A conjugated microporous polymer photocatalyst and its preparation method and application

Abstract

The present invention discloses a conjugated microporous polymer photocatalyst, its preparation method, and application, relating to the technical field of photocatalyst materials. The photocatalyst utilizes a carbazole intermediate as an electron donor and a naphthalimide intermediate as an electron acceptor, and constructs a conjugated microporous polymer skeleton through an aldehyde-amine condensation reaction. The preparation method includes: preparing a naphthalimide intermediate, preparing a carbazole intermediate, and conducting an aldehyde-amine condensation reaction. The photocatalyst obtained by the present invention through an optimized green synthesis route can efficiently utilize oxygen from water and air to directly synthesize H2O2 at room temperature and pressure. With the participation of a sacrificial agent, the yield can reach up to 6.09 mmol·g ‑1 ·h ‑1 , providing a new solution for the green synthesis of H2O2.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalyst materials, and in particular relates to a conjugated microporous polymer photocatalyst and a preparation method and application thereof. Background Art

[0002] H2O2 is a critically important chemical in high demand, widely used in diverse fields, including pharmaceuticals, textiles, papermaking, and environmental protection. This enormous demand necessitates large-scale H2O2 production. Conventional industrial production methods include the anthraquinone process, electrolytic synthesis, and alcohol oxidation. However, these methods still suffer from high energy consumption and secondary pollution. Photocatalysis, driven by solar energy, directly produces H2O2 from renewable resources such as water and oxygen. Its advantages include mild reaction conditions (typically ambient temperature and pressure), low energy consumption, and zero secondary pollution, making it a promising alternative to traditional methods. Photocatalysts are the core of photocatalytic processes. Currently, a variety of organic semiconductor materials have been successfully used as photocatalysts for H2O2 production. However, their practical application remains limited, primarily due to poor separation and transport of photogenerated charge carriers, resulting in a high probability of recombination and a low number of electrons and holes reaching the catalyst surface for surface-interfacial reactions, which in turn inhibits catalytic efficiency. Therefore, improving the separation and transport efficiency of photogenerated charge carriers in photocatalysts is crucial for enhancing catalytic performance.

[0003] Conjugated microporous polymers are an emerging class of organic semiconductor photocatalysts. Due to their high specific surface area, high porosity, conjugated backbone, and tunable structure, they offer inherent advantages in accelerating the separation and transport of photogenerated charge carriers and improving the efficiency of surface and interfacial reactions. Consequently, they have attracted considerable attention. To this end, several strategies have been proposed, including constructing electron donor-acceptor structures, post-modification with functional groups, molecular doping, and morphology design. Among these, constructing electron donor-acceptor structures can create a favorable electron transport pathway through uneven surface charge distribution, offering promising approaches for improving carrier separation and transport capabilities. Summary of the Invention

[0004] The purpose of the present invention is to construct an electron donor-acceptor structure in a conjugated microporous polymer, improve the separation and transmission capabilities of photogenerated carriers, inhibit carrier recombination, and enable more electrons and holes to reach the catalyst surface to participate in surface-interface reactions, thereby improving the efficiency of the photocatalyst in producing H2O2.

[0005] To this end, the first aspect of the present invention provides a conjugated microporous polymer photocatalyst, which uses a carbazole intermediate as an electron donor and a naphthalimide intermediate as an electron acceptor to construct a conjugated microporous polymer skeleton through an aldehyde-amine condensation reaction.

[0006] Furthermore, the structural formula of the photocatalyst includes:

[0007] or .

[0008] The second aspect of the present invention provides a method for preparing the above-mentioned conjugated microporous polymer photocatalyst, comprising the following steps:

[0009] Preparation of naphthalene imide intermediates: 4-bromo-1,8-naphthalene dicarboxylic anhydride is reacted with hydrazine hydrate in ethanol, and the naphthalene imide intermediate NI is obtained after recrystallization;

[0010] Carbazole intermediates are prepared by the following method 1 or method 2:

[0011] Method 1: 3,6-dibromocarbazole and p-fluorobenzaldehyde undergo a nucleophilic substitution reaction in N,N-dimethylformamide, followed by recrystallization to obtain 36-Cz-CHO; 36-Cz-CHO undergoes a Suzuki coupling reaction with 4-formylphenylboronic acid in a mixed solvent of ethanol and water, followed by column chromatography to obtain the carbazole intermediate 36-Cz-3CHO;

[0012] Method 2: 2,7-dibromocarbazole and p-fluorobenzaldehyde undergo a nucleophilic substitution reaction in N,N-dimethylformamide, followed by recrystallization to obtain 27-Cz-CHO; 27-Cz-CHO undergoes a Suzuki coupling reaction with 4-formylphenylboronic acid in a mixed solvent of ethanol and water, followed by column chromatography to obtain the carbazole intermediate 27-Cz-3CHO;

[0013] Aldehyde amine condensation reaction: The carbazole intermediate 36-Cz-3CHO or the carbazole intermediate 27-Cz-3CHO undergoes an aldehyde amine condensation reaction with the naphthalene imide intermediate NI. After the reaction is completed, the photocatalyst 36-NI-Cz-NI or the photocatalyst 27-NI-Cz-NI is obtained by filtering, washing, Soxhlet extraction and drying.

