{"paper_id":"30f0ea09-3a73-4012-bc1e-4e8b23c86285","body_text":"Fabrication of ZnFe2O4@g-C3N4 for Enhanced Photo-Fenton Effect and Visible Light-Driven Organic Dye Degradation | 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 Article Fabrication of ZnFe 2 O 4 @g-C 3 N 4 for Enhanced Photo-Fenton Effect and Visible Light-Driven Organic Dye Degradation Leyan Li, Wang Jianhua, Huihui Fang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6391826/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 01 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted 4 You are reading this latest preprint version Abstract A magnetically recoverable ZnFe₂O₄@g-C₃N₄ heterostructure was synthesized by anchoring ZnFe₂O₄ nanoparticles onto a mesoporous g-C₃N₄ framework. The composite was systematically characterized via XRD, SEM, TEM, and UV-Vis spectroscopy, confirming the successful formation of a porous multilayer structure with uniformly dispersed ZnFe₂O₄ nanoparticles on g-C₃N₄. BET analysis validated the mesoporous architecture, while TEM revealed an intimate heterojunction interface between ZnFe₂O₄ and g-C₃N₄, crucial for efficient charge carrier separation. The composite demonstrated exceptional photocatalytic activity under visible light, achieving complete degradation of methylene blue (MB) via synergistic effects of enhanced light absorption, interfacial charge transfer, and high surface area. Notably, the magnetic ZnFe₂O₄ component enabled facile recovery and reuse of the catalyst using external magnetic fields, with retained catalytic efficiency over multiple cycles. This work highlights the ZnFe₂O₄@g-C₃N₄ heterojunction as a durable, recyclable photocatalyst with significant potential for sustainable environmental remediation applications. Earth and environmental sciences/Environmental sciences Physical sciences/Materials science Photo-Fenton Heterojunction ZnFe2O4@g-C3N4 g-C3N4 Methlene blue Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 INTRODUCTION Water is an indispensable resource for sustaining life across ecosystems, yet its contamination by antibiotics, pesticides, and synthetic dyes has escalated into a global environmental crisis, jeopardizing human health and ecological stability. Addressing this challenge requires innovative solutions to degrade persistent pollutants effectively. Advanced oxidation processes (AOPs), particularly those leveraging visible-light-driven photocatalysis and Fenton-like reactions, have emerged as a frontier technology for water purification due to their capacity to generate highly reactive oxygen species (ROS) under mild conditions [1–4]. Central to these processes is the development of efficient, stable, and recyclable heterojunction catalysts capable of optimizing charge separation and ROS generation. Recent advancements highlight the potential of multiphase composite catalysts, where materials with distinct band structures synergize to enhance charge carrier dynamics. For instance, high-entropy catalysts with tailored conduction and valence band positions facilitate rapid separation of photogenerated electron-hole pairs, amplifying catalytic efficiency [5–10]. Mesoporous materials, in particular, serve as ideal substrates due to their high surface area and adsorption capacity. When functionalized with metals or metal oxides, they promote electron transfer and activate H₂O₂ decomposition into hydroxyl radicals (•OH), a critical step in pollutant degradation [5–10]. Zinc ferrite (ZnFe₂O₄, ZFO), a narrow-bandgap (1.0-2.0 eV) n-type semiconductor, has garnered attention for its visible-light absorption, magnetic recoverability, and photo-fenton effect, which synergize with H₂O₂ to generate ROS [11–16]. Concurrently, graphitic carbon nitride (g-C₃N₄), a metal-free polymeric semiconductor with a 2.7 eV bandgap and redox-active bands (-1.3 and +1.4 eV), offers tunable structural properties, high chemical stability, and enhanced charge migration via its 2D/3D architectures [13–18]. Integrating ZFO with g-C₃N₄ presents a promising strategy to bridge their complementary advantages: ZFO’s magnetic recyclability and ROS-generating capacity, coupled with g-C₃N₄’s expansive surface area and charge transport efficiency. In this study, mesoporous g-C₃N₄ was synthesized via thermal polymerization of urea and melamine, followed by the hydrothermal deposition of ZFO nanoparticles using zinc acetate and iron chloride precursors. The resultant ZnFe₂O₄@g-C₃N₄ heterostructure was systematically characterized through SEM, TEM, XRD, and UV-Vis spectroscopy to elucidate its structural, morphological, and optoelectronic properties. The photocatalytic performance was evaluated via visible-light-driven degradation of methylene blue (MB), with mechanistic insights into charge transfer pathways and ROS generation explored. Furthermore, the magnetic recoverability and cyclic stability of the composite were assessed to underscore its practical viability. This work not only advances the design of multifunctional heterojunction catalysts but also highlights their potential in environmental remediation, particularly for industrial wastewater treatment and water quality restoration. Experimental Section Reagents and Characterization All chemicals, including urea (CH₄N₂O, ≥99%), melamine (C₃H₆N₆, ≥99%), zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O, ≥99%), iron(III) chloride hexahydrate (FeCl₃·6H₂O, ≥98%), methylene blue (C₁₆H₁₈ClN₃S, ≥95%), and hydrogen peroxide (H₂O₂, 30 wt%), were of analytical grade and procured from Sinopharm Chemical Reagent Co., Ltd. (China). Deionized water (resistivity ≥18.2 MΩ·cm) was produced using a laboratory-grade purification system. The crystallographic properties of the synthesized g-C₃N₄ and ZnFe₂O₄@g-C₃N₄ composites were analyzed using an Ultima IV X-ray diffractometer (Rigaku Corporation, Japan) with Cu-Kα radiation (λ = 1.5406 Å) operated at 40 kV and 40 mA. Morphological and microstructural features were examined using a JEM-2100F field-emission transmission electron microscope (JEOL Ltd., Japan) at an accelerating voltage of 200 kV. The optical absorption properties and photocatalytic degradation kinetics of methylene blue were monitored via a PerkinElmer LAMBDA750 UV/Vis/NIR spectrophotometer, with spectra recorded in the range of 200–800 nm. Experimental process Preparation of g-C 3 N 4 nanoparticles Graphene-like g-C 3 N 4 was prepared using a thermal polymerization method. Details of the sample preparation can be found in references[10-11]. ZnFe 2 O 4 @g-C 3 N 4 Preparation of nanoparticles The ZnFe₂O₄@g-C₃N₄ heterostructure was synthesized via a hydrothermal route. Briefly, 0.5 g of g-C₃N₄ was uniformly dispersed in 50 mL of deionized water via ultrasonication (40 kHz, 30 min). Separately, stoichiometric ratios of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and iron(III) chloride hexahydrate (FeCl₃·6H₂O) (mass ratios detailed in Table 1) were dissolved in 25 mL of deionized water under magnetic stirring (500 rpm, 30 min). The metal precursor solution was then introduced dropwise into the g-C₃N₄ suspension, followed by the addition of 0.5 g urea as a pH-modulating agent. The mixture was stirred vigorously (60 min) to ensure homogeneity. The resultant suspension was transferred into a 100 mL polytetrafluoroethylene (PTFE)-lined autoclave and subjected to hydrothermal treatment in a programmable oven. The temperature was ramped to 150°C at a rate of 2°C/min and maintained for 4 h. After natural cooling to ambient temperature, the precipitate was isolated by centrifugation (7000 rpm, 15 min), followed by sequential washing with deionized water and ethanol (three cycles each) to remove residual impurities. The purified product was vacuum-dried at 60°C for 24 h and stored in an airtight container for subsequent characterization and application. The samples name are list in Table 1. The symbol “-0”, “-1”, “-2”, “-3”, “-4”, “-5”, “-6” and “-7” means the increasing mole of raw material “Zn(AC) 2 ” as 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, and 0.007 mol. As shown in last column, the mass ratio ZnFe 2 O 4 to g-C 3 N 4 and ZnFe 2 O 4 were 0, 0.325, 0.491, 0.591, 0.658, 0.707, 0.743, and 0.771 in different samples. Photocatalytic degradation of methylene blue The visible-light-driven photocatalytic activity of ZnFe₂O₄@g-C₃N₄ was assessed through the degradation of methylene blue (MB) in aqueous media. Prior to illumination, 50 mg of the catalyst was dispersed in 50 mL of MB solution (30 mg/L) within a 100 mL borosilicate glass reactor under darkroom conditions. The suspension was ultrasonicated (40 kHz, 3 min) to ensure uniform catalyst distribution, followed by magnetic stirring (60 min) to establish adsorption-desorption equilibrium between the dye and catalyst surface. A 300 W xenon lamp equipped with a 420 nm cutoff filter was positioned 20 cm above the reactor to simulate visible-light irradiation. Aliquots (3 mL) were extracted at 10-minute intervals and immediately centrifuged (7000 rpm, 2 min) to isolate the catalyst, thereby preventing interference in absorbance measurements. The residual MB concentration was quantified via UV-Vis spectroscopy by monitoring the attenuation of its characteristic absorption band at λ = 664 nm. The degradation efficiency (η, %) and real time change of absorption intensity were calculated using the equation: η=(1−C/C 0 )×100% (1) C/C 0 or C/C 0 × 100% (2) where C 0 and C represent the initial and time-dependent absorbance intensities of MB, respectively [10, 11]. Results and Discussion XRD structural characterization The crystallographic structures of pristine g-C₃N₄ and the ZnFe₂O₄@g-C₃N₄ composite were analyzed via X-ray diffraction (XRD). As illustrated in Figure 1, the XRD pattern of ZnFe₂O₄@g-C₃N₄ exhibits distinct diffraction peaks corresponding to both g-C₃N₄ and ZnFe₂O₄ phases, confirming the coexistence of the two components. For pristine g-C₃N₄, two characteristic peaks are observed at 13.1° and 27.5°, indexed to the (001) and (002) crystallographic planes, respectively. These reflections arise from the in-plane structural packing of tri-s-triazine units and the interlayer stacking of conjugated aromatic systems, consistent with the typical graphitic carbon nitride framework (JCPDS 87-1526) [10, 11]. In the composite, additional diffraction peaks at 2θ values of 30.2°, 35.6°, 43.3°, 53.7°, 57.3°, and 62.8° are assigned to the (220), (311), (400), (422), (511), and (440) planes of cubic spinel ZnFe₂O₄ (JCPDS 82-1049) [12, 13]. Notably, no extraneous peaks corresponding to impurities or secondary phases (e.g., ZnO, Fe₃O₄) are detected, indicating that the hydrothermal synthesis preserved the structural integrity of both g-C₃N₄ and ZnFe₂O₄ without inducing phase transitions. The coexistence of these distinct diffraction features confirms the successful formation of a heterostructure, where ZnFe₂O₄ nanoparticles are anchored onto the g-C₃N₄ matrix without disrupting its layered architecture. These results validate the effective synthesis of a phase-pure ZnFe₂O₄@g-C₃N₄ composite, laying a foundation for its enhanced photocatalytic functionality. Morphological