Electron acceptor, preparation method thereof, benzothiadiazole quinoxaline covalent organic framework material and application of benzothiadiazole quinoxaline covalent organic framework material

Abstract

The invention relates to the technical field of covalent organic framework materials, in particular to an electron acceptor, a preparation method thereof, a benzothiadiazole quinoxaline covalent organic framework material and application. The invention provides an electron acceptor, then the electron acceptor and an electron donor are subjected to a Schiff base reaction to prepare the benzothiadiazole quinoxaline covalent organic framework material, the electron donor is selected from pyrene tetramine or 1, 3, 5-tri (4-aminophenyl) benzene, and then the benzothiadiazole quinoxaline covalent organic framework material is applied as a photocatalytic material. Quinoxaline benzothiadiazole is used as an electron acceptor, donor-acceptor arrangement is adjusted, and a donor-acceptor structure is formed after arrangement, so that the charge transfer process is enhanced, constraint is relieved, the photocatalytic efficiency is improved, and a molecular structure basis is provided for the structure-performance relationship of the covalent organic framework material; a high-performance photocatalyst is designed and developed, and the defect of low catalytic efficiency of a covalent organic framework material in the prior art is overcome.

Description

Technical Field

[0001] The invention belongs to the technical field of covalent organic framework materials, in particular to an electron acceptor and a preparation method thereof, and a benzothiadiazolequinoxaline covalent organic framework material and application thereof. Background Art

[0002] Covalent organic frameworks (COFs) have attracted extensive research attention due to their advantages of light weight, strong crystal structure, high specific surface area, easy recycling and tunable band gap. COFs have been widely used in the field of photocatalysis, including hydrogen evolution, carbon dioxide reduction, pollutant degradation and organic transformation reactions, due to their tunable optoelectronic properties and permanent porosity.

[0003] In order to significantly improve the photocatalytic activity of covalent organic framework materials, optimizing light absorption, carrier generation and transport processes is a key factor in improving the efficiency of the catalytic system. However, since the existing electron acceptors are limited by their electron-withdrawing ability, it is not conducive to the dissociation and transport of excitons. The photoexcited electron-hole pairs are strongly bound, which prevents them from dissociating into free charge carriers, greatly limiting the catalytic effect of the synthesized covalent organic framework materials as catalysts. Summary of the invention

[0004] In view of the deficiencies of the above-mentioned prior art, the purpose of the present invention is to provide an electron acceptor and a preparation method thereof, and a benzothiadiazole quinoxaline covalent organic framework material and application. The present invention first provides an electron acceptor to strengthen the intramolecular charge transfer process, and then uses the electron acceptor and the electron donor to carry out Schiff base reaction to obtain the benzothiadiazole quinoxaline covalent organic framework material, the electron donor is selected from the tetramine of pyrene or 1,3,5-tri(4-aminophenyl)benzene, and then the benzothiadiazole quinoxaline covalent organic framework material is used as a photocatalytic material. The present invention uses quinoxaline benzothiadiazole as an electron acceptor, and adjusts the arrangement of the donor-acceptor to form a donor-acceptor structure after the arrangement, thereby enhancing the charge transfer process, slowing down the binding, and improving the photocatalytic efficiency, providing a molecular structure basis for the structure-performance relationship of the covalent organic framework material, designing and developing a high-performance photocatalyst, and overcoming the defect of low catalytic efficiency in the covalent organic framework material of the prior art.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The first object of the present invention is to protect an electron acceptor having the structural formula: The electron acceptor is quinoxalinebenzothiadiazole.

[0007] The second object of the present invention is a method for preparing a protected electron acceptor, comprising the following steps:

[0008] S1, using p-bromobenzaldehyde, 2,2-dimethyl-1,3-propanediol and p-toluenesulfonic acid monohydrate as catalyst as raw materials, in an inert atmosphere, undergoing acetalization reaction to obtain

[0009] S2, Bis(2-pinacol) borate and catalyst 1,1-bis(diphenylphosphino)ferrocenepalladium dichloride were used as raw materials and subjected to Miyaura borate esterification reaction under an inert atmosphere to obtain

[0010]

[0011] S3, 4,9-Dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, catalyst tris(dibenzylideneacetone)dipalladium, tri-tert-butylphosphine tetrafluoroborate and pH regulator potassium phosphate were used as raw materials, and Suzuki-Miyaura coupling reaction was carried out under inert atmosphere to obtain After the design of steps S1 to S3, quinoxaline benzothiadiazole is introduced as an electron acceptor.