[0014] Furthermore, the solvent used for the recrystallization of the naphthalene imide intermediate NI is a mixed solvent of N,N-dimethylformamide and acetonitrile; the solvent used for the recrystallization of 36-Cz-CHO is a mixed solvent of acetone and water; and the solvent used for the recrystallization of 27-Cz-CHO is a mixed solvent of acetone and water.

[0015] Furthermore, the eluent used for column chromatography of the carbazole intermediate 36-Cz-3CHO is a mixed solvent of dichloromethane and petroleum ether; the eluent used for column chromatography of the carbazole intermediate 27-Cz-3CHO is a mixed solvent of dichloromethane and petroleum ether.

[0016] Furthermore, in the aldehyde-amine condensation reaction, the molar ratio of the carbazole intermediate 36-Cz-3CHO or the carbazole intermediate 27-Cz-3CHO to the naphthaleneimide intermediate NI is 1:(1.4~1.6), the reaction solvent is 1,4-dioxane and 1,3,5-mesitylene, the reaction catalyst is acetic acid, the reaction temperature is 115°C~125°C, and the reaction time is 70h-80h.

[0017] Furthermore, in the aldehyde-amine condensation reaction, the washing solvent is water, dichloromethane and methanol, and the Soxhlet extraction solvent is tetrahydrofuran, dichloromethane and methanol.

[0018] A third aspect of the present invention provides the use of the conjugated microporous polymer photocatalyst described above, wherein the photocatalyst is used for photocatalytically producing hydrogen peroxide in an air atmosphere, an oxygen atmosphere, or an oxygen-free atmosphere using water as a solvent.

[0019] Furthermore, the photocatalyst dosage is: the volume ratio of the mass of the photocatalyst to water is 1 mg: (3-5) mL.

[0020] Furthermore, the photocatalyst 27-NI-Cz-NI was used to produce hydrogen peroxide in air and water. In the presence of the sacrificial agent disodium ethylenediaminetetraacetic acid, the yield reached 6.09 mmol·g -1 ·h -1 After five consecutive photocatalytic cycles of 1 hour each, the hydrogen peroxide yield of the photocatalyst 27-NI-Cz-NI is not less than 85% of the initial value;

[0021] The photocatalyst 36-NI-Cz-NI was used to produce hydrogen peroxide in air and water. With the participation of the sacrificial agent disodium ethylenediaminetetraacetic acid, the yield reached 4.66 mmol g -1 ·h -1 After five consecutive photocatalytic cycles of 1 hour each, the hydrogen peroxide yield of the photocatalyst 36-NI-Cz-NI is not less than 80% of the initial value.

[0022] Compared with the prior art, the present invention has at least the following beneficial effects:

[0023] This invention utilizes carbazole intermediates as electron donors and naphthalimide intermediates as electron acceptors to construct a conjugated microporous polymer photocatalyst through an aldehyde-amine condensation reaction. The preparation method is efficient, controllable, environmentally friendly, requires mild conditions, is simple to operate, and is easily scalable. The photocatalyst, obtained through an optimized green synthesis route, can efficiently synthesize H2O2 directly from water and oxygen in the air at room temperature and pressure. With the participation of a sacrificial agent, the yield can reach up to 6.09 mmol·g -1 ·h -1, providing a new solution for the green synthesis of H2O2. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is the H NMR spectrum of the intermediate NI prepared in Example 1.

[0025] Figure 2 This is the H NMR spectrum of the intermediate 36-Cz-CHO prepared in Example 1.

[0026] Figure 3 This is the H NMR spectrum of the intermediate 36-Cz-3CHO prepared in Example 1.

[0027] Figure 4 This is the H NMR spectrum of the intermediate 27-Cz-CHO prepared in Example 1.

[0028] Figure 5 This is the H NMR spectrum of the intermediate 27-Cz-3CHO prepared in Example 1.

[0029] Figure 6 1 and 2 are infrared spectra of the photocatalysts and intermediate products prepared in Example 1 and Example 2.

[0030] Figure 7 It is the solid carbon spectrum of the photocatalyst prepared in Example 1 and Example 2.

[0031] Figure 8 1 is a scanning electron microscope image of the photocatalyst prepared in Example 1 and Example 2.

[0032] Figure 9 1 and 2 are the UV-visible diffuse reflectance spectra of the photocatalysts prepared in Example 1 and Example 2.

