Electron acceptors, methods of making the same, and benzothiadiazole quinoline covalent organic framework materials and applications

Abstract

The application belongs to the technical field of covalent organic framework materials, and particularly relates to an electron acceptor, a preparation method thereof, and a benzothiadiazole quinoxaline covalent organic framework material and application. The application first provides an electron acceptor, then adopts the electron acceptor and an electron donor to perform Schiff base reaction to prepare a benzothiadiazole quinoxaline covalent organic framework material, the electron donor is selected from tetramine of pyrene or 1, 3, 5-tri (4-aminophenyl) benzene, and the benzothiadiazole quinoxaline covalent organic framework material is applied as a photocatalytic material. The application takes quinoxaline benzothiadiazole as an electron acceptor, adjusts donor-acceptor arrangement, and arranges a donor-acceptor structure, so as to enhance a charge transfer process, slow down binding, improve photocatalytic efficiency, provide a molecular structure basis for a structure-performance relationship of covalent organic framework materials, design and develop a high-performance photocatalyst, and overcome the defects of low catalytic efficiency of the existing covalent organic framework materials.

Description

Technical Field

[0001] This invention belongs to the field of covalent organic framework materials technology, specifically electron acceptors and their preparation methods, and benzothiadiazole quinoxaline covalent organic framework materials and their applications. Background Technology

[0002] Covalent organic frameworks (COFs) have attracted widespread research attention due to their advantages such as lightweight, strong crystal structure, high specific surface area, easy recyclability, and tunable band gap. With their tunable photoelectric properties and permanent porosity, COFs have been widely applied in photocatalysis, including hydrogen evolution, carbon dioxide reduction, pollutant degradation, and organic conversion reactions.

[0003] To significantly improve the photocatalytic activity of covalent organic framework materials, optimizing the light absorption, carrier generation, and transport processes is crucial for enhancing the efficiency of the catalytic system. However, the limited electron-withdrawing ability of existing electron acceptors hinders exciton dissociation and transport, resulting in strongly bound photoexcited electron-hole pairs that impede their dissociation into free charge carriers. This severely limits the catalytic performance of synthesized covalent organic framework materials as catalysts. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide an electron acceptor, its preparation method, and a benzothiadiazole quinoxaline covalent organic framework material and its applications. The invention first provides an electron acceptor to enhance intramolecular charge transfer. Then, a Schiff base reaction is performed between the electron acceptor and an electron donor to prepare the benzothiadiazole quinoxaline covalent organic framework material. The electron donor is selected from pyrene tetraamine or 1,3,5-tris(4-aminophenyl)benzene. The benzothiadiazole quinoxaline covalent organic framework material is then used as a photocatalytic material. This invention uses quinoxaline benzothiadiazole as the electron acceptor. By adjusting the donor-acceptor arrangement to form a donor-acceptor structure, the charge transfer process is enhanced, the binding is reduced, and the photocatalytic efficiency is improved. This provides a molecular structural basis for the structure-property relationship of covalent organic framework materials, and a high-performance photocatalyst is designed and developed, overcoming the low catalytic efficiency of existing covalent organic framework materials.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] The first objective of this invention is to protect an electron acceptor, the structural formula of which is: The electron acceptor is quinoxaline benzothiadiazole.

[0007] The second objective of this invention is to protect a method for preparing an electron acceptor, comprising the following steps:

[0008] S1. Using p-bromobenzaldehyde, 2,2-dimethyl-1,3-propanediol, and the catalyst p-toluenesulfonic acid monohydrate as raw materials, an acetal reaction is carried out under an inert atmosphere to obtain...

[0009] S2, with Using bis(pinacol)boronic acid ester and catalyst 1,1-bis(diphenylphosphine)ferrocene palladium dichloride as raw materials, a Miyaura boronic acid esterification reaction was carried out under an inert atmosphere to obtain...

[0010]

[0011] S3, with Using 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, tris(dibenzylindeneacetone)dipalladium as catalyst, tritert-butylphosphine tetrafluoroborate, and potassium phosphate as pH adjuster as raw materials, a Suzuki-Miyaura coupling reaction was carried out under an inert atmosphere to obtain... Following steps S1 to S3, quinoxaline benzothiadiazole is introduced as an electron acceptor.

[0012] Preferably, the conditions for the acetal reaction are: stirring at 110℃~150℃ for 12h~18h.

