This growth suggests a rising concentration of paramagnetic Fe\u003csup\u003e3+\u003c/sup\u003e or Fe-Co solid solutions. However, a decline occurs at FCZ5, probably due to a partial Fe\u003csup\u003e3+\u003c/sup\u003e reduction to metallic Fe\u003csup\u003e0\u003c/sup\u003e or a decrease in Fe-Co solid solution content caused by the generation of Fe\u003csub\u003e3\u003c/sub\u003eZnC\u003csub\u003e0.5\u003c/sub\u003e and Fe phases.\u003c/p\u003e\n\u003cp\u003eThe thermal stability of the composites was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The decomposition of CZ in an air atmosphere begins at approximately 327 \u0026deg;C, with a sharp mass reduction above 548 \u0026deg;C, culminating in a loss of roughly 40.89% of its mass at 950 \u0026deg;C (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS37\u003c/strong\u003e). In comparison, FCZ4 exhibits an elevated decomposition temperature of 345 \u0026deg;C and a final mass loss of about 38.30%. This implies that multiple phases raise the temperature at which carbon decomposes by facilitating the generation of a highly eutectic mixture [45]. N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption isotherms were utilized to assess the specific surface area and pore size distribution of the composites. All samples demonstrate type IV isotherms with a distinct hysteresis loop, signifying the existence of mesoporous features (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS38\u003c/strong\u003e) [46]. The specific surface area of the composites progressively reduces with the incorporation of Fe\u003csup\u003e3+\u003c/sup\u003e, varying from an initial value of 223.3 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e to 47.4 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e. At the same time, the average pore size continuously rises, ranging from 3.62 nm to 18.60 nm (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e2i\u003c/strong\u003e). The hierarchical self-assembly process and subsequent structural reconfiguration of the leaf-like architectures lead to a decrease in specific surface area while promoting the generation of a higher density of mesoporous structures. These mesopores are conducive to multiple internal reflections of incident EMW within the material matrix, extending their propagation pathway and favoring enhanced attenuation efficiency of EMW.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.3 Outstanding EMW Absorption Performances\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe composites with tunable phases and structures were ingeniously applied to absorb EMW at gigahertz frequencies. The reflection loss (RL) intensity and effective absorption bandwidth (EAB, the frequency range for RL \u0026le;\u0026minus;10 dB) were employed to assess the EMW capacity of the composites with a mass filler loading of 50%. As illustrated in \u003cstrong\u003eFig. 3a\u0026nbsp;\u003c/strong\u003eand\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eFig. S39-S40\u003c/strong\u003e, CZ exhibits relatively general absorption properties at high frequency, achieving a minimum RL (RL\u003csub\u003emin\u003c/sub\u003e) of \u0026minus;50.99 dB at a thickness of 2.97 mm and a\u0026nbsp;maximum EAB of 0.48 GHz at a thickness of 1.50 mm. Nevertheless, CZ demonstrates remarkable EMW attenuation performance in the low-to-mid frequency range, showing an absorption bandwidth of 4.32 GHz spanning from 5.60 to 9.92 GHz. It is noteworthy that the remarkably enhanced comprehensive performance of the bimetallic MOF-derived composites compared to their monometallic counterparts may be ascribed to the multicomponent competitive synergies (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS41\u003c/strong\u003e). As the leaf-like morphology gradually occurs, FCZ1 presents an improvement in RL and EAB, with RL\u003csub\u003emin\u003c/sub\u003e of \u0026minus;61.67 [email protected] mm and a 5.20 [email protected] mm wide EAB, covering 12.80-18.00 GHz (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3b\u003c/strong\u003e). Then, despite the reduction in RL\u003csub\u003emin\u003c/sub\u003e (\u0026minus;22.26 dB) of the FCZ2, its EAB elevates to 5.60 GHz at a matched thickness of 1.83 mm (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3c\u003c/strong\u003e). The absorption band progressively shifts from the low-to-mid frequency range toward the higher frequency region. Consequently, the effective bandwidth in the low-to-mid frequency range gradually narrows, while the EAB in the high-frequency range demonstrates continuous broadening. When increasing the level of Fe\u003csup\u003e3+\u003c/sup\u003e, the absorption capacity of FCZ3 is ameliorated with an EAB of 5.84 [email protected] mm (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3d\u003c/strong\u003e). This suggests that the hierarchical self-assembly architecture is critical in facilitating enhanced geometric scattering and optimized interfacial charge polarization mechanisms, thereby boosting the electromagnetic response.