[0033] Figure 10 2 is the Tauc plot of the photocatalysts prepared in Example 1 and Example 2.

[0034] Figure 11 2 are photocurrent response diagrams of the photocatalysts prepared in Example 1 and Example 2.

[0035] Figure 12 1 is the electrochemical impedance spectroscopy diagram of the photocatalysts prepared in Example 1 and Example 2.

[0036] Figure 13 3 is the Mott-Schottky plot of the photocatalysts prepared in Example 1 and Example 2.

[0037] Figure 14 2 is a graph showing the rate of photocatalytic H2O2 production by the photocatalysts prepared in Example 1 and Example 2 under different atmospheres.

[0038] Figure 15This is a photocatalytic H2O2 production rate diagram after adding different hole sacrificial agents to the photocatalysts prepared in Example 1 and Example 2.

[0039] Figure 16 This is a test chart of the cyclic stability performance of the photocatalyst prepared in Example 1 and Example 2. DETAILED DESCRIPTION

[0040] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] In a first aspect of an embodiment of the present invention, a conjugated microporous polymer photocatalyst is provided. The photocatalyst utilizes a carbazole intermediate as an electron donor and a naphthalimide intermediate as an electron acceptor to construct a conjugated microporous polymer backbone via an aldehyde-amine condensation reaction. Optionally, the structural formula of the photocatalyst includes:

[0042] or .

[0043] A second aspect of the present invention provides a method for preparing the above-mentioned conjugated microporous polymer photocatalyst, comprising the following steps:

[0044] Preparation of naphthalene imide intermediates: 4-bromo-1,8-naphthalene dicarboxylic anhydride is reacted with hydrazine hydrate in ethanol, and the naphthalene imide intermediate NI is obtained after recrystallization;

[0045] Carbazole intermediates are prepared by the following method 1 or method 2:

[0046] Method 1: 3,6-dibromocarbazole and p-fluorobenzaldehyde undergo nucleophilic substitution reaction in N,N-dimethylformamide, followed by recrystallization to obtain 36-Cz-CHO; 36-Cz-CHO undergoes Suzuki coupling reaction with 4-formylphenylboronic acid in a mixed solvent of ethanol and water, followed by column chromatography to obtain the carbazole intermediate 36-Cz-3CHO;

[0047] Method 2: 2,7-dibromocarbazole and p-fluorobenzaldehyde undergo nucleophilic substitution reaction in N,N-dimethylformamide, and 27-Cz-CHO is obtained after recrystallization; 27-Cz-CHO undergoes Suzuki coupling reaction with 4-formylphenylboronic acid in a mixed solvent of ethanol and water, and the carbazole intermediate 27-Cz-3CHO is obtained after column chromatography;

[0048] Aldehyde amine condensation reaction: The carbazole intermediate 36-Cz-3CHO or the carbazole intermediate 27-Cz-3CHO undergoes an aldehyde amine condensation reaction with the naphthalene imide intermediate NI. After the reaction is completed, the photocatalyst 36-NI-Cz-NI or the photocatalyst 27-NI-Cz-NI is prepared by filtering, washing, Soxhlet extraction and drying.

[0049] Specifically, the reaction raw materials used in the present invention are simple in structure, cheap and easily available, and have high reaction yield.

[0050] In some embodiments, the solvent used for the recrystallization of the naphthalene imide intermediate NI is a mixed solvent of N,N-dimethylformamide and acetonitrile, preferably the volume ratio of N,N-dimethylformamide and acetonitrile is 1:1; the solvent used for the recrystallization of 36-Cz-CHO is a mixed solvent of acetone and water, preferably the volume ratio of acetone and water is 1:1; the solvent used for the recrystallization of 27-Cz-CHO is a mixed solvent of acetone and water, preferably the volume ratio of acetone and water is 1:1.

[0051] Specifically, the recrystallization solvent used is non-toxic and harmless, low in price, easy to condense and reflux, and has a large solubility change of the product at different temperatures, so it is suitable as a recrystallization solvent.

[0052] In some embodiments, the eluent used for column chromatography of the carbazole intermediate 36-Cz-3CHO is a mixed solvent of dichloromethane and petroleum ether; the eluent used for column chromatography of the carbazole intermediate 27-Cz-3CHO is a mixed solvent of dichloromethane and petroleum ether.

[0053] Specifically, the eluent used is a mixed solvent of dichloromethane and petroleum ether, both of which are inexpensive and suitable for large-scale use. A preferred eluent is a mixed solvent of dichloromethane and petroleum ether in a volume ratio of 1:10. Dichloromethane has high polarity and good solubility for the product, while petroleum ether has low polarity, allowing the preparation of a mixed solvent of appropriate polarity for column chromatography of the intermediate.

