Beta-ketoenamine type covalent organic framework material cof-n32 with triazine structure, preparation method thereof and application in photosynthesis of hydrogen peroxide

Abstract

The application provides a beta-ketoenamine type covalent organic framework material COF-N32 with a triazine structure and a preparation method and application thereof in photosynthesis of hydrogen peroxide. The preparation method comprises the following steps: adding 2,4,6-trihydroxybenzene-1,3,5-trimethyl formaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine into a solvent system comprising 1,4-dioxane, mesitylene and a 3 mol / L acetic acid solution, performing ultrasonic oscillation, heating and reacting, and washing and drying to obtain the covalent organic framework material COF-N32. The beta-ketoenamine type covalent organic framework material COF-N32 with a triazine structure is synthesized through a solvothermal reaction, is used as a photocatalyst for synthesis of hydrogen peroxide, does not need to be modified through a heterojunction, protonation and the like subsequently, is simple and convenient to operate, is simple, efficient, safe, stable, and has no risk of release of metal ions in the photocatalytic synthesis of hydrogen peroxide, and the prepared material can be effectively regenerated and reused after use.

Description

Technical Field

[0001] This invention relates to a covalent organic framework material, its preparation method, and its application, specifically to a β-ketoenamine covalent organic framework material COF-N32 with a triazine structure, its preparation method, and its application in the photosynthesis of hydrogen peroxide. Background Technology

[0002] Hydrogen peroxide (H2O2) is widely used in chemical synthesis, energy storage, and water treatment. Currently, anthraquinone synthesis, electrochemical synthesis, and noble metal catalysis are commonly used methods for H2O2 synthesis, but these require high energy input and release toxic byproducts, leading to environmental pollution. H2O2 photosynthesis, utilizing naturally occurring water and oxygen as raw materials and sunlight as energy input, is considered a green and sustainable synthesis method. However, due to the metastable nature of H2O2 during synthesis, some side reactions (such as the decomposition of H2O2 into oxygen and water) limit the performance of H2O2 photosynthesis.

[0003] Covalent organic frameworks (COFs) are novel non-metallic crystalline polymers that can form suitable intermediates to avoid side reactions in H2O2 synthesis, showing great promise in the field of H2O2 photosynthesis. However, in existing COF materials, insufficient exciton (bound states of electron-hole pairs) generation or separation often reduces the generation of free charges, thus limiting the efficiency of H2O2 photosynthesis.

[0004] For example, prior art 1 (CN112538167B) discloses an alkyl chain-modified acylhydrazone-linked covalent organic framework material and its application in photocatalytic hydrogen peroxide production. However, the yield of this COF material for photocatalytic hydrogen peroxide synthesis is low, only 160 μmol g. -1 h -1 Furthermore, it is limited to a laboratory environment, requiring an O2 atmosphere and deionized water. The actual water quality conditions are very complex, making it impossible to infer the application of this material in the natural environment based on the deionized water yield.

[0005] To improve the photoexcitation and charge separation of COFs, some existing technologies employ interface control strategies, such as constructing heterojunctions, doping with single atoms, or promoting material reactions through electrocatalysis to enhance charge separation of COFs. However, these methods require multi-step, complex, and time-consuming synthesis processes.

[0006] For example, prior art 2 (CN114164449A) discloses a method for preparing hydrogen peroxide by catalytic oxygen reduction using a covalent organic framework catalyst. This COF material, when applied to electrocatalysis, requires significant electrical energy, increasing costs. Furthermore, COFs themselves have poor conductivity and a large overpotential. Therefore, carbon black needs to be added to improve conductivity during the electrocatalytic process, making the operation cumbersome.

[0007] It is evident that the application of COFs materials for efficient H2O2 photosynthesis under natural conditions still faces significant challenges. Therefore, it is essential to develop simple and economical charge control strategies to avoid side reactions and improve the efficiency of H2O2 photosynthesis. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the present invention aims to provide a β-ketoenamine covalent organic framework material COF-N32 with a triazine structure capable of efficiently synthesizing H2O2, its preparation method, and its application in the photosynthesis of hydrogen peroxide.

