Acrylonitrile functionalized covalent organic framework material and preparation method and application thereof

Abstract

This invention discloses an acrylonitrile-functionalized covalent organic framework material, its preparation method, and its applications. The material framework contains both acrylonitrile and benzoxoxadiazole groups, and is prepared through stepwise synthesis of amine monomer QA and aldehyde monomer OA, followed by solvothermal condensation of the two. During the preparation process, parameters such as the raw material ratio, reaction temperature, and time are precisely controlled. The material obtained by this invention exhibits good crystallinity, high photogenerated carrier separation efficiency, and, without sacrificial agents, a photocatalytic synthesis yield of over-H₂O₂ of no less than 3500 μmol / g under visible light irradiation. ‑1 h ‑1 In a seawater system with 0.5~1.0 mol / L chloride ions, the activity retention rate is not less than 85% after continuous catalysis for 4~5 days. The preparation process is mild, environmentally friendly, and easy to scale up. It can be efficiently applied to the photocatalytic synthesis of H2O2 in high-salt environments such as pure water and seawater.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor photocatalytic materials technology, specifically relating to an acrylonitrile-functionalized covalent organic framework material, its preparation method, and its application. Background Technology

[0002] Hydrogen peroxide (H2O2) is an environmentally friendly green oxidant and an important liquid fuel with irreplaceable and wide-ranging applications in chemical synthesis, environmental protection, energy conversion, medical and health care, pulp bleaching, and many other fields. With the increasing demand for H2O2 across various industries, its large-scale and green production has become a core requirement for industry development.

[0003] Currently, the mainstream method for industrial production of H2O2 is the anthraquinone process. This method prepares H2O2 through the hydrogenation-oxidation cycle of anthraquinone, but it has many inherent drawbacks: the production process has high energy consumption and requires high temperature and high pressure reaction conditions; the process route is complex, involving multiple separation and purification operations, resulting in high equipment investment and operating costs; and a large amount of organic solvent is required during the reaction, which can easily cause the volatilization and leakage of organic solvents. At the same time, the residual organic solvent in the product will also affect the purity of H2O2.

[0004] The photocatalytic synthesis of H2O2 from water and oxygen using solar energy is considered an ideal alternative to the anthraquinone process due to its mild reaction conditions, clean and renewable solar energy source, green and pollution-free process, and widely available raw materials. Among numerous photocatalytic materials, covalent organic frameworks (COFs), as a novel type of crystalline organic porous material, exhibit great application potential in the photocatalytic synthesis of H2O2 due to their pre-designable covalent framework structure, high specific surface area, good chemical and thermal stability, and functionalizable pore environment. The structure of COFs can be precisely controlled at the molecular level, allowing the introduction of specific functional groups into the framework, thereby achieving targeted regulation of its photoelectric properties and providing a structural basis for optimizing photocatalytic performance.

[0005] However, existing COF photocatalysts still face many technical bottlenecks and shortcomings when practically applied to the photocatalytic synthesis of H2O2, which severely limits their industrial application:

[0006] (1) Photogenerated carrier recombination is severe and quantum efficiency is low: In most COF materials, photogenerated electrons and holes recombine rapidly after generation, resulting in low separation and migration efficiency of photogenerated carriers. They cannot effectively participate in subsequent redox reactions, making it difficult to improve photoquantum efficiency and directly restricting the yield of H2O2.

[0007] (2) Insufficient surface active sites and low catalytic reaction efficiency: Relying solely on the intrinsic framework structure of COF, the number of active sites on its surface that can be used for oxygen adsorption and activation is limited, making it impossible to efficiently capture oxygen molecules and drive the two-electron oxygen reduction reaction (ORR), resulting in a low overall reaction efficiency of photocatalytic synthesis of H2O2.

[0008] (3) Poor adaptability to complex aquatic environments, limiting practical applications: Most current research on the synthesis of H2O2 by COF photocatalysts focuses on pure water systems. However, in practical applications, directly utilizing abundant seawater resources as the reaction medium will face severe challenges. Seawater contains high concentrations of chloride ions, as well as various metal ions and impurities. Chloride ions easily combine with active sites on the catalyst surface, inhibiting the catalyst's catalytic activity and potentially corroding the catalyst's framework structure, leading to a sharp decline in H2O2 yield. Furthermore, in open seawater, the photocatalyst surface is prone to microbial contamination, covering active sites and further reducing the catalyst's catalytic performance, affecting its long-term operational stability.