[0054] In some embodiments, in the aldehyde-amine condensation reaction, the molar ratio of the carbazole intermediate 36-Cz-3CHO to the naphthalene imide intermediate NI is 1:(1.4~1.6), and preferably the molar ratio of the carbazole intermediate 36-Cz-3CHO to the naphthalene imide intermediate NI is 2:3; the reaction solvent is 1,4-dioxane and 1,3,5-mesitylene, and preferably the volume ratio of 1,4-dioxane and 1,3,5-mesitylene is 1:1; the reaction catalyst is acetic acid; the reaction temperature is 115°C~125°C, and preferably the reaction temperature is 120°C; the reaction time is 70h-80h, and preferably the reaction time is 72h; the washing solvents are water, dichloromethane and methanol, and the solvents for Soxhlet extraction are tetrahydrofuran, dichloromethane and methanol.

[0055] In some embodiments, the molar ratio of the carbazole intermediate 27-Cz-3CHO to the naphthalene imide intermediate NI is 1:(1.4~1.6), and preferably the molar ratio of the carbazole intermediate 27-Cz-3CHO to the naphthalene imide intermediate NI is 2:3; the reaction solvent is 1,4-dioxane and 1,3,5-mesitylene, and preferably the volume ratio of 1,4-dioxane and 1,3,5-mesitylene is 1:1; the reaction catalyst is acetic acid; the reaction temperature is 115°C~125°C, and preferably the reaction temperature is 120°C; the reaction time is 70h-80h, and preferably the reaction time is 72h; the washing solvents are water, dichloromethane and methanol, and the solvents for Soxhlet extraction are tetrahydrofuran, dichloromethane and methanol.

[0056] In the above reaction process, the molar ratio of the raw materials is preferably 2:3 for the carbazole intermediate and the naphthalene imide intermediate, and the molar ratio of the functional groups used for the reaction, i.e., the aldehyde group and the amino group, is 1:1, so that the reaction is as complete as possible, thereby increasing the degree of polymerization of the reaction product photocatalyst; the reaction solvent is 1,4-dioxane and 1,3,5-mesitylene, which have good solubility for the reactants and a high boiling point, and can increase the reaction temperature, thereby accelerating the reaction rate and increasing the degree of polymerization of the reaction product photocatalyst; the reaction catalyst is acetic acid, which can protonate the carbonyl group of the aldehyde, increase the electrophilicity of the carbon atom, and facilitate the nitrogen atom with a lone pair of electrons in the amino group to attack the carbonyl carbon; the reaction temperature is preferably 1 20 ° C, the reaction time is preferably 72h. A higher reaction temperature and a longer reaction time can make the reactants react as completely as possible; the washing solvents used are water, dichloromethane and methanol, all of which are cheap and easily available and can be used in large quantities, wherein water is used to remove the catalyst, and dichloromethane and methanol are used to preliminarily remove the reactants that have not reacted completely; the solvents used for Soxhlet extraction are tetrahydrofuran, dichloromethane and methanol, all of which have low boiling points and are easy to condense and reflux, wherein tetrahydrofuran and dichloromethane are used to remove small molecular monomers that have not reacted or are embedded in the polymer, and methanol is used to remove oligomers with a low degree of polymerization, thereby ultimately obtaining the target photocatalyst material with a high degree of polymerization.

[0057] A third aspect of the present invention provides a use of the conjugated microporous polymer photocatalyst described above, wherein the photocatalyst is used to photocatalytically produce hydrogen peroxide using water as a solvent in an air atmosphere, an oxygen atmosphere, or an oxygen-free atmosphere. Optionally, the photocatalyst is used in a ratio of 1 mg of photocatalyst to 3-5 mL of water by volume, preferably 1 mg of photocatalyst to 4 mL of water by volume.

[0058] Example 1 Preparation of Conjugated Microporous Polymer Photocatalyst 36-NI-Cz-NI

[0059] The steps include:

[0060] Step 1: Dissolve 4-bromo-1,8-naphthalene dicarboxylic anhydride (2.77 g, 10 mmol) in ethanol (100 mL). Add hydrazine hydrate (80% by mass, 5 mL) to the above solution, and reflux the mixture under a nitrogen atmosphere for 4 hours. After cooling to room temperature, the precipitate is washed three times with water and then recrystallized from a mixed solvent with a volume ratio of N,N-dimethylformamide: acetonitrile = 1:1 to obtain a dark red powder, which is the intermediate NI, with a yield of 90%. Its H NMR spectrum is as follows: Figure 1 shown.

