Construction of triazine-based COF/Zr-based MOF S-scheme heterojunctions for efficient photocatalytic H2O2 production under simulated sunlight irradiation

Construction of triazine-based COF/Zr-based MOF S-scheme heterojunctions for efficient photocatalytic H2O2 production under simulated sunlight irradiation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Construction of triazine-based COF/Zr-based MOF S-scheme heterojunctions for efficient photocatalytic H 2 O 2 production under simulated sunlight irradiation Lisong Chen, Yunchao Zhang, Yan Yan, Jinhui Jiang, Rongfeng Guan, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8762228/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 21 Apr, 2026 Read the published version in Research on Chemical Intermediates → Version 1 posted 9 You are reading this latest preprint version Abstract The anthraquinone method for commercial hydrogen peroxide (H 2 O 2 ) synthesis is plagued by organic pollution and elevated prices, necessitating the advancement of eco-friendly photocatalytic alternatives. Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) exhibit potential; yet, they are constrained by inferior charge separation and limited light absorption. Considering triazine-based TFPT-Pa(CH 3 ) 2 -COF has a distinctive Schiff structure and amino-containing Zr-based MOF (e.g., NH 2 -UiO-66) has superior visible light absorption and stability, covalently integrated TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 COF/MOF heterojunctions were synthesized by solvothermal methods, and photocatalytic H 2 O 2 production experiments were conducted. The results show that optimum TNU-2 (mass ratio 1:0.5) exhibits a significant H 2 O 2 generation rate of 0.19 mmol g -1 h -1 , which is 3.8-fold and 2.4-fold higher than that of pure TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, respectively. Furthermore, TNU-2 demonstrates its remarkable cycle stability after five cycles. The constructed COF/MOF S-scheme heterojunction, which creates an internal electric field to promote charge separation, prevent recombination, and preserve strong redox capabilities, is responsible for the enhanced performance. This work offers a novel method for building efficient COF/MOF-based photocatalysts for the production of H 2 O 2 . Photocatalytic H2O2 production S-scheme heterojunction Triazine-based COF Zr-based MOF Charge separation Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Introduction The industrial manufacture of hydrogen peroxide (H 2 O 2 ) mostly utilizes the anthraquinone method. This process, however, presents hazards of organic contamination and entails substantial storage and transportation expenses, hence prompting the formulation of more ecologically friendly preparation pathways. H 2 O 2 is widely used in antimicrobial treatment, sanitation disinfection, and environmental cleanup owing to its robust oxidative stability [1]. Photocatalytic technology has recently emerged as a promising solution to environmental degradation and energy deficits by turning solar energy into clean chemical energy [2]. Photocatalytic H 2 O 2 synthesis has attracted considerable interest owing to its clean and efficient benefits, facilitating the conversion and production of H 2 O 2 by solar energy [3, 4]. Prior research has shown that covalent organic frameworks (COFs), noted for their high crystallinity, porosity, remarkable stability, adjustable chemical structures, and semiconductor characteristics, are crucial in the photocatalytic creation of H 2 O 2 [5, 6]. Nonetheless, the actual implementation of COFs encounters obstacles like sluggish charge transport kinetics, recombination of photogenerated carriers, and restricted processability [7, 8]. These characteristics limit their total photocatalytic efficiency and large-scale use. Consequently, the creation of highly effective photocatalytic COF-based heterojunctions for H 2 O 2 generation to realize synergistic "1 + 1 > 2" effects continues to pose a substantial challenge. Combining COFs with inorganic semiconductors that have appropriate band structures to create heterojunctions is regarded as a viable strategy to augment photocatalytic activity. In contrast to traditional II-type or Z-scheme heterojunctions [9], the recently discovered S-scheme heterojunction photocatalysts exhibit remarkable efficacy by integrating oxidizing and reducing photocatalysts to create an inherent electric field at the interface [10-19]. This electric field effectively promotes charge separation and migration, significantly increasing the reaction rate of H 2 O 2 generation. This structure effectively segregates high-energy electron-hole pairs while preserving robust redox properties, markedly reducing carrier recombination and augmenting photocatalytic performance. This process involves the photoelectron reduction of O 2 molecules, using H 2 O to provide protons. Consequently, it is essential to construct S-scheme heterojunctions exhibiting robust redox properties and elevated charge separation efficiency [20-23]. Conversely, owing to their highly organized structures, extensive specific surface areas, and adjustable pore and topological characteristics, metal-organic frameworks (MOFs) show great potential in photocatalytic H 2 O 2 generation [24, 25]. However, there are few reports available on the pure MOFs for photocatalytic H 2 O 2 generation, Nevertheless, there are limited reports on pure metal-organic frameworks (MOFs) for photocatalytic hydrogen peroxide production, mostly due to intrinsic constraints such as their restricted light absorption spectrum and inadequate charge separation efficiency [26, 27]. In comparison to other MOFs, amino-containing Zr-based MOF (e.g., NH 2 -UiO-66) has superior visible light absorption and stability [28, 29]. Combining COFs with MOFs is a viable strategy to augment photocatalytic activity. Such combinations may demonstrate distinctive qualities that individual components cannot achieve. Recent research has focused on the amalgamation of MOFs with COFs to produce COF-MOF hybrid materials [30]. These hybrids inherit the elevated porosity and structural organization of their progenitor materials while also improving light absorption, facilitating charge separation, and producing many catalytically active sites via intercomponent synergistic interactions [31]. Current research on COF-based heterojunction photocatalysts for H 2 O 2 generation mostly focuses on COF/inorganic material systems, with inadequate investigation into COF/MOF heterojunctions. Research on triazine-based COF/MOF heterojunctions is notably limited. Theoretically, meticulously engineered interfaces and covalent bonding methodologies may create stable, high-performance COF/MOF heterojunctions to synergistically improve photocatalytic efficacy. In S-scheme heterojunction configurations, the alignment of bandgaps between COFs and MOFs facilitates spatially directed charge transfer. This method preserves robust redox potentials while efficiently inhibiting hole recombination, markedly enhancing photocatalytic H 2 O 2 generation efficiency. This work developed covalently integrated COF/MOF heterojunctions, which exhibited a photocatalytic H 2 O 2 generation rate that was much more excellent than that of individual COF and MOF materials. Triazine TFPT-Pa(CH 3 ) 2 -COF was chosen as the framework for heterojunction fabrication due to its distinctive Schiff base triazine COF structure. Composites with different ratios of TFPT-Pa(CH 3 ) 2 to NH 2 -UiO-66 were effectively synthesized by including NH 2 -UiO-66 into the TFPT-Pa(CH 3 ) 2 production method. A series of heterojunctions exhibiting remarkable visible-light-driven photocatalytic H 2 O 2 production was produced by the congruent energy levels of triazine TFPT-Pa(CH 3 ) 2 -COF and NH 2 -UiO-66. The peak efficiency of these heterojunctions is 0.19 mmol g -1 h -1 , approximately 3.8 times higher than that of the original TFPT-Pa(CH 3 ) 2 . This research offers a guiding framework for the future advancement of diverse COF/MOF-based photocatalysts for H 2 O 2 synthesis. Experimental Preparation of NH 2 -UiO-66 The synthesis for NH 2 -UiO-66 is derived from previous reports with some alterations to the original protocol [32]. A standard experimental procedure is as follows: 0.2332 g of ZrCl 4 and 0.1812 g of 2-Aminoterephthalic Acid (H 2 ATA) were dissolved in 50 mL of N,N-dimethylformamide (DMF). Subsequently, 6 mL of acetic acid was added, and the mixture was transferred to a 100 mL stainless steel autoclave lined with Polytetrafluoroethylene (PTFE). Subsequent to sealing the reactor, it was subjected to heating at 120 °C for 24 h under autoclave pressure. Subsequent to natural cooling, the resultant sample was centrifuged and extensively washed with anhydrous methanol to eliminate residual DMF. The resulting light yellow solid was subjected to vacuum drying at 120 °C for 12 h. Synthesis of TFPT-Pa(CH 3 ) 2 -COF After combining 1,3,5-tris(4-formylphenyl)triazine (TFPT, 32.1 mg, 0.08 mmol) and 2,5-dimethyl-1,4-benzenediamine (Pa-(CH 3 ) 2 , 16.85 mg, 0.12 mmol) with o-dichlorobenzene (0.4 mL) and N-butanol (3.6 mL), the mixture was ultrasonicated for two minutes. After adding 0.4 mL of 3 M acetic acid, the mixture was ultrasonically agitated for one minute. The mixture was degassed three times. Over the course of three days, the sealed mixture was heated at 120 °C. Following centrifugation, the yellow powder was washed with 3 × 5 mL of acetone and 3 × 5 mL of tetrahydrofuran. TFPT-Pa(CH 3 ) 2 -COF was produced with 85% efficiency after the solid was recovered and vacuum-dried at 120 °C. Synthesis of TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 Heterojunction The pre-synthesised NH 2 -UiO-66, Pa-(CH 3 ) 2 (16.85 mg, 0.12 mmol), and TFPT (32.1 mg, 0.08 mmol). N-butanol (3.6 mL) and ortho-dichlorobenzene (0.4 mL) were mixed and sonicated for two minutes. After adding 0.4 mL of 3 M acetic acid, the mixture was sonicated for one minute. Three rounds of degassing were performed on the mixture. Over the course of three days, the sealed mixture was heated at 120 °C. Following centrifugation, the yellow powder was washed with 3 × 5 mL of acetone and 3 × 5 mL of tetrahydrofuran. After vacuum-drying the resultant solid at 120 °C, TFPT-Pa(CH 3 ) 2 was produced with 85% efficiency. By modifying the mass ratio between the fixed component TFPT-Pa(CH 3 ) 2 (designated as “1”) and the variable component NH 2 -UiO-66, heterojunction materials TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 (1:0.25) were synthesized and labeled TNU-1, TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 (1:0.5) as TNU-2, and TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 (1:0.75) as TNU-3. Materials characterization The crystal structure was determined by powder X-ray diffraction (XRD, Panalytical X'Pert3 Powder). The Nicolet NEXUS670 was used to acquire Fourier transform infrared (FT-IR) spectra. To evaluate permanent porosity, N 2 adsorption-desorption tests at 77 K were constantly monitored using a Micromeritics ASAP 2020 analyzer. A transmission electron microscope (TEM, JEOL JEM-2100F) equipped with scanning transmission electron microscopy (STEM) was used to analyze the morphology. X-ray photoelectron spectroscopy (XPS) at 1486.6 eV Al-Kα radiation with a spot size of 500 μm was recorded using a Thermo Fisher Scientific ESCALAB 250Xi. The binding energy was calibrated at C 1s at 284.8 eV. BaSO 