\u003c/p\u003e\n\u003cp\u003eAmong all the synthesized absorbers, FCZ4 with diverse microstructures possesses the most exceptional EMW absorption performance, featuring an ultra-wide EAB of up to 6.08 GHz only at 2.03 mm thickness, completely covering the Ku-band (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3e\u003c/strong\u003e). At this moment, the geometric scattering effects and electromagnetic component compatibility achieve an optimal equilibrium, thus realizing maximum EMW efficiency. Nevertheless, the structural reconfiguration and ordered rearrangement of FCZ5 induce simplified geometric scattering pathways and compromised impedance matching, resulting in a substantial decline of its EMW absorption capabilities, with an EAB of 5.60 [email protected] mm (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3f\u003c/strong\u003e). As the Fe\u003csup\u003e3+\u003c/sup\u003e concentration is promoted further and architectural features fade, this diminishing tendency becomes more prominent. Hence, the FCZ6 demonstrates an RL\u003csub\u003emin\u003c/sub\u003e of \u0026minus;17.71 dB and an EAB of 5.20 GHz (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS42\u003c/strong\u003e). Moreover, the monometallic MOF system reveals enhanced performance upon introduction of Fe\u003csup\u003e3+\u003c/sup\u003e, validating the efficacy and broad applicability of this strategic Fe\u003csup\u003e3+\u003c/sup\u003e incorporation approach in advanced absorber design engineering (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS43\u003c/strong\u003e). Notably, optimizing the FCZ4 filler loading enables a prominently strengthened reflection loss capability, with RL\u003csub\u003emin\u003c/sub\u003e values reaching \u0026minus;84.41 dB and \u0026minus;66.96 dB, as depicted in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3g, h\u0026nbsp;\u003c/strong\u003eand\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS44\u003c/strong\u003e. To explicitly reflect the excellent EMW absorption property exhibited by FCZ4, the performance of other recently reported MOF-derived absorbers is summarized for comparison. As displayed in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e3i, j\u003c/strong\u003e and \u003cstrong\u003eTable S6\u003c/strong\u003e, the minimum RL and maximum EAB of FCZ4 exceed those of other absorbers, along with its advantages in controlled structure and modifiable component, FCZ4 emerges as a promising candidate for customizable high-performance MOF-derived absorbers.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.4 Distinctive Electromagnetic Response Behaviors\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe exceptionally high-frequency EMW absorption property is linked to its distinct electromagnetic parameters. Thus, the related complex permittivity (\u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e, \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e) and complex permeability (\u003cem\u003e\u0026mu;ʹ\u003c/em\u003e, \u003cem\u003e\u0026mu;ʹʹ\u003c/em\u003e) are first analyzed. The real parts of the complex permittivity and complex permeability, which stand for the storage abilities for electrical polarization and magnetic polarization, respectively, are denoted by the terms \u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e and \u003cem\u003e\u0026mu;ʹ\u003c/em\u003e [47]. Conversely, the imaginary parts of the complex permittivity (\u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e) and complex permeability (\u003cem\u003e\u0026mu;ʹʹ\u003c/em\u003e) express the capability of electric dipole and magnetic dipole moments to dissipate EMW as they realign within an alternating electromagnetic field [27]. Besides, the tangent values of complex permittivity (tan\u003cem\u003e\u0026delta;\u003c/em\u003e\u003cem\u003e\u003csub\u003e\u0026epsilon;\u003c/sub\u003e\u003c/em\u003e = \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e/\u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e) and complex permeability (tan\u003cem\u003e\u0026delta;\u003c/em\u003e\u003cem\u003e\u003csub\u003e\u0026mu;\u003c/sub\u003e\u003c/em\u003e = \u003cem\u003e\u0026mu;ʹʹ\u003c/em\u003e/\u003cem\u003e\u0026mu;ʹ\u003c/em\u003e) represent the relationship between the ratio of loss and stored energy [48]. As illustrated in \u003cstrong\u003eFig. 4a, b\u003c/strong\u003e, the \u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e and \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e values of CZ exhibit marked fluctuations within the ranges of 6.81 to 12.96 and 1.65 to 6.63, respectively. Meanwhile, FCZ1 enhances both parameters following the incorporation of