[0061] Step 2: Mix 3,6-dibromocarbazole (4.8 g, 15 mmol) and potassium tert-butoxide (1.68 g, 15 mmol) and place them in a 250 mL Shrek bottle, and evacuate and replace the nitrogen three times. Then use a syringe to draw 75 mL of ultra-dry N, N-dimethylformamide into the Shrek bottle, and heat the mixture to 110 ° C under a nitrogen atmosphere for 0.5 hours. After cooling to room temperature, weigh p-fluorobenzaldehyde (2.8 g, 22.5 mmol) and slowly add it to the reaction bottle, and then react the mixture for 36 hours under a nitrogen atmosphere. After cooling to room temperature, the precipitate is washed three times with water, and then recrystallized with a mixed solvent with a mixed solvent volume ratio of acetone: water = 1:1 to obtain a white powder, which is the intermediate 36-Cz-CHO, with a yield of 80%. Its nuclear magnetic hydrogen spectrum is as follows Figure 2 shown.

[0062] Step 3: 36-Cz-CHO (2.5 g, 6 mmol), 4-formylphenylboronic acid (3.6 g, 24 mmol), anhydrous potassium carbonate (3.9 g, 30 mmol), ultrapure water (15 mL), and ethanol (150 mL) were added to a 500 mL Shrek bottle in sequence. The air was continuously driven out by bubbling with a nitrogen balloon, and then tetrakistriphenylphosphine palladium (0.5 g, 0.45 mmol) was added under a nitrogen atmosphere and refluxed at 80 ° C for 48 hours. After the reaction was completed, it was cooled to room temperature, and the mixture was filtered. The filter cake was purified by column chromatography with dichloromethane and petroleum ether to obtain the pure product, and dried in a vacuum oven at 60 ° C for 24 hours to obtain a light yellow product, which is the intermediate 36-Cz-3CHO, with a yield of 56%. Its nuclear magnetic hydrogen spectrum is as follows Figure 3 shown.

[0063] Step 4: Add the intermediate 36-Cz-3CHO (144 mg, 0.3 mmol) and NI (109 mg, 0.45 mmol) to a 50 mL reactor. Then, add 5 mL of 1,4-dioxane and 5 mL of 1,3,5-mesitylene. Ultrasonicate for 20 minutes. Separately, prepare a 6 mol / L acetic acid solution (1.72 mL of glacial acetic acid and 3.28 mL of ultrapure water). After the ultrasonication period, add 1 mL of this 6 mol / L acetic acid solution to the reactor. Continue bubbling with nitrogen for 15 minutes to remove oxygen from the reactor. Reaction is continued at 120°C for 72 hours. After the reaction is completed, the reaction solution is cooled to room temperature, filtered, washed with water, methanol, dichloromethane, and other solvents, and finally Soxhlet extraction is performed with tetrahydrofuran, dichloromethane, and methanol for 3 days, respectively. Then, the solution is dried in a vacuum oven at 60°C for 2 days to obtain 200 mg of a red product, which is the conjugated microporous polymer photocatalyst 36-NI-Cz-NI. The reaction formula is:

[0064]

[0065] Example 2 Preparation of Conjugated Microporous Polymer Photocatalyst 27-NI-Cz-NI

[0066] The steps include:

[0067] Step 1: The preparation of naphthalene imide intermediate NI is the same as that in Example 1.

[0068] Step 2: Mix 2,7-dibromocarbazole (4.8 g, 15 mmol) and potassium tert-butoxide (1.68 g, 15 mmol) and place them in a 250 mL Shrek bottle, and evacuate and replace the nitrogen three times. Then use a syringe to draw 75 mL of ultra-dry N, N-dimethylformamide into the Shrek bottle, and heat the mixture to 110 ° C under a nitrogen atmosphere for 0.5 hours. After cooling to room temperature, weigh p-fluorobenzaldehyde (2.8 g, 22.5 mmol) and slowly add it to the reaction bottle, and then react the mixture for 36 hours under a nitrogen atmosphere. After cooling to room temperature, the precipitate is washed three times with water, and then recrystallized with a mixed solvent with a mixed solvent volume ratio of acetone: water = 1:1 to obtain a white powder, which is the intermediate 27-Cz-CHO, with a yield of 75%. Its nuclear magnetic hydrogen spectrum is as follows Figure 4 shown.

[0069] Step 3: Add 27-Cz-CHO (2.5 g, 6 mmol), 4-formylphenylboronic acid (3.6 g, 24 mmol), anhydrous potassium carbonate (3.9 g, 30 mmol), ultrapure water (15 mL), and ethanol (150 mL) into a 500 mL Shrek bottle in sequence. Continue bubbling with a nitrogen balloon to drive out the air, then add tetrakistriphenylphosphine palladium (0.5 g, 0.45 mmol) under a nitrogen atmosphere, and reflux at 80 ° C for 48 hours. After the reaction is completed, cool to room temperature, and then filter the mixture. The filter cake is chromatographed with dichloromethane and petroleum ether to obtain a pure product, and dried in a vacuum oven at 60 ° C for 24 hours to obtain a light yellow product, which is the intermediate 27-Cz-3CHO, with a yield of 50%. Its nuclear magnetic hydrogen spectrum is as follows Figure 5 shown.