[0009] To address these issues, researchers have attempted to modify COF materials by introducing single functional groups, such as acrylonitrile and hydroxyl groups, to regulate their photoelectric properties. However, the effect of single-group modification is limited and cannot simultaneously achieve multiple objectives such as optimizing carrier dynamics, increasing active sites, and improving adaptability to complex aquatic environments.

[0010] Therefore, how to construct COF photocatalysts with multi-functional group synergistic regulation through reasonable molecular design, simultaneously optimize the photogenerated carrier separation efficiency and surface reaction activity of COF materials without sacrificial agents, and enable them to adapt to complex real water environments such as seawater, while maintaining high catalytic activity and long-term stability, is a key technical problem that urgently needs to be solved in the field of photocatalytic synthesis of H2O2. Summary of the Invention

[0011] To address the technical problems of existing COF photocatalysts, such as low photogenerated carrier separation efficiency, insufficient surface active sites, and poor adaptability to complex aquatic environments such as seawater, this invention provides an acrylonitrile-functionalized covalent organic framework material, its preparation method, and its application. Through molecular design, acrylonitrile and benzoxadiazole functional groups are simultaneously introduced into the COF framework, and their synergistic effect is utilized to achieve simultaneous optimization of the material's photoelectric properties, surface activity, and environmental adaptability.

[0012] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0013] A functionalized covalent organic framework material of acrylonitrile, whose framework structure contains both acrylonitrile and benzoxadiazole groups, is designated TAQ-COF. TAQ-COF is prepared by Schiff base condensation reaction of an acrylonitrile-containing amine monomer QA and a benzoxadiazole-containing aldehyde monomer OA. QA is (2Z,2'Z,2''Z)-3,3',3''-(phenyl-1,3,5-triyl)tris(2-(4-aminophenyl)acrylonitrile), and OA is 4,7-bis(5-formyl-1,3-phenylene)benzo[c][1,2,5]oxadiazole.

[0014] The structure of QA is:

[0015] ,

[0016] The structure of OA is:

[0017] ,

[0018] The structural formula of TAQ-COF is:

[0019] .

[0020] Furthermore, TAQ-COF is a highly crystalline material, exhibiting sharp and strong characteristic diffraction peaks at a 2θ angle of 4.5°–5.0°, demonstrating its regular crystal structure. Its infrared spectrum also shows peaks in the range of 2210–2220 cm⁻¹. -1 Characteristic absorption peaks of C≡N bonds are present at 1620~1625 cm⁻¹. -1 The presence of characteristic absorption peaks at the Schiff base condensation point indicates that acrylonitrile functional groups have been successfully introduced into the material framework and the Schiff base condensation reaction has been completed. This is the basis for determining the structural characteristics of TAQ-COF materials.

[0021] The preparation method of the above-mentioned acrylonitrile-functionalized covalent organic framework material includes the following steps:

[0022] S1. Synthesis of amine monomer QA: 1,3,5-benzenetriformaldehyde, 2-(4-aminophenyl)acetonitrile, sodium hydroxide, and solvent are added to a reactor. After thorough stirring to dissolve all raw materials and form a homogeneous system, the mixture is heated under reflux under a nitrogen atmosphere to carry out a condensation reaction. The resulting product is then filtered, washed, and dried to obtain the amine monomer (2Z,2'Z,2''Z)-3,3',3''-(benzene-1,3,5-triyl)tris(2-(4-aminophenyl)acrylonitrile), abbreviated as QA. Its chemical reaction formula is as follows:

[0023] ;

