Covalent organic framework photocatalytic material containing boat-shaped c=n conjugated fragments and design method and application thereof

Abstract

This invention discloses a covalent organic framework photocatalytic material containing a boat-shaped C=N conjugated segment, its design method, and its applications. The material framework contains a boat-shaped C=N conjugated segment composed of -C=N-C=N- or -N=C-C=N- linkage sequences, which can simulate the electron-proton co-transfer mechanism of the industrial anthraquinone process. This invention uses first-principles calculations to screen fragments with two-electron oxygen reduction reaction activity from 39 molecular fragments and constructs 106 two-dimensional COF structures; further, it proposes an electronic fingerprint descriptor based on density of states similarity to achieve high-throughput screening. Experimental verification shows that the representative material TRI-BIP-TRI (TBiT) achieves an H2O2 yield of 3084.27 μmol g in a pure water system under visible light irradiation without any sacrificial agent. ‑1 h ‑1 This invention provides a novel molecular engineering strategy and theoretical screening tool for efficient and stable photocatalytic hydrogen peroxide production materials.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a covalent organic framework (COF) material containing a boat-shaped C=N conjugated segment, its first-principles design method, and its application in the photocatalytic synthesis of hydrogen peroxide. Background Technology

[0002] Hydrogen peroxide (H2O2) is an important green oxidant with wide applications in chemical synthesis, environmental remediation, and medical and health fields. Currently, over 95% of the world's H2O2 is produced via the anthraquinone process, which involves multiple hydrogenation and oxidation steps. This process is not only energy-intensive but also generates a large amount of organic waste, failing to meet the requirements of green chemistry and sustainable development. Therefore, developing a photocatalytic synthesis technology for H2O2 using water and oxygen as raw materials and directly driven by solar energy is of significant strategic importance.

[0003] Two-dimensional covalent organic frameworks (2D COFs) are considered ideal non-metallic photocatalyst platforms due to their advantages such as designable structure, high specific surface area, ordered pores, and tunable photoelectric properties. However, existing 2D COFs generally have the following problems in the photocatalytic production of H2O2: (1) the two-electron oxygen reduction reaction (2e - (1) The selectivity of ORR is low and it is easy to generate water by four-electron side reaction; (2) It relies heavily on sacrificial agents such as alcohols to capture photogenerated holes, resulting in increased costs and decreased atom economy; (3) Traditional trial-and-error experimental screening is inefficient and lacks rational design and high-throughput screening methods from molecular fragments to two-dimensional frameworks.

[0004] Inspired by the electron-proton co-transfer mechanism of the quinone / hydroquinone active centers in the industrial anthraquinone process cycle, this invention proposes a novel molecular fragment engineering strategy. By precisely constructing boat-shaped C=N conjugated fragments mimicking anthraquinone function within a 2D COF framework, it is hoped that the catalytic cycle of anthraquinone can be simulated at the atomic scale, fundamentally solving the problems of low selectivity and sacrificial agent dependence. Summary of the Invention

[0005] To address the aforementioned shortcomings in the prior art, this invention provides a covalent organic framework photocatalytic material containing a boat-shaped C=N conjugated segment, its design method, and its application.

[0006] The technical concept of this invention is as follows:

[0007] This invention proposes a reverse design strategy. First, simulating the active center of the industrial anthraquinone process, a C=N conjugated molecular fragment with a boat-like configuration (-C=NC=N- or -N=CC=N-) is designed. The nitrogen atom of this fragment can act as a proton acceptor (simulating the role of carbonyl oxygen in the anthraquinone process), and the adjacent carbon atom can act as an oxygen adsorption and activation center (simulating the role of adjacent aromatic carbons in the anthraquinone process), thereby constructing a cyclic electron shuttle pathway of "protonated nitrogen → carbon → adsorbed oxygen" (H... + -NC→O2). This mechanism chemically simulates the key steps in the anthraquinone cycle where quinone sites sequentially hydrogenate and release H2O2. Then, these molecular fragments are screened using first-principles calculations, and the selected fragments are used as structural units to modularly assemble COFs with periodic two-dimensional structures. Finally, their band structure and reaction thermodynamics (Gibbs free energy change) are evaluated through calculations to obtain high-performance catalysts. Furthermore, this invention proposes an electronic fingerprint descriptor based on density of states (DOS) similarity for high-throughput and rapid screening of a large number of candidate COF materials.