Fe\u003csup\u003e3+\u003c/sup\u003e. Then, despite the continued increase in Fe\u003csup\u003e3+\u003c/sup\u003e concentration leading to a decrease in the \u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e value (from 7.19 to 14.05), FCZ2 displays a significant improvement in \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e value (from 5.13 to 8.62). As the Fe\u003csup\u003e3+\u003c/sup\u003e level progressively rises, the composites show a gradual enhancement in both \u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e and \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e values alongside reduced curve fluctuations, with FCZ5 achieving the highest \u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e (from 7.41 to 16.20) and \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e (from 3.71 to 9.84) values among all samples.\u003c/p\u003e\n\u003cp\u003eHowever, the \u003cem\u003e\u0026mu;ʹ\u0026nbsp;\u003c/em\u003eand\u003cem\u003e\u0026nbsp;\u003c/em\u003e\u003cem\u003e\u0026mu;ʹʹ\u0026nbsp;\u003c/em\u003evalues\u003cem\u003e\u0026nbsp;\u003c/em\u003efluctuate around 1 and 0, respectively (\u003cstrong\u003eFig.\u0026nbsp;S45\u003c/strong\u003e). This behavior may also be attributed to the intrinsic resonance frequency shift caused by nanoscale magnetic metallic particles, insufficient magnetic coupling interactions, and negligible eddy current generation resulting from the amorphous carbon encapsulation layer.\u0026nbsp;These factors prevent the establishment of frequency-specific magnetically responsive characteristics within the system [49]. The considerably higher tan\u003cem\u003e\u0026delta;\u003c/em\u003e\u003cem\u003e\u003csub\u003e\u0026epsilon;\u003c/sub\u003e\u003c/em\u003e values than tan\u003cem\u003e\u0026delta;\u003c/em\u003e\u003cem\u003e\u003csub\u003e\u0026mu;\u003c/sub\u003e\u003c/em\u003e values in the composites reveal that the EMW dissipation capability originates primarily from dielectric loss rather than magnetic loss contributions (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4c\u003c/strong\u003e). Additionally, FCZ4 demonstrates the highest tan\u003cem\u003e\u0026delta;\u003c/em\u003e\u003cem\u003e\u003csub\u003e\u0026epsilon;\u003c/sub\u003e\u003c/em\u003e value throughout the frequency band, which accounts for its exceptional EMW absorption performance among all samples. Instead, despite possessing the highest values of \u003cem\u003e\u0026epsilon;ʹ\u003c/em\u003e and \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e, the formation of new phases elevates electrical conductivity (\u003cem\u003e\u0026sigma;\u003c/em\u003e), which induces impedance mismatch and compromises EMW attenuation efficiency, thereby reducing the tan\u003cem\u003e\u0026delta;\u003c/em\u003e\u003cem\u003e\u003csub\u003e\u0026epsilon;\u003c/sub\u003e\u003c/em\u003e value of FCZ5 (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4d\u0026nbsp;\u003c/strong\u003eand\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS46\u003c/strong\u003e).\u003c/p\u003e\n\u003cp\u003eThe Co\u003csub\u003e3\u003c/sub\u003eZnC and metallic Co phases, with superb electrical properties, are responsible for the highest \u003cem\u003e\u0026sigma;\u003c/em\u003e of the CZ sample. Nevertheless, the gradual reduction in \u003cem\u003e\u0026sigma;\u003c/em\u003e of the composites with the rise in Fe\u003csup\u003e3+\u003c/sup\u003e amount reaches a minimum at FCZ3. The result is primarily driven by the synergistic effects of Fe-Co solid solution formation with enhanced electrical resistivity relative to metallic Co and the progressive depletion of Co\u003csub\u003e3\u003c/sub\u003eZnC phase content. Subsequently, the highly conductive Fe\u003csub\u003e3\u003c/sub\u003eZnC\u003csub\u003e0.5\u003c/sub\u003e and Fe phases progressively nucleate and grow, while the structural evolution involving reorganization facilitates a partial restoration of the conductive network, thereby contributing to the recovery of the electrical conductivity. Therefore, the conductivity loss (\u003cem\u003e\u0026epsilon;\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e\u003cem\u003eʹʹ\u003c/em\u003e), which is directly proportional to the material conductivity (\u003cem\u003e\u0026epsilon;\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e\u003cem\u003eʹʹ\u0026nbsp;\u003c/em\u003e= \u003cem\u003e\u0026sigma;\u003c/em\u003e/\u003cem\u003e\u0026omega;\u003c/em\u003e\u003cem\u003e\u0026epsilon;\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e), also exhibits a sharp initial decline followed by a slow climb (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4e-g\u003c/strong\u003e) [38]. The polarization loss (\u003cem\u003e\u0026epsilon;\u003c/em\u003e\u003csub\u003ep\u003c/sub\u003e\u003cem\u003eʹʹ\u003c/em\u003e), which additionally contributes to the dielectric loss (\u003cem\u003e\u0026epsilon;\u003c/em\u003e\u003csub\u003ep\u003c/sub\u003e\u003cem\u003eʹʹ\u003c/em\u003e\u003csub\u003e\u0026nbsp;\u003c/sub\u003e= \u003cem\u003e\u0026epsilon;ʹʹ-\u0026epsilon;\u003c/em\u003e\u003csub\u003ec\u003c/sub\u003e\u003cem\u003eʹʹ\u003c/em\u003e), shows an opposite trend. In brief, introducing Fe\u003csup\u003e3+\u003c/sup\u003e induces a substantial alteration in the dielectric response by shifting the primary energy dissipation mechanism from conductive loss to polarization-controlled processes.