[0024] S2. Synthesis of aldehyde monomer OA: 3,5-dimethylphenylboronic acid pinacol ester, 4,7-dibromo-2,1,3-benzoxadiazole, potassium carbonate, and solvent were added to a reactor. After degassing, palladium catalyst Pd(PPh3)4 was added. The reaction was carried out under nitrogen atmosphere with heating and stirring to perform Suzuki coupling and subsequent oxidation reactions. After cooling, filtration, washing, and drying, the aldehyde monomer 4,7-bis(5-formyl-1,3-phenylene)benzo[c][1,2,5]oxadiazole, abbreviated as OA, was obtained. Its chemical reaction formula is as follows: ;

[0025] Synthesis of S3 and TAQ-COF: Aldehyde monomer OA and amine monomer QA are added to an organic solvent, ultrasonically mixed, and then acetic acid is added as a condensation reaction catalyst. After degassing and sealing, the mixture is heated for a solvothermal reaction. After filtration, washing, and drying, TAQ-COF is obtained.

[0026] Further, in step S1, the molar ratio of 1,3,5-benzyltricarboxaldehyde, 2-(4-aminophenyl)acetonitrile, and sodium hydroxide is 1:(3.0~3.5):(10~15), the solvent is a mixture of water and ethanol, the volume ratio of water to ethanol is 1~1.2:1, the reaction temperature is 80~90℃, and the reaction time is 3~5h.

[0027] Further, in step S2, the molar ratio of 3,5-dimethylphenylboronic acid pinacol ester, 4,7-dibromo-2,1,3-benzoxadiazole, potassium carbonate, and Pd(PPh3)4 is (2.4~2.6):1:(5.5~6.0):(0.08~0.09), the solvent is a mixture of water and 1,4-dioxane, the volume ratio of water to 1,4-dioxane is 1:(3.5~4.5), the degassing time is 25~35 min, the heating reaction temperature is 95~105℃, the reaction time is 20~28 h, and the drying temperature is 55~65℃.

[0028] Further, in step S3, the molar ratio of OA to QA is 1:0.9~1.1, the volume ratio of n-butanol to o-dichlorobenzene is (8~10):1, the concentration of acetic acid is 5~7 mol / L, the degassing adopts a freezing-nitrogen pumping-thawing cycle, the number of cycles is 2~4, the solvothermal reaction temperature is 115~125℃, and the reaction time is 2~4 days.

[0029] Further, in step S1, the washing is carried out sequentially using sodium hydroxide solution, ethanol and water; in step S2, the washing is carried out sequentially using water, methanol and toluene; in step S3, the washing is carried out sequentially using tetrahydrofuran and acetone, and the number of washing cycles is 3 to 5 times.

[0030] The aforementioned acrylonitrile-functionalized covalent organic framework material TAQ-COF can be efficiently applied in the field of photocatalytic synthesis of H2O2. Specifically, TAQ-COF is dispersed in the reaction medium as a photocatalyst. Without the addition of any sacrificial agents, visible light irradiation alone can drive the redox reaction between water and oxygen in the reaction medium, efficiently catalyzing the generation of H2O2. This application method does not require the addition of additional additives, the reaction conditions are mild and environmentally friendly, and it significantly reduces the preparation cost of hydrogen peroxide.

[0031] Furthermore, the photocatalytic reaction system is a pure water system or a high-salt complex aquatic environment system including seawater. The chloride ion concentration in the seawater system is 0.5~1.0 mol / L. Due to the synergistic effect of acrylonitrile and benzoxadiazole groups in the framework, the TAQ-COF material has excellent salt resistance and chemical stability. It can effectively resist the adsorption and corrosion of chloride ions and other impurities in seawater, avoid the inhibition of catalyst active sites and the destruction of framework structure, and realize efficient photocatalysis in complex aquatic environments.

[0032] The TAQ-COF prepared in this invention exhibits a photocatalytic synthesis yield of H2O2 of no less than 3500 μmol / g under visible light irradiation. -1 h -1 The catalytic efficiency is far higher than that of existing conventional COF photocatalysts, exhibiting excellent photocatalytic activity. Moreover, the material can continuously catalyze reactions in seawater systems with chloride ion concentrations of 0.5~1.0 mol / L for 4~5 days, and the catalytic activity retention rate is still not less than 85%. It also has antibacterial properties, which can effectively prevent the adsorption and contamination of microorganisms on the catalyst surface, ensuring its stability and high efficiency in complex aquatic environments for a long time. This enables the green and sustainable preparation of hydrogen peroxide in real aquatic environments such as seawater.

