Nanocomposite composition of covalent organic framework (COF) and metal oxide for photocatalytic water splitting

Abstract

A nanocomposite composition for photocatalytic water splitting, comprising a covalent organic framework (COF) integrated with a metal oxide semiconductor, wherein the COF and the metal oxide are chemically bonded and form a heterojunction structure exhibiting photocatalytic activity in the visible light range, wherein the nanocomposite composition comprises: (a) 40-75 wt% of a covalent organic framework consisting of a π-conjugated donor-acceptor polymer network formed by condensation of electron-rich and electron-poor monomers selected from triazine-, benzothiadiazole-, porphyrin- or bipyridine-based units; (b) 20-55 wt.% of a metal oxide semiconductor selected from titanium dioxide (TiO2), zinc oxide (ZnO), iron(III) oxide (Fe2O3), tin oxide (SnO2) or bismuth vanadate (BiVO4); and (c) 0.5-5 wt% of a co-catalyst selected from platinum (Pt), nickel (Ni), cobalt oxide (CoO₂) x ) or molybdenum disulfide (MoS2), evenly distributed on the surface of the nanocomposite to improve the redox kinetics at the surface.

Description

Technical field of the invention:

[0001] The present invention relates to photocatalytic materials and the production of renewable hydrogen. More specifically, it relates to a nanocomposite composition consisting of a covalent organic framework (COF) integrated with a metal oxide semiconductor for photocatalytic water splitting under visible light irradiation. The invention further relates to a photocatalytic reactor device or structure that utilizes this nanocomposite composition for the efficient production of hydrogen and oxygen from water. Background of the invention:

[0002] Photocatalytic water splitting is a promising technique for the sustainable production of hydrogen using solar energy. However, the efficiency of conventional photocatalysts such as titanium dioxide (TiO2), zinc oxide (ZnO), or tungsten trioxide (WO3) is limited by their large band gap and the rapid recombination of electrons and holes. Covalent organic frameworks (COFs) have emerged as a new class of crystalline, porous materials with tunable electronic properties, large surface area, and good chemical stability, and are therefore promising candidates for photocatalysis. However, pure COFs often exhibit low charge carrier mobility and limited absorption in the visible range.

[0003] To overcome these limitations, heterostructures have been investigated. Nanocomposites combining COFs with metal oxide semiconductors have been studied. Such hybrid structures promote charge separation at the interface and extend the photosensitivity range, thereby improving photocatalytic performance. However, existing COF-metal oxide composites often exhibit poor interfacial contact, disordered distribution, and inefficient charge transfer pathways, resulting in low photocatalytic efficiency. Therefore, there is a need for a specifically designed nanocomposite composition that maximizes interfacial contact, improves charge transfer, and optimizes activity in the visible light range for efficient water splitting.

[0004] Photocatalytic water splitting has established itself as one of the most promising and sustainable methods for directly producing hydrogen from water using solar energy. Hydrogen, a clean and renewable energy carrier, holds enormous potential for replacing fossil fuels and reducing global CO2 emissions. The basic principle of photocatalytic water splitting relies on the use of a semiconductor material that absorbs photons and generates electron-hole pairs. These drive the redox reactions necessary to split water into hydrogen and oxygen.

[0005] While considerable progress has been made in the development of photocatalysts for water splitting, existing solutions still exhibit shortcomings in terms of high efficiency, long-term stability, and scalable fabrication. Conventional metal oxides are limited by large band gaps and rapid charge recombination, while pure COFs, despite their tunability, suffer from low conductivity and stability. Current COF-metal oxide composites, though promising, are hampered by weak interfacial interactions, random dispersion, and a lack of controlled synthesis. There remains an urgent need for a nanocomposite system that combines the structural precision and optical tunability of COFs with the charge transport efficiency and robustness of metal oxides through strong chemical coupling and optimized band matching.Such a system must enable efficient absorption of visible light, long-lasting charge carrier separation, and high catalytic conversion, while ensuring durability and scalability for practical hydrogen production. Summary of the invention:

[0006] The present invention relates to a novel nanocomposite composition consisting of a covalent organic framework (COF) chemically bonded to a metal oxide semiconductor, forming a hybrid heterostructure with enhanced photocatalytic activity. The invention further relates to a photocatalytic reactor or device in which the nanocomposite composition is applied to a conductive substrate or dispersed in a reactor housing to generate hydrogen and oxygen from water under sunlight or artificial light.