\u003c/p\u003e\n\u003cp\u003eIntriguingly, two prominent polarization relaxation peaks are observed in the \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e-curve for the CZ. These characteristic peaks demonstrate a continuous reduction in intensity with increasing Fe\u003csup\u003e3+\u003c/sup\u003e concentration. The relaxation feature eventually diminished to baseline levels upon reaching the FCZ3. The Cole-Cole plots, based on the Debye theory, were utilized to elaborate on this unique polarization behavior. Individual semicircles correspond to specific relaxation processes induced by interfacial polarization or dipole reorientation in the Cole-Cole plots, and the trailing straight lines signify electronic conduction losses arising from charge carrier migration [50]. The CZ plot presents two conspicuous semicircles accompanied by linear tails, indicating the concurrent presence of multiple polarization processes coupled with conduction loss (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4i\u003c/strong\u003e) [51]. The semicircular features progressively decline in prominence as Fe\u003csup\u003e3+\u003c/sup\u003e levels rise, while the linear components reveal enhanced definition, which seems to imply a gradual transition from polarization-dominated to conductivity-dominated dielectric response. The result, however, contradicts the conclusions from the quantitative studies mentioned above.\u003c/p\u003e\n\u003cp\u003eConsequently, we posit that the anomalous dielectric behavior is inextricably linked to the compositional variations. Specifically, in the bimetallic CZ system before Fe\u003csup\u003e3+\u003c/sup\u003e incorporation, dipole polarization mainly originates from lattice defects in amorphous ZnO, while interfacial polarization is predominantly governed by the heterointerfaces at Co\u003csub\u003e3\u003c/sub\u003eZnC/C and Co/C boundaries. These independent polarization mechanisms collectively give rise to the formation of two well-separated relaxation peaks.\u0026nbsp;Upon adding Fe\u003csup\u003e3+\u003c/sup\u003e, the progressive increase of Fe-Co solid solution content facilitates the generation of extensive and sophisticated heterogeneous interfacial structures, considerably amplifying the interfacial polarization response. The incremental raising of the amorphous ZnO level\u0026nbsp;also induces higher concentrations of lattice defects, thereby boosting the defect-induced polarization effect and further enhancing dipole polarization relaxation. Hence, the intensified synergistic coupling within the multipolarization mechanism may lead to the progressive overlap of relaxation peaks into a single, broad dielectric response, culminating in the gradual smoothing of the curve.\u003c/p\u003e\n\u003cp\u003eThe polarization relaxation parameters could be obtained from fitting analysis using a modified Havriliak-Negami model, thus quantitatively accounting for the observed concurrent reduction in relaxation peak intensity and elevation of polarization loss (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS47\u003c/strong\u003e and \u003cstrong\u003eTable S7\u003c/strong\u003e) [52]. As depicted in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4q\u003c/strong\u003e, the parameter \u003cem\u003e\u0026alpha;\u003c/em\u003e, which governs the breadth of the relaxation time distribution, demonstrates a consistent downward trend. This suggests broadening the relaxation time distribution, thus diminishing the distinct peak shape in the \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e curve. Besides, the gradual increase of the relaxation time (\u003cem\u003e\u0026tau;\u003c/em\u003e) results in the characteristic relaxation frequency shift to a lower frequency. When this frequency progressively falls outside the detectable frequency range (i.e., less than 2.0 GHz), it manifests as the \u0026quot;disappearance\u0026quot; of the relaxation peak phenomenon. Notably, even in the vanishing of the relaxation peak, the substantial enhancement in dielectric strength (\u0026Delta;\u003cem\u003e\u0026epsilon;\u0026nbsp;\u003c/em\u003e= \u003cem\u003e\u0026epsilon;\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e-\u003cem\u003e\u0026epsilon;\u003csub\u003e\u0026infin;\u003c/sub\u003e\u003c/em\u003e) sustains the overall polarization loss at elevated levels, which corroborates the earlier findings derived from experimental conductivity measurements. These results deviate from the expected behavior of the classical relaxation model, implying the presence of intricate multiscale polarization coupling mechanisms within the material. In summary, the anomalous dielectric characteristics can be ascribed to the coupling effect of multi-polarization mechanisms primarily governed by the Fe-Co solid solution and amorphous ZnO phases.