Polyimide material and method for photocatalytic synthesis of hydrogen peroxide

Abstract

The invention discloses a method for photocatalytically synthesizing a polyimide material of hydrogen peroxide, and belongs to the fields of environmental chemistry, chemical engineering and material science. The polyimide catalytic material is prepared by carrying out thermal imidization on an aromatic triamine monomer and an aromatic dianhydride monomer; wherein the aromatic triamine monomer is selected from TABPB, TAB and TBZ; the aromatic dianhydride monomer is BDA. The polyimide material with excellent photocatalytic activity is obtained by adopting raw materials with wide sources and a simple synthesis method. The polyimide material is used as a catalyst, is dispersed in an oxygen-containing aqueous solution on photocatalytic hydrogen peroxide production, and is irradiated by light for a period of time to obtain hydrogen peroxide. The method is green, environment-friendly, safe and pollution-free, uses water and oxygen as raw materials and solar energy as an energy source, and has the advantages of simple synthesis, mild reaction conditions, stable catalyst, convenience in circulation, high yield of hydrogen peroxide and the like.

Description

Technical Field

[0001] The present invention belongs to the fields of environmental chemistry, chemical engineering and materials science, and relates to a polyimide material for photocatalytic synthesis of hydrogen peroxide, and its preparation and use methods. Background Art

[0002] With the development of society and the needs of human life, energy issues have attracted wide attention. Hydrogen peroxide is an important chemical reagent and has extensive applications in fields such as medical environmental protection, environmental disinfection, wastewater treatment, and chemical synthesis. It is estimated that by 2027, the market demand for hydrogen peroxide may increase to 5.7 million tons. China ranks first in the world in terms of hydrogen peroxide production capacity, output, and consumption, but there is a shortage in supply. It is expected that by 2030, the global hydrogen peroxide market will reach $15.4 billion. Currently, more than 95% of the hydrogen peroxide in the market is mainly produced by the anthraquinone method, which involves noble metal catalysts, has a complex reaction process, high energy consumption, and also brings a large amount of toxic by-products. The direct mixing method of hydrogen and oxygen faces serious safety problems such as explosion, and the electrochemical method has problems of high cost and high energy consumption. Therefore, it is necessary to explore an environmentally friendly, efficient, and stable method for synthesizing hydrogen peroxide. Photocatalytic synthesis of hydrogen peroxide uses sunlight as the only energy source, water and oxygen as raw materials, and realizes the synthesis of hydrogen peroxide through a semiconductor photocatalyst. It has the advantages of being green, sustainable, safe, pollution-free, energy-saving, and environmentally friendly. In the face of a sustainable energy future, it is an ideal way to replace industrial anthraquinone. Using an organic semiconductor photocatalyst for artificial photosynthesis to prepare hydrogen peroxide is a green, sustainable, and energy-saving method.

[0003] Despite the remarkable progress made, the catalytic efficiency still fails to meet industrial requirements. Therefore, numerous efficient modification methods have been explored to increase the production of photo-generated H2O2, such as morphology regulation, doping, constructing composite materials, surface modification, and nanoparticle deposition. However, there are still significant limitations, and there is an urgent need to develop advanced organic semiconductor materials for the efficient photocatalytic synthesis of hydrogen peroxide in pure water systems. In particular, most hydrogen peroxide production experiments are conducted in solution-powder photocatalyst systems, which are not conducive to the extraction of hydrogen peroxide and the recovery of photocatalysts. Although some studies are carried out in pure water, their photocatalytic efficiency is always lower than that of sacrificial agent-assisted reactions. Therefore, there is an urgent need to explore new catalysts to achieve stable and efficient hydrogen peroxide production in a sacrificial agent-free system. Among many organic photocatalysts, polyimide is a new type of conjugated polymer photocatalyst with abundant sources, low production costs, high chemical stability, strong thermal stability, adjustable electronic structure, strong mechanical properties, and easy processing. It is a highly potential material known as "engineering plastics" and is applied in membrane separation, coatings, aerospace, microelectronics and optoelectronics industries, lithium-ion batteries, and sensing fields. However, due to severe photogenerated charge recombination, lack of effective active sites, poor two-electron selectivity, and low adsorption capacity for oxygen and protons, polyimide materials cannot be efficiently used for the photocatalytic synthesis of hydrogen peroxide. Therefore, there is an urgent need to develop effective strategies to improve polyimide materials for efficient and stable hydrogen peroxide synthesis in pure water systems. Summary of the Invention

[0004] The present invention develops a polyimide material and method for photocatalytic synthesis of hydrogen peroxide, achieving efficient and stable synthesis of hydrogen peroxide. This method has groundbreaking value and meets the current practical requirements of chemical industry compatibility with the ecological environment and sustainable development, thus having important industrial application value and social significance.