[0008] The present invention provides a covalent organic framework material for photocatalytic synthesis of hydrogen peroxide, characterized in that its framework contains a boat-shaped C=N conjugated segment with anthraquinone-like reactivity, wherein the boat-shaped C=N conjugated segment contains a -C=NC=N- or -N=CC=N- linkage sequence.

[0009] Preferably, the boat-shaped C=N conjugate segment serves as a connecting unit or node unit of the covalent organic framework material.

[0010] Preferably, the topological structure of the covalent organic framework material is a honeycomb lattice (hcb).

[0011] More preferably, the covalent organic framework material has the structural formula TRI-BIP-TRI (TBiT), where TRI is a triazine ring unit and BIP is a bipyridine unit.

[0012] This invention provides a method for high-throughput screening of photocatalytic materials based on first-principles calculations, comprising:

[0013] A. Establish a crystal structure model for the material to be screened;

[0014] B. Calculate the total density of states of the material to be screened and the partial density of states of the specified element;

[0015] C. Calculate the thermodynamic reaction processes of some reference materials and the pairwise total density of states similarity and the partial wave density of states similarity of specified elements to confirm the screening threshold.

[0016] D. Calculate the total density of states similarity and the partial density of states similarity of specified elements between the material to be screened and the high-performance reference material;

[0017] E. When both the total density of states similarity and the partial density of states similarity of the specified element exceed a preset threshold, the material to be screened is predicted as a candidate material with high photocatalytic activity.

[0018] This invention also provides a design method for the above-mentioned covalent organic framework material, comprising the following steps:

[0019] S1: Construct multiple boat-shaped C=N conjugated molecular fragments, wherein the molecular fragments contain -C=NC=N- or -N=CC=N- linker sequences;

[0020] S2: Using the target molecular fragments designed in S1 as nodes or connecting units, construct candidate two-dimensional covalent organic framework materials with periodic structures;

[0021] S3: Select several candidate two-dimensional covalent organic framework materials constructed in S2 as benchmark materials to determine the following state density similarity descriptor screening threshold.

[0022] S4: Through first-principles calculations, evaluate the electronic structure, band edge positions, and thermodynamic free energy changes of the selected candidate benchmark two-dimensional covalent organic framework materials to determine the materials that meet the thermodynamic conditions for photocatalytic hydrogen peroxide production (Gibbs free energy changes are all less than 0 eV).

[0023] S5: Analyze the density of states of the reference materials selected in S3 to confirm the similarity between their total density of states and the similarity between the partial density of states of carbon.

[0024] S6: Analyze the similarity values ​​of the total density of states and the partial density of states of carbon element among the materials that meet the thermodynamic conditions for photocatalytic hydrogen peroxide production (Gibbs free energy change is less than 0 eV) determined by first-principles calculations in S4. Determine the similarity numerical characteristics of two-dimensional covalent organic frameworks with the same hydrogen peroxide generation capacity, and determine the high-throughput screening threshold.

[0025] S7: Select a known two-dimensional covalent organic framework material with excellent photocatalytic hydrogen peroxide production performance as a reference, and calculate its total density of states and partial density of states of carbon.

[0026] S8: Calculate the total density of states similarity and carbon fractional density of states similarity between other candidate two-dimensional covalent organic framework materials and the reference benchmark;

[0027] S9: Candidate materials with a total density of states similarity greater than the total density of states similarity threshold determined in S6 and a carbon partial density of states similarity greater than the carbon partial density of states threshold determined in S6 are identified as high-activity candidate materials.

[0028] More preferably, the similarity threshold of the total density of states is 70%, and the similarity threshold of the partial density of states of carbon element is 60%.

[0029] Preferably, the steps for the thermodynamic activity of the two-dimensional covalent organic framework constructed in S2 for the two-electron oxygen reduction reaction include: calculating the free energies of the intermediate diproton adsorption (*H*H), diproton and oxygen adsorption (*H*H-O2) and the product H2O2, determining that the rate-controlling step of the reaction is the protonation step, and calculating the free energies of the oxygen evolution reaction (OER) intermediates *OH, *O*, *O*OH, and *OO*.