\u003c/p\u003e\n\u003cp\u003eThe D and G bands are critical features for characterizing carbon-based materials in Raman spectroscopy [37]. The D band, appearing near 1350 cm\u003csup\u003e-1\u003c/sup\u003e, is associated with structural defects and arises from the breathing mode of sp\u003csup\u003e3\u003c/sup\u003e-hybridized carbon atoms [14]. The G band, typically observed around 1580 cm\u003csup\u003e-1\u003c/sup\u003e, corresponds to the in-plane vibrational mode of sp\u003csup\u003e2\u003c/sup\u003e-hybridized carbon atoms and reflects the crystallinity of the graphitic structure [53]. The intensity ratio of these bands (I\u003csub\u003eD\u003c/sub\u003e/I\u003csub\u003eG\u003c/sub\u003e) is a quantitative indicator of defect density within the material. As depicted in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4h\u003c/strong\u003e, the I\u003csub\u003eD\u003c/sub\u003e/I\u003csub\u003eG\u003c/sub\u003e ratio exhibits a progressive increase with incremental Fe\u003csup\u003e3+\u003c/sup\u003e concentration, reaching peak values at FCZ3 and FCZ4 before demonstrating a subsequent decline. This trend suggests that the defect density within the system initially rises and then decreases, causing corresponding variations in the defect-induced polarization loss. Moreover, photoluminescence (PL) spectroscopy was employed to characterize the concentration of defects within the materials, including vacancies, interstitials, and dislocations. These crystal defects act as nonradiative recombination centers, dissipating excitation energy through phonon interactions, which results in the intensity of the PL spectra being inversely proportional to the level of the defects [36]. The observed tendency of spectral intensity displays an initial reduction followed by an elevation with gradual Fe\u003csup\u003e3+\u003c/sup\u003e incorporation (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS48\u003c/strong\u003e). This provides compelling evidence that polarization relaxation triggered by high-concentration defects progressively emerges as a key factor governing the system\u0026apos;s dielectric behavior.\u003c/p\u003e\n\u003cp\u003eHRTEM analysis of FCZ4 reveals the existence of multiple homogeneous interfaces composed of the Co phase, along with heterogeneous interfaces consisting of both Fe and Co phases embedded within an amorphous carbon matrix (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4j, k\u003c/strong\u003e). These interfaces promote substantial electron aggregation at interfacial boundaries, generating robust interfacial polarization phenomena [54]. Meanwhile, several stress concentration points are intuitively observed, derived from geometrical phase analysis (GPA), and this inhomogeneous stress fraction, due to an unbalanced charge distribution at the interface, could be a defect-induced polarization center (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4n, o\u003c/strong\u003e) [18]. Similarly, through inverse fast Fourier transform (IFFT) research, well-defined grain boundaries and lattice stacking are resolved, with these lattice deficiencies demonstrating the capacity to act as polarization-active centers owing to their localized structural distortions (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4p\u003c/strong\u003e) [55]. In conjunction with N atoms doped into the carbon lattice, which can also serve as polarization-triggered centers, these substantial polarization centers generate pronounced polarization relaxation phenomena, thereby amplifying the dielectric response under alternating electromagnetic fields [38]. Furthermore, the high density of oxygen vacancies, point defects, lattice discontinuities, and dislocations induces local electric field distortions, which yield a dipole polarization response that effectively lowers the polarization relaxation energy barrier, thereby significantly enhancing polarization relaxation loss (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e4l, m\u003c/strong\u003e) [53]. The synergistic interface and dipole polarization interaction facilitate a distinctive and efficient dielectric response for reinforced EMW attenuation.