[0005] The present invention aims to provide a polyimide material and method for photocatalytic synthesis of hydrogen peroxide, achieving efficient and stable synthesis of hydrogen peroxide, and providing a material capable of efficiently photocatalytically producing hydrogen peroxide without sacrificial reagents. Photocatalytic production of hydrogen peroxide is a green, environmentally friendly, and pollution-free approach; using oxygen and water as raw materials and sunlight as the sole energy source, it has the advantages of low energy consumption, high safety, simple operation, mild reaction conditions, relatively high hydrogen peroxide concentration per unit time, efficient accumulation, and long-term stable cycling.

[0006] Specific Scheme:

[0007] The present invention provides a polyimide catalytic material for photocatalytic synthesis of hydrogen peroxide, and the polyimide catalytic material is prepared by thermal imidization of an aromatic triamine monomer and an aromatic dianhydride monomer; the aromatic triamine monomer is selected from any one or more of the following: 5”-(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1':4',1”:3”,1”':4”',1””-quaterphenyl]-4,4””-diamine (TABPB), 1,3,5-triaminobenzene (TAB), 1,3,5-tris(4-aminophenyl)benzene (TBZ); the aromatic dianhydride monomer is 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA).

[0008] In one embodiment of the present invention, the preparation method of the polyimide catalytic material includes the following process:

[0009] (1) Dissolve the aromatic triamine monomer in solvent A to prepare an aromatic triamine monomer solution; dissolve the aromatic dianhydride monomer in solvent B to prepare an aromatic dianhydride monomer solution; mix the two solutions, then add isoquinoline, mix well and react to obtain a reaction solution;

[0010] (2) Pour the obtained reaction solution into a mold, first gel at 0-5°C for a period of time, then continue heat treatment at 150-200°C for a period of time to obtain a primary product; soak the primary product in a gradient of N-methylpyrrolidone-ethanol solution, then wash and dry.

[0011] In one embodiment of the present invention, in step (1), solvent A is mesitylene, N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), N,N-dimethylacetamide (DMAc). Mesitylene is preferred.

[0012] In one embodiment of the present invention, in step (1), solvent B is NMP, DMF, DMAc, mesitylene.

[0013] In one embodiment of the present invention, in step (1), preferably: solvent A is mesitylene and solvent B is NMP.

[0014] In one embodiment of the present invention, in step (1), the volume ratio of solvent A to solvent B is 1:1.

[0015] In one embodiment of the present invention, in step (1), the concentration of the aromatic triamine monomer solution is 0.1-0.5 mmol / mL; specifically, 0.3 mmol / mL can be selected.

[0016] In one embodiment of the present invention, in step (1), the concentration of the aromatic dianhydride monomer solution is 0.1-1.0 mmol / mL; 0.45 mmol / mL.

[0017] In one embodiment of the present invention, in step (1), the molar ratio of the aromatic triamine monomer to the aromatic dianhydride monomer is 1:(1 - 2); specifically, 1:1.5 can be selected.

[0018] In one embodiment of the present invention, in step (1), the dosage of isoquinoline relative to the aromatic triamine monomer is 0.02 - 0.05 ml / mmol.

[0019] In one embodiment of the present invention, in step (2), the obtained reaction solution is poured into a mold, first gelled at 0°C for 60 min, and then further subjected to solvent heat treatment at 180°C for 48 h.

[0020] In one embodiment of the present invention, in step (2), the gradient soaking means first soaking in a 75% organic solvent - ethanol solution for 24 h, then exchanging the solvent with a 25% - 50% organic solvent - ethanol solution every 24 h, and then exchanging the solvent with ethanol three times. The organic solvent refers to N-methylpyrrolidone, dimethylformamide or dimethylacetamide.

[0021] In one embodiment of the present invention, in step (2), the drying is freeze-drying.

[0022] In one embodiment of the present invention, the preparation method of the polyimide catalytic material specifically includes:

[0023] (1) A polyimide photocatalyst was prepared by thermal imidization of an aromatic triamine and an aromatic dianhydride. Usually, the aromatic dianhydride is dissolved in a polar solvent solution such as N-methylpyrrolidone, dimethylformamide or dimethylacetamide, then a certain proportion of the aromatic triamine is dispersed in a mesitylene solution, and then a small amount of the catalyst isoquinoline is added; after ultrasonic treatment for 10 - 30 min, a transparent and homogeneous solution is obtained; then it is poured into a suitable mold and gelled in an ice-water bath at about 0 - 5°C within 30 - 60 min, and then placed in an oven for heat treatment at 120 - 180°C for 48 - 60 h;

[0024] (2) The product obtained by heat treatment in step (1) is soaked in a 75% N-methylpyrrolidone or dimethylformamide or dimethylacetamide - ethanol mixed solution for 24 - 48 hours; subsequently, the solvent is exchanged with a 50% N-methylpyrrolidone or dimethylformamide or dimethylacetamide - ethanol mixed solvent and a 25% N-methylpyrrolidone or dimethylformamide or dimethylacetamide - ethanol mixed solvent every 24 - 48 hours, and then the solvent is exchanged with an ethanol solution three times; finally, the product is rinsed with deionized water and dried to obtain the final product.