[0030] The present invention further provides a catalyst for the photocatalytic synthesis of hydrogen peroxide, the catalyst comprising the covalent organic framework material described in any of the preceding claims or obtained by the design method described in any of the preceding claims.

[0031] The present invention also provides the application of the catalyst for generating hydrogen peroxide from water and oxygen via a photocatalytic reaction under sacrificial agent-free conditions; the conditions for the photocatalytic reaction are: visible light irradiation (λ > 400 nm), pure water system, and oxygen atmosphere.

[0032] The beneficial effects of this invention are as follows:

[0033] 1. Innovative biomimetic / industrial-inspired mechanism design: For the first time, the catalytic cycle of the industrial anthraquinone process is abstracted into a precisely constructible boat-shaped C=N conjugated segment, and an electron shuttle mechanism of "protonated nitrogen → carbon → adsorbed oxygen" is proposed, providing a new and predictable chemical model for the design of COF photocatalysts.

[0034] 2. Abundant library of active fragments: Based on the above mechanism, 39 molecular fragments were designed (36 of which are novel structures), which greatly expands the design space of COFs photocatalysts.

[0035] 3. High-throughput theoretical screening method: For the first time, an electronic fingerprint descriptor based on density of states (DOS) similarity is proposed, which enables rapid screening of 106 candidate COFs with a prediction accuracy of 81%, transforming the material discovery mode from "trial and error" to "rational design".

[0036] 4. Excellent catalytic performance: TBiT, a representative material screened and synthesized by this method, exhibits a high H2O2 yield of 3084.27 μmol g under conditions of no sacrificial agent, pure water, and visible light. -1 h-1 Furthermore, no hydrogen byproducts were detected, demonstrating high selectivity and high activity.

[0037] 5. Green and sustainable: The entire process uses water and oxygen as raw materials and visible light as energy, without relying on any organic sacrificial agents or precious metal co-catalysts, achieving a truly green and sustainable chemical transformation. Attached Figure Description

[0038] Figure 1 This is a schematic diagram comparing the industrial anthraquinone process with the boat-type C=N conjugated fragment photocatalytic cycle of this invention.

[0039] Figure 2 Molecular structure diagrams of 39 boat-shaped C=N conjugated molecular fragments designed for this invention.

[0040] Figure 3 Excited-state charge distribution diagrams of representative molecular fragments (HEP, TRI, BIP)

[0041] Figure 4 This is a schematic diagram of the construction strategy and topology model for integrating ship-shaped C=N segments into two-dimensional COFs in this invention.

[0042] Figure 5 The structures of 6 out of 106 designed COFs materials are shown.

[0043] Figure 6 Optimize the structure of COFs with HEP nodes and BIP, BEN, IMI or ALK connectors from the selected 20 materials.

[0044] Figure 7 Optimize the structure of COFs with hybrid HEP and TRI nodes and BIP, BEN, IMI or ALK connectors from 20 selected materials.

[0045] Figure 8 Optimize the structure of COFs with hybrid HEP and BEN nodes and BIP, BEN, IMI or ALK connectors from 20 selected materials.

[0046] Figure 9 Optimize the structure of COFs with TRI nodes and BIP, BEN, IMI or ALK connectors from the selected 20 materials.

[0047] Figure 10 Optimize the structure of COFs with mixed TRI and BEN nodes and BIP, BEN, IMI or ALK connectors from 20 selected materials.

[0048] Figure 11 This is a diagram showing the band edge positions of 20 reference 2D COFs of this invention.

[0049] Figure 12 Thermodynamic reactivity diagram of photocatalytic reactions of 20 COFs

[0050] Figure 13 To assess the similarity of the density of states among 20 benchmark COFs, pairwise comparisons were performed based on the total density of states (TDOS) and the carbon partial density of states (C_PDOS), respectively.

[0051] Figure 14 This is a diagram showing the results of high-throughput screening of 106 2D COFs based on density of states similarity in this invention.

[0052] Figure 15 Nine COFs with photocatalytic H2O2 generation capability were selected after passing the density of states similarity screening and then the Gibbs free energy change (i.e., thermodynamic feasibility) test.

[0053] Figure 16 This is a synthetic route diagram for the target material TBiT of this invention.