[0009] The present invention adopts the following technical solution:

[0010] According to a first aspect of the present invention, a β-ketoenamine covalent organic framework material COF-N32 having a triazine structure is provided. The material COF-N32 comprises periodic structural units as shown below:

[0011]

[0012] The “~” connected to the benzene ring in the periodic structural unit indicates an omitted repeating structural unit.

[0013] According to a second aspect of the present invention, a method for preparing COF-N32, a β-ketoenamine covalent organic framework material having a triazine structure according to a first aspect of the present invention, is provided. The preparation method comprises the following steps:

[0014] Step A1: 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine are added to a solvent system including 1,4-dioxane, mesitylene and acetic acid solution to obtain a mixed solution and mix it thoroughly and uniformly.

[0015] Step A2: The mixed solution is heated to react and a primary product is obtained;

[0016] Step A3: The primary product is washed and dried to obtain the β-ketoenamine covalent organic framework material with a triazine structure.

[0017] In one embodiment, step A1 further includes: introducing nitrogen gas into the mixed solution and ultrasonically vibrating for 20 minutes to achieve thorough and uniform mixing;

[0018] In one embodiment, step A2 further includes: placing the mixed solution in a sealed reaction vessel and reacting it at a temperature of 100–120°C for 2–4 days to obtain the initial product.

[0019] In one embodiment, step A3 further includes: after cooling the sealed reaction vessel to room temperature, filtering the primary product in the reaction vessel and washing it with acetone 3 to 5 times, and then drying the washed primary product at 60°C for 12 hours to prepare the β-ketoenamine covalent organic framework material with a triazine structure.

[0020] In one embodiment, in step A1, the molar ratio of the first reactant to the second reactant is 1:1.

[0021] In one embodiment, the amount of the first reactant is 0.3 to 0.9 mmol, and the amount of the second reactant is 0.3 to 0.9 mmol.

[0022] In one embodiment, in the solvent system of step A1, the acetic acid solution is a 3 mol / L acetic acid solution, and the volume ratio of 1,4-dioxane, mesitylene, and 3 mol / L acetic acid solution is (2.8-3.2):(2.8-3.2):1, and the total amount of the solvent system is 3.5-10.5 mL.

[0023] According to a third aspect of the present invention, the application of COF-N32, a β-ketoenamine covalent organic framework material having a triazine structure according to the first aspect of the present invention, in the photosynthesis of hydrogen peroxide is provided. The application includes the following steps:

[0024] Step B1: The β-ketoenamine covalent organic framework material with a triazine structure is dispersed in ultrapure water to obtain a dispersed liquid;

[0025] Step B2: In the dark, oxygen is introduced into the dispersed liquid and stirred for 15 to 30 minutes to allow it to reach adsorption and desorption equilibrium.

[0026] Step B3 involves irradiating the stirred liquid with visible light for at least 12 hours to achieve the photocatalytic synthesis of hydrogen peroxide.

[0027] In one embodiment, the above application further includes:

[0028] Step B4: The β-ketoenamine covalent organic framework material with a triazine structure is separated from the liquid after photocatalytic synthesis in step B3 by filtration, and the material is regenerated by washing with deionized water and filtering.

[0029] In one embodiment, in step B1, the concentration of the β-ketoenamine covalent organic framework material with a triazine structure in the dispersed liquid is 100–1500 mg / L.