4 as the reference material, diffuse reflectance spectroscopy (DRS) in the ultraviolet-visible range was recorded using a Shimadzu UV-3600 spectrophotometer. For photo-electrochemistry testing, the standard three-electrode setup consisted of a proprietary platinum plate with a counter electrode, 0.5 mol L -1 Na 2 SO 4 solution as the electrolyte, an Ag/AgCl (saturated KCl) electrode as the reference electrode, and an indium tin oxide (ITO) coating with the photocatalyst as the working electrode. Using a CHI 660E electrochemical workstation, Mott-Schottky plots, photocurrent-time (I-t) responses, and electrochemical impedance spectroscopy (EIS) were produced. Photoluminescence (PL) spectra were measured using a fluorescence spectrometer (FLS980, Edinburgh, UK) with an excitation source set at 350 nm. Photocatalytic H 2 O 2 evolution test The technique outlined in the literature was followed in the photocatalytic H 2 O 2 evolution reaction experiment [33]. The following are specific steps: After adding 10 mg of the photocatalyst into 50 mL of deionized water and uniformly disperse it with ultrasonication for 10 min. With the flask neck open, transfer the resultant mixture to a reaction flask and stir in an oxygenated environment. To reach adsorption-desorption equilibrium with the surrounding air, stir in the dark for 30 min. At 25 ± 1 °C, a 300 W xenon lamp (CEL-HXUV300) was used to irradiate the flask as it is magnetically stirred. Using a 0.22 μm filter membrane, separate liquids from solids and take samples every 15 min. Iodometric titration was used to measure the H 2 O 2 content in the residual liquid, and a standard curve was used to compute the H 2 O 2 production. The details of the iodometric titration and the standard fitting curves of H 2 O 2 (Fig. S1) are shown in the Supplementary Material. The total amount of H 2 O 2 produced in a single hour was used to compute the average photocatalytic H 2 O 2 production rate. Five cycles of photocatalytic H 2 O 2 generation studies, each lasting one hour and carried out under identical circumstances, were carried out to evaluate photocatalyst stability. In addition, the measurement and calculation of apparent quantum efficiency (AQE) were shown in the Supplementary Material. Results and discussion Synthetic strategy and microstructural feature The TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction was synthesized using a solvothermal technique, as shown in Scheme 1. Initially, pure NH 2 -UiO-66 powder was synthesized in an oven by a solvothermal method. Subsequently, the synthesized NH 2 -UiO-66 and TFPT-Pa(CH 3 ) 2 precursors (comprising TFPT, Pa-(CH 3 ) 2 , o-dichlorobenzene, N-butanol, and acetic acid) were transferred to a heat-resistant glass tube. Ultrasonic treatment produced a homogeneously distributed slurry, which was then exposed to liquid nitrogen degassing. The combination was ultimately subjected to heat at 120 °C for a duration of 3 days in an oil bath. The TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction was obtained after washing and vacuum drying. The NH 2 -UiO-66 powder has a light yellow, but the TFPT-Pa(CH 3 ) 2 , TNU-1, TNU-2, and TNU-3 powders have a yellow coloration, as seen in Fig. S2. The phase composition of the produced samples was ascertained using X-ray diffraction (as seen in Fig. 1a). Diffraction peaks at 7.24°, 8.39°, and 25.71° correspond to the (111), (002), and (006) crystal planes in NH 2 -UiO-66, respectively [34]. Two diffraction peaks were detected in the TFPT-Pa(CH 3 ) 2 sample at 2.76° and 4.78°, attributed to the (010) and (011) crystal planes, respectively. The XRD patterns of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunctions exhibit an increase in peak intensity corresponding to NH 2 -UiO-66 as the concentration of NH 2 -UiO-66 rises. Fig. 1b illustrates that the peaks at 665, 1384, and 1576 cm -1 are attributed to the stretching vibrations of the Zr–O bond, C–O bond, and C=O bond in the NH 2 -UiO-66 sample, respectively [35]. FT-IR spectra of both TFPT-Pa(CH 3 ) 2 and the TNU-2 display a distinctive signal for the imine (C=N) bond at approximately 1624 cm -1 , while the peaks corresponding to C=O and N–H from the TFPT and Pa-(CH 3 ) 2 are nearly nonexistent, signifying the successful synthesis of TFPT-Pa(CH 3 ) 2 -COF through a Schiff base reaction [36, 37]. Additionally, the peaks associated with Zr–O, C–O, and C=O stretching vibrations were detected in the TNU-2 sample, indicating the existence of NH 2 -UiO-66 and further validating the synthesis of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction. The nitrogen adsorption-desorption isotherms and associated pore size distribution curves for TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and TNU-2 are shown in Fig. 2a. The adsorption isotherms of TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66 are categorized as H3 type. Additionally, as indicated in Table S1, the Brunauer-Emmett-Teller (BET) specific surface areas of TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and TNU-2 are 794.67, 788.82, and 467.07 m 2 g -1 , respectively. The pore size distribution of TNU-2 predominantly centers about 2.4 nm, aligning with the mesoporous structure of TFPT-Pa(CH 3 ) 2 (Fig. 2b). The BET-specific surface area was shown to be effectively improved by mixing TFPT-Pa(CH 3 ) 2 with NH 2 -UiO-66, which may result in more reactive sites. The enhanced dispersity of TFPT-Pa(CH 3 ) 2 onto the NH 2 -UiO-66 surfaces during the in situ synthesis process may have prevented the agglomeration of NH 2 -UiO-66 particles, which might account for the significantly increased specific surface area of TNU-2. XPS analyses clarified the chemical states and composition of the photocatalyst surface. Fig. 2c illustrates the photoelectron spectra of TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and the TNU-2 heterojunction. The results demonstrate that TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 presents no supplementary impurity peaks, comprising carbon, nitrogen, oxygen, and zirconium constituents. The C 1s spectra in Fig. 2d display peaks at about 284.8, 286.5, and 288.8 eV for all three materials, representing C–C/C=C, C=N/C–N, and C–O bonds, respectively [36, 38-40]. The N 1s spectra of TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and TNU-2 exhibit peaks at 398.7 eV, 399.4 eV, and 400.5 eV, in addition to a peak in the 402.0–404.0 eV range (Fig. 2e), corresponding to C=N, C–N, N–H, and π–π* satellite peaks, respectively [38]. The peaks at 183.1 eV and 185.5 eV in the Zr 3d spectrum (Fig. 2f) correspond to the Zr 3d 5/2 and Zr 3d 3/2 transitions, respectively. In comparison to NH 2 -UiO-66, the binding energies of the Zr 3d peaks in TNU-2 exhibit a shift toward lower energies. The binding energies of Zr 3d 5/2 and Zr 3d 3/2 diminished by 0.05 and 0.01 eV, respectively [40, 41]. The results demonstrate that NH 2 -UiO-66 acquires free electrons in the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterostructure relative to pure NH 2 -UiO-66. Simultaneously, the C 1s binding energy in TNU-2 displays a negative shift relative to pure TFPT-Pa(CH 3 ) 2 , signifying an electron capture phenomenon in TFPT-Pa(CH 3 ) 2 [39, 40]. Consequently, Changes in the binding energy of the above elements indicate a reallocation of free electrons between TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66. The N 1s peak positions in the TNU-2 spectrum are 132.1 and 133.7 eV, while the Zr 3d peak binding energy in the TNU-2 heterostructure changes to higher energies, suggesting a reduction in electron density in TFPT-Pa(CH 3 ) 2 . Consequently, the depletion of free electrons in TFPT-Pa(CH 3 ) 2 and the accumulation of free electrons in NH 2 -UiO-66 may generate a robust internal electric field (IEF) at the interface between TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, thereby facilitating carrier diffusion and separation [42]. Fig. 3a–d display TEM images of the TNU-2 heterojunction. NH 2 -UiO-66 has a smooth, normal octahedral form with distinct edges and a diameter of roughly 350 nm, whereas TFPT-Pa(CH 3 ) 2 demonstrates a diminutive, slender, and uneven plate-like morphology. It demonstrates a strong correlation between TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, signifying the establishment of a TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction. Moreover, STEM and EDS mapping of TNU-2 (Fig. 3e) corroborates the establishment of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction by demonstrating its anticipated elemental composition of C, N, O, and Zr, together with a uniform distribution. Fig. 4a illustrates the comparative photocatalytic H 2 O 2 production efficacy of TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunctions at varying mass ratios. TNU-2 demonstrated the most H 2 O 2 production within 60 min. Fig. 4b illustrates the H 2 O 2 production rates of these samples. The rate for TNU-2 attained 0.19 mmol g -1 h -1 , which is 3.8 times and 2.4 times greater than that of TFPT-Pa(CH 3 ) 2 (0.05 mmol g -1 h -1 ) and NH 2 -UiO-66 (0.08 mmol g -1 h -1 ), respectively. The improved H 2 O 2 generation efficacy of TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 is ascribed to the establishment of a heterojunction. In Fig. 4c, the stability of TNU-2 catalyst was characterized by five cycles of photocatalytic H 2 O 2 production experiments. Following five cycles, the XRD diffraction patterns of samples with different ratios are shown in Fig. S3 to evaluate the structural integrity of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction, while the XPS spectra of the TNU-2 after cycling are illustrated in Fig. S4. The results indicated that the diffraction peaks in the XRD spectra before and after cycling exhibited similar shapes, and there was no significant change in the binding energy of the XPS spectra, demonstrating that the synthesized TNU-2 heterojunction possesses exceptional structural stability following photocatalysis. The specifics of AQE measurement and computation are available in the supplementary materials. Fig. 4d displays the AQE values across several wavelengths (420, 450, 500, and 550 nm). Utilizing a 420 nm bandpass filter, TNU-2 attained a peak AQE of 0.83%, aligning with the UV-Vis DRS findings. The wettability of the produced products was assessed to comprehend how the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction enhances photocatalytic activity. The contact angle of TNU-2 (108.04°) is positioned between that of NH 2 -UiO-66 (54.56°) and TFPT-Pa(CH 3 ) 2 (121.35°), as shown in Fig. 4e-g. This suggests that the integration of NH 2 -UiO-66 enhances the hydrophilicity of TFPT-Pa(CH 3 ) 2 , improving its dispersion in aqueous photocatalytic systems and making it easier for reactant molecules like H 2 O. Fig. 5a presents the UV-Vis DRS spectra of the synthesized materials, with TFPT-Pa(CH 3 ) 2 demonstrating a pronounced absorption edge around 500 nm. Upon the establishment of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction, the light absorption spectrum encompasses both UV and visible light areas. Moreover, it is significant that the UV light absorption intensity of the TNU-2 heterojunction is intermediate to that of the individual TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66 materials. The integration of NH 2 -UiO-66 markedly amplifies the optical absorption intensity of TFPT-Pa(CH 3 ) 2 in the ultraviolet