[0054] Figure 17 The Fourier transform infrared spectrum of the material TBiT of this invention.

[0055] Figure 18 The solid form of the material TBiT of this invention 13 C CP-MAS NMR spectrum

[0056] Figure 19 This is a comparison chart of the photocatalytic H2O2 production yields of TBiT and TPymPymT in this invention.

[0057] Figure 20 This is the mass spectrum of the TBiT photocatalytic experiment under Ar atmosphere (proving in-situ O2 generation).

[0058] Figure 21 This is a synthetic route diagram for the material TPymPymT of this invention.

[0059] Figure 22 The Fourier transform infrared spectrum of the material TPymPymT of this invention.

[0060] Figure 23 The solid form of the material TPymPymT of this invention 13 C CP-MAS NMR spectrum Detailed Implementation

[0061] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0062] Example 1: Design of boat-shaped C=N conjugated molecular fragments

[0063] like Figure 1 As shown, this invention simulates the active center of the industrial anthraquinone process and designs a class of C=N conjugated molecular fragments with a boat-shaped configuration, whose core linking sequence is -C=NC=N- or -N=CC=N-.

[0064] Through systematic screening and derivation design of chemical molecular libraries, 39 candidate fragments were ultimately identified. Figure 2 The proposed fragments include the heptaazine fragment HEP, the triazine fragment TRI, and the bipyridine fragment BIP, which have been reported in the literature, as well as 36 novel structures designed in this invention. All 39 candidate fragments are classified into three types: Type-I, Type-II, and Type-III. Type-I consists of systems formed by conjugation of a nitrogen-containing heterocyclic core with an imine bond (such as PYI, PYDI, and PYMI); Type-II consists of fused bicyclic central structures (such as PYPYD, PYPYM, and PYQUI); and Type-III consists of systems containing a fused triazole five-membered ring (such as TRZCPYO and TRZNIMZ).

[0065] The excited-state electron-hole distribution of each fragment was calculated using Gaussian software at the B3LYP / 6-31G level. Results ( Figure 3 This indicates that these fragments generally exhibit significant electron-hole spatial separation in the excited state: holes are enriched at nitrogen sites (favorable for protonation), and electrons are enriched at nearby carbon sites (favorable for O2 activation).

[0066] Based on the computational hydrogen electrode (CHE) model, the 2e content of each segment was calculated under pH=7 conditions. - The Gibbs free energy change (ΔG) of ORR was determined. The results indicate that both O2 adsorption and H2O2 desorption are exothermic and spontaneous processes (ΔG < 0), while the protonation step (* + (H...)... + +e - The step ⇌ *H) is the rate-determining step, with a ΔG of approximately 0.8 eV. This step can be driven by an overpotential provided by photogenerated electrons in photocatalysis, confirming the potential of the boat-shaped segment to photocatalyze the generation of H₂O₂.

[0067] Example 2: Construction and High-Throughput Screening of Target 2D COFs

[0068] Using HEP, TRI, etc. designed in Example 1 as C3 symmetric nodes and ship-shaped segments such as BIP, PYI, and PYPYD as C2 symmetric connecting units, 106 honeycomb lattice (hcb) topologies were constructed. Figure 4 The 2D COFs model, with some structures as follows: Figure 5 .

[0069] First, 20 COFs containing only known experimentally reported fragments (HEP, TRI, BIP) were selected from the designed 106 COFs as the baseline system. Figures 6-10 This was used to explore its reactive power and obtain the threshold for determining the similarity of subsequent density of states. The band edge positions were calculated using VASP software and the HSE06 hybrid functional. Results ( Figure 11 This indicates that the conduction band bottom (CBM) of these benchmark COFs is higher than that of H. + The reduction potential of H2 (-4.02 eV vs. vacuum) is sufficient to drive 2e - Thermodynamic premise of ORR.