[0070] Step 4: Add the intermediate 27-Cz-3CHO (144 mg, 0.3 mmol) and NI (109 mg, 0.45 mmol) to a 50 mL reactor. Then, add 5 mL of 1,4-dioxane and 5 mL of 1,3,5-mesitylene. Ultrasonicate for 20 minutes. Separately, prepare a 6 mol / L acetic acid solution (1.72 mL of glacial acetic acid and 3.28 mL of ultrapure water). After the ultrasonication period, add 1 mL of this 6 mol / L acetic acid solution to the reactor. Continue bubbling with nitrogen for 15 minutes to remove oxygen from the reactor. Reaction is continued at 120°C for 72 hours. After the reaction is completed, the reaction solution is cooled to room temperature, filtered, washed with water, methanol, dichloromethane, and other solvents, and finally Soxhlet extraction is performed with tetrahydrofuran, dichloromethane, and methanol for 3 days, respectively. Then, the solution is dried in a vacuum oven at 60°C for 2 days to obtain 200 mg of a red product, which is the conjugated microporous polymer photocatalyst 27-NI-Cz-NI. The reaction formula is:

[0071]

[0072] Structural characterization of the conjugated microporous polymer photocatalysts prepared in Example 1 and Example 2

[0073] Fourier transform infrared spectroscopy (FT-IR) and solid 13 C NMR spectra (ss- 13 The structures of 27-NI-Cz-NI, 36-NI-Cz-NI and their intermediates were systematically characterized by C NMR.

[0074] FT-IR spectroscopy showed that ( Figure 6 ), monomers 27-NI-Cz-NI and 36-NI-Cz-NI at 3358 cm -1The characteristic peak of the precursors NI, 27-Cz-3CHO and 36-Cz-3CHO is at 1626 cm -1 Strong absorption peaks appeared near the α-amino group, which are all attributed to the stretching vibration of the carbonyl group (-C=O). The expected characteristic peaks of the imine bond (-C=N) in the conjugated microporous polymers 27-NI-Cz-NI and 36-NI-Cz-NI prepared after aldehyde-amine condensation (about 1643 cm -1 ) Due to the overlap with the -C=O vibration peak position, the signal is weakened and needs to be combined with ss- 13 C NMR further confirmed the structure. 13 C NMR spectrum ( Figure 7 ), the characteristic peak at δ = 161 ppm is attributed to the -C=O carbon atom of the intermediate NI, while the peak at δ = 147 ppm corresponds to the carbon atom in the -C=N region, directly confirming the successful aldehyde-amine condensation reaction between the precursor aldehyde group and the amine group. Furthermore, a series of peaks in the δ = 110-140 ppm range are attributed to aromatic carbons in the catalyst skeleton (such as carbazole and naphthalimide units), further demonstrating the rigid conjugated structure of the conjugated microporous polymer.

[0075] The morphology of the catalysts was determined by scanning electron microscopy, and both photocatalysts had a porous heterogeneous structure ( Figure 8 Compared to the smoother surface morphology of 36-NI-Cz-NI, the surface morphology of 27-NI-Cz-NI is rougher. This structure increases the specific surface area of ​​the material, helping to expose more active sites, thereby effectively improving photocatalytic performance. Its micron-scale structure can enhance the light scattering effect, extend the light propagation path, and improve the utilization rate of light energy. At the same time, the crisscrossing grooves and fine undulations on the surface help promote the separation and migration of photogenerated carriers, reduce the probability of recombination, and thus enhance charge transport performance.

[0076] Photoelectrochemical characterization of the conjugated microporous polymer photocatalysts prepared in Example 1 and Example 2