[0012] Preferably, the acetalization reaction conditions are: stirring at 110° C. to 150° C. for 12 h to 18 h.

[0013] Preferably, the molar ratio of p-bromobenzaldehyde to 2,2-dimethyl-1,3-propanediol is 1:1 to 1.2.

[0014] Preferably, the conditions for the Miyaura boronate esterification reaction are: stirring at 80° C. to 120° C. for 24 h to 32 h.

[0015] Preferably, The molar ratio of the bis-pinacol borate is 1:1 to 1.2.

[0016] Preferably, the conditions for the Suzuki-Miyaura coupling reaction are: stirring at 80° C. to 120° C. for 24 h to 26 h.

[0017] Preferably, The molar ratio of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline is 2 to 2.2:1.

[0018] The third purpose of the present invention is to protect the benzothiadiazole quinoxaline covalent organic framework material, which is prepared from an electron acceptor.

[0019] Preferably, the benzothiadiazole quinoxaline covalent organic framework material is prepared by a Schiff base reaction of an electron acceptor and an electron donor to achieve condensation of the electron acceptor and the electron donor, wherein the electron donor is

[0020]

[0021] Preferably, the benzothiadiazole quinoxaline covalent organic framework material is prepared according to the following steps: using an electron acceptor, an electron donor and a mixture of trifluoroacetic acid and acetic acid as a catalyst as raw materials, after mixing, flash freezing in a liquid nitrogen bath at 77K, degassing, sealing, and then heating at 120°C to 150°C for 72h to 76h to obtain the benzothiadiazole quinoxaline covalent organic framework material.

[0022] Preferably, and The molar ratio is 3:2 to 2.6. Preferably, and The molar ratio is 2 to 2.6:1. Preferably, the structural formula of the benzothiadiazole quinoxaline covalent organic framework material is:

[0023]

[0024] or

[0025]

[0026] The fourth objective of the present invention is to protect the application of benzothiadiazolequinoxaline covalent organic framework materials in the preparation of photocatalytic materials.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. The present invention first proposes a new electron acceptor-quinoxaline benzothiadiazole, which has strong electron-withdrawing property. Then, the electron acceptor is used to react with different electron donors to undergo Schiff base reaction to prepare two benzothiadiazole-quinoxaline covalent organic framework materials. The present invention introduces the strongly electron-withdrawing quinoxaline benzothiadiazole as an acceptor unit and adopts pyrene tetramine or 1,3,5-tri(4-aminophenyl)benzene as a donor unit. After the two undergo Schiff base reaction, a covalent organic framework material with a strong electron donor-acceptor structure is formed in the molecule, which overcomes the strong binding of electron-hole pairs, has a stable two-dimensional layered structure, expands the light absorption range, promotes light collection, accelerates the photogenerated charge transfer within the molecule, and enhances the photocatalytic activity. The covalent organic framework material can be widely used in medicines and pesticides.

[0029] In addition, the benzothiadiazole-quinoxaline covalent organic framework material prepared by the electron acceptor of the present invention has high crystallinity, high thermal stability, a structure rich in quinoxaline benzothiadiazole, and has high planarity, which is conducive to strong pi-pi stacking between molecules and exhibits high porosity.