[0070] We then systematically evaluated the reaction thermodynamics of 20 benchmark COFs, and calculated 2e based on DFT calculations. - The free energies of the ORR reaction intermediates, including the adsorption of two protons (*H*H), the adsorption of two protons and oxygen (*H*H-O2), and the product H2O2, are calculated, and the rate-determining step of the reaction is determined to be the protonation step. The free energies of the oxygen evolution reaction (OER) intermediates *OH*, *O*, *O*OH, and *OO* are calculated. A thermodynamic reaction activity scatter plot is constructed using the obtained ΔG data. Figure 12 To establish functional classification boundaries, two key thermodynamic boundaries are introduced in the figure: (1) Reduction boundary (pink horizontal dashed line): corresponding to ΔG(*H) – eUr = 0. A line segment below this line indicates that the reduction potential generated by photoexcitation is sufficient to cross the protonation barrier; (2) Oxidation boundary (blue vertical dashed line): corresponding to ΔG(OER) – eUo = 0. A line segment to the right of this line indicates that the system possesses the thermodynamic conditions to drive the oxygen evolution reaction. The region in the lower right corner is the ideal region where H2O2 can be generated without a sacrificial agent.

[0071] The density of states (DSO) of 20 baseline 2D COFs was calculated, and the similarity between their overall DSO and the similarity between their partial wavelet DSOs was analyzed. The results are as follows: Figure 13 When the similarity of the total density of states of two materials exceeds 70%, and the similarity of the partial density of states of carbon exceeds 60%, their thermodynamic activity distribution diagram ( Figure 12 They always cluster in the same active quadrant.

[0072] Then, using the high-performance benchmark material HBiT (HEP-BIP-TRI) as a reference, the similarity of the total density of states (TDOS) and carbon partial density of states (C_PDOS) of all other candidate materials relative to HBiT was calculated. The screening criteria were set as TDOS similarity > 70% and C_PDOS similarity > 60%. Figure 14As shown, 11 high-potential COFs were selected from 106 candidate structures, including TPymPymBe, BePyPydT, and TBiT. The other materials did not meet the criteria of TDOS similarity > 70% and C_PDOS similarity > 60%.

[0073] ΔG verification calculations were performed on the above 11 candidate materials. The Gibbs free energy change at all steps in the reaction pathway was less than 0 eV, proving that the reaction is thermodynamically feasible. The calculation results show that 9 of these materials (81% accuracy) possess the thermodynamic feasibility of generating H₂O₂ without a sacrificial agent. Figure 15 These nine materials, named according to the node-connection-node naming convention, are: TRI-BIP-TRI (TBiT), BEN-pyridine-pyridazine-TRI (BePyPydT), TRI-pyridazine-pyrazine-BEN (TPydPyrBe), TRI-pyrimidine-pyrimidine-BEN (TPymPymBe), TRI-pyrazine-pyrazine-BEN (TPyrPyrBe), TRI-pyridine-pyrimidine-TRI (TPyPymT), TRI-pyridine-pyrazine-TRI (TPyPyrT), TRI-pyridazine-quinoline-TRI (TPydQuiT), and TRI-pyrimidine-isoquinoline-TRI (TPymIquiT). All nine materials contain the aforementioned boat-shaped C=N conjugated segment. Figure 15 ).

[0074] Example 3: Synthesis and Performance Verification of the Target Material TBiT

[0075] Based on the high-throughput screening results of Example 2, TBiT (TRI-BIP-TRI) was selected as the target material for experimental synthesis and performance verification.

[0076] Synthesis method (see) Figure 16Under argon protection, the precursor 4,4′-([2,2′-bipyridine]-5,5′-diyl)dibenzonitrile (BPDDBN, 100 mg) was cooled to 0 °C in an ice-water bath. Trifluoromethanesulfonic acid (CF3SO3H, 1 mL) was added dropwise, followed by stirring at 0 °C for 20 min, 25 °C for 1.5 h, and 60 °C for 40 min, respectively. The reaction mixture was quenched in cold deionized water, and the resulting solid product was washed successively with dilute ammonia (NH4OH) and ethanol. The material was ground into a fine powder and then subjected to Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone. The final product was dried under vacuum at 60 °C to obtain a brown solid, TBiT, with a yield of 52%.

[0077] Fourier transform infrared spectroscopy (FTIR) Figure 17 The data shows that the nitrile peak of the raw material is at 2229 cm⁻¹. -1 The peak completely disappeared, and at the same time, the characteristic peak of the triazine ring (1520 cm⁻¹) appeared. -1 and 1384 cm -1 This proves that the triazine skeleton was successfully constructed.