[0007] The nanocomposite features a covalent organic framework with donor-acceptor linkers that interact chemically or via coordination bonds with the surface hydroxyl groups of the metal oxide. This interaction enables direct electron transport between the COF and the metal oxide, thereby suppressing charge recombination and improving quantum efficiency.

[0008] The present invention aims to provide a novel nanocomposite composition comprising a covalent organic framework (COF) with a metal oxide semiconductor for efficient photocatalytic water splitting under visible light irradiation. The invention seeks to overcome the inherent limitations of conventional photocatalysts, such as low absorption of visible light, rapid charge recombination, and insufficient stability, by developing a chemically bonded heterostructure that ensures strong interfacial contact and efficient charge transfer between the COF and metal oxide components. Through targeted design of the electronic structure and surface chemistry, superior hydrogen and oxygen evolution rates are to be achieved, along with long-term photochemical stability under aqueous conditions and light irradiation.

[0009] A further objective of the invention is to provide a nanocomposite structure that utilizes the complementary properties of organic and inorganic materials—in particular, the tunable light absorption and extended π-conjugation of COFs, combined with the robust charge transport and stability of metal oxides. By integrating these materials via covalent or coordinate bonds, a type II heterostructure is to be formed, enabling spatial separation of photoinduced electrons and holes, thereby minimizing recombination losses and improving quantum efficiency. This interface architecture is also intended to facilitate directed electron flow from the photoexcited COF to the conduction band of the metal oxide, thus leading to efficient hydrogen production, while the holes remaining in the valence band of the COF contribute to oxygen evolution.

[0010] A further objective of the invention is to provide a photocatalytic reactor device or structure that utilizes the described nanocomposite composition in a functional form suitable for practical hydrogen production. The invention aims to develop a photocatalytic reactor in which the nanocomposite is immobilized on conductive substrates such as fluorinated tin oxide (FTO) glass or stainless steel mesh to ensure efficient charge collection and reusability. The reactor structure is intended to enable uniform light irradiation, a controlled liquid flow, and effective separation of the resulting hydrogen and oxygen gases, thereby achieving high reaction efficiency and operational reliability.In certain embodiments, the invention aims to provide a compact, scalable and modular photocatalytic cell that can be operated under both solar and artificial lighting for decentralized hydrogen production systems.

[0011] A further objective of the invention is to provide an adaptable material platform that allows modification of the COF structure and selection of the metal oxide to optimize bandgap matching for different energy requirements and light sources. This adaptability is intended to make the system usable under various environmental and operating conditions, including solar, UV LED, or artificial light sources. By adapting the electronic configuration through molecular design of the COF linkers and nodes, the invention aims to enable controlled absorption edges, redox potentials, and optimal matching of the energy levels to the metal oxide component.

[0012] A key objective of the invention is to bridge the gap between high-performance photocatalysts on a laboratory scale and durable, economically viable solar hydrogen production systems. This is to be achieved through a synergistic nanocomposite material that combines stability, efficiency, and scalability, and its integration into a practical reactor structure for long-term operation. The design philosophy of the invention is to combine material development at the molecular level with device optimization to ensure that all aspects—from light absorption and charge separation to gas collection—are optimized for maximum performance.Through this combination of advanced materials science and applied engineering, the invention aims to establish a new class of photocatalysts and reactor systems that enable large-scale, sustainable hydrogen production using the abundant energy of sunlight and water. BRIEF DESCRIPTION OF THE IMAGES

[0013] These and other features, aspects and advantages of the present invention will be better understood if the following detailed description is read with reference to the accompanying drawings, in which identical symbols represent identical parts: Fig. Figure 1 shows a table illustrating the improvement in the hydrogen evolution rate achieved by the COF metal oxide composite, demonstrating a significant synergistic improvement compared to the individual components. Fig. Figure 2 shows a table illustrating the synergistic improvement of the electronic and structural properties, including a reduced charge transfer resistance and an optimized band gap in the composite material. Fig. Figure 3 shows a table illustrating the improved photostability and photophysical behavior of the composite, confirming its extended carrier lifetime and higher AQY.