[0033] Compared with the prior art, the beneficial effects of the present invention are reflected in:

[0034] (1) This invention optimizes the band structure of TAQ-COF by synergistic regulation of acrylonitrile and benzoxadiazole groups, effectively suppresses the recombination of photogenerated electron-hole pairs, improves carrier migration efficiency, and its photocurrent density is significantly better than that of COF materials modified with a single functional group, providing sufficient active carriers for photocatalytic reaction and greatly improving photoquantum efficiency.

[0035] (2) This invention provides abundant oxygen adsorption and activation sites on the material surface by introducing bifunctional groups, which can efficiently drive the two-electron oxygen reduction reaction. Under visible light irradiation without sacrificial agents, the hydrogen peroxide yield in pure water is not less than 3500 μmol g. -1 h -1 Its catalytic performance is superior to most existing COF photocatalysts.

[0036] (3) The TAQ-COF framework structure obtained by the present invention has good chemical stability and can resist the corrosion and activity inhibition of 0.5~1.0 mol / L chloride ions and impurities in the seawater system. It also has antibacterial properties. In the high-salt complex water environment such as seawater, the activity retention rate is not less than 85% after continuous catalysis for 4~5 days, realizing the direct utilization of real water environment.

[0037] (4) The preparation method of the present invention adopts a mild solvothermal reaction, the raw material ratio is reasonable, the reaction conditions of each step are easy to control, the product washing and purification operation is simple, the yield of each monomer and the final product is high, and no toxic by-products are generated in the preparation process. The process has good repeatability and is suitable for laboratory small-scale testing and industrial scale-up production. Attached Figure Description

[0038] Figures 1 to 3 The X-ray diffraction patterns are for TAQ-COF, TBQ-COF, and TCQ-COF, respectively.

[0039] Figure 4 This is a scanning electron microscope (SEM) image of TAQ-COF.

[0040] Figure 5 Fourier transform infrared spectra of TAQ-COF, TBQ-COF, and TCQ-COF.

[0041] Figure 6 The graph shows the rate of H2O2 production by TAQ-COF, TBQ-COF, and TCQ-COF under conditions of no sacrificial agent, visible light irradiation, and oxygen saturation.

[0042] Figure 7 The transient photocurrent response curves of TAQ-COF, TBQ-COF, and TCQ-COF are shown. Detailed Implementation

[0043] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, but the present invention is not limited thereto.

[0044] Example 1

[0045] Step 1: Synthesis of amine monomers

[0046] 1,3,5-Benzenetricarbonaldehyde (162.1 mg, 1 mmol), 2-(4-aminophenyl)acetonitrile (436.1 mg, 3.3 mmol), sodium hydroxide (500 mg), water (15 mL), and ethanol (15 mL) were uniformly mixed. Under a nitrogen atmosphere, the mixture was heated to 85 °C and stirred under reflux for 4 hours. After the reaction was completed, the precipitate was collected by vacuum filtration, washed thoroughly with sodium hydroxide solution, ethanol, and water in sequence, and finally dried under vacuum at 60 °C for 6 hours to obtain the product (2Z,2'Z,2''Z)-3,3',3''-(benzene-1,3,5-triyl)tris(2-(4-aminophenyl)acrylonitrile) (QA) in 87% yield.

[0047] Step 2: Synthesis of Aldehyde Monomers

[0048] In a round-bottom flask, 3,5-dimethylphenylboronic acid pinacol ester (0.38 g, 1.50 mmol), 4,7-dibromo-2,1,3-benzoxadiazole (0.17 g, 0.60 mmol), and potassium carbonate (0.48 g, 3.50 mmol) were dissolved in a mixed solvent of water (5.0 mL) and 1,4-dioxane (20.0 mL). The mixture was degassed by purging nitrogen for 30 minutes. Pd(PPh3)4 (0.05 g, 0.05 mmol) was then added, and the reaction mixture was heated to 100°C and stirred for 24 hours under a nitrogen atmosphere. After the reaction was complete, the mixture was cooled to room temperature and poured into water (100 mL). The precipitate was collected by filtration, washed successively with water, methanol and toluene, and dried at 60°C to give the solid product 4,7-bis(5-formyl-1,3-phenylene)benzo[c][1,2,5]oxadiazole (OA) (164.1 mg, yield 71%).