[0078] solid 13 C CP-MAS NMR ( Figure 18 This further confirms the formation of the TBiT framework structure. The signal at approximately 166 ppm is attributed to the C=N carbon in the triazine ring; the signals at approximately 154 and 147 ppm are attributed to the carbons adjacent to the N atom in the nitrogen-containing aromatic unit; and the broad peak in the range of 113–142 ppm is attributed to the remaining aromatic carbons in the framework.

[0079] Photocatalytic H2O2 production performance test: 1 mg TBiT was dispersed in 22 mL of O2-saturated deionized water, and the photocatalytic activity was tested under visible light (λ > 400 nm, 300 W xenon lamp). Samples were taken periodically, and the H2O2 concentration was determined using the iodometric method. Results are as follows: Figure 19 As shown, under conditions without any sacrificial agents, the H2O2 yield of TBiT reached 3084.27 μmol g. -1 h -1 Mass spectra of the control experiment under Ar atmosphere ( Figure 20 The detection of O2 signal indicates that TBiT can provide oxygen in situ through water oxidation reaction (WOR) and drive 2e⁻ ORR to generate H2O2, thus realizing the whole reaction photocatalytic synthesis.

[0080] Control experiment: TPymPymT, a material with low similarity (60% TDOS similarity, 45% C_PDOS similarity), was synthesized using the same method, but its H2O2 yield was only 507.82 μmol g. -1 h-1 This verifies the effectiveness of the DOS similarity descriptor.

[0081] Synthesis method (see) Figure 21 : Under an argon atmosphere, 100 mg of 4,4'-([2,2'-bipyrimidine]-5,5'-diyl)benzonitrile was cooled to 0 °C in an ice-water bath. Trifluoromethanesulfonic acid (CF3SO3H, 1.0 mL) was then added dropwise, followed by stirring at 0 °C for 20 min, 25 °C for 2 h, and 150 °C for 8 h. The reaction mixture was quenched in ice-cooled deionized water. The resulting solid product was washed sequentially with dilute ammonia (NH4OH) and ethanol. The material was ground into a fine powder and then subjected to Soxhlet extraction with deionized water, ethanol, acetonitrile, and acetone. The final product was dried under vacuum at 60 °C to give a brown solid TPymPymT with a mass of 38 mg and a yield of 38%.

[0082] Fourier transform infrared spectroscopy (FTIR) Figure 22 The data shows that the nitrile peak of the raw material is at 2226 cm⁻¹. -1 The peak completely disappeared, and at the same time, the characteristic peak of the triazine ring (1522 cm⁻¹) appeared. -1 and 1373 cm -1 ), and 1605 cm -1 The peak at the point is enhanced due to the formation of C=N bonds, proving that the triazine skeleton was successfully constructed.

[0083] solid 13 C CP-MAS NMR ( Figure 23 This further confirms the formation of the TPymPymT framework structure. The signal at approximately 170 ppm is attributed to the C=N carbon in the triazine ring. The resonance peak at approximately 155 ppm can be attributed to the aromatic carbon atom adjacent to the nitrogen atom in the nitrogen-containing aromatic unit, while the broad peak in the 117-142 ppm region is attributed to the remaining aromatic carbon atoms in the framework.

[0084] Photocatalytic H2O2 production performance test: 1 mg TPymPymT was dispersed in 22 mL of O2-saturated deionized water, and photocatalytic testing was conducted under visible light (λ > 400 nm, 300 W xenon lamp) irradiation. Samples were taken periodically, and the H2O2 concentration was determined using the iodometric method. The results showed that, without any sacrificial agent, the H2O2 yield of TPymPymT was 507.82 μmol g. -1 h -1 ( Figure 19 ).

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A covalent organic framework material for photocatalytic synthesis of hydrogen peroxide, characterized in that, The framework of the covalent organic framework material contains a boat-shaped C=N conjugated segment with anthraquinone-like reactivity, wherein the boat-shaped C=N conjugated segment contains a -C=NC=N- or -N=CC=N- linker sequence.

2. The covalent organic framework material according to claim 1, characterized in that, The ship-shaped C=N conjugate segment serves as the connecting unit or node unit of the covalent organic framework material.

3. The covalent organic framework material according to claim 1, characterized in that, The covalent organic framework material has a honeycomb lattice topology.