[0014] Furthermore, those skilled in the art will recognize that the elements in the drawings are simplified and not necessarily drawn to scale. For example, the flowcharts illustrate the process by highlighting the main steps to facilitate understanding of this disclosure. With regard to the construction of the device, one or more components may be represented in the drawings by conventional symbols. The drawings may show only those specific details relevant to understanding the embodiments of this disclosure, so as not to clutter the drawings with details that are already apparent to those skilled in the art from the description contained herein. Detailed description of the invention

[0015] To facilitate understanding of the principles of the invention, reference is made below to the embodiment illustrated in the drawings, which is described using specific terms. It is understood, however, that this does not limit the scope of protection of the invention. Rather, modifications and further developments of the illustrated system, as well as further applications of the inventive principles depicted therein, are conceivable, insofar as they would typically occur to a person skilled in the art in the field of the invention.

[0016] It will be clear to those skilled in the art that the foregoing general description and the following detailed description are exemplary and explanatory of the invention and are not to be understood as a limitation of it.

[0017] References to “an aspect”, “another aspect”, or similar phrases in this description mean that a particular feature, structure, or property described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, phrases such as “in one embodiment”, “in another embodiment”, and similar expressions in this description may, but do not necessarily, all refer to the same embodiment.

[0018] The terms "includes," "comprehensive," or similar expressions denote non-exclusive inclusion. Thus, a procedure or method containing a list of steps does not only include those steps but may also include further steps not explicitly listed or inherent in the procedure or method. Likewise, the statement "includes..." for one or more devices, subsystems, elements, structures, or components, without further limitations, does not preclude the existence of other devices, subsystems, elements, structures, or components.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meanings generally known to those skilled in the art in the field to which this invention belongs. The systems, methods, and examples described herein serve only for illustration and are not to be understood as limiting.

[0020] Embodiments of the present disclosure are described in detail below with reference to the accompanying drawings.

[0021] The present invention presents a nanocomposite composition for photocatalytic water splitting, consisting of a covalent organic framework (COF) integrated into a metal oxide semiconductor, wherein the COF and the metal oxide are chemically bonded and form a heterostructure exhibiting photocatalytic activity in the visible light range. The nanocomposite composition comprises: (a) 40-75 wt% of a covalent organic framework consisting of a π-conjugated donor-acceptor polymer network formed by condensation of electron-rich and electron-poor monomers selected from triazine-, benzothiadiazole-, porphyrin- or bipyridine-based units; b) 20-55 wt.% of a metal oxide semiconductor selected from titanium dioxide (TiO2), zinc oxide (ZnO), iron(III) oxide (Fe2O3), tin oxide (SnO2) or bismuth vanadate (BiVO4); and (c) 0.5-5 wt% of a co-catalyst selected from platinum (Pt), nickel (Ni), cobalt oxide (CoO₂) x ) or molybdenum disulfide (MoS2), evenly distributed on the surface of the nanocomposite to improve the redox kinetics at the surface.

[0022] In one embodiment, the covalent organic framework consists of 1,3,5-triazine-2,4,6-triyltriphenylamine (TAPT) and terephthalaldehyde monomers, which are polymerized by Schiff base condensation to form an imine-linked COF. This exhibits a band gap of 1.8–2.3 eV and a BET surface area of ​​500–800 m². 2 / g, with the COF content being between 50 and 65 wt.% based on the total weight of the nanocomposite.

[0023] In one embodiment, the metal oxide semiconductor consists of anatase-TiO2 nanoparticles with a particle size between 10 and 50 nm and a specific surface area of ​​100 to 200 m². 2 / g and a proportion of 30 to 45 wt.% of the total nanocomposite.

[0024] In one embodiment, the COF is covalently bonded to the surface hydroxyl groups of TiO2 via imine or boronate ester bonds formed during the in-situ reaction. Solvothermal synthesis achieving an interfacial coverage density of 0.4–0.8 mg / cm². 2 and ensures an interface thickness of 5-15 nm.