\u003c/p\u003e\n\u003cp\u003eImpedance matching (\u003cem\u003eZ\u003c/em\u003e) and attenuation constant (\u003cem\u003eAC\u003c/em\u003e) constitute two vital performance metrics for evaluating EMW absorption efficiency. The \u003cem\u003eZ\u003c/em\u003e ensures minimal interfacial reflection to maximize EMW penetration into the material\u0026apos;s interior, while the AC governs the rapid energy conversion of incident waves into thermal or other forms of energy for dissipation. The impedance matching region is defined when the input impedance (\u003cem\u003eZ\u003c/em\u003e\u003csub\u003ein\u003c/sub\u003e) approaches the free space impedance (\u003cem\u003eZ\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e) with a normalized magnitude ratio |\u003cem\u003eZ\u003c/em\u003e\u003csub\u003ein\u003c/sub\u003e/\u003cem\u003eZ\u003c/em\u003e\u003csub\u003e0\u003c/sub\u003e| ranging between 0.8 and 1.2, as this specific impedance range allows near-complete penetration of EMW into the material\u0026apos;s interior [50]. As illustrated in \u003cstrong\u003eFig.\u0026nbsp;S49\u003c/strong\u003e, the impedance characteristics demonstrate progressive deviation from the ideal matching area, with the FCZ4 also failing to attain optimal impedance matching performance. Although the impedance matching declines in FCZ4, the enhanced attenuation capability resulting from the elevated \u003cem\u003e\u0026epsilon;ʹʹ\u003c/em\u003e partially compensates for reflection losses, thereby substantially broadening the EAB. By adjusting the FCZ4 filler loading in the composites to modulate the complex permittivity, optimal impedance matching can be realized. This leads to an improved reflection loss intensity while simultaneously narrowing the EAB due to the constraints imposed by the quarter-wavelength matching mechanism (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS50-S52\u003c/strong\u003e) [56]. Besides, the variation trend of the \u003cem\u003eAC\u0026nbsp;\u003c/em\u003eis observed in \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS53\u003c/strong\u003e. The progressive degradation of impedance characteristics prevents FCZ5 from attaining satisfactory absorption performance despite exhibiting the maximum \u003cem\u003eAC\u003c/em\u003e value among the investigated materials [57].\u003c/p\u003e\n\u003cp\u003eThus, the low doping ratio fulfills excellent impedance matching and strong reflection loss, but is unable to achieve the best EAB. In contrast, the high doping ratio enhances dielectric loss and broadband attenuation capability, thereby boosting EAB at the expense of impedance mismatch, which weakens the absorption peak intensity and induces a high-frequency shift. This requires balanced optimization between these competing mechanisms for optimal EMW performance. Moreover, the thermal field modulation results demonstrate that controlled annealing temperature not only dominates the phase evolution path of the composites but also enables effective regulation of the electromagnetic response, rendering the synthesized materials potential for multifunctional EMW management (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS54-S55\u003c/strong\u003e). The ingeniously designed gradient Fe\u003csup\u003e3+\u003c/sup\u003e introduction achieves the tailoring of dielectric response characteristics through precise phase modulation engineering. This combines hierarchical architectures that enhance electromagnetic impedance compatibility, collectively establishing an intelligent platform for developing high-performance EMW absorbers with tunable electromagnetic properties.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e2.5 EMW Absorption Mechanisms\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTo assess the effectiveness of the synthesized composites in absorbing EMW for practical applications, computational simulations of the far-field radar scattering cross section (RCS) were implemented using the CST electromagnetic simulation platform [53]. As displayed in \u003cstrong\u003eFig. 5a\u003c/strong\u003e and \u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003eS56-S57\u003c/strong\u003e, FCZ4 demonstrates the lowest RCS signals. The analysis of the specific functional relationship between the RCS value and the incident angle exhibits that the FCZ4 is capable of reducing RCS signal strength by up to 10.7 dB m\u003csup\u003e2\u003c/sup\u003e compared to the PEC (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e5b\u003c/strong\u003e) [36]. This indicates that the FCZ4 reveals good environmental adaptability to complex far-field conditions while fulfilling practical application requirements. The electromagnetic power loss density (EPLD) analysis of composites simulated using COMSOL Multiphysics software suggests that progressive geometric structural optimization effectively enhances the scattering effect toward EMW, enabling the FCZ4 to possess superior EMW consumption efficiency (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e5c\u003c/strong\u003e) [38].