[0030] In one embodiment, step B3 further includes: irradiating the stirred liquid with visible light at a temperature of 15–35°C for no less than 60 minutes to complete the photocatalytic synthesis of hydrogen peroxide.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The triazine-structured covalent organic framework material COF-N32 synthesized in this invention uses 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine as reactants, added to a mixed system containing 1,4-dioxane, mesitylene, and 3 mol / L acetic acid solution. The β-ketoenamine covalent organic framework material COF-N32 with a triazine structure can be synthesized solely through a solvothermal reaction and used as a photocatalyst for hydrogen peroxide synthesis. This invention experimentally demonstrates that the triazine structure combined with enamine bonds is more conducive to electron transfer in the photocatalytic process of COFs materials, thus eliminating the need for modification through heterojunctions, protonation, or other methods after the solvothermal reaction, making the synthesis method simpler and more convenient. Meanwhile, creative density functional theory calculations revealed that COF-N31 has high polarity, and although its absorbance is low, its excitons are easily separated; COF-N33 has low polarity, and although it absorbs light easily, its excitons are difficult to separate; while COF-N32 has moderate polarity, good absorbance, and its excitons are also easy to separate, so it is the most effective for synthesizing H2O2.

[0033] 2. The chemical reagents and equipment required for the synthesis method of this invention are readily available, the operation is simple, the application value is high, and it is easy to promote.

[0034] 3. The β-ketoenamine covalent organic framework material COF-N32 with a triazine structure synthesized in this invention can efficiently synthesize H2O2, with a synthesis efficiency far exceeding that of common photocatalysts TiO2, WO3, and g-C3N4. In particular, when using the synthesized covalent organic framework material COF-N32 as a photocatalyst, under visible light catalysis conditions with a dosage of 500 mg / L, the average yield reaches as high as 605 μmol g / L over 12 hours. -1 h -1This yield data is significantly better than that of COF-N31 (434 μmol g). -1 h -1 ) and COF-N33 (155 μmol g -1 h -1 It is also significantly superior to the alkyl chain-modified acylhydrazone-linked covalent organic framework materials mentioned in the background art (160 μmol g). -1 h -1 It significantly outperforms the yield of common photocatalysts (TiO2, WO3 and g-C3N4).

[0035] 4. The covalent organic framework material COF-N32 synthesized in this invention can efficiently synthesize H2O2 using actual water bodies and air under natural sunlight.

[0036] 5. The covalent organic framework material COF-N32 photocatalyst synthesized in this invention is safe and stable, with no risk of metal ion release.

[0037] 6. The covalent organic framework material COF-N32 photocatalyst synthesized in this invention can be effectively regenerated and reused after use, and can be used for a long time. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the preparation and synthesis of Example 1, Comparative Example 1, and Comparative Example 2;

[0039] Figure 2 The image shows a comparison of the visible light photocatalytic synthesis of H2O2 by COF-N32, COF-N31, and COF-N33 obtained in Examples 1, 1, and 2 of this invention with other common photocatalysts (TiO2, WO3, and g-C3N4).

[0040] Figure 3 This is a cycle test diagram of the COF-N32 obtained in Example 1.

[0041] Figure 4 The graph shows the performance test results of COF-N32 obtained in Example 1 under natural sunlight and in actual water.

[0042] Figure 5 The image shows the performance test results of the membrane reactor obtained in Example 1 under natural sunlight.

[0043] Figure 6 The image shows the performance test results of the COF-N32 immobilization device obtained in Example 1 under natural sunlight. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The embodiments described in this application are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of this invention.

[0045] To make the present invention clearer, the invention will be further described below with reference to the accompanying drawings and embodiments. These embodiments are only for illustrative purposes and are not intended to limit the invention.

[0046] This invention provides a β-ketoenamine covalent organic framework material with a triazine structure, wherein the covalent organic framework material is COF-N32, and comprises periodic structural units as shown in Formula I:

[0047]

[0048] The “~” connected to the benzene ring in the periodic structural unit indicates an omitted identical periodic structural unit.

[0049] The present invention also provides a method for preparing the above-mentioned β-ketoenamine type covalent organic framework catalyst COF-N32 with a triazine structure for hydrogen peroxide photosynthesis, comprising the following steps:

[0050] Step A1: 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine are added to a solvent system consisting of 1,4-dioxane, mesitylene and 3 mol / L acetic acid solution to obtain a mixed solution and mix it thoroughly and uniformly.

[0051] Step A2 involves heating the mixed solution to obtain the initial product.

[0052] Step A3: The primary product is washed and dried to obtain the β-ketoenamine covalent organic framework material with a triazine structure.