[0025] In one embodiment, the co-catalyst platinum is photochemically deposited in situ in an amount of 1.0-2.0 wt% based on the total weight of the composite, resulting in nanoparticles with a mean diameter of 2-6 nm that are uniformly distributed over the COF-TiO2 interface and increase the hydrogen evolution rate by 20-40% compared to the unmodified composite.

[0026] In one embodiment, the ratio of COF to metal oxide (w / w) is maintained between 1.2:1 and 1.8:1 to achieve optimal light absorption and charge separation. This ratio results in a composite with a band structure characterized by a conduction band potential of -0.9 V and a valence band potential of +1.4 V relative to the normal hydrogen electrode (NHE).

[0027] In one embodiment, the COF consists of alternating electron-donating and electron-withdrawing linkers in a molar ratio of 1:1, forming a donor-acceptor heterostructure which facilitates charge separation, and wherein the nitrogen content in the COF backbone is between 12 and 18 wt.% to modulate its electronic structure and improve the photocatalytic reaction under visible light (λ = 420-750 nm).

[0028] In one embodiment, the composite material is produced via a solvothermal route in which metal oxide nanoparticles are dispersed in a dimethylformamide (DMF)-acetonitrile mixture containing COF precursors. Subsequent condensation takes place at 150–180 °C for 18–24 hours, resulting in a crystalline hybrid with X-ray diffraction peaks at 20° = 7.2°, 13.6°, and 25.1°, confirming COF formation.

[0029] In one embodiment, the porosity of the COF component lies between 0.6 and 1.2 cm². 3 / g and the mean pore diameter between 2.5 and 4.0 nm, which facilitates the adsorption and diffusion of water molecules at the active interface.

[0030] In one embodiment, the COF-metal oxide interface exhibits a charge transfer resistance of less than 100 Ω·cm, as measured by electrochemical impedance spectroscopy. 2 This suggests efficient electronic coupling between the two phases.

[0031] In one embodiment, the COF consists of a β-ketoenamine-linked structure synthesized from 1,3,5-triformylphloroglucinol (TFP) and 1,4-phenylenediamine (PDA) in the presence of TiO2 nanoparticles, wherein the composite material contains 55-70 wt% COF and 25-40 wt% TiO2.

[0032] In one embodiment, the metal oxide is zinc oxide (ZnO) with a hexagonal wurtzite structure and an average crystallite size of 20–30 nm. The composite material consists of 60 wt% COF and 35 wt% ZnO and enables a hydrogen evolution rate of 3500–5000 µmol g. -1 h -1 under simulated sunlight.

[0033] In one embodiment, the surface of the metal oxide is pre-functionalized with amino or carboxyl groups to improve the covalent anchoring of the COF, wherein the atomic ratio of nitrogen to oxygen at the interface, as determined by X-ray photoelectron spectroscopy, is between 0.15 and 0.25.

[0034] In one embodiment, the COF content is 55-65 wt.%, the metal oxide content is 30-40 wt.% and the co-catalyst content is 1-2 wt.%, resulting in a photocatalytic quantum efficiency of over 12% at an illuminance of 420 nm.

[0035] In one embodiment, the COF component is a porphyrin-based COF (Por-COF) with Zn-porphyrin linkers and boronate ester bonds forming a crystalline layered structure with a π-π stacking distance of 0.36-0.38 nm, and the metal oxide component comprises 35 wt% SnO2 nanoparticles embedded between COF layers to enhance electron transport.

[0036] In one embodiment, the COF metal oxide composite is additionally supplemented with 1-3 wt% carbon quantum dots or reduced graphene oxide layers to increase the charge carrier mobility at the interface and to extend the absorption of visible light.

[0037] In one embodiment, the nanocomposite exhibits a hydrogen evolution rate of 4000-6000 µmol g under a 300 W Xe lamp (AM 1.5G filter) in an aqueous solution with 10 vol% methanol. -1 h -1on, with an apparent quantum yield (AQY) of over 10% at 420 nm.

[0038] In one embodiment, the thermal stability of the composite, determined by thermogravimetric analysis, is maintained up to 420°C with a weight loss of less than 5%, and the structural integrity of the COF network is maintained after 50 hours of continuous exposure to aqueous media.