4. The covalent organic framework material according to claim 1, characterized in that, The covalent organic framework material has any one of the following structural formulas: The covalent organic framework material TRI-BIP-TRI (TBiT) consists of TRI, which is a triazine ring unit used as a conjugated organic framework node, and BIP, which is a bipyridine unit used as a conjugated organic framework linker.

5. A method for high-throughput screening of photocatalytic materials based on first-principles calculations, characterized in that, include: A. Establish a crystal structure model for the material to be screened; B. Calculate the total density of states of the material to be screened and the partial density of states of the specified element; C. Calculate the thermodynamic reaction processes of some reference materials and the pairwise total density of states similarity and the partial wave density of states similarity of specified elements to confirm the screening threshold; D. Calculate the total density of states similarity and the partial density of states similarity of specified elements between the material to be screened and the high-performance reference material; E. When both the total density of states similarity and the partial density of states similarity of the specified element exceed a preset threshold, the material to be screened is predicted as a candidate material with high photocatalytic activity.

6. The design method for high-throughput screening photocatalytic materials according to claim 5, characterized in that, Includes the following steps: S1: Construct multiple boat-shaped C=N conjugated molecular fragments, wherein the molecular fragments contain -C=NC=N- or -N=CC=N- linker sequences; S2: Using the target molecular fragments designed in S1 as nodes or connecting units, construct candidate two-dimensional covalent organic framework materials with periodic structures; S3: Select several candidate two-dimensional covalent organic framework materials constructed in S2 as benchmark materials to determine the following state density similarity descriptor screening threshold. S4: Through first-principles calculations, evaluate the electronic structure, band edge positions, and thermodynamic free energy changes of the selected candidate benchmark two-dimensional covalent organic framework materials to determine the materials that meet the thermodynamic conditions for photocatalytic hydrogen peroxide production and whose Gibbs free energy changes are all less than 0 eV.

7. The design method for high-throughput screening photocatalytic materials according to claim 6, characterized in that, The method also includes a high-throughput screening step based on density of states similarity: S5: Analyze the density of states of the reference materials selected in S3 to confirm the similarity between their total density of states and the similarity between the partial density of states of carbon. S6: Analyze the similarity of the total density of states and the partial density of states of carbon elements among materials that meet the thermodynamic conditions for photocatalytic hydrogen peroxide production and whose Gibbs free energy changes are all less than 0 eV, as determined by first-principles calculations in S4. Determine the similarity numerical characteristics of two-dimensional covalent organic frameworks with the same hydrogen peroxide generation capacity, and determine the high-throughput screening threshold. S7: Select a known two-dimensional covalent organic framework material with excellent photocatalytic hydrogen peroxide production performance as a reference, and calculate its total density of states and partial density of states of carbon. S8: Calculate the total density of states similarity and carbon fractional density of states similarity between other candidate two-dimensional covalent organic framework materials and the reference benchmark; S9: Candidate materials with a total density of states similarity greater than the total density of states similarity threshold determined in S6 and a carbon partial density of states similarity greater than the carbon partial density of states threshold determined in S6 are identified as high-activity candidate materials; the total density of states similarity threshold is 70%, and the carbon partial density of states threshold is 60%.

8. The design method for high-throughput screening photocatalytic materials according to claim 6, characterized in that, The steps for the thermodynamic activity of the two-electron covalent organic framework constructed in S2 for the two-electron oxygen reduction reaction include: calculating 2e - The free energies of the ORR reaction intermediates, including the diproton adsorption of *H*H, the diproton adsorption of oxygen, *H*H-O2, and the product H2O2, are calculated. The rate-determining step of the reaction is determined to be the protonation step. The free energies of the oxygen evolution reaction (OER) intermediates *OH, *O*, *O*OH, and *OO* are also calculated.

9. A catalyst for the photocatalytic synthesis of hydrogen peroxide, characterized in that, The catalyst comprises the covalent organic framework material as described in any one of claims 1-4 or is selected by the design method described in any one of claims 5-8.

10. The application of the catalyst according to claim 9, characterized in that, This is used to generate hydrogen peroxide from water and oxygen via photocatalytic reaction under sacrificial agent-free conditions; the conditions for the photocatalytic reaction are: visible light irradiation λ > 400 nm, pure water system, and oxygen atmosphere.

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