[0053] Preferably, step A1 further includes: introducing nitrogen gas into the mixed solution and ultrasonically vibrating for 20 minutes to achieve thorough and uniform mixing.

[0054] Preferably, step A2 further includes: placing the mixed solution in a sealed reaction vessel and reacting it at a temperature of 100-120°C for 2-4 days to obtain the initial product.

[0055] Furthermore, the sealed reaction vessel can be a high-temperature, high-pressure reactor with a Teflon liner, which is removable for placement in or removal from the reactor as needed. The mixed solution is contained within the Teflon liner. The aforementioned temperature of 100–120°C can be achieved by placing the high-temperature, high-pressure reactor in an oven.

[0056] Preferably, step A3 further includes cooling the sealed reaction vessel to room temperature, filtering the initial product in the reaction vessel and washing it with acetone 3 to 5 times, and then drying the washed initial product at 60°C for 12 hours to prepare a β-ketoenamine covalent organic framework material COF-N32 with a triazine structure.

[0057] The initial product is an orange solid precipitate.

[0058] Preferably, in step A1, the molar ratio of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine is 1:1. Preferably, the molar amount of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde is 0.3–0.9 mmol, and the molar amount of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine is 0.3–0.9 mmol.

[0059] Preferably, in the solvent system of step A1, the acetic acid solution is a 3 mol / L acetic acid solution, and the volume ratio of 1,4-dioxane, mesitylene, and 3 mol / L acetic acid solution is (2.8-3.2):(2.8-3.2):1, and the total amount of solvent system used is 3.5-10.5 mL.

[0060] This invention also provides the application of the above-mentioned β-ketoenamine covalent organic framework material COF-N32 with a triazine structure in the photosynthesis of hydrogen peroxide, comprising the following steps:

[0061] Step B1: The β-ketoenamine covalent organic framework material COF-N32 with a triazine structure is dispersed in ultrapure water to obtain a dispersed liquid.

[0062] One approach is to disperse the aforementioned covalent organic framework material in ultrapure water using ultrasound to achieve better dispersion.

[0063] Step B2: In the dark, expose the dispersed liquid to oxygen and stir for 15-30 minutes to allow it to reach adsorption-desorption equilibrium.

[0064] Step B3 involves irradiating the stirred liquid with visible light for at least 12 hours to achieve the photocatalytic synthesis of H2O2.

[0065] Preferably, the above applications also include:

[0066] Step B4: The β-ketoenamine covalent organic framework material with a triazine structure is separated from the liquid after photocatalytic synthesis in step B3 by filtration. After washing with deionized water and filtration, the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure is regenerated.

[0067] Preferably, step B3 further includes irradiating the stirred liquid with visible light at a temperature of 15–35°C for no less than 12 hours to complete the photocatalytic synthesis of hydrogen peroxide.

[0068] Preferably, step B3 may further include: during the photocatalytic synthesis of H2O2, taking a certain amount of reaction suspension, such as 1 mL, at a specific time, collecting the filtrate through a 0.22 μm polyethersulfone needle filter and measuring its hydrogen peroxide concentration.

[0069] Preferably, in step B1, the concentration of the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure in the dispersed liquid is 100–1500 mg / L.

[0070] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] 0.9 mmol of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 0.9 mmol of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine were accurately weighed and added to a 20 mL Teflon-coated reactor liner. Subsequently, 4.5 mL of 1,4-dioxane, 4.5 mL of mesitylene, and 1.5 mL of 3M acetic acid solution were added to the Teflon liner. Nitrogen gas was introduced, and the mixture was ultrasonically vibrated for 20 minutes to ensure homogeneity. The liner was then placed in a high-temperature, high-pressure reactor, sealed, and placed in an oven at 120°C for 3 days. After the reactor was removed and cooled to room temperature, the orange solid precipitate in the liner was filtered and carefully washed five times with acetone. The orange powder was then dried in an oven at 60°C for 12 hours to prepare the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure.