and Microstructural Analysis The morphological evolution and interfacial characteristics of pristine g-C₃N₄ and the ZnFe₂O₄@g-C₃N₄ composite were investigated via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As depicted in Figure 2a, the thermal polymerization of urea and melamine yielded g-C₃N₄ with a lamellar morphology characterized by pronounced wrinkling and sheet-like stacking, a hallmark of its graphitic architecture. Upon integration with ZnFe₂O₄ (Figure 2b), the composite retained the layered framework of g-C₃N₄ but exhibited reduced lateral dimensions of the individual sheets, likely due to fragmentation during hydrothermal processing. Crucially, ZnFe₂O₄ nanoparticles (20–50 nm diameter) were uniformly dispersed across the g-C₃N₄ matrix without agglomeration, confirming the successful formation of an intimate heterointerface between the two phases. This structural synergy is anticipated to enhance charge carrier separation and surface reactivity, thereby augmenting photocatalytic efficiency. Further insights into the microstructural features were obtained through TEM (Figure 3a–b). Pristine g-C₃N₄ displayed a highly porous, crumpled 2D structure with abundant in-plane voids (Figure 3a), attributed to the release of gaseous byproducts (e.g., NH₃) during thermal condensation. These mesopores (5–15 nm diameter) not only increase the material’s specific surface area but also facilitate reactant diffusion and active site accessibility. In the ZnFe₂O₄@g-C₃N₄ composite (Figure 3b), the g-C₃N₄ sheets maintained their layered topology, while ZnFe₂O₄ nanoparticles were anchored uniformly across the surface. High-resolution TEM (inset, Figure 3b) revealed lattice fringes corresponding to the (311) plane of cubic ZnFe₂O₄ and the (002) interlayer spacing of g-C₃N₄ , corroborating the coexistence of both phases without interfacial contamination. The absence of particle aggregation and the coherent integration of ZnFe₂O₄ within the g-C₃N₄ scaffold underscore the efficacy of the synthesis strategy in fostering a well-defined heterostructure, a critical determinant of enhanced catalytic performance. Nitrogen Adsorption-Desorption Analysis The textural properties of the ZnFe₂O₄@g-C₃N₄ composite were evaluated through nitrogen adsorption-desorption measurements. As depicted in Figure 4a, the composite exhibits a type IV isotherm with an H3 hysteresis loop, characteristic of mesoporous materials featuring slit-like pores formed by platelet aggregates. A sharp uptake at high relative pressure (P/P₀ > 0.95) signifies the coexistence of macropores, attributed to the volatilization of ammonia gas during the thermal polymerization of g-C₃N₄ precursors. The Brunauer-Emmett-Teller (BET) specific surface area of the g-C₃N₄ was calculated as 855.9 m²·g⁻¹, with reduced surface areas of 654.2, 358.4, 37.9, 29.2, 23.2, 20.22, and 14.1 m²·g⁻¹ observed under increased ZnFe₂O₄. According to nitrogen adsorption-desorption analysis, the ZnFe₂O₄@g-C₃N₄ composite exhibited a significant reduction in specific surface area with increasing ZnFe₂O₄ loading. This decrease can be attributed to the partial occupation of the porous g-C₃N₄ framework by ZnFe₂O₄ nanoparticles. However, the formation of a well-defined ZnFe₂O₄/g-C₃N₄ heterojunction became more prominent at higher ZnFe₂O₄ content, as evidenced by the concomitant rise in catalytically active sites. While the pore-blocking effect of ZnFe₂O₄ diminished the surface area, the enhanced interfacial charge transfer and increased density of reactive sites at the heterojunction interface counterbalanced this limitation. The interplay between these competing factors—surface area reduction and active site enrichment—culminated in the ZnFe₂O₄@g-C₃N₄-3 composite demonstrating optimal catalytic performance, highlighting the critical role of heterojunction engineering in optimizing activity despite structural trade-offs. Pore size distribution derived from the Barrett-Joyner-Halenda (BJH) model (Figure 4b) reveals a bimodal architecture dominated by mesopores (2.5–10 nm, average diameter: 3.4–5.6 nm) and subsidiary macropores (10–100 nm). The mesopores originate from interparticle voids within the aggregated g-C₃N₄ layers, while macropores arise from gas evolution during synthesis. Such hierarchical porosity facilitates efficient mass transport of reactants and access to catalytic sites, synergistically enhancing degradation kinetics. These structural attributes—high surface area, dual-scale porosity, and interfacial connectivity—underscore the ZnFe₂O₄@g-C₃N₄ composite’s suitability for advanced photocatalytic applications. Surface Elemental and Chemical State Analysis The chemical composition and interfacial interactions within the ZnFe₂O₄@g-C₃N₄ heterostructure were probed via X-ray photoelectron spectroscopy (XPS). The survey spectrum (Figure 5a) confirms the coexistence of oxygen (O), nitrogen (N), carbon (C), zinc (Zn), and iron (Fe), corroborating the composite’s hybrid nature. High-resolution spectra were deconvoluted to elucidate bonding configurations and oxidation states. In O 1s Spectrum ( Figure 5b) , the O 1s envelope resolves into four components at 529.75, 530.95, 531.45, and 531.95 eV. Peaks at 529.75 and 530.95 eV are attributed to Zn–O–Fe coordination in the spinel ZnFe₂O₄ lattice, while contributions at 531.45 and 531.95 eV correspond to surface-adsorbed hydroxyl (–OH) and carboxyl (–HO–C=O) groups, indicative of oxygen-containing functional moieties. In N 1s Spectrum ( Figure 5c) , the N 1s profile exhibits three distinct binding energies at 398.55, 399.00, and 399.55 eV. The dominant peak at 398.44 eV arises from C–N–C coordination in the tri-s-triazine units of g-C₃N₄, while contributions at 399.00 and 399.55 eV correspond to sp²-hybridized nitrogen (N–(C)₃) and terminal amino groups (–NH₂), respectively, confirming the integrity of the g-C₃N₄ framework. In C 1s Spectrum ( Figure 5d) , deconvolution of the C 1s signal reveals four components: (i) adventitious carbon (C=C/C–C, 284.95 eV), (ii) Zn–C bonds (284.55 eV) associated with oxygen vacancies, (iii) graphitic sp² carbon (285.45 eV), and (iv) a prominent peak at 288.1 eV assigned to N–C=N coordination in the aromatic triazine rings of g-C₃N₄. In Fe 2p Spectrum ( Figure 5e) , the Fe 2p region displays spin-orbit doublets for Fe 2p₃/₂ (710.56 eV) and Fe 2p₁/₂ (724.66 eV), accompanied by a satellite peak at 718.96 eV. The Fe 2p₃/₂ peak splits into two components at 710.56 eV (Fe³⁺ in octahedral sites) and 712.36 eV (Fe³⁺ with ligand field effects), confirming the dominance of Fe³⁺ in the ZnFe₂O₄ lattice. The absence of Fe²⁺ signatures (typically <709 eV) underscores the stability of the spinel structure. In Zn 2p Spectrum ( Figure 5f) , the Zn 2p spectrum exhibits symmetric peaks at 1021.92 eV (Zn 2p₃/₂) and 1045.02 eV (Zn 2p₁/₂), characteristic of Zn²⁺ in tetrahedral coordination within ZnFe₂O₄. The 23.1 eV spin-orbit splitting further validates the +2 oxidation state of Zn. The XPS analysis confirms the coexistence of ZnFe₂O₄ and g-C₃N₄ phases with interfacial Zn–C and Fe–O–N bonding, indicative of strong electronic coupling. This synergy, coupled with oxygen vacancies and surface functional groups, underpins the composite’s enhanced photocatalytic activity. Photocatalytic performance The photocatalytic activity of the ZnFe 2 O 4 @g-C 3 N 4 heterostructure was rigorously assessed via visible-light-driven degradation of methylene blue (MB), a model organic pollutant [19-20]. As depicted in Figure 6, time-resolved ultraviolet-visible (UV-Vis) spectroscopy demonstrated a monotonic decline in the characteristic absorbance intensity of MB at λ = 664 nm as a function of irradiation duration, with the signal diminishing to near-background levels after prolonged exposure. The absence of hypsochromic or bathochromic shifts in the primary absorption band, coupled with no detectable emergence of secondary absorption features within the spectral range (400–800 nm), strongly indicates the complete mineralization of MB rather than transient intermediate formation or structural isomerization. These observations unequivocally validate the robust photocatalytic efficacy of the ZnFe 2 O 4 @g-C 3 N 4 composite, highlighting its capacity for efficient visible-light harvesting and redox-driven degradation of organic contaminants. The photocatalytic degradation of methylene blue (MB) by ZnFe₂O₄@g-C₃N₄ under visible light irradiation is governed by the generation of reactive oxygen species (ROS), notably hydroxyl radicals (·OH) and superoxide anions (·O₂⁻), facilitated by the heterojunction’s electronic structure [19-20]. As illustrated in Figure 7a, the degradation efficiency correlates with ZnFe₂O₄ doping concentration, achieving optimal performance at 74.3 wt% loading. Under dark conditions (Figure 7a, black curve), the composite exhibits substantial adsorption of MB molecules due to its mesoporous g-C₃N₄ framework, yet no degradation occurs in the absence of light. Upon visible-light irradiation, photogenerated electrons (e⁻) and holes (h⁺) are formed, with the heterojunction interface promoting efficient charge separation. This suppresses recombination, enabling prolonged ROS generation and rapid MB decomposition. Exceeding the optimal ZnFe₂O₄ loading (>74.3 wt%) diminishes performance due to nanoparticle aggregation, which obstructs the porous g-C₃N₄ layers, reduces active site accessibility, and impedes dye-catalyst contact. Kinetic analysis (Figure 7c, Table 2) confirms pseudo-first-order behavior, with rate constants peaking at 74.3 wt% (0.12697 min⁻¹) and declining thereafter. The synergy between g-C₃N₄’s adsorption capacity and ZnFe₂O₄’s visible-light activation is critical for maximizing degradation efficiency. The introduction of H₂O₂ (0.5 mL, 30%) amplifies catalytic activity via a photo-Fenton mechanism (Figure 7b, d), where H₂O₂ reacts with photogenerated electrons to yield additional ·OH radicals. This dual catalytic pathway achieves complete MB degradation within 40 min, with kinetic coefficients increasing by 2.7-fold at 59.1 wt% ZnFe₂O₄ (Table 2). However, excessive doping (> 59.1 wt%) under H₂O₂ conditions induces shielding effects, wherein dense ZnFe₂O₄ layers hinder H₂O₂ diffusion and ROS generation, underscoring the necessity of balanced compositional design. A above analysis, the photocatalytic performance of the ZnFe₂O₄@g-C₃N₄ composites exhibited an optimal threshold when an equilibrium between specific surface area and active site density was achieved. During the initial reaction stage, the degradation efficiency remained limited due to the high initial dye concentration and insufficient generation of photoinduced reactive species. As the reaction progressed, the accumulation of reactive species significantly increased their collision frequency with dye molecules, thereby enhancing the degradation kinetics. Notably, the density of these reactive species was directly modulated by the ZnFe₂O₄ loading within the composite. As demonstrated in Figure 7, the ZnFe₂O₄@g-C₃N₄-3 composite displayed superior photocatalytic activity, which originated from a synergistic effect arising from