[0077] Firstly, the light-harvesting properties of the two conjugated microporous polymer photocatalysts were studied by UV-visible diffuse reflectance spectroscopy. The results showed that both of them have a wide absorption range in the visible light region ( Figure 9 According to the derived Tauc plot, the band gaps of 36-NI-Cz-NI and 27-NI-Cz-NI are 1.85 eV and 1.95 eV respectively ( Figure 10). Secondly, the photogenerated carrier separation, transport performance and energy band characteristics of the two photocatalysts were deeply explored through photocurrent response, electrochemical impedance spectroscopy and Mott-Schottky curve. The photocurrent response results show that under the same illumination conditions, the photocurrent intensity of 27-NI-Cz-NI is slightly enhanced compared with 36-NI-Cz-NI, indicating that more electrons can be transferred to the catalyst surface to be captured by the photocurrent test and participate in the surface-interface reaction ( Figure 11 Electrochemical impedance spectroscopy analysis shows that the impedance arc radius of 27-NI-Cz-NI is smaller, corresponding to a lower charge transfer resistance, indicating that its interface electron transport resistance is smaller and the photogenerated carriers can participate in the surface redox reaction more efficiently ( Figure 12 The slopes of the Mott-Schottky curves of the two photocatalysts are both positive, proving that both are typical n-type semiconductors ( Figure 13 The flat band potentials of 36-NI-Cz-NI and 27-NI-Cz-NI are -0.68 V and -0.70 V (vs. standard hydrogen electrode), respectively, which are more negative than the standard potential of O2 reduction to H2O2 (E (O2 / H2O2) = 0.28 eV vs. standard hydrogen electrode) and the standard potential of O2 reduction to superoxide radicals (·O2 ⁻ ) standard potential (E(O2 / ·O2 ⁻ ) = -0.33 eV vs. standard hydrogen electrode). This result indicates that the conduction band positions of both catalysts meet the thermodynamic requirements for driving the photocatalytic reduction of O2 to directly generate H2O2, or to generate ·O2 ⁻ The intermediate is further protonated to generate H2O2. Based on the band gap and conduction band results, the valence bands of 36-NI-Cz-NI and 27-NI-Cz-NI were calculated to be 1.37 eV and 1.45 eV, respectively. These are higher than the standard potentials for water oxidation via the four-electron pathway to generate O2 (E(H2O / O2) = 0.83 eV vs. standard hydrogen electrode) and the direct two-electron pathway to generate H2O2 (E(H2O / H2O2) = 1.35 eV vs. standard hydrogen electrode), but lower than the standard potential for the indirect two-electron pathway to generate hydroxyl radicals (·OH) (E(H2O / ·OH) = 2.31 eV vs. standard hydrogen electrode). In summary, 27-NI-Cz-NI exhibits excellent carrier separation efficiency and interfacial reaction kinetics, providing theoretical and experimental evidence for its efficient photocatalytic synthesis of H2O2.

[0078] Application of the conjugated microporous polymer photocatalysts prepared in Examples 1 and 2 - Photocatalytic H2O2 production performance test

[0079] Firstly, pure water was used as solvent to study the photocatalytic activities of the two photocatalysts in different atmospheres ( Figure 14In air, the photocatalytic H2O2 production rate of 27-NI-Cz-NI reached 2.29 mmol·g -1 ·h -1 , than 36-NI-Cz-NI (1.77mmol·g -1 ·h -1 In an oxygen atmosphere, the photocatalytic H2O2 production rate of 27-NI-Cz-NI increased to 2.59 mmol·g -1 ·h -1 , proving that oxygen and electron-driven oxygen reduction reaction plays a key role, and an oxygen-saturated environment is conducive to improving performance. In a nitrogen atmosphere, 36-NI-Cz-NI and 27-NI-Cz-NI still have 0.49mmol·g -1 ·h -1 and 0.65mmol·g -1 ·h -1 The H2O2 generation rate was significantly increased, proving that hole-driven water oxidation also plays an important role in the production of H2O2 by this type of photocatalyst. Then, under air atmosphere, different hole sacrificial agents were added to the catalytic system, including methanol (MeOH), ethanol (EtOH), isopropyl alcohol (IPA) and disodium ethylenediaminetetraacetic acid (EDTA-2Na) to consume holes, accelerate the separation of photogenerated carriers and inhibit their recombination, which can further improve the catalytic performance ( Figure 15 The results showed that all hole-sacrificing agents could improve the catalytic performance. Among them, EDTA-2Na had the most significant effect on promoting the photocatalytic H2O2 production, increasing the yields of 36-NI-Cz-NI and 27-NI-Cz-NI by about 2.6 times to 4.66 mmol·g -1 ·h -1 and 6.09mmol·g -1 ·h -1 Finally, the stability of the two photocatalysts was studied through multiple cycles. After five consecutive photocatalytic cycles (1 hour each, totaling 5 hours), the H2O2 yield of 36-NI-Cz-NI still maintained 80.2% of the initial value (from 1.77mmol·g -1 ·h -1 Reduced to 1.42 mmol·g -1 ·h -1 ), while the activity of 27-NI-Cz-NI was 85.6% of the initial value (from 2.29 mmol·g -1 ·h -1 Reduced to 1.96mmol·g -1 ·h -1 ), proving that both have excellent catalytic stability ( Figure 16 ).

[0080] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed. The above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application. The above is only a preferred embodiment of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and variations can be made without departing from the technical principles of the present application. These improvements and variations should also be regarded as the scope of protection of the present application.

Claims

1. A conjugated microporous polymer photocatalyst, characterized in that: The photocatalyst uses a carbazole intermediate as an electron donor and a naphthalimide intermediate as an electron acceptor to construct a conjugated microporous polymer skeleton through an aldehyde-amine condensation reaction; The structural formula of the photocatalyst includes: or .