[0039] In one embodiment, the ratio of carbon to titanium (C / Ti) in the composite is between 3.5:1 and 5.0:1, and the oxygen vacancy concentration in the TiO2 phase is adjusted to 1.2-1.8% to increase the efficiency of the photoinduced charge transfer at the heterojunction interface.

[0040] The present invention relates to a nanocomposite composition consisting of a covalent organic framework (COF) and a metal oxide semiconductor for efficient photocatalytic water splitting under visible light irradiation. The invention focuses in particular on the structural, chemical, and interfacial optimization of the COF-metal oxide heterostructure to achieve improved charge separation, extended carrier lifetime, and enhanced catalytic performance. The composition, as defined in the preceding claims, comprises 40-75 wt% of a covalent organic framework, 20-55 wt% of a metal oxide semiconductor, and 0.5-5 wt% of a co-catalyst. The synergistic interaction of these components results in a nanocomposite with strong absorption of visible light, a large surface area, chemical stability, and high redox activity, leading to superior hydrogen and oxygen evolution rates.

[0041] The co-catalyst component, typically present at a concentration of 0.5–5 wt%, plays a crucial role in improving surface reaction kinetics. In one embodiment, platinum nanoparticles are photochemically deposited in situ at a loading of 1.0–2.0 wt% based on the total weight of the composite. The Pt nanoparticles act as electron scavengers, accumulating photogenerated electrons and catalyzing the hydrogen evolution reaction (HER) with a reduced overpotential. The co-catalyst distribution is optimized to avoid shadowing effects or excessive coverage of active COF oxide sites. The average Pt nanoparticle size of 2–6 nm ensures maximum dispersion and optimal interface accessibility. Measurements using electrochemical impedance spectroscopy (EIS) confirm a reduced charge transfer resistance (<100 Ω·cm). 2) and improved charge carrier mobility after the installation of the co-catalyst, thus demonstrating an efficient synergy between the three components.

[0042] The interaction between light absorption, charge separation, and catalytic conversion in the nanocomposite can be summarized using quantum efficiency and rate constants derived from transient photoluminescence (PL) and time-resolved photovoltage (TRPV) measurements. The reduced PL intensity in the composite compared to pure COF indicates reduced recombination and improved charge extraction. The lifetime of the photogenerated charge carriers, τ, is extended approximately threefold by hybridization, confirming the efficiency of charge transfer at the interface. Furthermore, the conduction band shift of approximately -0.15 eV observed in the Mott-Schottky analysis reflects the formation of an internal electric field that drives unidirectional electron transport.

[0043] The physical morphology and porosity of the nanocomposite play a crucial role in mass transport and photon yield. The COF component exhibits a porosity of 0.6–1.2 cm. 3 / g and a pore size of 2.5–4.0 nm, allowing water molecules and sacrificial reagents to easily diffuse into the active areas. The hierarchical porosity promotes multiple reflections of light, thus improving the photon absorption probability. The specific surface area is 500–800 m². 2 / g ensures a multitude of active sites, while the strong chemical interface minimizes photocorrosion of both organic and inorganic phases. Thermogravimetric analyses (TGA) confirm thermal stability up to 420 °C, and long-term illumination tests show a decrease in the hydrogen evolution rate of less than 5% over 50 hours of continuous operation, indicating high structural integrity.

[0044] In an exemplary embodiment, the COF-TiO2 composite material with 60 wt.% COF, 35 wt.% TiO2 and 1.5 wt.% Pt shows a hydrogen evolution rate of approximately 4800 µmol g under a 300 W Xe lamp with AM-1.5G filter. -1 h -1 The apparent quantum yield (AQY) measured at 420 nm exceeds 10%, thus demonstrating the high efficiency of solar hydrogen production of the nanocomposite. Comparative studies show that pure TiO2 under identical conditions yields less than 600 µmol g. -1 h -1 generated. This confirms an eightfold increase due to the synergistic effect of the COF oxide heterostructure.

[0045] The nanocomposite composition of the present invention thus represents an integrated, fully optimized system that converts solar energy into chemical energy with high efficiency, adjustable band structure, and superior stability. The composition can be synthesized reproducibly and adapted to various metal oxides or COF chemistries, making it suitable for scalable hydrogen production systems and industrial applications for photocatalytic water splitting.