two competing factors: (i) the formation of an efficient ZnFe₂O₄/g-C₃N₄ heterojunction, which facilitated interfacial charge separation and amplified reactive species generation, and (ii) the retention of sufficient surface accessibility despite partial pore occlusion by ZnFe₂O₄ nanoparticles. This balance between heterojunction-driven electronic enhancement and structural porosity underscores the critical role of compositional optimization in maximizing photocatalytic performance. To elucidate the reactive species governing the photocatalytic degradation mechanism, radical scavenging experiments were conducted under visible light irradiation. The active species photogenerated holes (h⁺), hydroxyl radicals (•OH), and superoxide anions (•O₂⁻) were systematically investigated using targeted quenchers: p-benzoquinone (BQ, •O₂⁻ scavenger), tert-butanol (TBA, •OH scavenger), and disodium ethylenediaminetetraacetate dihydrate (EDTA-2Na, h⁺ scavenger). As depicted in Figure 8a, the degradation efficiency of methylene blue (MB) by ZnFe₂O₄@g-C₃N₄-3 was significantly attenuated in the presence of these inhibitors. The degradation rate declined from 99.99% (pristine system) to 81.12%, 73.11%, and 82.52% upon introduction of BQ, TBA, and EDTA-2Na, respectively, over 40 minutes. The pronounced suppression of activity with TBA (73.11% remaining MB) underscores •OH as the predominant reactive species, attributable to its potent oxidative capacity. Concurrently, the inhibition by BQ (81.12% residual MB) and EDTA-2Na (82.52% residual MB) confirms the ancillary roles of •O₂⁻ and h⁺ in the degradation pathway. These findings align with the heterojunction’s electronic structure, which promotes charge separation, enabling h⁺ to directly oxidize MB or react with H₂O to generate •OH, while •O₂⁻ forms via oxygen reduction by photogenerated electrons. This study conclusively identifies •OH as the primary active species, with synergistic contributions from h⁺ and •O₂⁻, underpinning the composite’s robust photocatalytic performance. The reusability and structural stability of the ZnFe₂O₄@g-C₃N₄-5 catalyst were evaluated through successive degradation cycles under consistent experimental conditions. As illustrated in Figure 8b, the composite retained >95% of its initial degradation efficiency after ten reuse cycles, demonstrating robust operational durability. The material’s inherent ferromagnetism, derived from ZnFe₂O₄, enabled facile magnetic recovery using an external magnetic field, circumventing secondary pollution risks associated with conventional filtration methods. The marginal efficiency decline is attributed to partial active site deactivation via adsorbed intermediates, rather than structural degradation. These results underscore the catalyst’s viability for sustainable wastewater treatment, balancing high recyclability with minimal performance attenuation. Catalytic mechanism The photocatalytic activity of the ZnFe₂O₄@g-C₃N₄ heterostructure arises from its capacity to generate reactive oxygen species (ROS), including photogenerated holes (h⁺), hydroxyl radicals (·OH), and superoxide anions (·O₂⁻), under visible light irradiation. Upon photon absorption (hν), photoexcitation induces charge separation, with electrons (e⁻) transitioning from the valence band (VB) of g-C₃N₄ to its conduction band (CB), leaving h⁺ in the VB (Equation 1, Figure 9). The staggered band alignment between g-C₃N₄ and ZnFe₂O₄ facilitates interfacial electron transfer, whereby e⁻ migrate from g-C₃N₄ to ZnFe₂O₄ (Equation 2, Figure 9). These electrons reduce adsorbed O₂ to yield ·O₂⁻, while h⁺ in the VB of g-C₃N₄ oxidize H₂O or surface hydroxyl groups to produce ·OH. Concurrently, ·O₂⁻ undergoes protonation to form hydroperoxyl radicals (·OOH), which further react with e⁻ to generate H₂O₂ (Equation 3, Figure 9). The Fenton-like decomposition of H₂O₂, catalyzed by Fe²⁺/Fe³⁺ redox pairs in ZnFe₂O₄, liberates additional ·OH (Equation 4, Figure 9). This synergistic ROS cascade (·OH, ·O₂⁻, h⁺) constitutes a mixed oxidative system capable of degrading methylene blue (MB) via demethylation, aromatic ring cleavage, and mineralization into CO₂, H₂O, and inorganic ions (NH₄⁺/NO₃⁻) (Equation 5, Figure 9). The mesoporous architecture of g-C₃N₄ enhances MB adsorption, concentrating dye molecules near active sites, while the heterojunction’s charge separation efficiency minimizes e⁻–h⁺ recombination. This dual function—adsorption enrichment and ROS generation—ensures rapid degradation kinetics and complete pollutant mineralization, underscoring the composite’s efficacy as a sustainable photocatalyst for environmental remediation. Conclusion The ZnFe₂O₄@g-C₃N₄ heterostructure, synthesized via hydrothermal integration of ZnFe₂O₄ nanoparticles onto mesoporous g-C₃N₄, demonstrates exceptional visible-light-driven photocatalytic degradation of methylene blue (MB), achieving 99.99% decolorization within 40 min at an optimal ZnFe₂O₄ loading of 59.1 wt%. Structural analyses (XRD, TEM, SEM) confirmed a well-defined heterojunction with uniform ZnFe₂O₄ dispersion, enhancing charge separation and reactive oxygen species (ROS) generation through hierarchical porosity and broad light absorption. Radical scavenging experiments identified hydroxyl radicals (•OH) as dominant oxidative species, supported by superoxide anions (•O₂⁻) and holes (h⁺), with H₂O₂ addition accelerating degradation via a photo-Fenton mechanism. The composite’s magnetic ZnFe₂O₄ enabled facile recovery, retaining >95% activity over ten cycles due to structural durability, with minimal efficiency loss from intermediate adsorption. However, while UV-Vis spectroscopy tracks chromophore degradation, it cannot confirm complete mineralization (CO₂/H₂O conversion) or detect non-absorbing intermediates (e.g., aromatic fragments). Advanced techniques—total organic carbon (TOC) analysis and HPLC-MS—are essential to quantify mineralization and identify byproducts. Prior studies on analogous systems (Refs. 19–22) reported TOC removal, suggesting significant mineralization potential, though direct validation is critical. This work establishes ZnFe₂O₄@g-C₃N₄ as a durable, recyclable photocatalyst for wastewater treatment, with scalable synthesis addressing pollutant degradation and catalyst reuse challenges. Future research should integrate TOC/HPLC-MS analyses and extend applications to diverse contaminants, advancing sustainable water purification technologies. Declarations Declaration of competing interest The authors declare that they have no known competing for financial interest or personal relationships that could have appeared to influence the work reported in this paper. Author statement Jianhua Wang as corresponding authors: Conceptualization, Methodology, Software, Data curation, Writing- Original draft preparation, Validation, Writing- Reviewing and Editing, Funding acquisition. Funding This project was founded by the Liaoning Natural Science Foundation [Nos.2020-Ms-306]. Author Contribution Leyan LI-article writing, chart output, grammar correction；Jianhua Wang-material synthesis, article writing, chart output, grammar correction, etc. Huihui FANG-Material preparation, degradation experiments, grammar correction, etc. References Jiang X, Wang Z, Zhang M, Wang M,Wu R, Shi X, Luo B, Zhang D, Pu X，Li H (2022) A novel direct Z-scheme heterojunction BiFeO 3 /ZnFe 2 O 4 photocatalyst for enhanced photocatalyst degradation activity under visible light irradiation 912:165185 Ge, Y., Wang, Z., Yi, M., Ran, L. P. Fabrication and magnetic transformation from paramagnetic to ferrimagnetic of ZnFe 2 O 4 hollow spheres, Trans. Nonferrous Met. Soc. China, 2019, vol.29, pp.1503−1509. https://doi.org/10.1016/S1003-6326(19)65057-0 Wang, M., Sun, L., Cai, J., Huang, P.，Su, Y.，Lin, C. 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Fabrication of a magnetically separable Cu 2 ZnSnS 4 /ZnFe 2 O 4 p-n heterostructured nano-photocatalyst for synergistic enhancement of photocatalytic activity combining with photo-Fenton reaction, Applied Surface Science, 2019, vol.479, pp.86–95. https://doi.org/ 10.1016/j.apsusc.2019.02.045 Mady, A. H., Baynosa, M. L., Tuma, D., Shim, J. J. Facile microwave-assisted green synthesis of Ag-ZnFe 2 O 4 @rGO nanocomposites for efficient removal of organic dyes under UV- and visible-light irradiation[J]. Journal of Physics and Chemistry of Solids, 2014, vol.75,pp.441–446. http://dx.doi.org/ doi:10.1016/j.apcatb.2016.10.033 Yao, Y., Cai, Y., Lu, F., Qin, J.; Wei, F.; Xu, C.; Wang, S. Magnetic ZnFe 2 O 4 −C 3 N 4 Hybrid for photocatalytic Degradation of Aqueous Organic Pollutants by Visible Light, Ind. Eng. Chem. Res, 2014, vol.53, pp.17294−17302. https://pubs.acs. org/doi/pdf/10.1021/ie503437z Yang, D., Cai X., Zhang, J., Ding, B.，Qiang, Y., Preparation of 0D/2D ZnFe 2 O 4 /Fe-doped g-C 3 N 4 hybrid photocatalysts for visible light N 2 fixation, Journal of Alloys and Compounds, 2021, vol.869, pp. 158809. https://doi. org/10.1016/j.jallcom.2021.158809 Wang, J., Zhang, W., Oxidative degradation of methylene blue by Ag 2 O@g-C 3 N 4 photocatalysts under visible light, T oxicological & Environmental Chemistry , 2023, vol.105, pp.60-74. https://doi.org/10.1080/02772248.2023.2211700. Wang, J., Construction of ternary heterostructured Ag/Ag 2 O@ZnO@g-C 3 N 4 nanocomposite as an widened visible light photocatalyst for the organic oxidation, Journal of Physics and Chemistry of Solids, 2023, vol.180, pp.111389 . https://doi.org/10.1016/j.jpcs.2023.111389. Yang, N., Hu, P., Chen, C., Wang, Y.，Pan, L., Ternary Composite of g-C 3 N 4 /ZnFe 2 O 4 /Fe 2 O 3 : Hydrothermal Synthesis and Enhanced Photocatalytic Performance, ChemistrySelect, 2019, vol. 4 , pp.7308 –7316. https: //doi.org/10.1002/slct.201901543 Borthakur, S., Saikia, L., ZnFe 2 O 4 @g-C 3 N 4 nanocomposites: An efficient catalyst for Fenton-like photodegradation of environmentally pollutant Rhodamine B, Journal of Environmental Chemical Engineering, 2019,vol.7 , pp.103035. https://doi.org/10.1016/j.jece.2019.103035 Meng, Y., Zhang, L., Jiu, H., Zhang, H., Zhang, Q., Ren, Hong., Sun, W., Li, Yu., Dan, T., Construction of g-C 3 N 4 /ZIF-67 photocatalyst with enhanced photocatalytic CO 2 reduction activity, Materials Science in Semiconductor Processing, 2019, vol.95, pp.35–41. https://doi.org/10.1016/j.mssp.2019.02.010 Lu, T., Zhao H., Jian, L., Ji, R.，Pan, C.，Wang, G.，Dong, Y.，Zhu, Y ., Photocatalysis-self-Fenton system over edge covalently modified g-C 3 N 4 with high mineralization of persistent organic pollutants, Environmental ResearchVolume, 2023, vol.222, pp.115361. https://doi.org/10.1016/j.envres.2023.115361 Tang, J., Wang, J., Tang, L., Feng, C., Zhu, X., Yi, Y., Feng, H., Yu, J., Ren, X., Preparation of floating porous g-C 3 N 4 photocatalyst via a facile one-pot method for efficient photocatalytic elimination of tetracycline under visible light irradiation, Chemical Engineering Journal, 2022, vol.430,pp.132669. https://doi.org/10.1016/j.cej.2021.132669 Shi, Lei., Zhang, J., Liu, H., Que, M.，Cai, X.，Tan, S.