2. A method for preparing a conjugated microporous polymer photocatalyst, characterized in that: The method for preparing the photocatalyst according to claim 1 comprises the following steps: Preparation of naphthalene imide intermediates: 4-bromo-1,8-naphthalene dicarboxylic anhydride is reacted with hydrazine hydrate in ethanol, and the naphthalene imide intermediate NI is obtained after recrystallization; Carbazole intermediates are prepared by the following method 1 or method 2: Method 1: 3,6-dibromocarbazole and p-fluorobenzaldehyde undergo a nucleophilic substitution reaction in N,N-dimethylformamide, followed by recrystallization to obtain 36-Cz-CHO; 36-Cz-CHO undergoes a Suzuki coupling reaction with 4-formylphenylboronic acid in a mixed solvent of ethanol and water, followed by column chromatography to obtain the carbazole intermediate 36-Cz-3CHO; Method 2: 2,7-dibromocarbazole and p-fluorobenzaldehyde undergo a nucleophilic substitution reaction in N,N-dimethylformamide, followed by recrystallization to obtain 27-Cz-CHO; 27-Cz-CHO undergoes a Suzuki coupling reaction with 4-formylphenylboronic acid in a mixed solvent of ethanol and water, followed by column chromatography to obtain the carbazole intermediate 27-Cz-3CHO; Aldehyde amine condensation reaction: The carbazole intermediate 36-Cz-3CHO or the carbazole intermediate 27-Cz-3CHO undergoes an aldehyde amine condensation reaction with the naphthalene imide intermediate NI. After the reaction is completed, the photocatalyst 36-NI-Cz-NI or the photocatalyst 27-NI-Cz-NI is obtained by filtering, washing, Soxhlet extraction and drying.

3. The method for preparing the conjugated microporous polymer photocatalyst according to claim 2, characterized in that: The solvent used for the recrystallization of the naphthalene imide intermediate NI is a mixed solvent of N,N-dimethylformamide and acetonitrile; the solvent used for the recrystallization of 36-Cz-CHO is a mixed solvent of acetone and water; and the solvent used for the recrystallization of 27-Cz-CHO is a mixed solvent of acetone and water.

4. The method for preparing the conjugated microporous polymer photocatalyst according to claim 2, wherein: The eluent used for column chromatography of the carbazole intermediate 36-Cz-3CHO is a mixed solvent of dichloromethane and petroleum ether; the eluent used for column chromatography of the carbazole intermediate 27-Cz-3CHO is a mixed solvent of dichloromethane and petroleum ether.

5. The method for preparing the conjugated microporous polymer photocatalyst according to claim 2, characterized in that: In the aldehyde-amine condensation reaction, the molar ratio of the carbazole intermediate 36-Cz-3CHO or the carbazole intermediate 27-Cz-3CHO to the naphthaleneimide intermediate NI is 1:(1.4-1.6), the reaction solvent is 1,4-dioxane and 1,3,5-mesitylene, the reaction catalyst is acetic acid, the reaction temperature is 115°C-125°C, and the reaction time is 70h-80h.

6. The method for preparing a conjugated microporous polymer photocatalyst according to claim 2, wherein: In the aldehyde-amine condensation reaction, the washing solvent is water, dichloromethane and methanol, and the Soxhlet extraction solvent is tetrahydrofuran, dichloromethane and methanol.

7. An application of a conjugated microporous polymer photocatalyst, characterized in that: The photocatalyst according to claim 1 or 2 is used for photocatalytically producing hydrogen peroxide in an air atmosphere, an oxygen atmosphere or an oxygen-free atmosphere using water as a solvent.

8. The use according to claim 7, characterized in that The dosage of the photocatalyst is as follows: the volume ratio of the mass of the photocatalyst to water is 1 mg: (3-5) mL.

9. The use according to claim 7, characterized in that The photocatalyst 27-NI-Cz-NI was used to produce hydrogen peroxide in air and water. With the participation of the sacrificial agent disodium ethylenediaminetetraacetic acid, the yield reached 6.09 mmol g -1 ·h -1 After five consecutive photocatalytic cycles of 1 hour each, the hydrogen peroxide yield of the photocatalyst 27-NI-Cz-NI is not less than 85% of the initial value; The photocatalyst 36-NI-Cz-NI was used to produce hydrogen peroxide in air and water. With the participation of the sacrificial agent disodium ethylenediaminetetraacetic acid, the yield reached 4.66 mmol g -1 ·h -1 After five consecutive photocatalytic cycles of 1 hour each, the hydrogen peroxide yield of the photocatalyst 36-NI-Cz-NI is not less than 80% of the initial value.

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