spectrum, potentially resulting in an increased generation of photoexcited electrons under simulated sunlight exposure, thus contributing to the photocatalytic H 2 O 2 production reaction of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction. Additionally, the bandgaps ( E g ) of 2.40 eV and 2.89 eV were determined for TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, respectively, utilizing Tauc plots (Fig. 5b). The n-type semiconductor characteristics of TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66 are shown by the positive slopes of their Mott-Schottky curves at different frequencies, as shown in Fig. 5c and d. The flat-band potential ( E fb ) and the energy level of the conduction band minimum (E CBM ) in a typical n-type semiconductor are typically equal [43, 44]. According to predictions, the valence band maximum (E VBM ) energy levels for TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66 are 1.43 V and 2.29 V (vs. NHE), respectively. The photocatalytic synthesis of H 2 O 2 may be categorized into three consecutive phases. Initially, upon light exposure, the photocatalyst assimilates photons. When the energy of the input photon surpasses E g of the photocatalyst, electrons are elevated from the VBM to the CBM [45]. Secondly, the excited electrons and produced holes either move or recombine inside the photocatalyst. Upon excitation, both electrons and holes migrate to the photocatalytic interface, enabling concurrent reduction and oxidation reactions [46]. The synthesis of H 2 O 2 mostly involves ORR and WOR, which occur simultaneously to produce H 2 O 2 . The pertinent response stages are as follows [7]: WOR: (1) 2e - direct pathway: 2H 2 O + 2h + → H 2 O 2 + 2H + (1.76 V vs . NHE) (2) 2e - indirect pathway: H 2 O + 2h + → • OH + H + (2.73 V vs . NHE) 2 • OH → H 2 O 2 (3) 4e - pathway: 2H 2 O + 4h + → O 2 + 4H + (1.23 V vs . NHE) ORR: (1) 2e - direct pathway: O 2 + 2e - +2H + → H 2 O 2 (0.68 V vs . NHE) (2) 2e - indirect pathway: O 2 + e - → • O 2 - (-0.33 V vs. NHE) O 2 - + e - + 2H + → H 2 O 2 (3) 4e - pathway: O 2 + 4e - + 4H + → 2H 2 O (1.23 V vs. NHE) The CBM values for NH 2 -UiO-66 and TFPT-Pa(CH 3 ) 2 -COF in the band structure diagram of Fig. 5e are -0.6 V ( vs . NHE) and -0.97 V, respectively. These comparably low values are under the thermodynamic potential for the 2e - oxygen reduction reaction (ORR) (0.68 V vs . NHE for direct ORR and -0.33 V vs . NHE for indirect ORR, at pH = 0) [47-50]. The VBM values for TFPT-Pa(CH 3 ) 2 -COF and NH 2 -UiO-66 are 1.43 V and 2.29 V ( vs . NHE), respectively. These exceed the thermodynamic potential for direct 2e - water oxidation process (1.76 V vs . NHE, at pH = 0). Thus, the staggered band structures of TFPT-Pa(CH 3 ) 2 -COF and NH 2 -UiO-66 are perfectly suited for the formation of heterojunctions and thermodynamically enhance the ORR and water oxidation reaction (WOR) routes for H 2 O 2 generation [51]. EIS Nyquist charts illustrate the comparison of semicircle diameters for TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and TNU-2 heterojunctions. EIS data were analyzed utilizing an analogous circuit model with Zview software, as depicted in the Fig. 6a. R ct and R s denote the charge transfer resistance and equivalent series resistance, respectively [52, 53]. The fitting results demonstrate that the R ct value (17.79 Ω) of the TNU-2 heterojunction is inferior to that of TFPT-Pa(CH 3 ) 2 (20.35 Ω), suggesting that the introduction of NH 2 -UiO-66 increased its conductivity, consequently signaling that the TNU-2 heterojunction demonstrated better charge transfer properties and lowered interfacial charge transfer resistance. The effectiveness of charge separation is evaluated using the photocurrent response, which is shown in Fig. 6b. The TNU-2 heterojunction had the highest photocurrent density among the produced samples. This is explained by the creation of an interfacial electric field in the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction, which ultimately improves effective electron-hole separation by facilitating electron transmission between the two phases [12]. Photoluminescence spectroscopy was used to measure charge transfer efficiency in order to evaluate charge transfer kinetics. Information on charge generation, transport, and recombination processes may be gained from the carrier recombination. In comparison to the TNU-2 heterojunction and TFPT-Pa(CH 3 ) 2 , which have a photoluminescence peak at 590 nm, pure NH 2 -UiO-66 had a more intense fluorescence emission peak at roughly 480 nm (Fig. 6c) [53]. This suggests that the overwhelming presence of TFPT-Pa(CH 3 ) 2 inside the heterojunction may be the primary cause of the recombination rate of photogenerated carriers in the TNU-2 heterojunction. The peak intensity of the TNU-2 heterojunction diminished upon coupling with TFPT-Pa(CH 3 ) 2 , signifying a substantial suppression of the recombination impact on the TNU-2 heterojunction. The time-resolved photoluminescence (TRPL) spectra of the products are presented in Fig. 6d [54]. The average lifetime (τ ave ) can be determined from the relevant fitting parameters of the exponential fitting curve. The τ ave values for TFPT-Pa(CH 3 ) 2 , NH 2 -UiO-66, and the TNU-2 heterojunction were determined to be 3.13, 2.43, and 2.99 ns, respectively. The τ ave of the TNU-2 heterojunction is situated between those of TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, due to the heterojunction creation significantly improving the transport of photogenerated carriers within the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction. Moreover, the extended τ ave of TFPT-Pa(CH 3 ) 2 indicates that it necessitates a protracted duration for decay. Furthermore, we examined in situ XPS spectra to monitor variations in binding energy during illuminated and dark circumstances, which is essential for validating interfacial charge routes. In situ XPS investigations were conducted under illumination to observe electronic states and evaluate the impact of intra-band transitions on charge dynamics. In dark circumstances, the high-resolution Zr 3d spectrum of the TNU-2 sample, shown in Fig. 7a, displays two peaks corresponding to Zr 3d 3/2 and Zr 3d 5/2 , respectively. Illuminated in situ XPS data indicate a change of the Zr 3d binding energy to elevated energy levels in TNU-2. Furthermore, C/C=C, C=N/C–N, and C–O were recognized as the origins of the peaks in the C 1s spectra of TNU-2 in the absence of light (Fig. 7b). The peaks in the N 1s spectra of TNU-2 (Fig. 7c) correspond to C=N, C–N, and N–H in the absence of light. Fig. 7d illustrates that the three different peaks in the O 1s spectrum correspond to C=O, C–O, and O 2 ads. In contrast to dark circumstances, the binding energies of C 1s, N 1s, and O 1s decreased under light. This signifies that photo-induced electrons produced under illuminated circumstances are conveyed from the NH 2 -UiO-66 surface to the TFPT-Pa(CH 3 ) 2 surface. This charge transfer pathway clearly demonstrates the successful formation of the S-scheme heterojunction [55-60]. When TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66 are in proximity in the absence of light (Fig. 8 (left)), free electrons transfer from NH 2 -UiO-66 to TFPT-Pa(CH 3 ) 2 until the Fermi level equilibrium is attained. Consequently, NH 2 -UiO-66 acquires electrons and attains a negative charge, whereas TFPT-Pa(CH 3 ) 2 relinquishes electrons and assumes a positive charge, therefore establishing an IEF from TFPT-Pa(CH 3 ) 2 to NH 2 -UiO-66 (Fig. 8 (middle)). This corresponds with the previously announced XPS analysis findings. Throughout this process, the energy bands at the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 interface exhibit downward and upward bending, respectively. Under simulated sunlight irradiation, photo-generated electrons are transferred from the CBM of NH 2 -UiO-66 to the VBM of TFPT-Pa(CH 3 ) 2 , thereafter adhering to the S-scheme heterojunction mechanism. Fig. 8 (right) depicts the electron transport process of the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 S-scheme heterojunction under simulated solar irradiation. The transfer of photo-generated electrons can be expedited by the IEF established in the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 S-scheme heterojunction, resulting in recombination between the photo-generated holes at the VBM of TFPT-Pa(CH 3 ) 2 and the photo-generated electrons at the CBM of NH 2 -UiO-66 [61]. Unlike II-type heterojunctions, the S-scheme heterojunction enables the incorporation of low-energy carriers to mitigate recombination, while maintaining elevated redox potentials for catalytic processes [62]. The resulting heterojunctions showed better crystallinity, porous framework topologies, and increased specific surface area. Thus, the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 synthesis in comparison to single-component TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, the S-scheme heterojunction has enhanced photocatalytic H 2 O 2 generation efficiency relative to its monomeric counterparts. This enhancement is accomplished by optimizing the separation and migration of photogenerated charge carriers, particularly by substantially augmenting the quantity of reactive photogenerated electrons in the conduction band of TFPT-Pa(CH 3 ) 2 . Conclusion The band alignment of TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66 promotes the transfer of photogenerated electrons via an S-scheme process, in which electrons from the conduction band minimum of NH 2 -UiO-66 recombine with holes from the VBM of TFPT-Pa(CH 3 ) 2 . This method enhances charge separation by establishing an IEF and inhibits carrier recombination. Photoelectrochemical tests and photoluminescence spectroscopy validate a markedly improved charge separation efficiency in the TFPT-Pa(CH 3 ) 2 /NH 2 -UiO-66 heterojunction. The results demonstrate that under simulated sunlight irradiation, the photocatalytic H 2 O 2 production rate of TNU-2 attains 0.19 mmol g −1 h −1 , signifying increases of 3.8-fold and 2.4-fold compared to pure TFPT-Pa(CH 3 ) 2 and NH 2 -UiO-66, respectively, due to the unique advantages of S-scheme heterojunctions in enhancing carrier use efficiency. This study introduces a novel method for the fabrication of triazine-based COF/Zr-based MOF heterojunctions to achieve highly efficient photocatalytic H 2 O 2 generation. Declarations Supplementary Information The online version contains supplementary material available at Ethical approval This work is submitted in Compliance with Ethical Standards. It is not being submitted nor published elsewhere in any form or language. Consent to participate Not applicable, no human subjects are involved. Consent to publish The participant has consented to the submission of this work to the journal. Competing interests The authors declare that they have no conflicts to declare. Author contributions LC contributed to investigation, Visualization, data curation, writing-original draft. YZ contributed to methodology, visualization. YY contributed to methodology. JJ contributed to validation, writing-review and editing. RG contributed to supervision, project administration. PD contributed to conceptualization, supervision, writing-review and editing. Funding This article was supported by the National Natural Science Foundation of China (Grant Nos. 21878257, 21276220, 51772258, 21403184), Major Research & Development Projects (Social Development) of Jiangsu Province (BE2020671), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant Nos. 22KJA430008 and 22KJD150007), and High Technology R & D demonstration project, Department of Emergency Management of Jiangsu Province (YJGL-YF-2020-4). In addition, we want to thank the Yancheng Institute of Technology’s Analysis and Testing Center for their assistance. Availability of data and materials The data used to support the findings of this study are available from the corresponding author upon request. References Y. Sun, L. Han, P. Strasser, Chem. Soc. Rev. 49, 6605-6631 (2020). https://doi.org/10.1039/D0CS00458H. H. Hou, X. Zeng, X. Zhang, Angew. Chem. Int. Ed. 59, 17356-17376 (2020). https://doi.org/10.1002/anie.201911609. A. Hayat, Z. Ajmal, A.Y.A. 