，Huang, L ., Flower-like Ni(OH) 2 hybridized g-C 3 N 4 for high-performance supercapacitor electrode material, Materials Letters, 2015, vol.145, pp. 150-153. https://doi.org/ 10.1016/j.matlet.2015.01.083 Zhang, X., Sun, C., Li, R., Jin, X.，Wu, Y.，Fu, F., Dual-Loading of Fe 3 O 4 and Pd Nanoparticles on g‑C 3 N 4 Nanosheets Toward a Magnetic Nanoplatform with Enhanced Peroxidase-like Activity for Loading Various Enzymes for Visual Detection of Small Molecules, Anal. Chem, 2023, vol.95, pp.5024−5033. https://doi.org/ 10.1021/acs.analchem.2c05503 Zhong, Q., Lan, H., Zhang, M., Zhu, H., Bu, M., Preparation of heterostructure g-C 3 N 4 /ZnO nanorods for high photocatalytic activity on different pollutants (MB, RhB, Cr(VI) and eosin),Ceramics International, 2020, Vol. 46, pp. 12192-12199. https://doi.org/10.1016/j.ceramint.2020.01.265 Vijayan, M., Easwaran, G., Sivakumar, K., Palanisamy, G., Bhuvaneswari, K., Energetic two-dimensional g-C 3 N 4 nanosheets combined with ZnO nanoparticles as effectual catalyst for degradation of MB dye under UV–Visible-light Irradiation, J Mater Sci: Mater Electron, 2022 Vol. 33 pp. 24340–24353. https://doi.org/ 10.1007/s10854-022-09153-1 Gao, M., Feng, J., He, F., Zeng, W., Wang, X., Ren, Y., Wei, T., Carbon microspheres work as an electron bridge for degrading high concentration MB in CoFe 2 O 4 @carbon microsphere/g-C 3 N 4 with a hierarchical sandwich-structure, Applied Surface Science, 2020, Vol.507, pp.145167. https://doi.org/ 10.1016/j.apsusc.2019.145167 Sun, S., Li, S., Hao, Y., Yang, X., Dou, X., Construction of g/C 3 N 4 -ZnO composites with enhanced visible-light photocatalytic activity for degradation of amoxicillin,Korean J. Chem. Eng., 2022, Vol.39, pp.3377-3388. https://doi.org/10.1007/s11814-022-1181-5 Tables Table 1 and 2 are available in the Supplementary Files section. Additional Declarations No competing interests reported. Supplementary Files Tables1and2.docx Cite Share Download PDF Status: Published Journal Publication published 01 Jul, 2025 Read the published version in Scientific Reports → Version 1 posted Editorial decision: Revision requested 09 Apr, 2025 Editor assigned by journal 07 Apr, 2025 Submission checks completed at journal 07 Apr, 2025 First submitted to journal 07 Apr, 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. 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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-6391826\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":false,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":439610816,\"identity\":\"afe8d402-c340-4413-95f7-31203c8a72cc\",\"order_by\":0,\"name\":\"Leyan Li\",\"email\":\"\",\"orcid\":\"\",\"institution\":\"Shenyang university\",\"correspondingAuthor\":false,\"prefix\":\"\",\"firstName\":\"Leyan\",\"middleName\":\"\",\"lastName\":\"Li\",\"suffix\":\"\"},{\"id\":439610817,\"identity\":\"8b221adb-ebde-402d-8f96-3a6cdc34aaea\",\"order_by\":1,\"name\":\"Wang 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ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"1.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/89c4b263c2ed951c49ae7dfa.png\"},{\"id\":80112120,\"identity\":\"e437a6df-fa07-4b9e-a4ce-2b44d577f21b\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:04:32\",\"extension\":\"png\",\"order_by\":2,\"title\":\"Figure 2\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":539385,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eThe SEM images of samples g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4 \\u003c/sub\\u003eand ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"2.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/d1a8916fc8f7e31f8af87953.png\"},{\"id\":80112125,\"identity\":\"ab52b4c2-ef45-4b78-9323-857e987b7167\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:04:32\",\"extension\":\"png\",\"order_by\":3,\"title\":\"Figure 3\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":663645,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eThe TEM images of samples g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4 \\u003c/sub\\u003eand ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"3.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/1711d6bcce8b5edd01a62aac.png\"},{\"id\":80112119,\"identity\":\"fa36a2d8-4f9d-4dbb-a057-e42437b5bb26\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:04:32\",\"extension\":\"png\",\"order_by\":4,\"title\":\"Figure 4\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":305642,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eThe absorption curves of samples ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"4.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/d39a274b3d46a0c2d610dab3.png\"},{\"id\":80112123,\"identity\":\"faf8faac-5862-4b99-807b-c80901f9c4ad\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:04:32\",\"extension\":\"png\",\"order_by\":5,\"title\":\"Figure 5\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":407235,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eX-ray photoelectron spectrum of ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"5.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/e0a88d867fb6733db8d42c78.png\"},{\"id\":80112773,\"identity\":\"808a4f6c-3768-4cdf-909e-50eee50daf8e\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:12:32\",\"extension\":\"png\",\"order_by\":6,\"title\":\"Figure 6\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":153586,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eThe changed absorption peak of MB with visible light irradiated\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"6.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/a5176065c17085277aff60f0.png\"},{\"id\":80113374,\"identity\":\"75ae54a1-530b-4a96-aa52-bf715cb7143f\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:28:34\",\"extension\":\"png\",\"order_by\":7,\"title\":\"Figure 7\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":427479,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eThe changed catalytic performance with visible light irradiated\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"7.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/b7ee4ffe9abc55211d49555c.png\"},{\"id\":80112121,\"identity\":\"dd0e12c7-8ae8-4a65-9901-e50736d9ecc9\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:04:32\",\"extension\":\"png\",\"order_by\":8,\"title\":\"Figure 8\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":98448,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eElemental trapping experiment, recycled degradation rate and Vsm of catalysis\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"8.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/7d0a537a7ae9cff944289f9a.png\"},{\"id\":80113616,\"identity\":\"487a4d30-6e14-48ea-86f9-d98f7a958dc5\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:36:32\",\"extension\":\"png\",\"order_by\":9,\"title\":\"Figure 9\",\"display\":\"\",\"copyAsset\":false,\"role\":\"figure\",\"size\":242452,\"visible\":true,\"origin\":\"\",\"legend\":\"\\u003cp\\u003eVisible light absorption, charge transfer and schematic diagram of degraded methylene blue by ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e\\u003c/p\\u003e\",\"description\":\"\",\"filename\":\"9.png\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/7095795c4fcac108ed966a47.png\"},{\"id\":86179082,\"identity\":\"754575a4-22f7-494a-b69a-1e721783e82b\",\"added_by\":\"auto\",\"created_at\":\"2025-07-07 16:15:30\",\"extension\":\"pdf\",\"order_by\":0,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"manuscript-pdf\",\"size\":3551499,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"manuscript.pdf\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/9193107c-0161-4fbd-aa35-cfc05bb2d412.pdf\"},{\"id\":80112118,\"identity\":\"058b4d47-7e0f-4092-9f34-5290048cafbf\",\"added_by\":\"auto\",\"created_at\":\"2025-04-08 05:04:32\",\"extension\":\"docx\",\"order_by\":1,\"title\":\"\",\"display\":\"\",\"copyAsset\":false,\"role\":\"supplement\",\"size\":23327,\"visible\":true,\"origin\":\"\",\"legend\":\"\",\"description\":\"\",\"filename\":\"Tables1and2.docx\",\"url\":\"https://assets-eu.researchsquare.com/files/rs-6391826/v1/08fac2616e8d7dc7905b0084.docx\"}],\"financialInterests\":\"No competing interests reported.\",\"formattedTitle\":\"\\u003cp\\u003eFabrication of ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e for Enhanced Photo-Fenton Effect and Visible Light-Driven Organic Dye Degradation\\u003c/p\\u003e\",\"fulltext\":[{\"header\":\"INTRODUCTION\",\"content\":\"\\u003cp\\u003eWater is an indispensable resource for sustaining life across ecosystems, yet its contamination by antibiotics, pesticides, and synthetic dyes has escalated into a global environmental crisis, jeopardizing human health and ecological stability. Addressing this challenge requires innovative solutions to degrade persistent pollutants effectively. Advanced oxidation processes (AOPs), particularly those leveraging visible-light-driven photocatalysis and Fenton-like reactions, have emerged as a frontier technology for water purification due to their capacity to generate highly reactive oxygen species (ROS) under mild conditions [1\\u0026ndash;4]. Central to these processes is the development of efficient, stable, and recyclable heterojunction catalysts capable of optimizing charge separation and ROS generation.\\u003c/p\\u003e\\n\\u003cp\\u003eRecent advancements highlight the potential of multiphase composite catalysts, where materials with distinct band structures synergize to enhance charge carrier dynamics. For instance, high-entropy catalysts with tailored conduction and valence band positions facilitate rapid separation of photogenerated electron-hole pairs, amplifying catalytic efficiency [5\\u0026ndash;10]. Mesoporous materials, in particular, serve as ideal substrates due to their high surface area and adsorption capacity. When functionalized with metals or metal oxides, they promote electron transfer and activate H₂O₂ decomposition into hydroxyl radicals (\\u0026bull;OH), a critical step in pollutant degradation [5\\u0026ndash;10].\\u003c/p\\u003e\\n\\u003cp\\u003eZinc ferrite (ZnFe₂O₄, ZFO), a narrow-bandgap (1.0-2.0 eV) n-type semiconductor, has garnered attention for its visible-light absorption, magnetic recoverability, and photo-fenton effect, which synergize with H₂O₂ to generate ROS [11\\u0026ndash;16]. Concurrently, graphitic carbon nitride (g-C₃N₄), a metal-free polymeric semiconductor with a 2.7 eV bandgap and redox-active bands (-1.3 and +1.4 eV), offers tunable structural properties, high chemical stability, and enhanced charge migration via its 2D/3D architectures [13\\u0026ndash;18]. Integrating ZFO with g-C₃N₄ presents a promising strategy to bridge their complementary advantages: ZFO\\u0026rsquo;s magnetic recyclability and ROS-generating capacity, coupled with g-C₃N₄\\u0026rsquo;s expansive surface area and charge transport efficiency.