[0025] In one embodiment of the present invention, the method is specifically as follows:

[0026] (1) Scheme 1: The polyimide BTABPB photocatalyst was prepared by the thermal imidization method using the aromatic triamine 5-(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1':4',1'':3'',1''':4''',1'''-pentaphenyl]-4,4''-diamine (TABPB) and the aromatic dianhydride 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA). Usually, BDA (0.9 mmol) was dissolved in 2 mL of N-methylpyrrolidone solution, then TABPB (0.6 mmol) was dispersed in 2 mL of mesitylene solution, and finally isoquinoline (0.02 mL) was added. After ultrasonic treatment at a power of 100 w for 10 min, a transparent and colorless solution was rapidly obtained. Then it was poured into a mold and gelled at 0 °C for 60 min. The gel was further subjected to solvent heat treatment at 180 °C for 48 h. The product was soaked in 75% N-methylpyrrolidone-ethanol solution for 24 h. Subsequently, the solvent was exchanged with 25% N-methylpyrrolidone-ethanol every 24 h, and then exchanged with ethanol three times. Finally, it was rinsed with deionized water and freeze-dried to obtain the final product BTABPB.

[0027] (2) Scheme 2: The polyimide BTAB photocatalyst was prepared by the thermal imidization method using the aromatic triamine 1,3,5-triaminobenzene (TAB) and the aromatic dianhydride 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA). Usually, BDA (0.9 mmol)

[0028] was dissolved in 2 mL of N-methylpyrrolidone solution, then TAB (0.6 mmol) was dispersed in 2 mL of mesitylene solution, and finally isoquinoline (0.02 mL) was added. After ultrasonic treatment at a power of 100 w for 10 min, a transparent and colorless solution was rapidly obtained. Then it was poured into a mold and gelled at 0 °C for 60 min. The gel was further subjected to solvent heat treatment at 180 °C for 48 h. The product was soaked in 75% N-methylpyrrolidone-ethanol solution for 24 h. Subsequently, the solvent was exchanged with 25% N-methylpyrrolidone-ethanol every 24 h, and then exchanged with ethanol three times. Finally, it was rinsed with deionized water and freeze-dried to obtain the final product BTAB.

[0029] (3) Scheme Three: The polyimide BTBZ photocatalyst was prepared by the thermal imidization method using aromatic triamine 1,3,5-tris(4-aminophenyl)benzene (TBZ) and aromatic dianhydride 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA). Usually, BDA (0.9 mmol) was dissolved in 2 mL of N-methylpyrrolidone solution, then TAB (0.6 mmol) was dispersed in 2 mL of mesitylene solution, and finally isoquinoline (0.02 mL) was added. After ultrasonic treatment at a power of 100 w for 10 min, a transparent and colorless solution was rapidly obtained. Then it was poured into a mold and gelled at 0 °C for 60 min. The gel was further subjected to solvent heat treatment at 180 °C for 48 h. The product was soaked in 75% N-methylpyrrolidone-ethanol solution for 24 h. Subsequently, the solvent was exchanged with 25% N-methylpyrrolidone-ethanol every 24 h, and then exchanged with ethanol three times. Finally, it was rinsed with deionized water and freeze-dried to obtain the final product BTBZ.

[0030] The present invention also provides the application of the above polyimide catalytic material in the photocatalytic synthesis of hydrogen peroxide.

[0031] The present invention provides a method for photocatalytic synthesis of hydrogen peroxide, which uses the above polyimide catalytic material as a photocatalyst.

[0032] In one embodiment of the present invention, the method is to add the polyimide catalytic material into water, introduce air or oxygen, and carry out a photocatalytic reaction for a period of time under light irradiation.

[0033] In one embodiment of the present invention, the method uses water and oxygen as raw materials, and the above polyimide catalytic material as a photocatalyst to photocatalytically synthesize hydrogen peroxide under light irradiation.

[0034] In one embodiment of the present invention, a polyimide material for photocatalytic synthesis of hydrogen peroxide is prepared, and the polyimide material can efficiently and stably photocatalytically synthesize hydrogen peroxide based on the photocatalytic method.