[0073] The structure of COF-N32 is represented by Equation I:

[0074]

[0075] Comparative Example 1

[0076] 0.3 mmol of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 0.3 mmol of melamine were accurately weighed and added to a sealed container. Subsequently, 4 mL of dimethylacetamide, 2 mL of dimethyl sulfoxide, and 0.6 mL of 6 mol / L acetic acid solution were added to the sealed reactor. After three cycles of freezing-degassing-melting and ultrasonic vibration for 20 minutes to ensure homogeneity of all reactants, the sealed reactor was placed in an oven at 120°C for 3 days. After removing the reactor and cooling to room temperature, the brown solid precipitate in the inner liner was filtered and carefully washed with dimethylacetamide and acetone. The brown powder was then vacuum-dried in an oven at 60°C for 12 hours to prepare the β-ketoenamine covalent organic framework material COF-N31.

[0077] The structure of COF-N31 is represented by Equation II:

[0078]

[0079] Comparative Example 2

[0080] 0.9 mmol of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 0.9 mmol of 4',4”',4””'-(1,3,5-triazine-2,4,6-tris(([1,1'-biphenyl]-4-amine)) were accurately weighed and added to a 20 mL Teflon-coated reactor liner. Subsequently, 4.5 mL of 1,4-dioxane, 4.5 mL of mesitylene, and 1.5 mL of 3M acetic acid solution were added. The reaction mixture was placed in a Teflon liner. Nitrogen gas was introduced, and the mixture was ultrasonically vibrated for 20 minutes to ensure homogeneity. The liner was then placed in a high-temperature, high-pressure reactor, sealed, and placed in an oven at 120°C for 3 days. After removing the reactor and cooling to room temperature, the orange solid precipitate in the liner was filtered and carefully washed five times with acetone. The orange powder was then dried in an oven at 60°C for 12 hours to prepare the β-ketoenamine covalent organic framework material COF-N33.

[0081] The structure of COF-N33 is represented by Equation III:

[0082]

[0083] Figure 1 This is a schematic diagram of the preparation and synthesis of Example 1, Comparative Example 1, and Comparative Example 2.

[0084] Application Example 1

[0085] Application Example 1 relates to the synthesis of H2O2 under visible light using COF-N32 prepared in this invention.

[0086] 50 mL of ultrapure water was added to a sealed double-layered beaker reactor, and the pH was adjusted to 7.0 with 0.1 M HClO4. Photocatalysts COF-N31, COF-N32, and COF-N33, prepared according to methods in Examples 1-3, along with other common photocatalysts TiO2, WO3, and g-C3N4, were added to different double-layered beakers, and each was ultrasonically dispersed for 1 minute. Oxygen was then introduced and the mixture was stirred for 30 minutes in the dark to reach adsorption-desorption equilibrium. Subsequently, the reaction systems corresponding to each different photocatalyst were placed under visible light for photocatalytic reaction, and the reaction systems were maintained at a constant temperature of 25°C through a circulating water system. The change in H2O2 concentration in the water over time was determined using iodometric titration (with potassium iodide and potassium hydrogen phthalate for color development, showing an absorption peak at 350 nm).

[0087] Figure 2 The results showed that the H2O2 production of COF-N32 could reach 605 μmol g / L within 12 hours of illumination. -1 h -1 Higher than Example 2 (434 μmol g) -1 h -1 ) and Example 3 (155 μmol g -1 h -1 It achieves a yield significantly higher than that of common photocatalysts (TiO2, WO3 and g-C3N4).

[0088] Application Example 2

[0089] Application Example 2 involves the reuse test of COF-N32.

[0090] Following the steps and methods in Application Example 1, the reacted COF-N32 was separated and recovered from the system by vacuum filtration, washed with ultrapure water, and then ultrasonically dispersed in ultrapure water. The next cycle was then started, for a total of 5 cycles. Figure 3 It can be concluded that COF-N32 can be recycled after simple recycling treatment, and its performance in the visible light photocatalytic synthesis of hydrogen peroxide is not weakened after 5 cycles, proving that COF-N32 photocatalyst can be reused after use.