\\u003c/p\\u003e\\n\\u003cp\\u003eIn this study, mesoporous g-C₃N₄ was synthesized via thermal polymerization of urea and melamine, followed by the hydrothermal deposition of ZFO nanoparticles using zinc acetate and iron chloride precursors. The resultant ZnFe₂O₄@g-C₃N₄ heterostructure was systematically characterized through SEM, TEM, XRD, and UV-Vis spectroscopy to elucidate its structural, morphological, and optoelectronic properties. The photocatalytic performance was evaluated via visible-light-driven degradation of methylene blue (MB), with mechanistic insights into charge transfer pathways and ROS generation explored. Furthermore, the magnetic recoverability and cyclic stability of the composite were assessed to underscore its practical viability. This work not only advances the design of multifunctional heterojunction catalysts but also highlights their potential in environmental remediation, particularly for industrial wastewater treatment and water quality restoration.\\u003c/p\\u003e\"},{\"header\":\"Experimental Section\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eReagents\\u003c/em\\u003e\\u003c/strong\\u003e\\u003cstrong\\u003e\\u003cem\\u003e\\u0026nbsp;and\\u0026nbsp;\\u003c/em\\u003e\\u003c/strong\\u003e\\u003cstrong\\u003e\\u003cem\\u003eCharacterization\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eAll chemicals, including urea (CH₄N₂O, \\u0026ge;99%), melamine (C₃H₆N₆, \\u0026ge;99%), zinc acetate dihydrate (Zn(CH₃COO)₂\\u0026middot;2H₂O, \\u0026ge;99%), iron(III) chloride hexahydrate (FeCl₃\\u0026middot;6H₂O, \\u0026ge;98%), methylene blue (C₁₆H₁₈ClN₃S, \\u0026ge;95%), and hydrogen peroxide (H₂O₂, 30 wt%), were of analytical grade and procured from Sinopharm Chemical Reagent Co., Ltd. (China). Deionized water (resistivity \\u0026ge;18.2 M\\u0026Omega;\\u0026middot;cm) was produced using a laboratory-grade purification system.\\u003c/p\\u003e\\n\\u003cp\\u003eThe crystallographic properties of the synthesized g-C₃N₄ and ZnFe₂O₄@g-C₃N₄ composites were analyzed using an Ultima IV X-ray diffractometer (Rigaku Corporation, Japan) with Cu-K\\u0026alpha; radiation (\\u0026lambda; = 1.5406 \\u0026Aring;) operated at 40 kV and 40 mA. Morphological and microstructural features were examined using a JEM-2100F field-emission transmission electron microscope (JEOL Ltd., Japan) at an accelerating voltage of 200 kV. The optical absorption properties and photocatalytic degradation kinetics of methylene blue were monitored via a PerkinElmer LAMBDA750 UV/Vis/NIR spectrophotometer, with spectra recorded in the range of 200\\u0026ndash;800 nm.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003e\\u0026nbsp;Experimental process\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003ePreparation of g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e nanoparticles\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eGraphene-like g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e was prepared using a thermal polymerization method. Details of the sample preparation can be found in references[10-11].\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e Preparation of nanoparticles\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe ZnFe₂O₄@g-C₃N₄ heterostructure was synthesized via a hydrothermal route. Briefly, 0.5 g of g-C₃N₄ was uniformly dispersed in 50 mL of deionized water via ultrasonication (40 kHz, 30 min). Separately, stoichiometric ratios of zinc acetate dihydrate (Zn(CH₃COO)₂\\u0026middot;2H₂O) and iron(III) chloride hexahydrate (FeCl₃\\u0026middot;6H₂O) (mass ratios detailed in Table 1) were dissolved in 25 mL of deionized water under magnetic stirring (500 rpm, 30 min). The metal precursor solution was then introduced dropwise into the g-C₃N₄ suspension, followed by the addition of 0.5 g urea as a pH-modulating agent. The mixture was stirred vigorously (60 min) to ensure homogeneity.\\u003c/p\\u003e\\n\\u003cp\\u003eThe resultant suspension was transferred into a 100 mL polytetrafluoroethylene (PTFE)-lined autoclave and subjected to hydrothermal treatment in a programmable oven. The temperature was ramped to 150\\u0026deg;C at a rate of 2\\u0026deg;C/min and maintained for 4 h. After natural cooling to ambient temperature, the precipitate was isolated by centrifugation (7000 rpm, 15 min), followed by sequential washing with deionized water and ethanol (three cycles each) to remove residual impurities. The purified product was vacuum-dried at 60\\u0026deg;C for 24 h and stored in an airtight container for subsequent characterization and application. The samples name are list in Table 1. The symbol \\u0026ldquo;-0\\u0026rdquo;, \\u0026ldquo;-1\\u0026rdquo;, \\u0026ldquo;-2\\u0026rdquo;, \\u0026ldquo;-3\\u0026rdquo;, \\u0026ldquo;-4\\u0026rdquo;, \\u0026ldquo;-5\\u0026rdquo;, \\u0026ldquo;-6\\u0026rdquo; and \\u0026ldquo;-7\\u0026rdquo; means the increasing mole of raw material \\u0026ldquo;Zn(AC)\\u003csub\\u003e2\\u003c/sub\\u003e\\u0026rdquo; as 0, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, and 0.007 mol. As shown in last column, the mass ratio ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e\\u003csub\\u003e\\u0026nbsp;\\u003c/sub\\u003eto\\u003csub\\u003e\\u0026nbsp;\\u003c/sub\\u003eg-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u0026nbsp;\\u003c/sub\\u003eand\\u0026nbsp;ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e were 0, 0.325, 0.491, 0.591, 0.658, 0.707, 0.743, and 0.771 in different samples.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003ePhotocatalytic degradation of methylene blue\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe visible-light-driven photocatalytic activity of ZnFe₂O₄@g-C₃N₄ was assessed through the degradation of methylene blue (MB) in aqueous media. Prior to illumination, 50 mg of the catalyst was dispersed in 50 mL of MB solution (30 mg/L) within a 100 mL borosilicate glass reactor under darkroom conditions. The suspension was ultrasonicated (40 kHz, 3 min) to ensure uniform catalyst distribution, followed by magnetic stirring (60 min) to establish adsorption-desorption equilibrium between the dye and catalyst surface.\\u003c/p\\u003e\\n\\u003cp\\u003eA 300 W xenon lamp equipped with a 420 nm cutoff filter was positioned 20 cm above the reactor to simulate visible-light irradiation. Aliquots (3 mL) were extracted at 10-minute intervals and immediately centrifuged (7000 rpm, 2 min) to isolate the catalyst, thereby preventing interference in absorbance measurements. The residual MB concentration was quantified via UV-Vis spectroscopy by monitoring the attenuation of its characteristic absorption band at \\u0026lambda; = 664 nm. The degradation efficiency (\\u0026eta;, %) and real time change of absorption intensity were calculated using the equation:\\u003c/p\\u003e\\n\\u003cp\\u003e\\u0026eta;=(1\\u0026minus;C/C\\u003csub\\u003e0\\u003c/sub\\u003e)\\u0026times;100% \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; (1)\\u003c/p\\u003e\\n\\u003cp\\u003eC/C\\u003csub\\u003e0\\u003c/sub\\u003e or C/C\\u003csub\\u003e0\\u0026nbsp;\\u003c/sub\\u003e\\u0026times; 100% \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp; \\u0026nbsp;(2)\\u003c/p\\u003e\\n\\u003cp\\u003ewhere\\u0026nbsp;C\\u003csub\\u003e0\\u003c/sub\\u003e\\u003csub\\u003e\\u0026nbsp;\\u003c/sub\\u003eand C represent the initial and time-dependent absorbance intensities of MB, respectively [10, 11].\\u003c/p\\u003e\"},{\"header\":\"Results and Discussion\",\"content\":\"\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eXRD structural characterization\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe crystallographic structures of pristine g-C₃N₄ and the ZnFe₂O₄@g-C₃N₄ composite were analyzed via X-ray diffraction (XRD). As illustrated in Figure 1, the XRD pattern of ZnFe₂O₄@g-C₃N₄ exhibits distinct diffraction peaks corresponding to both g-C₃N₄ and ZnFe₂O₄ phases, confirming the coexistence of the two components. For pristine g-C₃N₄, two characteristic peaks are observed at 13.1\\u0026deg; and 27.5\\u0026deg;, indexed to the (001) and (002) crystallographic planes, respectively. These reflections arise from the in-plane structural packing of tri-s-triazine units and the interlayer stacking of conjugated aromatic systems, consistent with the typical graphitic carbon nitride framework (JCPDS 87-1526) [10, 11].\\u003c/p\\u003e\\n\\u003cp\\u003eIn the composite, additional diffraction peaks at 2\\u0026theta; values of 30.2\\u0026deg;, 35.6\\u0026deg;, 43.3\\u0026deg;, 53.7\\u0026deg;, 57.3\\u0026deg;, and 62.8\\u0026deg; are assigned to the (220), (311), (400), (422), (511), and (440) planes of cubic spinel ZnFe₂O₄ (JCPDS 82-1049) [12, 13]. Notably, no extraneous peaks corresponding to impurities or secondary phases (e.g., ZnO, Fe₃O₄) are detected, indicating that the hydrothermal synthesis preserved the structural integrity of both g-C₃N₄ and ZnFe₂O₄ without inducing phase transitions. The coexistence of these distinct diffraction features confirms the successful formation of a heterostructure, where ZnFe₂O₄ nanoparticles are anchored onto the g-C₃N₄ matrix without disrupting its layered architecture. These results validate the effective synthesis of a phase-pure ZnFe₂O₄@g-C₃N₄ composite, laying a foundation for its enhanced photocatalytic functionality.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eMorphological and Microstructural Analysis\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe morphological evolution and interfacial characteristics of pristine g-C₃N₄ and the ZnFe₂O₄@g-C₃N₄ composite were investigated via scanning electron microscopy (SEM) and transmission electron microscopy (TEM). As depicted in Figure 2a, the thermal polymerization of urea and melamine yielded g-C₃N₄ with a lamellar morphology characterized by pronounced wrinkling and sheet-like stacking, a hallmark of its graphitic architecture. Upon integration with ZnFe₂O₄ (Figure 2b), the composite retained the layered framework of g-C₃N₄ but exhibited reduced lateral dimensions of the individual sheets, likely due to fragmentation during hydrothermal processing. Crucially, ZnFe₂O₄ nanoparticles (20\\u0026ndash;50 nm diameter) were uniformly dispersed across the g-C₃N₄ matrix without agglomeration, confirming the successful formation of an intimate heterointerface between the two phases. This structural synergy is anticipated to enhance charge carrier separation and surface reactivity, thereby augmenting photocatalytic efficiency.\\u003c/p\\u003e\\n\\u003cp\\u003eFurther insights into the microstructural features were obtained through TEM (Figure 3a\\u0026ndash;b). Pristine g-C₃N₄ displayed a highly porous, crumpled 2D structure with abundant in-plane voids (Figure 3a), attributed to the release of gaseous byproducts (e.g., NH₃) during thermal condensation. These mesopores (5\\u0026ndash;15 nm diameter) not only increase the material\\u0026rsquo;s specific surface area but also facilitate reactant diffusion and active site accessibility. In the ZnFe₂O₄@g-C₃N₄ composite (Figure 3b), the g-C₃N₄ sheets maintained their layered topology, while ZnFe₂O₄ nanoparticles were anchored uniformly across the surface. High-resolution TEM (inset, Figure 3b) revealed lattice fringes corresponding to the (311) plane of cubic ZnFe₂O₄ and the (002) interlayer spacing of g-C₃N₄ , corroborating the coexistence of both phases without interfacial contamination. The absence of particle aggregation and the coherent integration of ZnFe₂O₄ within the g-C₃N₄ scaffold underscore the efficacy of the synthesis strategy in fostering a well-defined heterostructure, a critical determinant of enhanced catalytic performance.