[0030] The present invention first uses p-bromobenzaldehyde, 2,2-dimethyl-1,3-propanediol and p-toluenesulfonic acid monohydrate as raw materials to prepare To protect the aldehyde group; then The Miyaura borate esterification reaction was carried out with bipinacol borate under the catalysis to prepare Then The electron acceptor is prepared by Suzuki-Miyaura coupling reaction with 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline under catalysis, and benzothiadiazole and isoquinoline groups are introduced into the electron acceptor. Finally, the electron acceptor is reacted with Two benzothiadiazolequinoxaline COFs materials were obtained by Schiff base reaction under the catalysis of trifluoroacetic acid and acetic acid. Pyrene tetramine and 1,3,5-tri(4-aminophenyl)benzene were excellent electron donor units. The acceptor unit and the donor unit were condensed and connected to form a quadrilateral ring or hexagonal covalent organic framework material. The synthesis route is simple, the cost is low, the reaction conditions are mild, and large-scale preparation can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 These are infrared spectra of the benzothiadiazolequinoxaline covalent organic framework materials of Examples 1 and 2, wherein (a) is the sample of Example 2, and (b) is the sample of Example 1.

[0032] Figure 2 The solid-state carbon nuclear magnetic resonance spectra of the benzothiadiazole quinoxaline covalent organic framework materials of Example 1 and Example 2, wherein (a) is the sample of Example 1, and (b) is the sample of Example 2.

[0033] Figure 3 1 and 2 are XRD diagrams of the benzothiadiazolequinoxaline covalent organic framework materials of Examples 1 and 2, wherein (a) is the sample of Example 1 and (b) is the sample of Example 2.

[0034] Figure 4 The diagrams are structural diagrams of the benzothiadiazolequinoxaline covalent organic framework materials of Examples 1 and 2, wherein (a) is the sample of Example 1 and (b) is the sample of Example 2.

[0035] Figure 5 The nitrogen adsorption-desorption diagrams of the benzothiadiazolequinoxaline covalent organic framework materials of Example 1 and Example 2 are shown, wherein (a) is the sample of Example 1, and (b) is the sample of Example 2; the small figures are all pore size distribution diagrams.

[0036] Figure 6The thermogravimetric analysis diagrams of the benzothiadiazolequinoxaline covalent organic framework materials of Examples 1 and 2, wherein (a) is the sample of Example 1, and (b) is the sample of Example 2.

[0037] Figure 7 The ultraviolet spectra of the benzothiadiazolequinoxaline covalent organic framework materials of Examples 1 and 2 are shown. DETAILED DESCRIPTION

[0038] The specific embodiments of the present invention are described in detail below, but it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work belong to the protection scope of the present invention. The experimental methods described in the embodiments of the present invention are conventional methods unless otherwise specified.

[0039] Example 1

[0040] The preparation method of the electron acceptor comprises the following steps:

[0041] S1. Add 1.0 g of p-bromobenzaldehyde, 675.46 mg of 2,2-dimethyl-1,3-propanediol, 30.84 mg of p-toluenesulfonic acid monohydrate and 10 mL of toluene into a 100 mL pressure tube, then degas with nitrogen three times, stir at 113 ° C for 12 hours, and cool naturally to room temperature; extract with saturated sodium chloride solution and ethyl acetate three times, collect the organic phase, dry the organic phase over anhydrous sodium sulfate, and remove the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder. The reaction equation is:

[0042]

[0043] S2. Add 400 mg of 450 mg of bis-pinacol borate, 54 mg of 1,1-bis(diphenylphosphino)ferrocene palladium dichloride and 10 mL of dioxane, then degassed with nitrogen three times, stirred at 80°C for 24 hours, and cooled naturally to room temperature; extracted with saturated sodium chloride solution and ethyl acetate three times, and collected the organic phase, dried the organic phase over anhydrous sodium sulfate, and removed the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder. The reaction equation is:

[0044]

[0045] S3. Add 374.3 mg of 200 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylideneacetone)dipalladium(0), 10.8 mg of tri-tert-butylphosphine tetrafluoroborate and 10 mL of tetrahydrofuran, 425 mg of potassium phosphate was dissolved in 1 mL of water and added to a pressure tube, then degassed with nitrogen three times, stirred at 80°C for 24 hours, and naturally cooled to room temperature; extracted with water, filtered and dried to obtain a yellow powder as a crude product. The crude product was purified by silica gel chromatography, and the eluent of the silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1 to obtain 260 mg of yellow powder 4,9-bis(4-(5,5-dimethyl-1,3-dioxaalkane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline with a yield of 81.4%. The reaction equation is:

[0046]

[0047] The preparation method of benzothiadiazole quinoxaline covalent organic framework material comprises the following steps:

[0048] To a 10 mL glass tube, 25.17 mg of 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline, 10 mg of 1,3,5-tri(4-aminophenyl)benzene and 600 μL of solvent were added. The solvent consisted of o-dichlorobenzene and n-butanol in a volume ratio of 1:1. After ultrasonic treatment for 1 min, a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid was added. The mixed aqueous solution was stirred for 1 min. The volume is 0.12 mL. After ultrasonication for 20 seconds, the glass tube is flash-frozen at 77 K in a liquid nitrogen bath, degassed by three freeze-pump thawing cycles, vacuum-sealed, and then heated at 120 ° C for 72 hours. After cooling to room temperature, a black precipitate is obtained. The black precipitate is collected by suction filtration and thoroughly washed with anhydrous ethanol, tetrahydrofuran and dichloromethane, respectively. The collected sample is then dried at 120 ° C under vacuum for 24 hours to obtain 22.1 mg of black powder, which is a benzothiadiazole quinoxaline covalent organic framework material, denoted as COF-1. The reaction equation is:

[0049]

[0050]

[0051] Example 2

[0052] The preparation method of the electron acceptor comprises the following steps:

[0053] S1. Add 1.0 g of p-bromobenzaldehyde, 675.46 mg of 2,2-dimethyl-1,3-propanediol, 30.84 mg of p-toluenesulfonic acid monohydrate and 10 mL of toluene into a 100 mL pressure tube, then degas with nitrogen three times, stir at 113 ° C for 12 hours, and cool naturally to room temperature; extract with saturated sodium chloride solution and ethyl acetate three times, collect the organic phase, dry the organic phase over anhydrous sodium sulfate, and remove the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder.

[0054] S2. Add 400 mg of 450 mg of bis-pinacol borate, 54 mg of 1,1-bis(diphenylphosphino)ferrocene palladium dichloride and 10 mL of dioxane, then degassed with nitrogen three times, stirred at 80°C for 24 hours, and cooled naturally to room temperature; extracted with saturated sodium chloride solution and ethyl acetate three times, and collected the organic phase, dried the organic phase over anhydrous sodium sulfate, and removed the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder.

[0055]

[0056] S3. Add 374.3 mg of 200 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylideneacetone)dipalladium(0), 10.8 mg of tri-tert-butylphosphine tetrafluoroborate and 10 mL of tetrahydrofuran, 425 mg of potassium phosphate was dissolved in 1 mL of water and added to a pressure tube, then degassed with nitrogen three times, stirred at 80°C for 24 hours, and naturally cooled to room temperature; extracted with water, filtered and dried to obtain a yellow powder as a crude product. The crude product was purified by silica gel chromatography, and the eluent of the silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1 to obtain 260 mg of yellow powder 4,9-bis(4-(5,5-dimethyl-1,3-dioxaalkane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline with a yield of 81.4%.

[0057] The preparation method of benzothiadiazole quinoxaline covalent organic framework material comprises the following steps:

[0058] 21.06 mg of 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline, 10 mg of pyrene tetramine and 600 μL of solvent were added to a 10 mL glass tube. The solvent consisted of o-dichlorobenzene and n-butanol in a volume ratio of 1:1. After ultrasonic treatment for 1 min, a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid was added. The volume of the mixed aqueous solution was 0.1 2mL, after ultrasonication for 20s, flash-freeze the glass tube at 77K in a liquid nitrogen bath, degas with three freeze-pump-thaw cycles, vacuum seal, and then heat at 120°C for 3 days. After cooling to room temperature, a black precipitate is obtained. The black precipitate is collected by suction filtration and thoroughly washed with anhydrous ethanol, tetrahydrofuran and dichloromethane, respectively. The collected sample is then dried at 120°C under vacuum for 24h to obtain 22.1mg of black powder, which is a benzothiadiazole quinoxaline covalent organic framework material, denoted as COF-2. The reaction equation is:

[0059]

[0060] Example 3

[0061] The preparation method of the electron acceptor comprises the following steps:

[0062] S1. Add 1.0 g of p-bromobenzaldehyde, 562.91 mg of 2,2-dimethyl-1,3-propanediol, 30.84 mg of p-toluenesulfonic acid monohydrate and 10 mL of toluene into a 100 mL pressure tube, then degas with nitrogen three times, stir at 150 ° C for 12 hours, and cool naturally to room temperature; extract with saturated sodium chloride solution and ethyl acetate three times, collect the organic phase, dry the organic phase over anhydrous sodium sulfate, and remove the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder.

[0063] S2. Add 400 mg of 470 mg of bis-pinacol borate, 54 mg of 1,1-bis(diphenylphosphino)ferrocene palladium dichloride and 10 mL of dioxane, then degassed with nitrogen three times, stirred at 100°C for 32 hours, and cooled naturally to room temperature; extracted with saturated sodium chloride solution and ethyl acetate three times, and collected the organic phase, dried the organic phase over anhydrous sodium sulfate, and removed the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder.

[0065] S3. Add 374.3 mg of 350.54 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylideneacetone)dipalladium(0), 10.8 mg of tri-tert-butylphosphine tetrafluoroborate and 10 mL of tetrahydrofuran, 425 mg of potassium phosphate was dissolved in 1 mL of water and added to a pressure tube, then degassed with nitrogen three times, stirred at 100°C for 25 hours, and naturally cooled to room temperature; extracted with water, filtered and dried to obtain a yellow powder as a crude product. The crude product was purified by silica gel chromatography, and the eluent of the silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1 to obtain 260 mg of yellow powder 4,9-bis(4-(5,5-dimethyl-1,3-dioxaalkane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline.

[0066] The preparation method of benzothiadiazole quinoxaline covalent organic framework material comprises the following steps:

[0067] 25.17 mg of 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline, 13.53 mg of 1,3,5-tri(4-aminophenyl)benzene and 600 μL of solvent were added to a 10 mL glass tube. The solvent consisted of o-dichlorobenzene and n-butanol in a volume ratio of 1:1. After ultrasonic treatment for 1 min, a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid was added. liquid, the volume of the mixed aqueous solution was 0.12 mL, and after ultrasonication for 20 seconds, the glass tube was flash frozen in a liquid nitrogen bath at 77 K, degassed with three freeze pump-thaw cycles, vacuum sealed, and then heated at 140 ° C for 76 hours. After cooling to room temperature, a black precipitate was obtained, and the black precipitate was collected by suction filtration and thoroughly washed with anhydrous ethanol, tetrahydrofuran and dichloromethane, respectively. The collected sample was then dried at 120 ° C under vacuum for 24 hours to obtain 22.1 mg of black powder, which is a benzothiadiazolequinoxaline covalent organic framework material.

[0068] Example 4

[0069] The preparation method of benzothiadiazole quinoxaline covalent organic framework material comprises the following steps:

[0070] S1. Add 1.0 g of p-bromobenzaldehyde, 675.46 mg of 2,2-dimethyl-1,3-propanediol, 30.84 mg of p-toluenesulfonic acid monohydrate and 10 mL of toluene into a 100 mL pressure tube, then degas with nitrogen three times, stir at 110 ° C for 18 hours, and cool naturally to room temperature; extract with saturated sodium chloride solution and ethyl acetate three times, collect the organic phase, dry the organic phase over anhydrous sodium sulfate, and remove the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder.