[0091] Application Example 3

[0092] Application Example 3 involves the synthesis of H2O2 in actual water and air using the catalyst COF-N32 under natural sunlight.

[0093] 50 mL of ultrapure water, river water, tap water, and seawater were respectively added to a double-walled beaker reactor. The photocatalyst COF-N32, prepared according to the method in Example 1, was added to the double-walled beaker and ultrasonically dispersed for 1 minute. The reaction system was then exposed to air and placed under natural sunlight for the photocatalytic reaction. The experimental location was E116°18'E, N39°59'N, and the reaction started at 10:00 AM. The measured natural light intensity during the reaction was 42–52 mW / cm². 2 . Figure 4 The results showed that the 3-hour average H2O2 production of COF-N32 in ultrapure water, river water, tap water, and seawater reached 602, 515, 475, and 396 μmol g, respectively. -1 h -1 .

[0094] Application Example 4

[0095] Application Example 4 involves the synthesis of H2O2 in a membrane reactor using the catalyst COF-N32 under natural sunlight.

[0096] Add 50 mL of ultrapure water to the membrane reactor. Add the photocatalyst COF-N32 prepared according to the method in Example 1 to the membrane reactor and ultrasonically disperse for 1 minute. Seal the filter opening with a rubber stopper. Then expose the reaction system to air and place it under natural sunlight for the photocatalytic reaction. The experimental location was E116°18' E, N39°59' N. The reaction started at 9:30 AM and 1:00 PM daily. The measured natural light intensity during the reaction was 15–55 mW / cm². 2 . Figure 5 The results showed that the yield of COF-N32 under natural sunlight was as high as 0.65–1.17 mmol g. -1 h -1 The yield is related to the intensity of natural sunlight.

[0097] Application Example 5

[0098] Application Example 5 involves the synthesis of H2O2 in an immobilized device using the catalyst COF-N32 under natural sunlight.

[0099] 60 mg of the photocatalyst COF-N32 prepared according to the method in Example 1 was dispersed in a mixture of ethanol (2.5 mL), ultrapure water (7.5 mL), and 5% Nafion solution (1 mL). After sonication for 1 hour, the mixture was uniformly coated onto a 10 cm × 10 cm conductive glass slide and dried overnight to obtain a COF-N32 immobilization device. The immobilization device was then placed in a reaction tank containing 200 mL of ultrapure water. The reaction system was exposed to air and placed under natural sunlight for photocatalytic reaction. The experimental location was E116°18' E, N39°59' N. The reaction started at 10:30 AM, and the measured natural light intensity during the reaction was 47–56 mW / cm². 2 . Figure 6 The results show that the COF-N32 immobilization device can stably produce 80-90 μmol of H2O2 under natural sunlight irradiation for 180 minutes.

[0100] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0101] 1. By using 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine as reactants, and adding them to a mixed system containing 1,4-dioxane, mesitylene, and 3 mol / L acetic acid solution, a β-ketoenamine covalent organic framework material COF-N32 with a triazine structure can be synthesized through a solvothermal reaction alone, and used as a photocatalyst for hydrogen peroxide synthesis. This invention experimentally demonstrates that the triazine structure combined with enamine bonds can better facilitate electron transfer in COF materials during photocatalysis, thus eliminating the need for modification through protonation or other methods after the solvothermal reaction, making the synthesis method simpler and more convenient. Meanwhile, creative density functional theory calculations revealed that COF-N31 has high polarity, and although its absorbance is low, its excitons are easily separated; COF-N33 has low polarity, and although it absorbs light easily, its excitons are difficult to separate; while COF-N32 has moderate polarity, good absorbance, and its excitons are also easy to separate, so it is the most effective for synthesizing H2O2.

[0102] 2. The chemical reagents and equipment required for the synthesis method of this invention are readily available, the operation is simple, the application value is high, and it is easy to promote.