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eNitrogen Adsorption-Desorption Analysis\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe textural properties of the ZnFe₂O₄@g-C₃N₄ composite were evaluated through nitrogen adsorption-desorption measurements. As depicted in Figure 4a, the composite exhibits a type IV isotherm with an H3 hysteresis loop, characteristic of mesoporous materials featuring slit-like pores formed by platelet aggregates. A sharp uptake at high relative pressure (P/P₀ \\u0026gt; 0.95) signifies the coexistence of macropores, attributed to the volatilization of ammonia gas during the thermal polymerization of g-C₃N₄ precursors. The Brunauer-Emmett-Teller (BET) specific surface area of the g-C₃N₄ was calculated as 855.9 m\\u0026sup2;\\u0026middot;g⁻\\u0026sup1;, with reduced surface areas of 654.2, 358.4, 37.9, 29.2, 23.2, 20.22, and 14.1 m\\u0026sup2;\\u0026middot;g⁻\\u0026sup1; observed under increased ZnFe₂O₄. According to nitrogen adsorption-desorption analysis, the ZnFe₂O₄@g-C₃N₄ composite exhibited a significant reduction in specific surface area with increasing ZnFe₂O₄ loading. This decrease can be attributed to the partial occupation of the porous g-C₃N₄ framework by ZnFe₂O₄ nanoparticles. However, the formation of a well-defined ZnFe₂O₄/g-C₃N₄ heterojunction became more prominent at higher ZnFe₂O₄ content, as evidenced by the concomitant rise in catalytically active sites. While the pore-blocking effect of ZnFe₂O₄ diminished the surface area, the enhanced interfacial charge transfer and increased density of reactive sites at the heterojunction interface counterbalanced this limitation. The interplay between these competing factors\\u0026mdash;surface area reduction and active site enrichment\\u0026mdash;culminated in the ZnFe₂O₄@g-C₃N₄-3 composite demonstrating optimal catalytic performance, highlighting the critical role of heterojunction engineering in optimizing activity despite structural trade-offs.\\u003c/p\\u003e\\n\\u003cp\\u003ePore size distribution derived from the Barrett-Joyner-Halenda (BJH) model (Figure 4b) reveals a bimodal architecture dominated by mesopores (2.5\\u0026ndash;10 nm, average diameter: 3.4\\u0026ndash;5.6 nm) and subsidiary macropores (10\\u0026ndash;100 nm). The mesopores originate from interparticle voids within the aggregated g-C₃N₄ layers, while macropores arise from gas evolution during synthesis. Such hierarchical porosity facilitates efficient mass transport of reactants and access to catalytic sites, synergistically enhancing degradation kinetics. These structural attributes\\u0026mdash;high surface area, dual-scale porosity, and interfacial connectivity\\u0026mdash;underscore the ZnFe₂O₄@g-C₃N₄ composite\\u0026rsquo;s suitability for advanced photocatalytic applications.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eSurface Elemental and Chemical State Analysis\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe chemical composition and interfacial interactions within the ZnFe₂O₄@g-C₃N₄ heterostructure were probed via X-ray photoelectron spectroscopy (XPS). The survey spectrum (Figure 5a) confirms the coexistence of oxygen (O), nitrogen (N), carbon (C), zinc (Zn), and iron (Fe), corroborating the composite\\u0026rsquo;s hybrid nature. High-resolution spectra were deconvoluted to elucidate bonding configurations and oxidation states. In \\u003cstrong\\u003eO 1s Spectrum (\\u003c/strong\\u003eFigure\\u003cstrong\\u003e\\u0026nbsp;5b)\\u003c/strong\\u003e\\u003cstrong\\u003e,\\u0026nbsp;\\u003c/strong\\u003ethe O 1s envelope resolves into four components at 529.75, 530.95, 531.45, and 531.95 eV. Peaks at 529.75 and 530.95 eV are attributed to Zn\\u0026ndash;O\\u0026ndash;Fe coordination in the spinel ZnFe₂O₄ lattice, while contributions at 531.45 and 531.95 eV correspond to surface-adsorbed hydroxyl (\\u0026ndash;OH) and carboxyl (\\u0026ndash;HO\\u0026ndash;C=O) groups, indicative of oxygen-containing functional moieties. In \\u003cstrong\\u003eN 1s Spectrum (\\u003c/strong\\u003eFigure\\u003cstrong\\u003e\\u0026nbsp;5c)\\u003c/strong\\u003e\\u003cstrong\\u003e,\\u003c/strong\\u003e\\u003cstrong\\u003e\\u0026nbsp;\\u003c/strong\\u003ethe N 1s profile exhibits three distinct binding energies at 398.55, 399.00, and 399.55 eV. The dominant peak at 398.44 eV arises from C\\u0026ndash;N\\u0026ndash;C coordination in the tri-s-triazine units of g-C₃N₄, while contributions at 399.00 and 399.55 eV correspond to sp\\u0026sup2;-hybridized nitrogen (N\\u0026ndash;(C)₃) and terminal amino groups (\\u0026ndash;NH₂), respectively, confirming the integrity of the g-C₃N₄ framework. In \\u003cstrong\\u003eC 1s Spectrum (\\u003c/strong\\u003eFigure\\u003cstrong\\u003e\\u0026nbsp;5d)\\u003c/strong\\u003e\\u003cstrong\\u003e,\\u003c/strong\\u003e\\u003cstrong\\u003e\\u0026nbsp;\\u003c/strong\\u003edeconvolution of the C 1s signal reveals four components: (i) adventitious carbon (C=C/C\\u0026ndash;C, 284.95 eV), (ii) Zn\\u0026ndash;C bonds (284.55 eV) associated with oxygen vacancies, (iii) graphitic sp\\u0026sup2; carbon (285.45 eV), and (iv) a prominent peak at 288.1 eV assigned to N\\u0026ndash;C=N coordination in the aromatic triazine rings of g-C₃N₄. In \\u003cstrong\\u003eFe 2p Spectrum (\\u003c/strong\\u003eFigure\\u003cstrong\\u003e\\u0026nbsp;5e)\\u003c/strong\\u003e\\u003cstrong\\u003e,\\u003c/strong\\u003e\\u003cstrong\\u003e\\u0026nbsp;\\u003c/strong\\u003ethe Fe 2p region displays spin-orbit doublets for Fe 2p₃/₂ (710.56 eV) and Fe 2p₁/₂ (724.66 eV), accompanied by a satellite peak at 718.96 eV. The Fe 2p₃/₂ peak splits into two components at 710.56 eV (Fe\\u0026sup3;⁺ in octahedral sites) and 712.36 eV (Fe\\u0026sup3;⁺ with ligand field effects), confirming the dominance of Fe\\u0026sup3;⁺ in the ZnFe₂O₄ lattice. The absence of Fe\\u0026sup2;⁺ signatures (typically \\u0026lt;709 eV) underscores the stability of the spinel structure. In \\u003cstrong\\u003eZn 2p Spectrum (\\u003c/strong\\u003eFigure\\u003cstrong\\u003e\\u0026nbsp;5f)\\u003c/strong\\u003e\\u003cstrong\\u003e,\\u0026nbsp;\\u003c/strong\\u003ethe Zn 2p spectrum exhibits symmetric peaks at 1021.92 eV (Zn 2p₃/₂) and 1045.02 eV (Zn 2p₁/₂), characteristic of Zn\\u0026sup2;⁺ in tetrahedral coordination within ZnFe₂O₄. The 23.1 eV spin-orbit splitting further validates the +2 oxidation state of Zn. The XPS analysis confirms the coexistence of ZnFe₂O₄ and g-C₃N₄ phases with interfacial Zn\\u0026ndash;C and Fe\\u0026ndash;O\\u0026ndash;N bonding, indicative of strong electronic coupling. This synergy, coupled with oxygen vacancies and surface functional groups, underpins the composite\\u0026rsquo;s enhanced photocatalytic activity.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003ePhotocatalytic performance\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe photocatalytic activity of the ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e heterostructure was rigorously assessed via visible-light-driven degradation of methylene blue (MB), a model organic pollutant [19-20]. As depicted in Figure 6, time-resolved ultraviolet-visible (UV-Vis) spectroscopy demonstrated a monotonic decline in the characteristic absorbance intensity of MB at \\u0026lambda; = 664 nm as a function of irradiation duration, with the signal diminishing to near-background levels after prolonged exposure. The absence of hypsochromic or bathochromic shifts in the primary absorption band, coupled with no detectable emergence of secondary absorption features within the spectral range (400\\u0026ndash;800 nm), strongly indicates the complete mineralization of MB rather than transient intermediate formation or structural isomerization. These observations unequivocally validate the robust photocatalytic efficacy of the ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e composite, highlighting its capacity for efficient visible-light harvesting and redox-driven degradation of organic contaminants.\\u003c/p\\u003e\\n\\u003cp\\u003eThe photocatalytic degradation of methylene blue (MB) by ZnFe₂O₄@g-C₃N₄ under visible light irradiation is governed by the generation of reactive oxygen species (ROS), notably hydroxyl radicals (\\u0026middot;OH) and superoxide anions (\\u0026middot;O₂⁻), facilitated by the heterojunction\\u0026rsquo;s electronic structure [19-20]. As illustrated in Figure 7a, the degradation efficiency correlates with ZnFe₂O₄ doping concentration, achieving optimal performance at 74.3 wt% loading. Under dark conditions (Figure 7a, black curve), the composite exhibits substantial adsorption of MB molecules due to its mesoporous g-C₃N₄ framework, yet no degradation occurs in the absence of light. Upon visible-light irradiation, photogenerated electrons (e⁻) and holes (h⁺) are formed, with the heterojunction interface promoting efficient charge separation. This suppresses recombination, enabling prolonged ROS generation and rapid MB decomposition. Exceeding the optimal ZnFe₂O₄ loading (\\u0026gt;74.3 wt%) diminishes performance due to nanoparticle aggregation, which obstructs the porous g-C₃N₄ layers, reduces active site accessibility, and impedes dye-catalyst contact. Kinetic analysis (Figure 7c, Table 2) confirms pseudo-first-order behavior, with rate constants peaking at 74.3 wt% (0.12697 min⁻\\u0026sup1;) and declining thereafter. The synergy between g-C₃N₄\\u0026rsquo;s adsorption capacity and ZnFe₂O₄\\u0026rsquo;s visible-light activation is critical for maximizing degradation efficiency.\\u003c/p\\u003e\\n\\u003cp\\u003eThe introduction of H₂O₂ (0.5 mL, 30%) amplifies catalytic activity via a photo-Fenton mechanism (Figure 7b, d), where H₂O₂ reacts with photogenerated electrons to yield additional \\u0026middot;OH radicals. This dual catalytic pathway achieves complete MB degradation within 40 min, with kinetic coefficients increasing by 2.7-fold at 59.1 wt% ZnFe₂O₄ (Table 2). However, excessive doping (\\u0026gt; 59.1 wt%) under H₂O₂ conditions induces shielding effects, wherein dense ZnFe₂O₄ layers hinder H₂O₂ diffusion and ROS generation, underscoring the necessity of balanced compositional design.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u0026nbsp;A above analysis, the photocatalytic performance of the ZnFe₂O₄@g-C₃N₄ composites exhibited an optimal threshold when an equilibrium between specific surface area and active site density was achieved. During the initial reaction stage, the degradation efficiency remained limited due to the high initial dye concentration and insufficient generation of photoinduced reactive species. As the reaction progressed, the accumulation of reactive species significantly increased their collision frequency with dye molecules, thereby enhancing the degradation kinetics. Notably, the density of these reactive species was directly modulated by the ZnFe₂O₄ loading within the composite. As demonstrated in Figure 7, the ZnFe₂O₄@g-C₃N₄-3 composite displayed superior photocatalytic activity, which originated from a synergistic effect arising from two competing factors: (i) the formation of an efficient ZnFe₂O₄/g-C₃N₄ heterojunction, which facilitated interfacial charge separation and amplified reactive species generation, and (ii) the retention of sufficient surface accessibility despite partial pore occlusion by ZnFe₂O₄ nanoparticles. This balance between heterojunction-driven electronic enhancement and structural porosity underscores the critical role of compositional optimization in maximizing photocatalytic performance.