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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-8762228","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":591854374,"identity":"fd2d5157-2f88-44d2-8511-2df9a1ab8f04","order_by":0,"name":"Lisong Chen","email":"","orcid":"","institution":"Yancheng Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Lisong","middleName":"","lastName":"Chen","suffix":""},{"id":591854378,"identity":"d8090806-0287-4e37-800e-13be1e7926e0","order_by":1,"name":"Yunchao Zhang","email":"","orcid":"","institution":"Yancheng Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yunchao","middleName":"","lastName":"Zhang","suffix":""},{"id":591854380,"identity":"3e3b929d-2ea9-4a01-8289-6999f35ab232","order_by":2,"name":"Yan Yan","email":"","orcid":"","institution":"Yancheng Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Yan","middleName":"","lastName":"Yan","suffix":""},{"id":591854382,"identity":"796a0508-e9a5-41bf-8239-7a8cbed8e01c","order_by":3,"name":"Jinhui Jiang","email":"","orcid":"","institution":"Yancheng Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Jinhui","middleName":"","lastName":"Jiang","suffix":""},{"id":591854384,"identity":"c023d0be-3183-4033-b85f-5154d96f0a76","order_by":4,"name":"Rongfeng Guan","email":"","orcid":"","institution":"Yancheng Institute of Technology","correspondingAuthor":false,"prefix":"","firstName":"Rongfeng","middleName":"","lastName":"Guan","suffix":""},{"id":591854386,"identity":"84fe78a9-cb2d-4efa-ae36-faaa5f99ebc3","order_by":5,"name":"Pengyu Dong","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA30lEQVRIiWNgGAWjYDCCA2BSgocfymZsIFKLhYwkUOmBAyRoqbAxOADhENbCd7z38OvCNgke4xvJDw9/YLCR3XCA+dkDfFokz5xLs54J1GJ2I80A6LA04w0H2MwN8GkxuJFjZswL1pID8svhxA0HeNgkiNJiPAOs5T9RWowfg7QYSIC1HCCsRfLMGTPmGeckeCTOPDM4cMYg2XjmYTYzvFr4jvcYfy4oq7Pnb09+/KGiwk6273jzM7xagIBNmpENSAkkgNwJxMwE1IOUfGb4A6T4DxBWOgpGwSgYBSMTAAAVFk9MWLB+ogAAAABJRU5ErkJggg==","orcid":"","institution":"Yancheng Institute of Technology","correspondingAuthor":true,"prefix":"","firstName":"Pengyu","middleName":"","lastName":"Dong","suffix":""}],"badges":[],"createdAt":"2026-02-02 08:24:03","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8762228/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8762228/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s11164-026-06006-y","type":"published","date":"2026-04-21T15:59:29+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":102992897,"identity":"8abddd20-86d8-40a4-8204-c7b594b4b02b","added_by":"auto","created_at":"2026-02-19 11:42:07","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":135728,"visible":true,"origin":"","legend":"\u003cp\u003e(a) X-ray diffraction patterns and (b) FT-IR spectra of the synthesized products.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/145014faf82bd85d2a14ac05.png"},{"id":103049813,"identity":"895546bb-3abf-41bc-b1d3-418e891352df","added_by":"auto","created_at":"2026-02-20 07:46:30","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":254197,"visible":true,"origin":"","legend":"\u003cp\u003e(a) N\u003csub\u003e2\u003c/sub\u003e adsorption isotherms and (b) variations in pore size for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TNU-2. XPS spectra for as-prepared samples: (c) survey, (d) high-resolution C 1s, (e) N 1s, and (f) Zr 3d.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/ccadc4475c650d74a178a94a.png"},{"id":103049665,"identity":"45c12239-aa71-40d3-b3d7-94695a48a23e","added_by":"auto","created_at":"2026-02-20 07:44:32","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":726385,"visible":true,"origin":"","legend":"\u003cp\u003e(a–d) TEM images and (e) STEM and EDS mapping images of TNU-2.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/f221d2bd3b0d0e51fdff07af.png"},{"id":102992899,"identity":"be575fc6-5b74-4788-a513-fc4fc6124ad1","added_by":"auto","created_at":"2026-02-19 11:42:07","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":211055,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Performance of the as-prepared samples in photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production. (b) Comparative analysis of photocatalytic hydrogen peroxide production rates among these photocatalysts. (c) Photocatalytic stability assessment of TNU-2 through cyclic testing. (d) AQE of TNU-2 across different wavelengths. Water contact angles of (e) TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, (f) NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and (g) TNU-2.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/a67de1b77f212b32c82ee84f.png"},{"id":103504194,"identity":"b7390a36-7312-4fea-a002-5d601e721312","added_by":"auto","created_at":"2026-02-26 13:18:18","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":176367,"visible":true,"origin":"","legend":"\u003cp\u003e(a) UV-vis DRS of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TNU-2 photocatalysts as produced. (b) Corresponding Tauc plots of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66. Mott-Schottky plots of (c) TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and (d) NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 measured at 1000, 2000, and 3000 Hz in the dark using Ag/AgCl as the reference electrode. (e) Energy band levels of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/b051924647e828a8cde5b863.png"},{"id":102992901,"identity":"2898b2b5-1326-4dca-9d57-4263539fc8fe","added_by":"auto","created_at":"2026-02-19 11:42:07","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":250562,"visible":true,"origin":"","legend":"\u003cp\u003e(a) Nyquist plots (EIS), (b) transient photocurrent response, (c) steady-state PL spectra excited at 350 nm, and (d) transient PL decay profiles for the as-prepared TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and the TNU-2 heterojunction.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/f1844abbad1a8798c4e0e3a9.png"},{"id":102992904,"identity":"80daf5ce-1b4a-4147-a427-68b9310fd232","added_by":"auto","created_at":"2026-02-19 11:42:07","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":259825,"visible":true,"origin":"","legend":"\u003cp\u003eIn situ illuminated XPS spectra of the TNU-2 sample: (a) high-resolution Zr 3d, (b) C 1s, (c) N 1s, and (d) O 1s.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/db30dd0dcb9ef711494b9888.png"},{"id":103049830,"identity":"af15cfec-3072-4d6c-89a5-1a3716c422ac","added_by":"auto","created_at":"2026-02-20 07:46:43","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":159109,"visible":true,"origin":"","legend":"\u003cp\u003eThe probable process of charge transfer across the S-scheme TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction is shown schematically both before and after contact in the absence of light and under irradiation.\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/f10411f51e1ad68ce208786e.png"},{"id":107928096,"identity":"e4357b55-64c6-498b-847e-2447dbd8afde","added_by":"auto","created_at":"2026-04-27 16:07:47","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":2540072,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/2c3e58a2-dc1e-4569-9aca-a9c47e67bf8b.pdf"},{"id":103050045,"identity":"48edb347-7e3b-4628-9e9e-5588ca2a4f72","added_by":"auto","created_at":"2026-02-20 07:47:51","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":756963,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial.docx","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/dc9692b0bd900fe839e5b32b.docx"},{"id":103028734,"identity":"7b8e59c3-a6d3-4765-b552-c510005768a5","added_by":"auto","created_at":"2026-02-19 21:24:29","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":756963,"visible":true,"origin":"","legend":"","description":"","filename":"Supplementarymaterial6.docx","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/99883c3b125a4a8164f5444e.docx"},{"id":103028732,"identity":"56e8cfa0-500a-474e-bcc4-73cd6008003a","added_by":"auto","created_at":"2026-02-19 21:24:28","extension":"docx","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":147435,"visible":true,"origin":"","legend":"","description":"","filename":"Scheme.docx","url":"https://assets-eu.researchsquare.com/files/rs-8762228/v1/098cbc0d1933c56106304ede.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"\u003cp\u003eConstruction of triazine-based COF/Zr-based MOF S-scheme heterojunctions for efficient photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production under simulated sunlight irradiation\u003c/p\u003e","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe industrial manufacture of hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) mostly utilizes the anthraquinone method. This process, however, presents hazards of organic contamination and entails substantial storage and transportation expenses, hence prompting the formulation of more ecologically friendly preparation pathways. H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e is widely used in antimicrobial treatment, sanitation disinfection, and environmental cleanup owing to its robust oxidative stability [1]. Photocatalytic technology has recently emerged as a promising solution to environmental degradation and energy deficits by turning solar energy into clean chemical energy [2]. Photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis has attracted considerable interest owing to its clean and efficient benefits, facilitating the conversion and production of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e by solar energy [3, 4].\u003c/p\u003e\n\u003cp\u003ePrior research has shown that covalent organic frameworks (COFs), noted for their high crystallinity, porosity, remarkable stability, adjustable chemical structures, and semiconductor characteristics, are crucial in the photocatalytic creation of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e [5, 6]. Nonetheless, the actual implementation of COFs encounters obstacles like sluggish charge transport kinetics, recombination of photogenerated carriers, and restricted processability [7, 8]. These characteristics limit their total photocatalytic efficiency and large-scale use. Consequently, the creation of highly effective photocatalytic COF-based heterojunctions for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation to realize synergistic \u0026quot;1 + 1 \u0026gt; 2\u0026quot; effects continues to pose a substantial challenge. Combining COFs with inorganic semiconductors that have appropriate band structures to create heterojunctions is regarded as a viable strategy to augment photocatalytic activity. In contrast to traditional II-type or Z-scheme heterojunctions [9], the recently discovered S-scheme heterojunction photocatalysts exhibit remarkable efficacy by integrating oxidizing and reducing photocatalysts to create an inherent electric field at the interface [10-19]. This electric field effectively promotes charge separation and migration, significantly increasing the reaction rate of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation. This structure effectively segregates high-energy electron-hole pairs while preserving robust redox properties, markedly reducing carrier recombination and augmenting photocatalytic performance. This process involves the photoelectron reduction of O\u003csub\u003e2\u003c/sub\u003e molecules, using H\u003csub\u003e2\u003c/sub\u003eO to provide protons. Consequently, it is essential to construct S-scheme heterojunctions exhibiting robust redox properties and elevated charge separation efficiency [20-23].