[0049] Step 3: Synthesis of TAQ-COF

[0050] OA (0.04 mmol, 15 mg) and QA (0.04 mmol, 20 mg) were added to a reaction tube containing n-butanol (1.8 mL) and o-dichlorobenzene (0.2 mL). The mixture was sonicated to ensure thorough mixing, followed by the addition of acetic acid (6 M, 0.2 mL). The reaction tube was degassed by a three-stage freeze-thaw cycle with nitrogen pumping, and then sealed. The reaction system was then heated at 120 °C for 3 days. After the reaction system cooled to room temperature, the mixture was filtered, and the collected solid was washed several times with tetrahydrofuran and acetone. Finally, the resulting yellow solid was dried under vacuum overnight to obtain a yellow powder, designated TAQ-COF, with a yield of 84%. The chemical reaction formula is as follows:

[0051] .

[0052] Experimental results show that the photocatalytic H2O2 production rate of TAQ-COF obtained in Example 1 in a pure water system is 4938 μmol g. -1 h -1 In a seawater system with a chloride ion concentration of 0.56 mol / L, the concentration was 4587 μmol g. -1 h -1 Furthermore, even after continuous catalytic reaction in the seawater system for 4-5 days, the catalytic activity retention rate remains no less than 85%.

[0053] Example 2

[0054] Step 1: Synthesis of amine monomers

[0055] Following the same procedure as in Example 1, we obtain QA.

[0056] Step 2: Synthesis of Aldehyde Monomers

[0057] The same as step two of Example 1, except that the volume ratio of water to 1,4-dioxane is 1:1, resulting in OA with a yield of 76%.

[0058] Step 3: Synthesis of TAQ-COF

[0059] Same as step three of Example 1, except that the volume of n-butanol and o-dichlorobenzene was adjusted to 1 mL to obtain TAQ-COF with a yield of 81%.

[0060] Experimental results show that the photocatalytic H2O2 production rate of TAQ-COF obtained in Example 1 in a pure water system is 4218 μmol / g. -1 h -1 The chloride ion concentration in the seawater system was 3921 μmol / g. -1 h -1 .

[0061] Example 3

[0062] Step 1: Synthesis of amine monomers

[0063] 1,3,5-Benzenetricarbonaldehyde (162.1 mg, 1 mmol), 2-(4-aminophenyl)acetonitrile (436.1 mg, 3.3 mmol), sodium hydroxide (500 mg), water (15 mL), and ethanol (15 mL) were uniformly mixed. The mixture was heated to 75°C and refluxed with stirring for 6 hours under a nitrogen atmosphere. Post-treatment was the same as in Example 1, yielding QA with a yield of 65%.

[0064] Step 2: Synthesis of Aldehyde Monomers

[0065] In a round-bottom flask, 3,5-dimethylphenylboronic acid pinacol ester (0.38 g, 1.50 mmol), 4,7-dibromo-2,1,3-benzoxadiazole (0.17 g, 0.60 mmol), and potassium carbonate (0.48 g, 3.50 mmol) were dissolved in a mixed solvent of water (5.0 mL) and 1,4-dioxane (20.0 mL). After degassing for 30 minutes, Pd(PPh3)4 (0.03 g, 0.03 mmol) was added, and the mixture was heated to 80 °C and stirred for 36 hours under a nitrogen atmosphere. Post-treatment was the same as in Example 1, yielding OA in 78% yield.

[0066] Step 3: Synthesis of TAQ-COF

[0067] OA (0.04 mmol, 15 mg) and QA (0.04 mmol, 20 mg) were added to a mixed solvent of n-butanol (1.0 mL) and o-dichlorobenzene (1.0 mL) (volume ratio 1:1), and after ultrasonic mixing, acetic acid (6 M, 0.1 mL) was added. After degassing, the mixture was sealed and heated at 100 °C for 2 days. Post-treatment was the same as in Example 1, yielding TAQ-COF in 63% yield.