\\u003c/p\\u003e\\n\\u003cp\\u003eTo elucidate the reactive species governing the photocatalytic degradation mechanism, radical scavenging experiments were conducted under visible light irradiation. The active species photogenerated holes (h⁺), hydroxyl radicals (\\u0026bull;OH), and superoxide anions (\\u0026bull;O₂⁻) were systematically investigated using targeted quenchers: p-benzoquinone (BQ, \\u0026bull;O₂⁻ scavenger), tert-butanol (TBA, \\u0026bull;OH scavenger), and disodium ethylenediaminetetraacetate dihydrate (EDTA-2Na, h⁺ scavenger). As depicted in Figure 8a, the degradation efficiency of methylene blue (MB) by ZnFe₂O₄@g-C₃N₄-3 was significantly attenuated in the presence of these inhibitors.\\u003c/p\\u003e\\n\\u003cp\\u003eThe degradation rate declined from 99.99% (pristine system) to 81.12%, 73.11%, and 82.52% upon introduction of BQ, TBA, and EDTA-2Na, respectively, over 40 minutes. The pronounced suppression of activity with TBA (73.11% remaining MB) underscores \\u0026bull;OH as the predominant reactive species, attributable to its potent oxidative capacity. Concurrently, the inhibition by BQ (81.12% residual MB) and EDTA-2Na (82.52% residual MB) confirms the ancillary roles of \\u0026bull;O₂⁻ and h⁺ in the degradation pathway. These findings align with the heterojunction\\u0026rsquo;s electronic structure, which promotes charge separation, enabling h⁺ to directly oxidize MB or react with H₂O to generate \\u0026bull;OH, while \\u0026bull;O₂⁻ forms via oxygen reduction by photogenerated electrons. This study conclusively identifies \\u0026bull;OH as the primary active species, with synergistic contributions from h⁺ and \\u0026bull;O₂⁻, underpinning the composite\\u0026rsquo;s robust photocatalytic performance.\\u003c/p\\u003e\\n\\u003cp\\u003eThe reusability and structural stability of the ZnFe₂O₄@g-C₃N₄-5 catalyst were evaluated through successive degradation cycles under consistent experimental conditions. As illustrated in Figure 8b, the composite retained \\u0026gt;95% of its initial degradation efficiency after ten reuse cycles, demonstrating robust operational durability. The material\\u0026rsquo;s inherent ferromagnetism, derived from ZnFe₂O₄, enabled facile magnetic recovery using an external magnetic field, circumventing secondary pollution risks associated with conventional filtration methods. The marginal efficiency decline is attributed to partial active site deactivation via adsorbed intermediates, rather than structural degradation. These results underscore the catalyst\\u0026rsquo;s viability for sustainable wastewater treatment, balancing high recyclability with minimal performance attenuation.\\u003c/p\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003e\\u003cem\\u003eCatalytic mechanism\\u003c/em\\u003e\\u003c/strong\\u003e\\u003c/p\\u003e\\n\\u003cp\\u003eThe photocatalytic activity of the ZnFe₂O₄@g-C₃N₄ heterostructure arises from its capacity to generate reactive oxygen species (ROS), including photogenerated holes (h⁺), hydroxyl radicals (\\u0026middot;OH), and superoxide anions (\\u0026middot;O₂⁻), under visible light irradiation. Upon photon absorption (h\\u0026nu;), photoexcitation induces charge separation, with electrons (e⁻) transitioning from the valence band (VB) of g-C₃N₄ to its conduction band (CB), leaving h⁺ in the VB (Equation 1, Figure 9). The staggered band alignment between g-C₃N₄ and ZnFe₂O₄ facilitates interfacial electron transfer, whereby e⁻ migrate from g-C₃N₄ to ZnFe₂O₄ (Equation 2, Figure 9). These electrons reduce adsorbed O₂ to yield \\u0026middot;O₂⁻, while h⁺ in the VB of g-C₃N₄ oxidize H₂O or surface hydroxyl groups to produce \\u0026middot;OH. Concurrently, \\u0026middot;O₂⁻ undergoes protonation to form hydroperoxyl radicals (\\u0026middot;OOH), which further react with e⁻ to generate H₂O₂ (Equation 3, Figure 9). The Fenton-like decomposition of H₂O₂, catalyzed by Fe\\u0026sup2;⁺/Fe\\u0026sup3;⁺ redox pairs in ZnFe₂O₄, liberates additional \\u0026middot;OH (Equation 4, Figure 9). This synergistic ROS cascade (\\u0026middot;OH, \\u0026middot;O₂⁻, h⁺) constitutes a mixed oxidative system capable of degrading methylene blue (MB) via demethylation, aromatic ring cleavage, and mineralization into CO₂, H₂O, and inorganic ions (NH₄⁺/NO₃⁻) (Equation 5, Figure 9).\\u003c/p\\u003e\\n\\u003cp\\u003eThe mesoporous architecture of g-C₃N₄ enhances MB adsorption, concentrating dye molecules near active sites, while the heterojunction\\u0026rsquo;s charge separation efficiency minimizes e⁻\\u0026ndash;h⁺ recombination. This dual function\\u0026mdash;adsorption enrichment and ROS generation\\u0026mdash;ensures rapid degradation kinetics and complete pollutant mineralization, underscoring the composite\\u0026rsquo;s efficacy as a sustainable photocatalyst for environmental remediation.\\u003c/p\\u003e\"},{\"header\":\"Conclusion\",\"content\":\"\\u003cp\\u003eThe ZnFe₂O₄@g-C₃N₄ heterostructure, synthesized via hydrothermal integration of ZnFe₂O₄ nanoparticles onto mesoporous g-C₃N₄, demonstrates exceptional visible-light-driven photocatalytic degradation of methylene blue (MB), achieving 99.99% decolorization within 40 min at an optimal ZnFe₂O₄ loading of 59.1 wt%. Structural analyses (XRD, TEM, SEM) confirmed a well-defined heterojunction with uniform ZnFe₂O₄ dispersion, enhancing charge separation and reactive oxygen species (ROS) generation through hierarchical porosity and broad light absorption. Radical scavenging experiments identified hydroxyl radicals (\\u0026bull;OH) as dominant oxidative species, supported by superoxide anions (\\u0026bull;O₂⁻) and holes (h⁺), with H₂O₂ addition accelerating degradation via a photo-Fenton mechanism. The composite\\u0026rsquo;s magnetic ZnFe₂O₄ enabled facile recovery, retaining \\u0026gt;95% activity over ten cycles due to structural durability, with minimal efficiency loss from intermediate adsorption. However, while UV-Vis spectroscopy tracks chromophore degradation, it cannot confirm complete mineralization (CO₂/H₂O conversion) or detect non-absorbing intermediates (e.g., aromatic fragments). Advanced techniques\\u0026mdash;total organic carbon (TOC) analysis and HPLC-MS\\u0026mdash;are essential to quantify mineralization and identify byproducts. Prior studies on analogous systems (Refs. 19\\u0026ndash;22) reported TOC removal, suggesting significant mineralization potential, though direct validation is critical. This work establishes ZnFe₂O₄@g-C₃N₄ as a durable, recyclable photocatalyst for wastewater treatment, with scalable synthesis addressing pollutant degradation and catalyst reuse challenges. Future research should integrate TOC/HPLC-MS analyses and extend applications to diverse contaminants, advancing sustainable water purification technologies.\\u003c/p\\u003e\"},{\"header\":\"Declarations\",\"content\":\"\\u003ch2\\u003eDeclaration of competing interest\\u003c/h2\\u003e\\n\\u003cp\\u003eThe authors declare that they have no known competing for financial interest or personal relationships that could have appeared to influence the work reported in this paper.\\u003c/p\\u003e\\n\\u003ch2\\u003eAuthor statement\\u003c/h2\\u003e\\n\\u003cp\\u003e\\u003cstrong\\u003eJianhua Wang as corresponding authors:\\u0026nbsp;\\u003c/strong\\u003eConceptualization, Methodology, Software, Data curation, Writing- Original draft preparation, Validation, Writing- Reviewing and Editing, Funding acquisition.\\u003c/p\\u003e\\n\\u003ch2\\u003eFunding\\u003c/h2\\u003e\\n\\u003cp\\u003eThis project was founded by the Liaoning Natural Science Foundation [Nos.2020-Ms-306].\\u003c/p\\u003e\\n\\u003ch2\\u003eAuthor Contribution\\u003c/h2\\u003e\\n\\u003cp\\u003eLeyan LI-article writing, chart output, grammar correction；Jianhua Wang-material synthesis, article writing, chart output, grammar correction, etc. Huihui FANG-Material preparation, degradation experiments, grammar correction, etc.\\u003c/p\\u003e\"},{\"header\":\"References\",\"content\":\"\\u003col\\u003e\\n\\u003cli\\u003eJiang X, Wang Z, Zhang M, Wang M,Wu R, Shi X, Luo B, Zhang D, Pu X，Li H (2022) A novel direct Z-scheme heterojunction BiFeO\\u003csub\\u003e3\\u003c/sub\\u003e/ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e photocatalyst for enhanced photocatalyst degradation activity under visible light irradiation 912:165185 \\u003c/li\\u003e\\n\\u003cli\\u003eGe, Y., Wang, Z., Yi, M., Ran, L. P. Fabrication and magnetic transformation from paramagnetic to ferrimagnetic of ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e hollow spheres, \\u003cem\\u003eTrans. Nonferrous Met. Soc. China,\\u003c/em\\u003e 2019, vol.29, pp.1503\\u0026minus;1509. https://doi.org/10.1016/S1003-6326(19)65057-0 \\u003c/li\\u003e\\n\\u003cli\\u003eWang, M., Sun, L., Cai, J., Huang, P.，Su, Y.，Lin, C. A facile hydrothermal deposition of ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4 \\u003c/sub\\u003enanoparticles on TiO\\u003csub\\u003e2\\u003c/sub\\u003e nanotube arrays for enhanced visible light photocatalytic activity, \\u003cem\\u003eJournal of Materials Chemistry A\\u003c/em\\u003e, 2013, vol.1 (39), pp.12082-12087. https://doi.org/10.1039/C3TA12577G\\u003c/li\\u003e\\n\\u003cli\\u003eZhao, W., Liang, C., Wang, B., Xin, S. Enhanced photocatalytic and fenton-like performance of CuOx-decorated ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e, \\u003cem\\u003eACS Applied Materials \\u0026amp; Interfaces\\u003c/em\\u003e, 2017, vol.9(48), pp.41927-41936. https://doi.org/10.1021/acsami. 7b14799\\u003c/li\\u003e\\n\\u003cli\\u003eZhang, Z.L., Wan, M., Mao, Y.L., Enhanced photovoltaic effect of TiO\\u003csub\\u003e2\\u003c/sub\\u003e-based composite ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e/TiO\\u003csub\\u003e2\\u003c/sub\\u003e, \\u003cem\\u003eJournal of Photochemistry and Photobiology A: Chemistry,\\u003c/em\\u003e 2012, vol.233, pp.15\\u0026ndash;19. https://doi.org/10.1016/j.jphotochem.2012.02.009\\u003c/li\\u003e\\n\\u003cli\\u003eWang, X., Li, Y., Zhang, X., Li, J.，Luo, Y.，Wang, C. 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Facile microwave-assisted green synthesis of Ag-ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@rGO nanocomposites for efficient removal of organic dyes under UV- and visible-light irradiation[J]. \\u003cem\\u003eJournal of Physics and Chemistry of Solids,\\u003c/em\\u003e 2014, vol.75,pp.441\\u0026ndash;446. http://dx.doi.org/ doi:10.1016/j.apcatb.2016.10.033\\u003c/li\\u003e\\n\\u003cli\\u003eYao, Y., Cai, Y., Lu, F., Qin, J.; Wei, F.; Xu, C.; Wang, S. Magnetic ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e\\u0026minus;C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e Hybrid for photocatalytic Degradation of Aqueous Organic Pollutants by Visible Light, \\u003cem\\u003eInd. Eng. Chem. Res,\\u003c/em\\u003e2014, vol.53, pp.17294\\u0026minus;17302. \\u003cu\\u003ehttps://pubs.acs. org/doi/pdf/10.1021/ie503437z\\u003c/u\\u003e\\u003c/li\\u003e\\n\\u003cli\\u003eYang, D., Cai X., Zhang, J., Ding, B.