[0035] In one embodiment of the present invention, the photocatalyst refers to a substance that can absorb photon energy after being excited by photons, and electrons undergo transitions or are excited to generate reducing photocurrent electrons.

[0036] In one embodiment of the present invention, the dosage of the polyimide catalytic material relative to water is 1 mg / mL.

[0037] In one embodiment of the present invention, the wavelength of light is determined according to the needs of the photocatalyst. Specifically, the light is sunlight or an artificial light source; the artificial light source includes: xenon lamp, ultraviolet lamp, LED lamp, laser, etc. The light source can be full-spectrum light, simulated sunlight, visible light, single-wavelength light source, and natural light.

[0038] In one embodiment of the present invention, the power of the light is 200 - 300 mM / cm 2 .

[0039] In one embodiment of the present invention, the oxygen-rich environment means that during the reaction, oxygen is bubbled into the water body at a flow rate of 20 - 80 mL / min. The specific flow rate can be 50 mL / min for introducing oxygen.

[0040] In one embodiment of the present invention, during the process of photocatalytic synthesis of hydrogen peroxide, the photocatalyst can perform photocatalytic synthesis of hydrogen peroxide in a pure water - oxygen or pure water - air or sacrificial reagent - oxygen or sacrificial reagent - air environment. The sacrificial reagent is a C1-4 alkyl alcohol. Specifically, sacrificial reagents such as methanol, ethanol, and isopropanol.

[0041] In one embodiment of the present invention, the photocatalytic synthesis of hydrogen peroxide can be carried out continuously to accumulate high-concentration hydrogen peroxide.

[0042] In one embodiment of the present invention, the photocatalytic synthesis of hydrogen peroxide can be carried out in a long-term cyclic reaction.

[0043] In one embodiment of the present invention, the method is specifically as follows:

[0044] Weigh 20 mg of the above-prepared BTABPB or BTAB or BTBZ photocatalyst and 20 mL of deionized water and put them into a quartz bottle (100 mL). Inject oxygen into the suspension for 30 min in the dark. During the reaction, oxygen is continuously bubbled to maintain an oxygen-rich environment. A xenon lamp is used as the light source. The concentration of hydrogen peroxide is determined by the potassium titanyl oxalate method. Take 2 mL of the reaction solution at different time points of 20, 40, and 60 min respectively, filter off the catalyst with a 0.45 μm filter membrane, and finally obtain a hydrogen peroxide solution.

[0045] In one embodiment of the present invention, the catalyst can efficiently photocatalytically produce hydrogen peroxide in a water - oxygen or water - air environment.

[0046] The present invention uses widely sourced raw materials and a simple synthesis method to obtain a polyimide material with excellent photocatalytic activity. The polyimide photocatalyst prepared by the present invention has excellent charge separation efficiency and well-defined redox sites, thus greatly promoting the photocatalytic production of hydrogen peroxide. In the photocatalytic production of hydrogen peroxide, a certain concentration of the polyimide catalyst is mainly dispersed in an aqueous solution. Under the conditions of introducing oxygen with a certain flow rate and stirring, and then irradiating with light under a xenon lamp for a period of time, the obtained reaction solution is filtered to remove the catalyst to obtain a hydrogen peroxide solution with a certain concentration.

[0047] The beneficial effects of the present invention:

[0048] (1) The present invention prepares a polyimide photocatalyst capable of efficiently and stably photocatalytically synthesizing hydrogen peroxide through a sol-gel-thermal amidation route. The conjugated cross-linked molecular structure contains electron donors and electron acceptors, which promotes the separation efficiency of photogenerated carriers and improves the disadvantage of poor intrinsic conductivity of polyimide materials.

[0049] (2) The polyimide photocatalyst prepared by the present invention has a clear oxygen reduction site, which promotes the adsorption and activation of oxygen, greatly improving the selectivity and activity of hydrogen peroxide generation. Moreover, the concentration of hydrogen peroxide synthesized per unit time by the material is high, and it also has the characteristics of long-term stable cyclic use.

[0050] (3) The polyimide photocatalytic material prepared by the present invention uses water and oxygen as raw materials and sunlight as the sole energy source at normal temperature and pressure. It has the advantages of simple synthesis, mild reaction conditions, stable catalyst and convenient recycling, and high yield of hydrogen peroxide. Compared with the indirect synthesis of hydrogen peroxide by the anthraquinone method in industry, the method of the present invention has lower energy consumption and is green and environmentally friendly. Brief Description of the Drawings

[0051] Figure 1 It is the synthesis spectrum of the catalyst BTABPB prepared in Example 1.