\u003c/p\u003e\n\u003cp\u003eConversely, owing to their highly organized structures, extensive specific surface areas, and adjustable pore and topological characteristics, metal-organic frameworks (MOFs) show great potential in photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation [24, 25]. However, there are few reports available on the pure MOFs for photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation, Nevertheless, there are limited reports on pure metal-organic frameworks (MOFs) for photocatalytic hydrogen peroxide production, mostly due to intrinsic constraints such as their restricted light absorption spectrum and inadequate charge separation efficiency [26, 27]. In comparison to other MOFs, amino-containing Zr-based MOF (e.g., NH\u003csub\u003e2\u003c/sub\u003e-UiO-66) has superior visible light absorption and stability [28, 29]. Combining COFs with MOFs is a viable strategy to augment photocatalytic activity. Such combinations may demonstrate distinctive qualities that individual components cannot achieve. Recent research has focused on the amalgamation of MOFs with COFs to produce COF-MOF hybrid materials [30]. These hybrids inherit the elevated porosity and structural organization of their progenitor materials while also improving light absorption, facilitating charge separation, and producing many catalytically active sites via intercomponent synergistic interactions [31]. Current research on COF-based heterojunction photocatalysts for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation mostly focuses on COF/inorganic material systems, with inadequate investigation into COF/MOF heterojunctions. Research on triazine-based COF/MOF heterojunctions is notably limited. Theoretically, meticulously engineered interfaces and covalent bonding methodologies may create stable, high-performance COF/MOF heterojunctions to synergistically improve photocatalytic efficacy. In S-scheme heterojunction configurations, the alignment of bandgaps between COFs and MOFs facilitates spatially directed charge transfer. This method preserves robust redox potentials while efficiently inhibiting hole recombination, markedly enhancing photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation efficiency.\u003c/p\u003e\n\u003cp\u003eThis work developed covalently integrated COF/MOF heterojunctions, which exhibited a photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation rate that was much more excellent than that of individual COF and MOF materials. Triazine TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF was chosen as the framework for heterojunction fabrication due to its distinctive Schiff base triazine COF structure. Composites with different ratios of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e to NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 were effectively synthesized by including NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 into the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e production method. A series of heterojunctions exhibiting remarkable visible-light-driven photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production was produced by the congruent energy levels of triazine TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66. The peak efficiency of these heterojunctions is 0.19 mmol g\u003csup\u003e-1\u003c/sup\u003e h\u003csup\u003e-1\u003c/sup\u003e, approximately 3.8 times higher than that of the original TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e. This research offers a guiding framework for the future advancement of diverse COF/MOF-based photocatalysts for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e synthesis.\u003c/p\u003e"},{"header":"Experimental","content":"\u003cp\u003e\u003cstrong\u003ePreparation of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe synthesis for NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 is derived from previous reports with some alterations to the original protocol [32]. A standard experimental procedure is as follows: 0.2332 g of ZrCl\u003csub\u003e4\u003c/sub\u003e and 0.1812 g of 2-Aminoterephthalic Acid (H\u003csub\u003e2\u003c/sub\u003eATA) were dissolved in 50 mL of N,N-dimethylformamide (DMF). Subsequently, 6 mL of acetic acid was added, and the mixture was transferred to a 100 mL stainless steel autoclave lined with Polytetrafluoroethylene (PTFE). Subsequent to sealing the reactor, it was subjected to heating at 120 °C for 24 h under autoclave pressure. Subsequent to natural cooling, the resultant sample was centrifuged and extensively washed with anhydrous methanol to eliminate residual DMF. The resulting light yellow solid was subjected to vacuum drying at 120 °C for 12 h.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAfter combining 1,3,5-tris(4-formylphenyl)triazine (TFPT, 32.1 mg, 0.08 mmol) and 2,5-dimethyl-1,4-benzenediamine (Pa-(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, 16.85 mg, 0.12 mmol) with o-dichlorobenzene (0.4 mL) and N-butanol (3.6 mL), the mixture was ultrasonicated for two minutes. After adding 0.4 mL of 3 M acetic acid, the mixture was ultrasonically agitated for one minute. The mixture was degassed three times. Over the course of three days, the sealed mixture was heated at 120 °C. Following centrifugation, the yellow powder was washed with 3 × 5 mL of acetone and 3 × 5 mL of tetrahydrofuran. TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF was produced with 85% efficiency after the solid was recovered and vacuum-dried at 120 °C.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSynthesis of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 Heterojunction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe pre-synthesised NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, Pa-(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (16.85 mg, 0.12 mmol), and TFPT (32.1 mg, 0.08 mmol). N-butanol (3.6 mL) and ortho-dichlorobenzene (0.4 mL) were mixed and sonicated for two minutes. After adding 0.4 mL of 3 M acetic acid, the mixture was sonicated for one minute. Three rounds of degassing were performed on the mixture. Over the course of three days, the sealed mixture was heated at 120 °C. Following centrifugation, the yellow powder was washed with 3 × 5 mL of acetone and 3 × 5 mL of tetrahydrofuran. After vacuum-drying the resultant solid at 120 °C, TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u0026nbsp;\u003c/sub\u003ewas produced with 85% efficiency. By modifying the mass ratio between the fixed component TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (designated as “1”) and the variable component NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, heterojunction materials TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 (1:0.25) were synthesized and labeled TNU-1, TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 (1:0.5) as TNU-2, and TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 (1:0.75) as TNU-3.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMaterials characterization\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe crystal structure was determined by powder X-ray diffraction (XRD, Panalytical X'Pert3 Powder). The Nicolet NEXUS670 was used to acquire Fourier transform infrared (FT-IR) spectra. To evaluate permanent porosity, N\u003csub\u003e2\u003c/sub\u003e adsorption-desorption tests at 77 K were constantly monitored using a Micromeritics ASAP 2020 analyzer. A transmission electron microscope (TEM, JEOL JEM-2100F) equipped with scanning transmission electron microscopy (STEM) was used to analyze the morphology. X-ray photoelectron spectroscopy (XPS) at 1486.6 eV Al-Kα radiation with a spot size of 500 μm was recorded using a Thermo Fisher Scientific ESCALAB 250Xi. The binding energy was calibrated at C 1s at 284.8 eV. BaSO\u003csub\u003e4\u003c/sub\u003e as the reference material, diffuse reflectance spectroscopy (DRS) in the ultraviolet-visible range was recorded using a Shimadzu UV-3600 spectrophotometer. For photo-electrochemistry testing, the standard three-electrode setup consisted of a proprietary platinum plate with a counter electrode, 0.5 mol L\u003csup\u003e-1\u003c/sup\u003e Na\u003csub\u003e2\u003c/sub\u003eSO\u003csub\u003e4\u003c/sub\u003e solution as the electrolyte, an Ag/AgCl (saturated KCl) electrode as the reference electrode, and an indium tin oxide (ITO) coating with the photocatalyst as the working electrode. Using a CHI 660E electrochemical workstation, Mott-Schottky plots, photocurrent-time (I-t) responses, and electrochemical impedance spectroscopy (EIS) were produced. Photoluminescence (PL) spectra were measured using a fluorescence spectrometer (FLS980, Edinburgh, UK) with an excitation source set at 350 nm.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003ePhotocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e evolution test\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe technique outlined in the literature was followed in the photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e evolution reaction experiment [33]. The following are specific steps: After adding 10 mg of the photocatalyst into 50 mL of deionized water and uniformly disperse it with ultrasonication for 10 min. With the flask neck open, transfer the resultant mixture to a reaction flask and stir in an oxygenated environment. To reach adsorption-desorption equilibrium with the surrounding air, stir in the dark for 30 min. At 25 ± 1 °C, a 300 W xenon lamp (CEL-HXUV300) was used to irradiate the flask as it is magnetically stirred. Using a 0.22 μm filter membrane, separate liquids from solids and take samples every 15 min. Iodometric titration was used to measure the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e content in the residual liquid, and a standard curve was used to compute the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production. The details of the iodometric titration and the standard fitting curves of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (Fig. S1) are shown in the Supplementary Material. The total amount of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e produced in a single hour was used to compute the average photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production rate. Five cycles of photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation studies, each lasting one hour and carried out under identical circumstances, were carried out to evaluate photocatalyst stability. In addition, the measurement and calculation of apparent quantum efficiency (AQE) were shown in the Supplementary Material.