[0071] S2. Add 400 mg of 450 mg of bis-pinacol borate, 54 mg of 1,1-bis(diphenylphosphino)ferrocene palladium dichloride and 10 mL of dioxane, then degassed with nitrogen three times, stirred at 120°C for 28 hours, and cooled naturally to room temperature; extracted with saturated sodium chloride solution and ethyl acetate three times, and collected the organic phase, dried the organic phase over anhydrous sodium sulfate, and removed the solvent in vacuo to obtain a crude product. The crude product was purified by silica gel chromatography, and the eluent of silica gel chromatography consisted of dichloromethane and petroleum ether in a volume ratio of 2:1 to obtain a white powder.

[0073] S3. Add 374.3 mg of 200 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylideneacetone)dipalladium(0), 10.8 mg of tri-tert-butylphosphine tetrafluoroborate and 10 mL of tetrahydrofuran, 425 mg of potassium phosphate was dissolved in 1 mL of water and added to a pressure tube, then degassed with nitrogen three times, stirred at 120°C for 26 hours, and naturally cooled to room temperature; extracted with water, filtered and dried to obtain a yellow powder as a crude product. The crude product was purified by silica gel chromatography, and the eluent of the silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1 to obtain 260 mg of yellow powder 4,9-bis(4-(5,5-dimethyl-1,3-dioxaalkane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline.

[0074] The preparation method of benzothiadiazole quinoxaline covalent organic framework material comprises the following steps:

[0075] 27.37 mg of 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline, 10 mg of pyrene tetramine and 600 μL of solvent were added to a 10 mL glass tube. The solvent consisted of o-dichlorobenzene and n-butanol in a volume ratio of 1:1. After ultrasonic treatment for 1 min, a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid was added. The mixed aqueous solution was stirred for 1 min. The volume was 0.12 mL. After ultrasonication for 20 s, the glass tube was flash frozen in a liquid nitrogen bath at 77 K, degassed with three freeze pump-thaw cycles, vacuum sealed, and then heated at 150 ° C for 75 h. After cooling to room temperature, a black precipitate was obtained. The black precipitate was collected by suction filtration and thoroughly washed with anhydrous ethanol, tetrahydrofuran and dichloromethane, respectively. The collected sample was then dried at 120 ° C under vacuum for 24 h to obtain 22.1 mg of black powder, which is a benzothiadiazolequinoxaline covalent organic framework material.

[0076] Examples 1 to 4 of the present invention all produce benzothiadiazole quinoxaline covalent organic framework materials with excellent photocatalytic performance. The benzothiadiazole quinoxaline covalent organic framework materials produced in Examples 1 and 2 are used as examples for research. The specific research methods and results are as follows:

[0077] Figure 1 The Fourier transform infrared spectroscopy test showed that after the Schiff base reaction, the NH stretching band of 1,3,5-tri(4-aminophenyl)benzene monomer was 3350cm -1 and 3424cm -1 , pyrene tetraamine monomer NH stretching band 3417cm -1 and 3346cm -1 , CH stretching band of the acceptor unit is 2800cm -1 -3000cm -1 、Receptor unit 115cm -1 The CO stretching bands of COF-1 disappeared. Two new C=N stretching bonds were observed, with displacements of 1693 cm -1 , 1699cm in COF-2 -1 , indicating that the imine-linked benzothiadiazolequinoxaline covalent organic framework material has been successfully formed.

[0078] Figure 2 The solid-state NMR spectrum of Figure 2The chemical shifts at δ158ppm in COF-1 and δ161ppm in COF-2 are attributed to the imine carbon, respectively. The peaks at δ152ppm and δ148ppm in COF-1 and δ152ppm and δ148ppm in COF-2 are attributed to the benzothiadiazole and quinoxaline units, respectively. The broad peaks at δ110.01-δ140.23 of the two benzothiadiazole-quinoxaline covalent organic framework materials belong to the carbon of the benzene ring.

[0079] Figure 3 The results show that the synthesized benzothiadiazole quinoxaline covalent organic framework materials exhibit extremely high crystallinity, which means that their crystal structure is very orderly and has good crystalline properties, thus having better stability and catalytic activity. Figure 4 This is the simulated structure diagram of the benzothiadiazole quinoxaline covalent organic framework material. Figure 4 Further verified Figure 3 .