[0052] Figure 2 It is the picture of the catalyst BTABPB prepared in Example 1.

[0053] Figure 3 It is the SEM spectrum of the catalyst BTABPB prepared in Example 1.

[0054] Figure 4 It is the infrared spectrum of the catalyst BTABPB prepared in Example 1.

[0055] Figure 5 It is the photocatalytic H2O2 production rate diagram of the catalyst BTABPB prepared in Example 1.

[0056] Figure 6 It is the cumulative photocatalytic H2O2 production diagram of the catalyst BTABPB prepared in Example 1.

[0057] Figure 7 It is the photocatalytic H2O2 cycle of the catalyst BTABPB prepared in Example 1.

[0058] Figure 8 It is the photocatalytic H2O2 production rate diagram of the catalysts BTAB and BTBZ prepared in Examples 2 and 3. Detailed Embodiments

[0059] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto.

[0060] The prepared catalyst in the present invention was subjected to an activity evaluation of photocatalytic performance:

[0061] (1) Weighed 20 mg of the prepared BTABPB photocatalyst and placed it in a quartz bottle containing 20 mL of deionized water. Oxygen was injected into the suspension for 30 minutes in the dark. During the reaction, oxygen was continuously bubbled to maintain an oxygen-rich environment. A 300-w xenon lamp was used as the light source. The concentration of hydrogen peroxide was determined by the potassium titanyl oxalate method. At 20, 40, and 60 minutes, 2 mL of the reaction solution was taken at different time points, filtered through a 0.45-μm filter membrane to remove the catalyst, and finally a hydrogen peroxide solution was obtained.

[0062] (2) Weighed 20 mg of the prepared BTABPB photocatalyst and placed it in a quartz bottle containing 20 mL of deionized water. Air was injected into the suspension for 30 minutes in the dark. During the reaction, air was continuously bubbled. A 300-w xenon lamp was used as the light source. The concentration of H2O2 was determined by the potassium titanyl oxalate method. At different time points, 2 mL of the reaction solution was taken and filtered through a 0.45-μm filter membrane to remove the catalyst, and finally a hydrogen peroxide solution was obtained.

[0063] (3) Put 20 mg of the prepared BTABPB photocatalyst and 20 mL of deionized water into a quartz bottle (100 mL). Air was injected into the suspension for 30 minutes in the dark. During the reaction, air was continuously bubbled. Visible light was used as the light source. The concentration of hydrogen peroxide was determined by the potassium titanyl oxalate method. At different time points, 2 mL of the reaction solution was taken and filtered through a 0.45-μm filter membrane to remove the catalyst, and finally a hydrogen peroxide solution was obtained.

[0064] Test method for the concentration of hydrogen peroxide:

[0065] Hydrogen peroxide can form a yellow solution with potassium titanyl oxalate. The absorbance at 400 nm was measured using a UV-visible spectrophotometer, and then the concentration of hydrogen peroxide was calculated through the Lambert-Beer law. Specifically: Every 20 minutes, 2 mL of the reaction solution was taken, filtered through a 0.45-μm filter to remove impurities, and then 1 mL of potassium titanyl oxalate was added. After reacting for more than 30 minutes, the absorbance of the solution was measured with a UV-visible spectrophotometer and the concentration of hydrogen peroxide was calculated.

[0066] Example 1: Preparation of polyimide aerogel photocatalyst BTABPB

[0067] The polyimide BTABPB photocatalyst was prepared by the thermal imidization method of aromatic triamine 5”-(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1':4',1”:3”,1”':4”',1””-quaterphenyl]-4,4””-diamine (TABPB) and aromatic dianhydride 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA)

[0068] Specific process: Usually, 53 mg of BDA is dissolved in 2.5 mL of N-methylpyrrolidone solution, and then 70 mg of TABPB is dispersed in 2.5 mL of mesitylene solution. The two are mixed, and finally isoquinoline (0.05 mL) is added. After ultrasonic treatment at a power of 100 w for 20 min, a transparent and colorless solution is quickly obtained. Then it is poured into a mold and gelled at 0 °C for 60 min. The gel is further subjected to solvothermal treatment at 180 °C for 48 h. The product is washed in 75% NMP ethanol solution for 24 h. Subsequently, the solvent is exchanged with 25% NMP ethanol every 24 h, and then exchanged with 100% ethanol three times. Finally, it is rinsed with deionized water and freeze-dried to obtain the final product, the BTABPB material.

[0069] The unit structure of the obtained BTABPB material is as follows:

[0070]

[0071] The prepared BTABPB material was scanned by scanning electron microscopy (SEM) ( Figure 3 as shown) and Fourier transform infrared spectroscopy (FTIR) ( Figure 4 as shown) to confirm the morphology and structure of BTABPB.