\u003c/p\u003e"},{"header":"Results and discussion","content":"\u003cp\u003e\u003cstrong\u003eSynthetic strategy and microstructural feature\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction was synthesized using a solvothermal technique, as shown in Scheme 1. Initially, pure NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 powder was synthesized in an oven by a solvothermal method. Subsequently, the synthesized NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 and TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e precursors (comprising TFPT, Pa-(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, o-dichlorobenzene, N-butanol, and acetic acid) were transferred to a heat-resistant glass tube. Ultrasonic treatment produced a homogeneously distributed slurry, which was then exposed to liquid nitrogen degassing. The combination was ultimately subjected to heat at 120 \u0026deg;C for a duration of 3 days in an oil bath. The TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction was obtained after washing and vacuum drying. The NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 powder has a light yellow, but the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, TNU-1, TNU-2, and TNU-3 powders have a yellow coloration, as seen in Fig. S2.\u003c/p\u003e\n\u003cp\u003eThe phase composition of the produced samples was ascertained using X-ray diffraction (as seen in Fig. 1a). Diffraction peaks at 7.24\u0026deg;, 8.39\u0026deg;, and 25.71\u0026deg; correspond to the (111), (002), and (006) crystal planes in NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, respectively [34]. Two diffraction peaks were detected in the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e sample at 2.76\u0026deg; and 4.78\u0026deg;, attributed to the (010) and (011) crystal planes, respectively. The XRD patterns of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunctions exhibit an increase in peak intensity corresponding to NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 as the concentration of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 rises. Fig. 1b illustrates that the peaks at 665, 1384, and 1576 cm\u003csup\u003e-1\u003c/sup\u003e are attributed to the stretching vibrations of the Zr\u0026ndash;O bond, C\u0026ndash;O bond, and C=O bond in the NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 sample, respectively [35]. FT-IR spectra of both TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and the TNU-2 display a distinctive signal for the imine (C=N) bond at approximately 1624 cm\u003csup\u003e-1\u003c/sup\u003e, while the peaks corresponding to C=O and N\u0026ndash;H from the TFPT and Pa-(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e are nearly nonexistent, signifying the successful synthesis of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF through a Schiff base reaction [36, 37]. Additionally, the peaks associated with Zr\u0026ndash;O, C\u0026ndash;O, and C=O stretching vibrations were detected in the TNU-2 sample, indicating the existence of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 and further validating the synthesis of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction.\u003c/p\u003e\n\u003cp\u003eThe nitrogen adsorption-desorption isotherms and associated pore size distribution curves for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TNU-2 are shown in Fig. 2a. The adsorption isotherms of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 are categorized as H3 type. Additionally, as indicated in Table S1, the Brunauer-Emmett-Teller (BET) specific surface areas of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TNU-2 are 794.67, 788.82, and 467.07 m\u003csup\u003e2\u003c/sup\u003e g\u003csup\u003e-1\u003c/sup\u003e, respectively. The pore size distribution of TNU-2 predominantly centers about 2.4 nm, aligning with the mesoporous structure of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (Fig. 2b). The BET-specific surface area was shown to be effectively improved by mixing TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e with NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, which may result in more reactive sites. The enhanced dispersity of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e onto the NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 surfaces during the in situ synthesis process may have prevented the agglomeration of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 particles, which might account for the significantly increased specific surface area of TNU-2. XPS analyses clarified the chemical states and composition of the photocatalyst surface. Fig. 2c illustrates the photoelectron spectra of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and the TNU-2 heterojunction. The results demonstrate that TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 presents no supplementary impurity peaks, comprising carbon, nitrogen, oxygen, and zirconium constituents. The C 1s spectra in Fig. 2d display peaks at about 284.8, 286.5, and 288.8 eV for all three materials, representing C\u0026ndash;C/C=C, C=N/C\u0026ndash;N, and C\u0026ndash;O bonds, respectively [36, 38-40]. The N 1s spectra of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TNU-2 exhibit peaks at 398.7 eV, 399.4 eV, and 400.5 eV, in addition to a peak in the 402.0\u0026ndash;404.0 eV range (Fig. 2e), corresponding to C=N, C\u0026ndash;N, N\u0026ndash;H, and \u0026pi;\u0026ndash;\u0026pi;* satellite peaks, respectively [38]. The peaks at 183.1 eV and 185.5 eV in the Zr 3d spectrum (Fig. 2f) correspond to the Zr 3d\u003csub\u003e5/2\u003c/sub\u003e and Zr 3d\u003csub\u003e3/2\u003c/sub\u003e transitions, respectively. In comparison to NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, the binding energies of the Zr 3d peaks in TNU-2 exhibit a shift toward lower energies. The binding energies of Zr 3d\u003csub\u003e5/2\u003c/sub\u003e and Zr 3d\u003csub\u003e3/2\u003c/sub\u003e diminished by 0.05 and 0.01 eV, respectively [40, 41]. The results demonstrate that NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 acquires free electrons in the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterostructure relative to pure NH\u003csub\u003e2\u003c/sub\u003e-UiO-66. Simultaneously, the C 1s binding energy in TNU-2 displays a negative shift relative to pure TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, signifying an electron capture phenomenon in TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e [39, 40]. Consequently, Changes in the binding energy of the above elements indicate a reallocation of free electrons between TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66. The N 1s peak positions in the TNU-2 spectrum are 132.1 and 133.7 eV, while the Zr 3d peak binding energy in the TNU-2 heterostructure changes to higher energies, suggesting a reduction in electron density in TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e. Consequently, the depletion of free electrons in TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and the accumulation of free electrons in NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 may generate a robust internal electric field (IEF) at the interface between TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, thereby facilitating carrier diffusion and separation [42].\u003c/p\u003e\n\u003cp\u003eFig. 3a\u0026ndash;d display TEM images of the TNU-2 heterojunction. NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 has a smooth, normal octahedral form with distinct edges and a diameter of roughly 350 nm, whereas TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e demonstrates a diminutive, slender, and uneven plate-like morphology. It demonstrates a strong correlation between TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, signifying the establishment of a TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction. Moreover, STEM and EDS mapping of TNU-2 (Fig. 3e) corroborates the establishment of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction by demonstrating its anticipated elemental composition of C, N, O, and Zr, together with a uniform distribution.\u003c/p\u003e\n\u003cp\u003eFig. 4a illustrates the comparative photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production efficacy of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunctions at varying mass ratios. TNU-2 demonstrated the most H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production within 60 min. Fig. 4b illustrates the H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production rates of these samples. The rate for TNU-2 attained 0.19 mmol g\u003csup\u003e-1\u003c/sup\u003e h\u003csup\u003e-1\u003c/sup\u003e, which is 3.8 times and 2.4 times greater than that of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (0.05 mmol g\u003csup\u003e-1\u003c/sup\u003e h\u003csup\u003e-1\u003c/sup\u003e) and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 (0.08 mmol g\u003csup\u003e-1\u003c/sup\u003e h\u003csup\u003e-1\u003c/sup\u003e), respectively. The improved H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation efficacy of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 is ascribed to the establishment of a heterojunction. In Fig. 4c, the stability of TNU-2 catalyst was characterized by five cycles of photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production experiments. Following five cycles, the XRD diffraction patterns of samples with different ratios are shown in Fig. S3 to evaluate the structural integrity of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction, while the XPS spectra of the TNU-2 after cycling are illustrated in Fig. S4. The results indicated that the diffraction peaks in the XRD spectra before and after cycling exhibited similar shapes, and there was no significant change in the binding energy of the XPS spectra, demonstrating that the synthesized TNU-2 heterojunction possesses exceptional structural stability following photocatalysis. The specifics of AQE measurement and computation are available in the supplementary materials. Fig. 4d displays the AQE values across several wavelengths (420, 450, 500, and 550 nm). Utilizing a 420 nm bandpass filter, TNU-2 attained a peak AQE of 0.83%, aligning with the UV-Vis DRS findings. The wettability of the produced products was assessed to comprehend how the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction enhances photocatalytic activity. The contact angle of TNU-2 (108.04\u0026deg;) is positioned between that of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 (54.56\u0026deg;) and TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (121.35\u0026deg;), as shown in Fig. 4e-g. This suggests that the integration of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 enhances the hydrophilicity of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, improving its dispersion in aqueous photocatalytic systems and making it easier for reactant molecules like H\u003csub\u003e2\u003c/sub\u003eO.