[0046] In one embodiment, the invention provides a nanocomposite composition comprising a covalent organic framework (COF) integrated with a metal oxide selected from TiO2, ZnO, Fe2O3, SnO2, BiVO4, or a combination thereof. The COF component can be synthesized from organic linkers containing electron-donating and -withdrawing groups such as triazine, benzothiadiazole, or porphyrin units, coupled to aldehyde- or amine-based connectors via Schiff base condensation or boronic ester formation. The resulting COF exhibits an extended π-conjugated network with an adjustable band gap in the range of 1.8–2.5 eV.

[0047] The metal oxide is present in the form of nanoparticles, nanorods, or nanoplatelets with a particle size between 10 and 100 nm. The COF-metal oxide nanocomposite is synthesized using an in-situ growth process in which the COF is formed on the previously synthesized metal oxide surface via solvothermal or interfacial polymerization. During synthesis, the organic monomers adsorb onto the hydroxylated metal oxide surface, forming a covalently bonded interface that ensures robust mechanical and electronic coupling.

[0048] The close contact between COF and the metal oxide forms a type II heterojunction, enabling directed electron transport. Upon irradiation with visible light, photoexcited electrons migrate from the conduction band of the COF to the conduction band of the metal oxide, while holes remain in the valence band of the COF. This spatial charge separation extends the carrier lifetime and increases the number of electrons available for hydrogen evolution at the catalyst surface.

[0049] In an exemplary embodiment, a triazine-based COF (CTF-type) on TiO2 nanoparticles is synthesized by a solvothermal reaction in N,N-dimethylformamide at 150 °C for 24 hours. The resulting CTF-TiO2 nanocomposite exhibits a specific surface area of ​​over 600 m². 2 / g and a band gap of approximately 2.1 eV. Photocatalytic hydrogen evolution experiments under a 300 W xenon lamp with an AM-1.5G filter show a hydrogen production rate of 4200 µmol / g. -1 h -1 , which is significantly higher than that of pure TiO2 or CTF alone.

[0050] The nanocomposite composition may further contain a co-catalyst such as Pt, Ni, or CoOx nanoparticles dispersed at a concentration of 0.5–2.0 wt% on the COF metal oxide surface to enhance charge storage and the density of catalytically active sites. During operation, the composite may be suspended in an aqueous electrolyte containing a sacrificial reagent such as methanol or triethanolamine.

[0051] Fig. Figure 1 shows a table illustrating the improvement in the hydrogen evolution rate achieved by the COF metal oxide composite, demonstrating a significant synergistic improvement compared to the individual components.

[0052] Fig. Figure 2 shows a table illustrating the synergistic improvement of the electronic and structural properties, including a reduced charge transfer resistance and an optimized band gap in the composite material.

[0053] Fig. Figure 3 shows a table illustrating the improved photostability and photophysical behavior of the composite, confirming its extended carrier lifetime and higher AQY.

[0054] The invention also relates to a photocatalytic reactor device that uses the nanocomposite composition described above. The device comprises: 1. A reaction chamber made of quartz or borosilicate glass, equipped with an inlet for water or aqueous electrolytes and an outlet for hydrogen and oxygen gases; 2. A photocatalytic film formed by coating a conductive substrate such as fluorinated tin oxide (FTO), indium tin oxide (ITO) or stainless steel mesh with the COF metal oxide nanocomposite; 3. A light source, such as a solar simulator or an LED array, positioned to illuminate the photocatalytic film evenly; 4. A gas separation membrane or a two-chamber configuration with a proton exchange membrane (PEM) to prevent the recombination of hydrogen and oxygen produced.

[0055] The invention offers potential for applications in solar-powered hydrogen production systems, photoelectrochemical cells, and self-sufficient water splitting plants. It enables a sustainable, cost-effective, and efficient method for producing renewable hydrogen and is suitable for both small laboratory systems and industrial solar hydrogen production plants.