[0068] Experimental results show that the photocatalytic H2O2 production rate of TAQ-COF obtained in Example 2 in a pure water system is 3980 μmol g. -1 h -1 In a seawater system with a chloride ion concentration of 0.56 mol / L, the concentration is 3540 μmol g. -1 h -1 .

[0069] Example 4

[0070] Step 1: Synthesis of amine monomers

[0071] 1,3,5-Benzenetriformaldehyde (162.1 mg, 1 mmol), 2-(4-aminophenyl)acetonitrile (436.1 mg, 3.3 mmol), sodium hydroxide (500 mg), water (15 mL), and ethanol (15 mL) were uniformly mixed. The mixture was heated to 95°C and refluxed with stirring for 10 hours under a nitrogen atmosphere. Post-treatment was the same as in Example 1, yielding QA with a yield of 79%.

[0072] Step 2: Synthesis of Aldehyde Monomers

[0073] In a round-bottom flask, 3,5-dimethylphenylboronic acid pinacol ester (0.38 g, 1.50 mmol), 4,7-dibromo-2,1,3-benzoxadiazole (0.17 g, 0.60 mmol), and potassium carbonate (0.48 g, 3.50 mmol) were dissolved in a mixed solvent of water (5.0 mL) and 1,4-dioxane (20.0 mL). After degassing for 30 minutes, Pd(PPh3)4 (0.03 g, 0.03 mmol) was added, and the mixture was heated to 110 °C and stirred for 36 hours under a nitrogen atmosphere. The post-treatment was the same as in Example 1, yielding OA in 81% yield.

[0074] Step 3: Synthesis of TAQ-COF

[0075] OA (0.04 mmol, 15 mg) and QA (0.04 mmol, 20 mg) were added to a reaction tube containing n-butanol (1.8 mL) and o-dichlorobenzene (0.2 mL). The mixture was sonicated to ensure thorough mixing, followed by the addition of acetic acid (6 M, 0.2 mL). The reaction tube was degassed by a three-stage freeze-thaw cycle with nitrogen pumping, and then sealed. The reaction system was then heated at 130 °C for 4 days. After the reaction system cooled to room temperature, the mixture was filtered, and the collected solid was washed several times with tetrahydrofuran and acetone. Finally, the resulting yellow solid was dried under vacuum overnight to obtain a yellow powder, designated TAQ-COF, with a yield of 82%.

[0076] Experimental results show that the photocatalytic H2O2 production rate of TAQ-COF obtained in Example 1 in a pure water system is 4561 μmol g. -1 h -1 In a seawater system with a chloride ion concentration of 0.56 mol / L, the concentration was 4178 μmol g. -1 h -1 .

[0077] Comparative Example 1

[0078] Step 1: Synthesis of amine monomers

[0079] Following the same procedure as in Example 1, we obtain QA.

[0080] Step 2: The aldehyde monomer used is commercially available 1,1':4',1''-terphenyl]-3,3'',5,5''-tetramethylaldehyde, denoted as TB.

[0081] Step 3: Synthesis of TBQ-COF

[0082] TBQ-COF was synthesized using the same solvothermal conditions and purification steps as TAQ-COF, the difference being that the starting material was replaced with TB instead of OA in Example 1. A yellow solid, denoted as TBQ-COF, was obtained with a yield of 79%. The chemical reaction formula is as follows:

[0083] .

[0084] Experimental results show that the photocatalytic H2O2 production rate of TBQ-COF obtained in Comparative Example 1 in a pure water system is 3071 μmol g. -1 h -1 In a seawater system with a chloride ion concentration of 0.56 mol / L, the concentration is 2707 μmol g. -1 h -1 The photocurrent density is much lower than that of TAQ-COF, and its catalytic activity decreases by more than 50% after reacting in seawater for 2-3 days, with no obvious antibacterial properties.