，Qiang, Y., Preparation of 0D/2D ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e/Fe-doped g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e hybrid photocatalysts for visible light N\\u003csub\\u003e2\\u003c/sub\\u003e fixation, \\u003cem\\u003eJournal of Alloys and Compounds,\\u003c/em\\u003e 2021, vol.869, pp. 158809. https://doi. org/10.1016/j.jallcom.2021.158809 \\u003c/li\\u003e\\n\\u003cli\\u003eWang, J., Zhang, W., Oxidative degradation of methylene blue by Ag\\u003csub\\u003e2\\u003c/sub\\u003eO@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e photocatalysts under visible light, T\\u003cem\\u003eoxicological \\u0026amp; Environmental Chemistry\\u003c/em\\u003e, 2023, vol.105, pp.60-74. https://doi.org/10.1080/02772248.2023.2211700.\\u003c/li\\u003e\\n\\u003cli\\u003eWang, J., Construction of ternary heterostructured Ag/Ag\\u003csub\\u003e2\\u003c/sub\\u003eO@ZnO@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e nanocomposite as an widened visible light photocatalyst for the organic oxidation, \\u003cem\\u003eJournal of Physics and Chemistry of Solids,\\u003c/em\\u003e 2023, vol.180, pp.111389 . https://doi.org/10.1016/j.jpcs.2023.111389.\\u003c/li\\u003e\\n\\u003cli\\u003eYang, N., Hu, P., Chen, C., Wang, Y.，Pan, L., Ternary Composite of g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e/ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e/Fe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e3\\u003c/sub\\u003e: Hydrothermal Synthesis and Enhanced Photocatalytic Performance, \\u003cem\\u003eChemistrySelect, \\u003c/em\\u003e2019, vol.\\u003cem\\u003e4\\u003c/em\\u003e, pp.7308 \\u0026ndash;7316. https: //doi.org/10.1002/slct.201901543\\u003c/li\\u003e\\n\\u003cli\\u003eBorthakur, S., Saikia, L., ZnFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e nanocomposites: An efficient catalyst for Fenton-like photodegradation of environmentally pollutant Rhodamine B, \\u003cem\\u003eJournal of Environmental Chemical Engineering,\\u003c/em\\u003e 2019,vol.7 , pp.103035. https://doi.org/10.1016/j.jece.2019.103035\\u003c/li\\u003e\\n\\u003cli\\u003eMeng, Y., Zhang, L., Jiu, H., Zhang, H., Zhang, Q., Ren, Hong., Sun, W., Li, Yu., Dan, T., Construction of g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e/ZIF-67 photocatalyst with enhanced photocatalytic CO\\u003csub\\u003e2\\u003c/sub\\u003e reduction activity, \\u003cem\\u003eMaterials Science in Semiconductor Processing,\\u003c/em\\u003e 2019, vol.95, pp.35\\u0026ndash;41. https://doi.org/10.1016/j.mssp.2019.02.010\\u003c/li\\u003e\\n\\u003cli\\u003eLu, T., Zhao H., Jian, L., Ji, R.，Pan, C.，Wang, G.，Dong, Y.，Zhu, Y ., Photocatalysis-self-Fenton system over edge covalently modified g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e with high mineralization of persistent organic pollutants, \\u003cem\\u003eEnvironmental ResearchVolume,\\u003c/em\\u003e 2023, vol.222, pp.115361. https://doi.org/10.1016/j.envres.2023.115361 \\u003c/li\\u003e\\n\\u003cli\\u003eTang, J., Wang, J., Tang, L., Feng, C., Zhu, X., Yi, Y., Feng, H., Yu, J., Ren, X., Preparation of floating porous g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e photocatalyst via a facile one-pot method for efficient photocatalytic elimination of tetracycline under visible light irradiation, \\u003cem\\u003eChemical Engineering Journal,\\u003c/em\\u003e 2022, vol.430,pp.132669. https://doi.org/10.1016/j.cej.2021.132669 \\u003c/li\\u003e\\n\\u003cli\\u003eShi, Lei., Zhang, J., Liu, H., Que, M.，Cai, X.，Tan, S.，Huang, L ., Flower-like Ni(OH)\\u003csub\\u003e2\\u003c/sub\\u003e hybridized g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e for high-performance supercapacitor electrode material, Materials Letters, 2015, vol.145, pp. 150-153. https://doi.org/ 10.1016/j.matlet.2015.01.083\\u003c/li\\u003e\\n\\u003cli\\u003eZhang, X., Sun, C., Li, R., Jin, X.，Wu, Y.，Fu, F., Dual-Loading of Fe\\u003csub\\u003e3\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e and Pd Nanoparticles on g‑C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e Nanosheets Toward a Magnetic Nanoplatform with Enhanced Peroxidase-like Activity for Loading Various Enzymes for Visual Detection of Small Molecules, \\u003cem\\u003eAnal. Chem, \\u003c/em\\u003e2023, vol.95, pp.5024\\u0026minus;5033. https://doi.org/ 10.1021/acs.analchem.2c05503\\u003c/li\\u003e\\n\\u003cli\\u003eZhong, Q., Lan, H., Zhang, M., Zhu, H., Bu, M., Preparation of heterostructure g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e/ZnO nanorods for high photocatalytic activity on different pollutants (MB, RhB, Cr(VI) and eosin),Ceramics International, 2020, Vol. 46, pp. 12192-12199. https://doi.org/10.1016/j.ceramint.2020.01.265\\u003c/li\\u003e\\n\\u003cli\\u003eVijayan, M., Easwaran, G., Sivakumar, K., Palanisamy, G., Bhuvaneswari, K., Energetic two-dimensional g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e nanosheets combined with ZnO nanoparticles as effectual catalyst for degradation of MB dye under UV\\u0026ndash;Visible-light Irradiation, J Mater Sci: Mater Electron, 2022 Vol. 33 pp. 24340\\u0026ndash;24353. https://doi.org/ 10.1007/s10854-022-09153-1\\u003c/li\\u003e\\n\\u003cli\\u003eGao, M., Feng, J., He, F., Zeng, W., Wang, X., Ren, Y., Wei, T., Carbon microspheres work as an electron bridge for degrading high concentration MB in CoFe\\u003csub\\u003e2\\u003c/sub\\u003eO\\u003csub\\u003e4\\u003c/sub\\u003e@carbon microsphere/g-C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e with a hierarchical sandwich-structure, Applied Surface Science, 2020, Vol.507, pp.145167. https://doi.org/ 10.1016/j.apsusc.2019.145167\\u003c/li\\u003e\\n\\u003cli\\u003eSun, S., Li, S., Hao, Y., Yang, X., Dou, X., Construction of g/C\\u003csub\\u003e3\\u003c/sub\\u003eN\\u003csub\\u003e4\\u003c/sub\\u003e-ZnO composites with enhanced visible-light photocatalytic activity for degradation of amoxicillin,Korean J. Chem. Eng., 2022, Vol.39, pp.3377-3388. https://doi.org/10.1007/s11814-022-1181-5\\u003c/li\\u003e\\n\\u003c/ol\\u003e\"},{\"header\":\"Tables\",\"content\":\"\\u003cp\\u003eTable 1 and 2 are available in the Supplementary Files section.\\u003c/p\\u003e\"}],\"fulltextSource\":\"\",\"fullText\":\"\",\"funders\":[],\"hasAdminPriorityOnWorkflow\":false,\"hasManuscriptDocX\":true,\"hasOptedInToPreprint\":true,\"hasPassedJournalQc\":\"\",\"hasAnyPriority\":true,\"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\":\"info@researchsquare.com\",\"identity\":\"scientific-reports\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"scirep\",\"sideBox\":\"Learn more about [Scientific Reports](http://www.nature.com/srep/)\",\"snPcode\":\"\",\"submissionUrl\":\"\",\"title\":\"Scientific Reports\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"Scientific Reports\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true},\"keywords\":\"Photo-Fenton, Heterojunction, ZnFe2O4@g-C3N4, g-C3N4, Methlene blue\",\"lastPublishedDoi\":\"10.21203/rs.3.rs-6391826/v1\",\"lastPublishedDoiUrl\":\"https://doi.org/10.21203/rs.3.rs-6391826/v1\",\"license\":{\"name\":\"CC BY 4.0\",\"url\":\"https://creativecommons.org/licenses/by/4.0/\"},\"manuscriptAbstract\":\"\\u003cp\\u003eA magnetically recoverable ZnFe₂O₄@g-C₃N₄ heterostructure was synthesized by anchoring ZnFe₂O₄ nanoparticles onto a mesoporous g-C₃N₄ framework. The composite was systematically characterized via XRD, SEM, TEM, and UV-Vis spectroscopy, confirming the successful formation of a porous multilayer structure with uniformly dispersed ZnFe₂O₄ nanoparticles on g-C₃N₄. BET analysis validated the mesoporous architecture, while TEM revealed an intimate heterojunction interface between ZnFe₂O₄ and g-C₃N₄, crucial for efficient charge carrier separation. The composite demonstrated exceptional photocatalytic activity under visible light, achieving complete degradation of methylene blue (MB) via synergistic effects of enhanced light absorption, interfacial charge transfer, and high surface area. Notably, the magnetic ZnFe₂O₄ component enabled facile recovery and reuse of the catalyst using external magnetic fields, with retained catalytic efficiency over multiple cycles. This work highlights the ZnFe₂O₄@g-C₃N₄ heterojunction as a durable, recyclable photocatalyst with significant potential for sustainable environmental remediation applications.\\u003c/p\\u003e\",\"manuscriptTitle\":\"Fabrication of ZnFe2O4@g-C3N4 for Enhanced Photo-Fenton Effect and Visible Light-Driven Organic Dye Degradation\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2025-04-08 05:04:27\",\"doi\":\"10.21203/rs.3.rs-6391826/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0},{\"type\":\"decision\",\"content\":\"Revision requested\",\"date\":\"2025-04-09T19:01:10+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"editorAssigned\",\"content\":\"\",\"date\":\"2025-04-07T14:51:16+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"checksComplete\",\"content\":\"\",\"date\":\"2025-04-07T14:49:13+00:00\",\"index\":\"\",\"fulltext\":\"\"},{\"type\":\"submitted\",\"content\":\"Scientific Reports\",\"date\":\"2025-04-07T08:11:45+00:00\",\"index\":\"\",\"fulltext\":\"\"}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"scientific-reports\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":false,\"externalIdentity\":\"scirep\",\"sideBox\":\"Learn more about [Scientific Reports](http://www.nature.com/srep/)\",\"snPcode\":\"\",\"submissionUrl\":\"\",\"title\":\"Scientific Reports\",\"twitterHandle\":\"\",\"acdcEnabled\":true,\"dfaEnabled\":true,\"editorialSystem\":\"stoa\",\"reportingPortfolio\":\"Scientific Reports\",\"inReviewEnabled\":true,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"6a74a2a7-216e-4ab4-98df-963cf6ccef68\",\"owner\":[],\"postedDate\":\"April 8th, 2025\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"published-in-journal\",\"subjectAreas\":[{\"id\":46825209,\"name\":\"Earth and environmental sciences/Environmental sciences\"},{\"id\":46825210,\"name\":\"Physical sciences/Materials science\"}],\"tags\":[],\"updatedAt\":\"2025-07-07T16:04:22+00:00\",\"versionOfRecord\":{\"articleIdentity\":\"rs-6391826\",\"link\":\"https://doi.org/10.1038/s41598-025-05096-9\",\"journal\":{\"identity\":\"scientific-reports\",\"isVorOnly\":false,\"title\":\"Scientific Reports\"},\"publishedOn\":\"2025-07-01 15:57:55\",\"publishedOnDateReadable\":\"July 1st, 2025\"},\"versionCreatedAt\":\"2025-04-08 05:04:27\",\"video\":\"\",\"vorDoi\":\"10.1038/s41598-025-05096-9\",\"vorDoiUrl\":\"https://doi.org/10.1038/s41598-025-05096-9\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-6391826\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-6391826\",\"identity\":\"rs-6391826\",\"version\":[\"v1\"]},\"buildId\":\"XKTyCvWXoU3ODBz1xrDgd\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}