\u003c/p\u003e\n\u003cp\u003eFig. 5a presents the UV-Vis DRS spectra of the synthesized materials, with TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e demonstrating a pronounced absorption edge around 500 nm. Upon the establishment of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction, the light absorption spectrum encompasses both UV and visible light areas. Moreover, it is significant that the UV light absorption intensity of the TNU-2 heterojunction is intermediate to that of the individual TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 materials. The integration of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 markedly amplifies the optical absorption intensity of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e in the ultraviolet spectrum, potentially resulting in an increased generation of photoexcited electrons under simulated sunlight exposure, thus contributing to the photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production reaction of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction. Additionally, the bandgaps (\u003cem\u003eE\u003c/em\u003e\u003csub\u003eg\u003c/sub\u003e) of 2.40 eV and 2.89 eV were determined for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, respectively, utilizing Tauc plots (Fig. 5b).\u0026nbsp;The n-type semiconductor characteristics of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 are shown by the positive slopes of their Mott-Schottky curves at different frequencies, as shown in Fig. 5c and d. The flat-band potential (\u003cem\u003eE\u003c/em\u003e\u003csub\u003efb\u003c/sub\u003e) and the energy level of the conduction band minimum (E\u003csub\u003eCBM\u003c/sub\u003e) in a typical n-type semiconductor are typically equal [43, 44]. According to predictions, the valence band maximum (E\u003csub\u003eVBM\u003c/sub\u003e) energy levels for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 are 1.43 V and 2.29 V (vs. NHE), respectively.\u003c/p\u003e\n\u003cp\u003eThe photocatalytic synthesis of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e may be categorized into three consecutive phases. Initially, upon light exposure, the photocatalyst assimilates photons. When the energy of the input photon surpasses \u003cem\u003eE\u003c/em\u003e\u003csub\u003eg\u003c/sub\u003e of the photocatalyst, electrons are elevated from the VBM to the CBM [45]. Secondly, the excited electrons and produced holes either move or recombine inside the photocatalyst. Upon excitation, both electrons and holes migrate to the photocatalytic interface, enabling concurrent reduction and oxidation reactions [46]. The synthesis of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e mostly involves ORR and WOR, which occur simultaneously to produce H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e. The pertinent response stages are as follows [7]:\u003c/p\u003e\n\u003cp\u003eWOR:\u003c/p\u003e\n\u003cp\u003e(1) 2e\u003csup\u003e-\u003c/sup\u003e direct pathway:\u003c/p\u003e\n\u003cp\u003e2H\u003csub\u003e2\u003c/sub\u003eO + 2h\u003csup\u003e+\u003c/sup\u003e \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e + 2H\u003csup\u003e+\u003c/sup\u003e (1.76 V \u003cem\u003evs\u003c/em\u003e. NHE)\u003c/p\u003e\n\u003cp\u003e(2) 2e\u003csup\u003e-\u003c/sup\u003e indirect pathway:\u003c/p\u003e\n\u003cp\u003eH\u003csub\u003e2\u003c/sub\u003eO + 2h\u003csup\u003e+\u003c/sup\u003e \u0026rarr;\u0026nbsp;\u003csup\u003e\u0026bull;\u003c/sup\u003eOH + H\u003csup\u003e+\u003c/sup\u003e (2.73 V \u003cem\u003evs\u003c/em\u003e. NHE)\u003c/p\u003e\n\u003cp\u003e2\u003csup\u003e\u0026bull;\u003c/sup\u003eOH \u0026rarr; H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003e(3) 4e\u003csup\u003e-\u003c/sup\u003e pathway:\u003c/p\u003e\n\u003cp\u003e2H\u003csub\u003e2\u003c/sub\u003eO + 4h\u003csup\u003e+\u003c/sup\u003e \u0026rarr; O\u003csub\u003e2\u003c/sub\u003e + 4H\u003csup\u003e+\u003c/sup\u003e (1.23 V \u003cem\u003evs\u003c/em\u003e. NHE)\u003c/p\u003e\n\u003cp\u003eORR:\u003c/p\u003e\n\u003cp\u003e(1) 2e\u003csup\u003e-\u003c/sup\u003e direct pathway:\u003c/p\u003e\n\u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e + 2e\u003csup\u003e-\u003c/sup\u003e +2H\u003csup\u003e+\u003c/sup\u003e \u0026rarr;\u0026nbsp;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e (0.68 V \u003cem\u003evs\u003c/em\u003e. NHE)\u003c/p\u003e\n\u003cp\u003e(2) 2e\u003csup\u003e-\u003c/sup\u003e indirect pathway:\u003c/p\u003e\n\u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e + e\u003csup\u003e-\u003c/sup\u003e \u0026rarr;\u0026nbsp;\u003csup\u003e\u0026bull;\u003c/sup\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e (-0.33 V vs. NHE)\u003c/p\u003e\n\u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e\u003csup\u003e-\u003c/sup\u003e + e\u003csup\u003e-\u003c/sup\u003e + 2H\u003csup\u003e+\u003c/sup\u003e \u0026rarr;\u0026nbsp;H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e\n\u003cp\u003e(3) 4e\u003csup\u003e-\u003c/sup\u003e pathway:\u003c/p\u003e\n\u003cp\u003eO\u003csub\u003e2\u003c/sub\u003e + 4e\u003csup\u003e-\u003c/sup\u003e + 4H\u003csup\u003e+\u003c/sup\u003e \u0026rarr;\u0026nbsp;2H\u003csub\u003e2\u003c/sub\u003eO (1.23 V vs. NHE)\u003c/p\u003e\n\u003cp\u003eThe CBM values for NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 and TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF in the band structure diagram of Fig. 5e are -0.6 V (\u003cem\u003evs\u003c/em\u003e. NHE) and -0.97 V, respectively. These comparably low values are under the thermodynamic potential for the 2e\u003csup\u003e-\u003c/sup\u003e oxygen reduction reaction (ORR) (0.68 V \u003cem\u003evs\u003c/em\u003e. NHE for direct ORR and -0.33 V \u003cem\u003evs\u003c/em\u003e. NHE for indirect ORR, at pH = 0) [47-50]. The VBM values for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 are 1.43 V and 2.29 V (\u003cem\u003evs\u003c/em\u003e. NHE), respectively. These exceed the thermodynamic potential for direct 2e\u003csup\u003e-\u003c/sup\u003e water oxidation process (1.76 V \u003cem\u003evs\u003c/em\u003e. NHE, at pH = 0). Thus, the staggered band structures of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 are perfectly suited for the formation of heterojunctions and thermodynamically enhance the ORR and water oxidation reaction (WOR) routes for H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation [51].\u003c/p\u003e\n\u003cp\u003eEIS Nyquist charts illustrate the comparison of semicircle diameters for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and TNU-2 heterojunctions. EIS data were analyzed utilizing an analogous circuit model with Zview software, as depicted in the Fig. 6a. \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e and \u003cem\u003eR\u003c/em\u003e\u003csub\u003es\u003c/sub\u003e denote the charge transfer resistance and equivalent series resistance, respectively [52, 53]. The fitting results demonstrate that the \u003cem\u003eR\u003c/em\u003e\u003csub\u003ect\u003c/sub\u003e value (17.79 \u0026Omega;) of the TNU-2 heterojunction is inferior to that of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e (20.35 \u0026Omega;), suggesting that the introduction of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 increased its conductivity, consequently signaling that the TNU-2 heterojunction demonstrated better charge transfer properties and lowered interfacial charge transfer resistance. The effectiveness of charge separation is evaluated using the photocurrent response, which is shown in Fig. 6b. The TNU-2 heterojunction had the highest photocurrent density among the produced samples. This is explained by the creation of an interfacial electric field in the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction, which ultimately improves effective electron-hole separation by facilitating electron transmission between the two phases [12].\u003c/p\u003e\n\u003cp\u003ePhotoluminescence spectroscopy was used to measure charge transfer efficiency in order to evaluate charge transfer kinetics. Information on charge generation, transport, and recombination processes may be gained from the carrier recombination. In comparison to the TNU-2 heterojunction and TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, which have a photoluminescence peak at 590 nm, pure NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 had a more intense fluorescence emission peak at roughly 480 nm (Fig. 6c) [53]. This suggests that the overwhelming presence of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e inside the heterojunction may be the primary cause of the recombination rate of photogenerated carriers in the TNU-2 heterojunction. The peak intensity of the TNU-2 heterojunction diminished upon coupling with TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, signifying a substantial suppression of the recombination impact on the TNU-2 heterojunction. The time-resolved photoluminescence (TRPL) spectra of the products are presented in Fig. 6d [54]. The average lifetime (\u0026tau;\u003csub\u003eave\u003c/sub\u003e) can be determined from the relevant fitting parameters of the exponential fitting curve. The \u0026tau;\u003csub\u003eave\u003c/sub\u003e values for TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, and the TNU-2 heterojunction were determined to be 3.13, 2.43, and 2.99 ns, respectively. The \u0026tau;\u003csub\u003eave\u003c/sub\u003e of the TNU-2 heterojunction is situated between those of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, due to the heterojunction creation significantly improving the transport of photogenerated carriers within the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction. Moreover, the extended \u0026tau;\u003csub\u003eave\u003c/sub\u003e of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e indicates that it necessitates a protracted duration for decay.\u003c/p\u003e\n\u003cp\u003eFurthermore, we examined in situ XPS spectra to monitor variations in binding energy during illuminated and dark circumstances, which is essential for validating interfacial charge routes. In situ XPS investigations were conducted under illumination to observe electronic states and evaluate the impact of intra-band transitions on charge dynamics. In dark circumstances, the high-resolution Zr 3d spectrum of the TNU-2 sample, shown in Fig. 7a, displays two peaks corresponding to Zr 3d\u003csub\u003e3/2\u003c/sub\u003e and Zr 3d\u003csub\u003e5/2\u003c/sub\u003e, respectively. Illuminated in situ XPS data indicate a change of the Zr 3d binding energy to elevated energy levels in TNU-2. Furthermore, C/C=C, C=N/C\u0026ndash;N, and C\u0026ndash;O were recognized as the origins of the peaks in the C 1s spectra of TNU-2 in the absence of light (Fig. 7b). The peaks in the N 1s spectra of TNU-2 (Fig. 7c) correspond to C=N, C\u0026ndash;N, and N\u0026ndash;H in the absence of light.\u0026nbsp;Fig. 7d illustrates that the three different peaks in the O 1s spectrum correspond to C=O, C\u0026ndash;O, and O\u003csub\u003e2\u003c/sub\u003e ads. In contrast to dark circumstances, the binding energies of C 1s, N 1s, and O 1s decreased under light. This signifies that photo-induced electrons produced under illuminated circumstances are conveyed from the NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 surface to the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e surface. This charge transfer pathway clearly demonstrates the successful formation of the S-scheme heterojunction [55-60].