[0080] Figure 5 The results show that the synthesized benzothiadiazolequinoxaline covalent organic framework material has a high specific surface area and porosity.

[0081] Figure 6 The results show that the synthesized benzothiadiazolequinoxaline covalent organic framework material has good thermal stability.

[0082] Figure 7 The results show that the synthesized benzothiadiazolequinoxaline covalent organic framework material has a wide light absorption range and provides a better catalytic environment.

[0083] The following is a photocatalytic reaction of anisole thioether to produce sulfoxide using COF-1 of Example 1 and COF-2 of Example 2. The operation is as follows: 0.3 mmol anisole thioether, 10 mg benzothiadiazole quinoxaline covalent organic framework material and 3 mL solvent ethanol are placed in a quartz tube and mixed, wherein the benzothiadiazole quinoxaline covalent organic framework material is selected from COF-1 or COF-2, and then a light power density of 1800 W / m is used in an oxygen atmosphere. 2 The photocatalytic experiment was carried out under irradiation of a 910W blue LED light, and the wavelength of the LED emission was 460nm. The reaction process was monitored by thin layer chromatography and nuclear magnetic resonance hydrogen spectrum, and the yield of sulfoxide produced by photocatalytic anisyl thioether is shown in Table 1.

[0084] Table 1 Photocatalytic sulfoxide production rate of anisole

[0085]

[0086] The results in Table 1 show that both COF-1 and COF-2 can achieve photocatalysis of sulfides, and compared with COF-2, COF-1 has better photocatalytic performance in selectively catalyzing sulfides.

[0087] Those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. An electron acceptor, characterized in that The structural formula of the electron acceptor is:

2. A method for preparing the electron acceptor according to claim 1, characterized in that: The steps include: Using p-bromobenzaldehyde, 2,2-dimethyl-1,3-propanediol and p-toluenesulfonic acid monohydrate as the catalyst as the raw materials, an acetal reaction was carried out under an inert atmosphere to obtain by Bis(2-pinacol) borate and catalyst 1,1-bis(diphenylphosphino)ferrocenepalladium dichloride were used as raw materials and subjected to Miyaura borate esterification reaction under an inert atmosphere to obtain by 4,9-Dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, catalyst tris(dibenzylideneacetone)dipalladium, tri-tert-butylphosphine tetrafluoroborate and pH regulator potassium phosphate were used as raw materials, and Suzuki-Miyaura coupling reaction was carried out under inert atmosphere to obtain 3. The method for preparing an electron acceptor according to claim 2, characterized in that: The conditions of the Suzuki-Miyaura coupling reaction are: stirring at 80°C to 120°C for 24h to 26h.

4. The method for preparing an electron acceptor according to claim 2, characterized in that: The molar ratio of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline is 2 to 2.2:

1.

5. Benzothiadiazolequinoxaline covalent organic framework material, characterized in that: The electron acceptor and the electron donor described in claim 1 are prepared by Schiff base reaction.

6. The benzothiadiazolequinoxaline covalent organic framework material according to claim 5, characterized in that: The electron donor is selected from 7. The benzothiadiazolequinoxaline covalent organic framework material according to claim 6, characterized in that: The benzothiadiazole-quinoxaline covalent organic framework material was prepared according to the following steps: The electron acceptor, electron donor and catalyst trifluoroacetic acid and acetic acid mixed solution are used as raw materials, after mixing, they are flash frozen at 77K in a liquid nitrogen bath, degassed and sealed, and then heated at 120°C to 150°C for 72h to 76h to obtain a benzothiadiazole quinoxaline covalent organic framework material.

8. The benzothiadiazolequinoxaline covalent organic framework material according to claim 7, characterized in that: and The molar ratio is 3:2~2.6, and The molar ratio is 2 to 2.6:

1.

9. The benzothiadiazolequinoxaline covalent organic framework material according to claim 5, characterized in that: The structural formula of the benzothiadiazole quinoxaline covalent organic framework material is: or 10. Use of the benzothiadiazolequinoxaline covalent organic framework material according to claim 5 in the preparation of photocatalytic materials.

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