[0072] Test Example 1: Photocatalytic H2O2 production rate of polyimide aerogel photocatalyst BTABPB in pure water

[0073] Take 20 mg of the photocatalyst BTABPB from Example 1 and disperse it in 20 mL of aqueous solution. Oxygen with a flow rate of 50 mL / min is introduced and stirred for 30 min to achieve oxygen saturation. Then, under simulated sunlight (light power 300 mM / cm 2 ), it is irradiated for 20, 40, and 60 min. At different time points, 2 mL of the reaction solution is taken and filtered through a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 5 (Full-arc O2) shown.

[0074] Test Example 2: Photocatalytic H2O2 production rate of polyimide aerogel photocatalyst BTABPB in pure water

[0075] Take 20 mg of the photocatalyst BTABPB from Example 1 and disperse it in 20 mL of aqueous solution. Oxygen with a flow rate of 50 mL / min is introduced and stirred for 30 min to achieve oxygen saturation. Then, under visible light (light power 245 mM / cm 2 ), it is irradiated for 20, 40, and 60 min. At different time points, 2 mL of the reaction solution is taken and filtered through a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 5 (Vis-lightO2) shown.

[0076] Test Example 3: Photocatalytic H2O2 production rate of polyimide aerogel photocatalyst BTABPB in pure water

[0077] Disperse 20 mg of the photocatalyst BTABPB from Example 1 in 20 mL of aqueous solution, open to the air, and then irradiate under simulated sunlight for 20, 40, and 60 min. Take 2 mL of the reaction solution at different time points and filter it through a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 5 (Full-arc Air) shown.

[0078] Test Example 4: Cumulative performance of polyimide aerogel photocatalyst BTABPB for photocatalytic H2O2 production in pure water

[0079] Disperse 20 mg of the photocatalyst BTABPB from Example 1 in 20 mL of aqueous solution, introduce oxygen with a flow rate of 50 mL / min and stir for 30 min to achieve oxygen saturation, and then irradiate under simulated sunlight (light power 300 mM / cm 2 ) for 0.5, 1, 2, 3, 4, 6, 8, 10, and 12 h. Take 2 mL of the reaction solution at each time point and filter it through a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 6 shown.

[0080] Test Example 5: Cumulative performance of polyimide aerogel photocatalyst BTABPB for photocatalytic H2O2 production in pure water

[0081] Disperse 20 mg of the photocatalyst BTABPB from Example 1 in 20 mL of aqueous solution, place it open to the air, and then irradiate under simulated sunlight for 0.5, 1, 2, 3, 4, 6, 8, 10, and 12 h. Take 2 mL of the reaction solution at each time point and filter it through a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 6 shown.

[0082] Test Example 6: Recycling performance of polyimide aerogel photocatalyst BTABPB for photocatalytic H2O2 production in pure water

[0083] Disperse 20 mg of the photocatalyst BTABPB from Example 1 in 20 mL of aqueous solution, introduce oxygen with a flow rate of 50 mL / min and stir for 30 min to achieve oxygen saturation, and then irradiate under simulated sunlight (light power 300 mM / cm 2 ) for 12 h. Take 2 mL of the reaction solution at different time points and filter it through a 0.45 μm filter to measure the hydrogen peroxide concentration. Between each test, remove the residual hydrogen peroxide and water on the catalyst surface by evaporation. After that, dry the remaining photocatalyst BTABPB in a vacuum drying oven at 60 °C for 12 h and then conduct the next 12-hour cycle experiment. The results are as Figure 7as shown

[0084] Example 2: Preparation of Polyimide Aerogel Photocatalyst BTAB

[0085] The polyimide BTAB photocatalyst was prepared by thermal imidization using aromatic triamine 1,3,5-triaminobenzene (TAB) and aromatic dianhydride 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA).

[0086] Specific process: Dissolve BDA (0.9 mmol) in 2 mL of N-methylpyrrolidone solution, then disperse TAB (0.6 mmol) in 2 mL of mesitylene solution, mix the two, and finally add isoquinoline (0.02 mL). After ultrasonic treatment at a power of 100 w for 10 min, a transparent and colorless solution is quickly obtained. Then pour it into a mold and gel at 0 °C for 60 min. The gel is further subjected to solvent heat treatment at 180 °C for 48 h. The product is soaked in 75% N-methylpyrrolidone-ethanol solution for 24 h. Subsequently, the solvent is exchanged with 25% N-methylpyrrolidone-ethanol every 24 h, and then exchanged with ethanol three times. Finally, it is rinsed with deionized water and freeze-dried to obtain the final product BTAB.