[0056] The present invention falls within the field of renewable energy materials and advanced photocatalysis. More specifically, it relates to the development of a nanocomposite composition based on the integration of covalent organic frameworks (COFs) with metal oxide semiconductors for solar-driven water splitting. The invention addresses key challenges of photocatalytic hydrogen production, including the low utilization of visible light, rapid charge recombination, and limited interfacial stability, by introducing a chemically optimized hybrid structure with improved electronic coupling between organic and inorganic domains. The invention relates to the design, synthesis, and characterization of COF-metal oxide heterostructures that enable efficient separation of photogenerated charges and long-term operational stability under aqueous conditions.It also concerns the use of these nanocomposite compositions in devices or reactors for visible-induced water splitting, photoelectrochemical hydrogen production, and artificial photosynthesis systems. The technical field thus encompasses materials chemistry, nanostructure development, the design of photocatalytic reactions, and solar energy conversion for sustainable hydrogen production technologies.

[0057] The drawings and the preceding description illustrate embodiments. Those skilled in the art will recognize that one or more of the described elements can be combined to form a single functional element. Alternatively, certain elements can be divided into several functional elements. Elements of one embodiment can be added to another. For example, the process sequences described here can be modified and are not limited to the manner described herein. Furthermore, the actions of a flowchart need not be performed in the sequence shown; nor do all actions necessarily need to be carried out. Actions that do not depend on other actions can be performed in parallel with the other actions. The scope of protection of the embodiments is in no way limited by these specific examples. Numerous variations, whether explicitly stated in the description or not, such as...Differences in structure, dimensions, and materials are possible. The scope of protection of the embodiments is at least as comprehensive as described by the following claims.

[0058] The advantages, other benefits, and problem solutions have been described above with reference to specific embodiments. However, the advantages, benefits, problem solutions, and any components that can effect or enhance an advantage, benefit, or solution are not to be construed as critical, necessary, or essential features or components of the claims.

Claims

[1] A nanocomposite composition for photocatalytic water splitting, comprising a covalent organic framework (COF) integrated with a metal oxide semiconductor, wherein the COF and the metal oxide are chemically bonded and form a heterojunction structure exhibiting photocatalytic activity in the visible light range, wherein the nanocomposite composition comprises: (a) 40-75 wt% of a covalent organic framework consisting of a π-conjugated donor-acceptor polymer network formed by condensation of electron-rich and electron-poor monomers selected from triazine-, benzothiadiazole-, porphyrin- or bipyridine-based units; (b) 20-55 wt.% of a metal oxide semiconductor selected from titanium dioxide (TiO2), zinc oxide (ZnO), iron(III) oxide (Fe2O3), tin oxide (SnO2) or bismuth vanadate (BiVO4); and (c) 0.5-5 wt% of a co-catalyst selected from platinum (Pt), nickel (Ni), cobalt oxide (CoO₂) x ) or molybdenum disulfide (MoS2), evenly distributed on the surface of the nanocomposite to improve the redox kinetics at the surface. [2] Nanocomposite composition according to claim 1, wherein the covalent organic framework comprises 1,3,5-triazine-2,4,6-triyltriphenylamine (TAPT) and terephthalaldehyde monomers which are condensed by Schiff base condensation to form an imine-linked COF with a band gap of 1.8-2.3 eV and a BET surface area of ​​500-800 m² 2 / g are polymerized, and the COF content is kept between 50 and 65 wt% based on the total weight of the nanocomposite. [3] Nanocomposite composition according to claim 1, wherein the metal oxide semiconductor is anatase-phase TiO2 nanoparticles with a particle size between 10 and 50 nm, a specific surface area of ​​100 to 200 m² 2 / g and these are present in a range of 30 to 45 wt.% of the total nanocomposite. [4] Nanocomposite composition according to claim 1, wherein the COF is covalently bonded to the surface hydroxyl groups of TiO2 via imine or boronate bonds formed during in situ synthesis. Solvothermal synthesis. [5] Nanocomposite composition according to claim 1, wherein the COF comprises alternating electron-donating and electron-withdrawing linkers in a molar ratio of 1:1, forming a donor-acceptor heterostructure which facilitates charge separation, and wherein the nitrogen content in the COF backbone is between 12 and 18 wt.% to modulate its electronic structure and improve the photocatalytic reaction under visible light (λ = 420-750 nm). [6] Nanocomposite composition according to claim 1, wherein the porosity of the COF component is in the range of 0.6 to 1.2 cm² 3 / g and the mean pore diameter is between 2.5 and 4.0 nm.