\u003c/p\u003e\n\u003cp\u003eThe main loss mechanisms responsible for the extraordinary absorption performance of FCZ4 are summarized as follows: i) The morphological evolution and configuration optimization within FCZ4 synergistically enhance EMW interactions through intensified multiple reflections and scattering [58]. ii) Rational modulation of intrinsic conductivity effectively reduces the reflection loss of EMW on the material surface. The three-dimensional conductive network, composed of metal and carbon components, facilitates the directional migration of free charge carriers in response to alternating electromagnetic fields. This microcurrent generation mechanism promotes efficient electromagnetic energy dissipation via conduction loss through thermal conversion [59]. iii) The dispersed heterogeneous structural units within the N-doped carbon matrix, particularly the Fe-Co solid solution, effectively modulate the carrier migration and separation behavior by constructing a high-density phase boundary/heterogeneous interface network [60]. This multiscale interface engineering induces the accumulation of directional spatial charge, forming a pronounced non-equilibrium charge distribution gradient that generates a strong built-in electric field via interfacial dielectric relaxation mechanisms and amplifies the effects of interfacial polarization [61]. iv) The competitive coordination interactions among ternary transition metal ions, coupled with the concurrent presence of multi-ligand configurations, trigger the development of lattice distortions and defect architectures generated during the pyrolysis of MOF materials. These topological defects, coupled with amorphous ZnO, function as localized polarization centers that induce relaxation losses associated with dipole orientation polarization by establishing asymmetric charge distributions [62]. The synergistic interaction among multifaceted dissipation mechanisms, including geometric scattering effects, conductive losses, interfacial polarization relaxation, and dipole relaxation processes, collectively contributes to the high-efficiency EMW attenuation characteristics in FCZ4 composites (\u003cstrong\u003eFig.\u003c/strong\u003e \u003cstrong\u003e5d\u003c/strong\u003e).\u003c/p\u003e"},{"header":"3. Conclusion","content":"\u003cp\u003eThis work successfully fabricates high-performance and customizable polymetallic MOF-derived EMW absorbers through an ingeniously designed gradient Fe\u003csup\u003e3+\u003c/sup\u003e incorporation strategy, synergizing ligand competition kinetics and reduction potential thermodynamics. By adjusting the Fe\u003csup\u003e3+\u003c/sup\u003e content, precise phase and structural regulation are achieved, thereby enabling controlled tuning of the dielectric response. The coupling effect between interfacial and dipole polarization induces anomalous dielectric behavior that breaks the perceived boundaries of the traditional polarization loss adjustment. Eventually, the optimized composites exhibit outstanding EMW absorption properties characterized by a strong RL\u003csub\u003emin\u003c/sub\u003e of \u0026minus;84.41 dB and a broad EAB spanning 6.08 GHz. Furthermore, investigating the thermal field modulation that governs electromagnetic parameters reveals the potential and benefits of the synthesized materials in multifunctional applications. This work opens new avenues for designing customizable MOF-derived absorbers, providing fresh insights into the dielectric polarization mechanism in amorphous-crystalline heterosystems.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAuthor Contribution\u0026nbsp;\u003c/strong\u003eSihao Dou: Writing - original draft, Validation, Methodology, Investigation, Conceptualization. Yunfei He: Writing - review \u0026amp; editing, Data curation, Validation, Software. Yuxiang Zheng, Yuefeng Yan, and Zhiyuan Dan: Writing - review \u0026amp; editing, Data curation. Long Ma and Minghao Yang: Validation, Software. Dongdong Liu, Xiaoxiao Huang, and Bo Zhong: Funding acquisition, Validation, Supervision, Project administration. All authors reviewed and approved the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u0026nbsp;\u003c/strong\u003eThis work was supported by the National Natural Science Foundation of China (NSFC 51872058), the Supporting Program for Innovation Team of Outstanding Youth in Colleges and Universities of Shandong Province (2020KJA005), the Natural Science Foundation of Shandong Province (ZR2022QB156), and the Foundation of State Key Laboratory of Precision Welding \u0026amp; Joining of Materials and Structures.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData Availability\u0026nbsp;\u003c/strong\u003eNo datasets were generated or analysed during the current study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eZhou X, Min P, Liu Y, Jin M, Yu Z, Zhang H (2024) Insulating electromagnetic-shielding silicone compound enables direct potting electronics. 