[0085] Comparative Example 2

[0086] The rest is the same as in Example 1, except that the amine monomer is replaced with 1,3,5-tris(4-aminophenyl)benzene without acrylonitrile groups, denoted as CA. The resulting material has no acrylonitrile groups in its skeleton, denoted as TCQ-COF. The chemical reaction formula is as follows:

[0087] .

[0088] Experimental results show that the TCQ-COF in this comparative example, under visible light irradiation, achieves a photocatalytic H2O2 production rate of 2435 μmol g in pure water. -1 h -1 In a seawater system with a chloride ion concentration of 0.56 mol / L, the concentration was 1978 μmol g. -1 h -1 Its photocurrent density is much lower than that of TAQ-COF, and its catalytic activity decreases by more than 50% after reacting in seawater for 2-3 days, with no obvious antibacterial properties.

[0089] TAQ-COF is illustrated using the product obtained in Example 1 as a typical example.

[0090] Powder X-ray diffraction (PXRD) patterns of TAQ-COF, TBQ-COF, and TCQ-COF are shown below. Figures 1 to 3 As shown, by Figures 1 to 3 It can be seen that TAQ-COF shows a distinct diffraction peak at 4.88°, TBQ-COF shows a diffraction peak at 4.92°, and TCQ-COF shows a diffraction peak at 5.86°, confirming that the above materials all have high crystallinity.

[0091] Scanning electron microscope (SEM) image of TAQ-COF as shown below Figure 4 As shown, Figure 4 The results show that TAQ-COF has a multi-level structure with a rough and porous surface supported by a fibrous substrate and accompanied by densely packed spherical nanoparticles.

[0092] Fourier transform infrared spectra of TAQ-COF, TBQ-COF, and TCQ-COF are shown below. Figure 5 As shown, Figure 5 The Schiff base condensation reaction was confirmed to have proceeded successfully, with all three materials reaching a depth of 1623 cm⁻¹. -1 Nearby, stretching vibration absorption bands of C=N bonds appear; TAQ-COF and TBQ-COF show absorption bands at 2215 cm⁻¹. -1 The observation of characteristic peaks of C≡N bonds indicates that acrylonitrile has been successfully introduced into the framework of these two materials.

[0093] The rate graphs of photocatalytic H2O2 production by TAQ-COF, TBQ-COF, and TCQ-COF under visible light irradiation without sacrificial agents are shown below. Figure 6 As shown, the yield of TAQ-COF is as high as 4938 μmol g. -1 h -1 It significantly outperforms the other two materials and surpasses most currently reported COF photocatalysts, demonstrating excellent photocatalytic performance.

[0094] The transient photocurrent response curves of TAQ-COF, TBQ-COF, and TCQ-COF are shown in the figure below. Figure 7 As shown, TAQ-COF exhibits the highest photocurrent density, indicating that it has the best separation efficiency for photogenerated electron-hole pairs.

Claims

1. An acrylonitrile-functionalized covalent organic framework material, characterized in that, The acrylonitrile-functionalized covalent organic framework material contains both acrylonitrile and benzoxadiazole groups in its skeletal structure, denoted as TAQ-COF. TAQ-COF is prepared by Schiff base condensation reaction of an acrylonitrile-containing amine monomer QA and a benzoxadiazole-containing aldehyde monomer OA. QA is (2Z,2'Z,2''Z)-3,3',3''-(benzyl-1,3,5-triyl)tris(2-(4-aminophenyl)acrylonitrile), and OA is 4,7-bis(5-formyl-1,3-phenylene)benzo[c][1,2,5]oxadiazole. The structure of QA is: ， The structure of OA is: ， The structural formula of TAQ-COF is: 。 2. The acrylonitrile-functionalized covalent organic framework material as described in claim 1, characterized in that, The TAQ-COF is a highly crystalline material, exhibiting characteristic diffraction peaks at a 2θ angle of 4.5°–5.0°, and its infrared spectrum ranges from 2210 to 2220 cm⁻¹. -1 Characteristic absorption peaks of C≡N bonds are present at 1620~1625 cm⁻¹. -1 The characteristic absorption peak of the C=N bond is present at this location.