\u003c/p\u003e\n\u003cp\u003eWhen TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 are in proximity in the absence of light (Fig. 8\u0026nbsp;(left)), free electrons transfer from NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 to TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e until the Fermi level equilibrium is attained. Consequently, NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 acquires electrons and attains a negative charge, whereas TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e relinquishes electrons and assumes a positive charge, therefore establishing an IEF from TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e to NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 (Fig. 8\u0026nbsp;(middle)). This corresponds with the previously announced XPS analysis findings. Throughout this process, the energy bands at the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 interface exhibit downward and upward bending, respectively. Under simulated sunlight irradiation, photo-generated electrons are transferred from the CBM of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 to the VBM of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, thereafter adhering to the S-scheme heterojunction mechanism. Fig. 8\u0026nbsp;(right) depicts the electron transport process of the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 S-scheme heterojunction under simulated solar irradiation. The transfer of photo-generated electrons can be expedited by the IEF established in the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 S-scheme heterojunction, resulting in recombination between the photo-generated holes at the VBM of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and the photo-generated electrons at the CBM of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 [61]. Unlike II-type heterojunctions, the S-scheme heterojunction enables the incorporation of low-energy carriers to mitigate recombination, while maintaining elevated redox potentials for catalytic processes [62]. The resulting heterojunctions showed better crystallinity, porous framework topologies, and increased specific surface area. Thus, the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 synthesis in comparison to single-component TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, the S-scheme heterojunction has enhanced photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation efficiency relative to its monomeric counterparts. This enhancement is accomplished by optimizing the separation and migration of photogenerated charge carriers, particularly by substantially augmenting the quantity of reactive photogenerated electrons in the conduction band of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe band alignment of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 promotes the transfer of photogenerated electrons via an S-scheme process, in which electrons from the conduction band minimum of NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 recombine with holes from the VBM of TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e. This method enhances charge separation by establishing an IEF and inhibits carrier recombination. Photoelectrochemical tests and photoluminescence spectroscopy validate a markedly improved charge separation efficiency in the TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 heterojunction. The results demonstrate that under simulated sunlight irradiation, the photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production rate of TNU-2 attains 0.19 mmol g\u003csup\u003e\u0026minus;1\u003c/sup\u003e h\u003csup\u003e\u0026minus;1\u003c/sup\u003e, signifying increases of 3.8-fold and 2.4-fold compared to pure TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, respectively, due to the unique advantages of S-scheme heterojunctions in enhancing carrier use efficiency. This study introduces a novel method for the fabrication of triazine-based COF/Zr-based MOF heterojunctions to achieve highly efficient photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eSupplementary Information\u003c/strong\u003eThe online version contains supplementary material available at\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthical approval\u0026nbsp;\u003c/strong\u003eThis work is submitted in Compliance with Ethical Standards. It is not being submitted nor published elsewhere in any form or language.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u0026nbsp;\u003c/strong\u003eNot applicable, no human subjects are involved.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to publish\u0026nbsp;\u003c/strong\u003eThe participant has consented to the submission of this work to the journal.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003eThe authors declare that they have no conflicts to declare.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003eLC contributed to investigation, Visualization, data curation, writing-original draft. YZ contributed to methodology, visualization. YY contributed to methodology. JJ contributed to validation, writing-review and editing. RG contributed to supervision, project administration. PD contributed to conceptualization, supervision, writing-review and editing.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003eThis article was supported by the National Natural Science Foundation of China (Grant Nos. 21878257, 21276220, 51772258, 21403184), Major Research \u0026amp; Development Projects (Social Development) of Jiangsu Province (BE2020671), Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant Nos. 22KJA430008 and 22KJD150007), and High Technology R \u0026amp; D demonstration project, Department of Emergency Management of Jiangsu Province (YJGL-YF-2020-4). In addition, we want to thank the Yancheng Institute of Technology\u0026rsquo;s Analysis and Testing Center for their assistance.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials\u003c/strong\u003e The data used to support the findings of this study are available from the corresponding author upon request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e\u003cbr\u003e\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eY. Sun, L. Han, P. Strasser, Chem. Soc. Rev. \u003cstrong\u003e49,\u0026nbsp;\u003c/strong\u003e6605-6631 (2020). https://doi.org/10.1039/D0CS00458H.\u003c/li\u003e\n \u003cli\u003eH. Hou, X. Zeng, X. Zhang, Angew. Chem. Int. Ed. \u003cstrong\u003e59,\u0026nbsp;\u003c/strong\u003e17356-17376 (2020). https://doi.org/10.1002/anie.201911609.\u003c/li\u003e\n \u003cli\u003eA. Hayat, Z. Ajmal, A.Y.A. Alzahrani, S.B. Moussa, M. Khered, N. Almuqati, A. Alshammari, Y. Al-Hadeethi, H. 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Mater. \u003cstrong\u003e37,\u0026nbsp;\u003c/strong\u003e2414803 (2025). https://doi.org/10.1002/adma.202414803.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Scheme","content":"\u003cp\u003eScheme 1 is available in the Supplementary Files section.\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"research-on-chemical-intermediates","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"rint","sideBox":"Learn more about [Research on Chemical Intermediates](http://link.springer.com/journal/11164)","snPcode":"11164","submissionUrl":"https://submission.nature.com/new-submission/11164/3","title":"Research on Chemical Intermediates","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Photocatalytic H2O2 production, S-scheme heterojunction, Triazine-based COF, Zr-based MOF, Charge separation","lastPublishedDoi":"10.21203/rs.3.rs-8762228/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8762228/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe anthraquinone method for commercial hydrogen peroxide (H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e) synthesis is plagued by organic pollution and elevated prices, necessitating the advancement of eco-friendly photocatalytic alternatives. Covalent organic frameworks (COFs) and metal-organic frameworks (MOFs) exhibit potential; yet, they are constrained by inferior charge separation and limited light absorption. Considering triazine-based TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e-COF has a distinctive Schiff structure and amino-containing Zr-based MOF (e.g., NH\u003csub\u003e2\u003c/sub\u003e-UiO-66) has superior visible light absorption and stability, covalently integrated TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e/NH\u003csub\u003e2\u003c/sub\u003e-UiO-66 COF/MOF heterojunctions were synthesized by solvothermal methods, and photocatalytic H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e production experiments were conducted. The results show that optimum TNU-2 (mass ratio 1:0.5) exhibits a significant H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e generation rate of 0.19 mmol g\u003csup\u003e-1\u003c/sup\u003e h\u003csup\u003e-1\u003c/sup\u003e, which is 3.8-fold and 2.4-fold higher than that of pure TFPT-Pa(CH\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e and NH\u003csub\u003e2\u003c/sub\u003e-UiO-66, respectively. Furthermore, TNU-2 demonstrates its remarkable cycle stability after five cycles. The constructed COF/MOF S-scheme heterojunction, which creates an internal electric field to promote charge separation, prevent recombination, and preserve strong redox capabilities, is responsible for the enhanced performance. This work offers a novel method for building efficient COF/MOF-based photocatalysts for the production of H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e.\u003c/p\u003e","manuscriptTitle":"Construction of triazine-based COF/Zr-based MOF S-scheme heterojunctions for efficient photocatalytic H2O2 production under simulated sunlight irradiation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-02-19 11:42:02","doi":"10.21203/rs.3.rs-8762228/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-25T08:06:55+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-24T06:42:17+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"86748031396546797399401114835489825921","date":"2026-03-19T14:18:58+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-02-26T06:50:11+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"172629674052941610244129556342205033712","date":"2026-02-16T04:43:03+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-13T15:04:12+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-04T18:50:04+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-04T18:47:20+00:00","index":"","fulltext":""},{"type":"submitted","content":"Research on Chemical Intermediates","date":"2026-02-02T08:01:06+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"research-on-chemical-intermediates","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"rint","sideBox":"Learn more about [Research on Chemical Intermediates](http://link.springer.com/journal/11164)","snPcode":"11164","submissionUrl":"https://submission.nature.com/new-submission/11164/3","title":"Research on Chemical Intermediates","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"4baf6583-a465-43df-bb6b-98bb374f5131","owner":[],"postedDate":"February 19th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-04-27T16:05:22+00:00","versionOfRecord":{"articleIdentity":"rs-8762228","link":"https://doi.org/10.1007/s11164-026-06006-y","journal":{"identity":"research-on-chemical-intermediates","isVorOnly":false,"title":"Research on Chemical Intermediates"},"publishedOn":"2026-04-21 15:59:29","publishedOnDateReadable":"April 21st, 2026"},"versionCreatedAt":"2026-02-19 11:42:02","video":"","vorDoi":"10.1007/s11164-026-06006-y","vorDoiUrl":"https://doi.org/10.1007/s11164-026-06006-y","workflowStages":[]},"version":"v1","identity":"rs-8762228","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8762228","identity":"rs-8762228","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}