[0087] The unit structure of the obtained BTAB material is as follows:

[0088]

[0089] Test Example 7: Photocatalytic H2O2 Production Rate of Polyimide Aerogel Photocatalyst BTAB in Pure Water

[0090] Take 20 mg of the photocatalyst BTAB from Example 2 and disperse it in 20 mL of aqueous solution. Pass oxygen with a flow rate of 50 mL / min and stir for 30 min to achieve oxygen saturation, and then under simulated sunlight (light power 300 mM / cm 2 ) irradiate for 10, 20, 30, 40, 50, 60 min. Take 2 mL of the reaction solution at different time points and filter it with a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 8 shown

[0091] Example 3: Preparation of Polyimide Aerogel Photocatalyst BTBZ

[0092] The polyimide BTAB photocatalyst was prepared by thermal imidization using aromatic triamine 1,3,5-tris(4-aminophenyl)benzene (TBZ) and aromatic dianhydride 3,3',4,4'-biphenyltetracarboxylic dianhydride (BDA).

[0093] Specific process: Dissolve BDA (0.9 mmol) in 2 mL of N-methylpyrrolidone solution, then disperse TAB (0.6 mmol) in 2 mL of mesitylene solution. Mix the two, and finally add isoquinoline (0.02 mL). After ultrasonic treatment at a power of 100 w for 10 min, a transparent and colorless solution is rapidly obtained. Then pour it into a mold and gel at 0 °C for 60 min. The gel is further subjected to solvothermal treatment at 180 °C for 48 h. The product is soaked in 75% N-methylpyrrolidone-ethanol solution for 24 h. Subsequently, exchange the solvent with 25% N-methylpyrrolidone-ethanol every 24 h, and then exchange the solvent with ethanol three times. Finally, rinse with deionized water and freeze-dry to obtain the final product BTBZ.

[0094] The unit structure of the obtained BTBZ material is as follows:

[0095]

[0096] Test Example 8: Photocatalytic H2O2 production rate of polyimide aerogel photocatalyst BTBZ in pure water

[0097] Take 20 mg of the photocatalyst BTBZ in Example 3 and disperse it in 20 mL of aqueous solution. Pass oxygen with a flow rate of 50 mL / min and stir for 30 min to achieve oxygen saturation. Then, under simulated sunlight (light power 300 mM / cm 2 ), irradiate for 10, 20, 30, 40, 50, 60 min. Take 2 mL of the reaction solution at different time points and filter it with a 0.45 μm filter to measure the hydrogen peroxide concentration. The results are as Figure 8 shown.

[0098] Comparative Example 1: Comparison with polyimide catalytic materials reported in existing literature

[0099] Sample: Polyamic acid monomer (diamine is 1,4-phenylenediamine, dianhydride is 1,2,4,5-benzenetetracarboxylic dianhydride) forms polyamic acid, and then undergoes ring-closing polycondensation to form polyimide. The polyimide catalytic material is as follows, and the structure is shown below:

[0100]

[0101] Measure the photocatalytic H2O2 production performance of this material according to the process of Test Example 1.

[0102] The test results of the above Test Examples 1, 7, and 8 are specifically shown in Table 1.

[0103] Table 1

[0104] catalyst <![CDATA[H2O2 concentration (60 min)]]> Example 1 (BTABPB) 2803.07 umol / L Example 2 (BTAB) 659.14 umol / L Example 3 (BTBZ) 1608.2 umol / L Comparative Example 1 35.89 umol / L

[0105] Note: The above yield data are all averages after three parallel experiments.

[0106] Comparative Example 2: Comparison of Different Polyimide Monomers

[0107] Referring to Example 1, replace the aromatic triamine with other monomers shown in Table 2, and keep the others unchanged to obtain the corresponding polyimide materials.

[0108] Measure the performance of the corresponding photocatalytic production of H2O2 according to the process of Test Example 1. The results are shown in Table 2.

[0109] Table 2

[0110] monomer number of the corresponding polymer <![CDATA[H2O2 concentration (60 min)]]> 1,4 - phenylenediamine 1 57.23 umol / L 1,3 - phenylenediamine 2 78.64 umol / L 2,4,6 - tris(4 - aminophenyl)-1,3,5 - triazine 3 437.68 umol / L tris(4 - aminophenyl)amine 4 198.12 umol / L diethylamine 5 12.59 umol / L pyrenediamine 6 335.59 umol / L biphenyldiamine 7 294.24 umol / L

[0111] Note: The above yield data are all the averages after three parallel experiments.