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Compos B Eng 284:111714. https://doi.org/10.1016/j.compositesb.2024.111714\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"advanced-composites-and-hybrid-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"achm","sideBox":"Learn more about [Advanced Composites and Hybrid Materials](https://link.springer.com/journal/42114)","snPcode":"42114","submissionUrl":"https://submission.nature.com/new-submission/42114/3","title":"Advanced Composites and Hybrid Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Phase-structure modulation, Trimetallic coordination competition, Crystal-amorphous synergy, Polarization relaxation peak, Electromagnetic wave absorption","lastPublishedDoi":"10.21203/rs.3.rs-7308006/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7308006/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"Modulating the phase composition and microstructural geometry in polymetallic metal-organic framework (MOF) derivatives represents a promising approach for achieving tunable electromagnetic response. However, deciphering the intrinsic phase-structure-property correlations in complex systems remains challenging. Herein, a competitive coordination and directed reduction strategy is employed to fabricate ternary Fe/Co/Zn (FCZ) composites with precisely controlled composition and architecture. Specifically, the topological structure progressively evolves from the inheritance of leaf-like precursors to hierarchical self-assembly and to final reconfiguration. Introducing Fe into the original Co/Zn bimetallic system progressively suppresses the Co3ZnC phase, while promoting the formation of the Fe-Co solid solution and amorphous ZnO. The construction of multiple heterointerfaces and high-density defects within nitrogen-doped carbon substrates facilitates the coupling effect of multiple polarization loss mechanisms. This synergistic effect induces an anomalous dielectric behavior, characterized by attenuated polarization relaxation peaks concurrent with enhanced polarization response. Consequently, the optimized FCZ4 demonstrates exceptional electromagnetic wave absorption performance, featuring an ultra-low reflection loss of −84.41 dB and an ultra-broad bandwidth of 6.08 GHz. Gradient regulation of Fe content enables the realization of tunable frequency response characteristics spanning the low-to-high frequency range. This work establishes a generalized phase-structure-dielectric correlation model, offering new insights into tailorable electromagnetic attenuation in multi-metallic systems.","manuscriptTitle":"Controlled phase and structure engineering-driven unique dielectric behavior enabling tailored electromagnetic attenuation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-10-08 17:54:51","doi":"10.21203/rs.3.rs-7308006/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Accepted","date":"2025-10-09T13:36:19+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-09T07:15:14+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-10-09T04:04:54+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"123550467461080535227315340138139163300","date":"2025-10-09T00:54:43+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"97670773027205639647904878845979347900","date":"2025-10-08T09:27:33+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-10-08T08:21:44+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-10-08T07:05:12+00:00","index":"","fulltext":""},{"type":"submitted","content":"Advanced Composites and Hybrid Materials","date":"2025-10-07T08:56:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"advanced-composites-and-hybrid-materials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"achm","sideBox":"Learn more about [Advanced Composites and Hybrid Materials](https://link.springer.com/journal/42114)","snPcode":"42114","submissionUrl":"https://submission.nature.com/new-submission/42114/3","title":"Advanced Composites and Hybrid Materials","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"1f725d97-d2d0-4d57-bb80-2f817f8b3f22","owner":[],"postedDate":"October 8th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-11-17T16:06:53+00:00","versionOfRecord":{"articleIdentity":"rs-7308006","link":"https://doi.org/10.1007/s42114-025-01506-8","journal":{"identity":"advanced-composites-and-hybrid-materials","isVorOnly":false,"title":"Advanced Composites and Hybrid Materials"},"publishedOn":"2025-11-10 15:58:42","publishedOnDateReadable":"November 10th, 2025"},"versionCreatedAt":"2025-10-08 17:54:51","video":"","vorDoi":"10.1007/s42114-025-01506-8","vorDoiUrl":"https://doi.org/10.1007/s42114-025-01506-8","workflowStages":[]},"version":"v1","identity":"rs-7308006","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7308006","identity":"rs-7308006","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}