[0103] 3. The β-ketoenamine covalent organic framework material COF-N32 with a triazine structure synthesized in this invention can efficiently synthesize H2O2, with a synthesis efficiency far exceeding that of common photocatalysts TiO2, WO3, and g-C3N4. In particular, when using the synthesized covalent organic framework material COF-N32 as a photocatalyst, under visible light catalysis conditions with a dosage of 500 mg / L, the average yield reaches as high as 605 μmol g / L over 12 hours. -1 h-1 This yield data is significantly better than that of COF-N31 (434 μmol g). -1 h -1 ) and COF-N33 (155 μmol g -1 h -1 It is also significantly superior to the alkyl chain-modified acylhydrazone-linked covalent organic framework materials mentioned in the background art (160 μmol g). -1 h -1 It significantly outperforms the yield of common photocatalysts (TiO2, WO3 and g-C3N4).

[0104] 4. The covalent organic framework material COF-N32 synthesized in this invention can efficiently synthesize H2O2 using actual water bodies and air under natural sunlight.

[0105] 5. The covalent organic framework material COF-N32 photocatalyst synthesized in this invention is safe and stable, with no risk of metal ion release.

[0106] 6. The covalent organic framework material COF-N32 photocatalyst synthesized in this invention can be effectively regenerated and reused after use, and can be used for a long time.

[0107] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. The application of a β-ketoenamine covalent organic framework material COF-N32 with a triazine structure in the photosynthesis of hydrogen peroxide, said material comprising the periodic structural units shown below: ， The "~" in the periodic structural unit indicates an omitted identical periodic structural unit, characterized in that... The preparation method of the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure includes the following steps: Step A1: 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde and 2,4,6-tris(4-aminophenyl)-1,3,5-triazine are added to a solvent system composed of 1,4-dioxane, mesitylene, and 3 mol / L acetic acid solution in a 1:1 molar ratio to obtain a mixed solution. Nitrogen gas is introduced into the mixed solution and ultrasonically vibrated for 15-25 minutes to achieve thorough and uniform mixing. The acetic acid solution is a 3 mol / L acetic acid solution, and the volume ratio of 1,4-dioxane, mesitylene, and 3 mol / L acetic acid solution is (2.8-3.2):(2.8-3.2):

1. Step A2: Place the mixed solution in a sealed reaction vessel and react at a temperature of 100~120 °C for 2~4 days to obtain the initial product; Step A3: After cooling the sealed reaction vessel to room temperature, the initial product in the reaction vessel is filtered and washed with acetone 3 to 5 times. Then, the washed initial product is dried at 60°C for 12 hours to prepare the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure. The application includes the following steps: Step B1: Disperse the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure in ultrapure water, river water, tap water or seawater to obtain a dispersed liquid; Step B2: In the dark, oxygen is introduced into the dispersed liquid and stirred for 15-30 minutes to allow it to reach adsorption-desorption equilibrium. Step B3: Irradiate the stirred liquid with visible light for no less than 12 hours to complete the photocatalytic synthesis of hydrogen peroxide.

2. The application according to claim 1, characterized in that: The amount of 2,4,6-trihydroxybenzene-1,3,5-tricarboxaldehyde is 0.3~0.9 mmol, and the amount of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine is 0.3~0.9 mmol.

3. The application according to claim 1, characterized in that: In the solvent system of step A1, the total amount of the solvent system used is 3.5~10.5 mL.

4. The application according to claim 1, characterized in that, Also includes: Step B4: The β-ketoenamine covalent organic framework material COF-N32 with a triazine structure is separated from the liquid after photocatalytic synthesis in step B3 by filtration. After washing with deionized water and filtration, the regeneration of the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure is completed.

5. The application according to claim 1, characterized in that, In step B1, the concentration of the β-ketoenamine covalent organic framework material COF-N32 with a triazine structure in the dispersed liquid is 100~1500 mg / L.

6. The application according to claim 1, characterized in that, Step B3 further includes: irradiating the stirred liquid with visible light at a temperature of 15~35℃ for no less than 12 hours to achieve photocatalytic synthesis of hydrogen peroxide.

Images