[0112] The corresponding unit structures of the above polymers 1-7 are as follows:

[0113]

[0114] Comparative Example 3: Comparative Optimization of Preparation Methods

[0115] Referring to Example 1, only adjust the solvent environment: Disperse TABPB in other organic solvents (shown in Table 3) with the same volume to prepare the corresponding catalytic materials.

[0116] Measure the performance of the corresponding photocatalytic production of H2O2 according to the process of Test Example 1. The results are shown in Table 3.

[0117] Table 3

[0118] solvent <![CDATA[H2O2 concentration (60 min)]]> mesitylene solution (of the present invention) 2803.07 umol / L DMF 892.13 umol / L DMSO 192.07 umol / L (low yield) m - hydroxy phenol 325.03 umol / L (low yield) NMP 1493.25 umol / L DMAc 1206.53 umol / L

[0119] Note: The above yield data are all the averages after three parallel experiments.

[0120] Explanation: The above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention; therefore, although this specification has described the present invention in detail with reference to the above respective embodiments, those of ordinary skill in the art should understand that the present invention can still be modified or equivalently replaced; and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention shall be covered within the scope of the claims of the present invention.

Claims

1. A polyimide catalytic material for photocatalytic synthesis of hydrogen peroxide, characterized in that, The polyimide catalytic material is prepared by thermal imidization of an aromatic triamine monomer and an aromatic dianhydride monomer; the aromatic triamine monomer is selected from any one or more of the following: 5''-(4'-amino-[1,1'-biphenyl]-4-yl)-[1,1':4',1'':3'',1''':4''',1'''-pentabiphenyl]-4,4''-diamine, 1,3,5-triaminobenzene, 1,3,5-tris(4-aminophenyl)benzene; the aromatic dianhydride monomer is 3,3',4,4'-biphenyltetracarboxylic dianhydride.

2. The preparation method of a polyimide catalytic material for photocatalytic synthesis of hydrogen peroxide according to claim 1, characterized in that, It includes the following process: (1) Dissolve the aromatic triamine monomer in solvent A to prepare an aromatic triamine monomer solution; dissolve the aromatic dianhydride monomer in solvent B to prepare an aromatic dianhydride monomer solution; mix the two solutions, then add isoquinoline, mix well and react to obtain a reaction solution; (2) Pour the obtained reaction solution into a mold, first gel at 0-5 °C for a period of time, then continue heat treatment at 150-200 °C for a period of time to obtain a preliminary product; soak the preliminary product in an N-methylpyrrolidone-ethanol solution in a gradient manner, then wash and dry.

3. The method according to claim 2, characterized in that In step (1), solvents A and B are each independently selected from any one or more of the following: mesitylene, DMF, NMP, DMAc.

4. The method according to claim 2, wherein In step (1), solvent A is mesitylene and solvent B is NMP.

5. The method according to claim 2, wherein In step (1), the concentration of the aromatic triamine monomer solution is 0.1-0.5 mmol / mL.

6. The method according to claim 2, characterized in that In step (1), the concentration of the aromatic dianhydride monomer solution is 0.1-1.0 mmol / mL; 0.45 mmol / mL.

7. The method according to claim 2, characterized in that, In step (1), the molar ratio of the aromatic triamine monomer to the aromatic dianhydride monomer is 1:(1-2).

8. The method according to claim 2, wherein In step (1), the dosage of isoquinoline relative to the aromatic triamine monomer is 0.02-0.05 ml / mmol.

9. The method according to any one of claims 2-8, characterized in that, In step (2), pour the obtained reaction solution into a mold, first gel at 0 °C for 60 min, then further perform solvent heat treatment at 180 °C for 48 h.

10. Use of the polyimide catalytic material according to claim 1 in the photocatalytic synthesis of hydrogen peroxide.

11. The application according to claim 10, wherein In the process of photocatalytic synthesis of hydrogen peroxide, the photocatalyst photocatalytically synthesizes hydrogen peroxide in a pure water-oxygen or pure water-air or sacrificial reagent-oxygen or sacrificial reagent-air environment; the sacrificial reagent is a C1-4 alkyl alcohol.

12. A method for photocatalytic synthesis of hydrogen peroxide, characterized in that, Using water and oxygen as raw materials, and using the polyimide catalytic material according to claim 1 as a photocatalyst, photocatalytically synthesize hydrogen peroxide under light irradiation.

13. The method according to claim 12, characterized in that, The dosage of the polyimide catalytic material relative to water is 1 mg / mL.

14. The method according to claim 12, wherein The light source is full-spectrum light, simulated sunlight, visible light, single-wavelength light source, or natural light.

15. The method according to any one of claims 12 - 14, characterized in that, The power of the light is 200 - 300 mM / cm 2 .

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