3. The method for preparing acrylonitrile-functionalized covalent organic framework materials as described in claim 1 or 2, characterized in that, The steps are as follows: S1. Synthesis of amine monomer QA: 1,3,5-benzenetriformaldehyde, 2-(4-aminophenyl)acetonitrile, sodium hydroxide and solvent are added to a reactor and heated under reflux under a nitrogen atmosphere. After filtration, washing and drying, (2Z,2'Z,2''Z)-3,3',3''-(benzene-1,3,5-triyl)tris(2-(4-aminophenyl)acrylonitrile), abbreviated as QA, is obtained. S2. Synthesis of aldehyde monomer OA: 3,5-dimethylphenylboronic acid pinacol ester, 4,7-dibromo-2,1,3-benzoxadiazole, potassium carbonate and solvent were added to a reactor. After degassing, Pd(PPh3)4 was added, and the reaction was heated and stirred under a nitrogen atmosphere. Then, after cooling, filtration, washing and drying, the aldehyde monomer 4,7-bis(5-formyl-1,3-phenylene)benzo[c][1,2,5]oxadiazole, abbreviated as OA, was obtained. Synthesis of S3 and TAQ-COF: OA and QA were added to an organic solvent, ultrasonically mixed, and then acetic acid was added. After degassing and sealing, the mixture was heated for a solvothermal reaction. TAQ-COF was then obtained by filtration, washing, and drying.

4. The preparation method according to claim 3, characterized in that, In step S1, the molar ratio of 1,3,5-benzyltriformaldehyde, 2-(4-aminophenyl)acetonitrile, and sodium hydroxide is 1:(3.0~3.5):(10~15), the solvent is a mixture of water and ethanol, the volume ratio of water to ethanol is 1~1.2:1, the reaction temperature is 80~90℃, and the reaction time is 3~5h.

5. The preparation method according to claim 3, characterized in that, In step S2, the molar ratio of 3,5-dimethylphenylboronic acid pinacol ester, 4,7-dibromo-2,1,3-benzoxadiazole, potassium carbonate, and Pd(PPh3)4 is (2.4~2.6):1:(5.5~6.0):(0.08~0.09), the solvent is a mixture of water and 1,4-dioxane, the volume ratio of water to 1,4-dioxane is 1:(3.5~4.5), the degassing time is 25~35 min, the heating reaction temperature is 95~105℃, the reaction time is 20~28 h, and the drying temperature is 55~65℃.

6. The preparation method according to claim 3, characterized in that, In step S3, the molar ratio of OA to QA is 1:0.9~1.1, the volume ratio of n-butanol to o-dichlorobenzene is (8~10):1, the concentration of acetic acid is 5~7 mol / L, the degassing adopts a freezing-nitrogen pumping-thawing cycle, the number of cycles is 2~4, the solvothermal reaction temperature is 115~125℃, and the reaction time is 2~4 days.

7. The preparation method according to claim 3, characterized in that, In step S1, washing is performed sequentially using sodium hydroxide solution, ethanol, and water; in step S2, washing is performed sequentially using water, methanol, and toluene; in step S3, washing is performed sequentially using tetrahydrofuran and acetone, and the number of washing cycles is 3 to 5.

8. The application of the acrylonitrile-functionalized covalent organic framework material as described in claim 1 in the photocatalytic synthesis of hydrogen peroxide, characterized in that, Using TAQ-COF as a photocatalyst, hydrogen peroxide is generated from the reaction of water and oxygen under visible light irradiation.

9. The application as described in claim 8, characterized in that, The photocatalytic reaction system is a pure water system or a high-salt complex aquatic environment system including seawater, wherein the chloride ion concentration in the high-salt complex aquatic environment system is 0.5~1.0 mol / L.

10. The application as described in claim 8 or 9, characterized in that, The TAQ-COF, under visible light irradiation, achieves a photocatalytic synthesis of hydrogen peroxide with a yield of no less than 3500 μmol / g. -1 h -1 Furthermore, the catalytic activity can be maintained at no less than 85% even after continuous catalytic reaction in a seawater system for 4-5 days.

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