[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 borate esterification reaction are: stirring at 80℃~120℃ for 24h~32h.

[0015] Preferred, The molar ratio with dipinazoboronic acid ester 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 to 26 hours.

[0017] Preferred, 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 objective of this invention is to protect benzothiadiazole quinoxaline covalent organic framework materials, which are obtained by electron acceptor.

[0019] Preferably, the benzothiadiazole quinoxaline covalent organic framework material is prepared by an electron acceptor and an electron donor via a Schiff base reaction, achieving the 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 a mixture of trifluoroacetic acid and acetic acid as raw materials, the mixture is flash-frozen in a liquid nitrogen bath at 77K, degassed, sealed, and then heated at 120℃~150℃ for 72h~76h to obtain the benzothiadiazole quinoxaline covalent organic framework material.

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

[0023]

[0024] or

[0025]

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

[0027] Compared with the prior art, the beneficial effects of the present invention are:

[0028] 1. This invention first proposes a novel electron acceptor—quinoxaline benzothiadiazole. Quinoxaline benzothiadiazole has strong electron-withdrawing properties. Then, by using the electron acceptor and different electron donors to carry out Schiff base reactions, two kinds of benzothiadiazole quinoxaline covalent organic framework materials are prepared. This invention introduces the strongly electron-withdrawing quinoxaline benzothiadiazole as the acceptor unit and uses pyrene tetraamine or 1,3,5-tris(4-aminophenyl)benzene as the donor unit. After the two undergo Schiff base reactions, a covalent organic framework material with a strong electron donor-acceptor structure is formed within the molecule. This overcomes the strong binding of electron-hole pairs, has a stable two-dimensional layered structure, expands the light absorption range, promotes light collection, accelerates intramolecular photogenerated charge transfer, and enhances photocatalytic activity. It can be widely used in pharmaceuticals and pesticides.

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

[0030] This 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 product undergoes a Miyaura boronication reaction with dipinalboronic acid ester under catalysis to prepare... Then The electron acceptor was prepared by a Suzuki-Miyaura coupling reaction with 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline under catalysis, incorporating benzothiadiazole and isoquinoline groups. Finally, the electron acceptor was coupled with... Two benzothiadiazole quinoxaline COFs materials were obtained by Schiff base reaction under the catalysis of trifluoroacetic acid and acetic acid. Pyrene tetraamine and 1,3,5-tris(4-aminophenyl)benzene are excellent electron donor units. The acceptor unit and the donor unit are condensed together to form a tetrahedral or hexagonal covalent organic framework material. The synthetic route is simple, low cost, mild reaction conditions, and can achieve large-area preparation. Attached Figure Description

[0031] Figure 1 The images show the infrared spectra of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2, where (a) is the sample of Example 2 and (b) is the sample of Example 1.

[0032] Figure 2 The images show the solid-state carbon NMR spectra of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2, where (a) is the sample of Example 1 and (b) is the sample of Example 2.

[0033] Figure 3 The images show the XRD patterns of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2, where (a) is the sample of Example 1 and (b) is the sample of Example 2.

[0034] Figure 4 The diagrams show the structural diagrams of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2, where (a) is the sample of Example 1 and (b) is the sample of Example 2.

[0035] Figure 5 The figures below show the nitrogen adsorption-desorption of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2, where (a) is the sample of Example 1 and (b) is the sample of Example 2; the insets are all pore size distribution diagrams.

[0036] Figure 6Thermogravimetric analysis (TGA) diagrams of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2 are shown, where (a) is the sample of Example 1 and (b) is the sample of Example 2.

[0037] Figure 7 The images show the UV spectra of the benzothiadiazole quinoxaline covalent organic framework materials of Examples 1 and 2. Detailed Implementation

[0038] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0039] Example 1

[0040] The method for preparing an electron acceptor includes 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 to a 100 mL pressure tube. Degas the solution three times with nitrogen, then stir at 113 °C for 12 h and allow to cool naturally to room temperature. Extract the solution three times with saturated sodium chloride solution and ethyl acetate, collecting the organic phase. Dry the organic phase on anhydrous sodium sulfate and remove the solvent under vacuum to obtain the crude product. Purify the crude product using silica gel chromatography. The eluent for silica gel chromatography consists of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder. The reaction equation is:

[0042]

[0043] S2. Add 400 mg of [unspecified substance] to a 100 mL pressure tube. 450 mg of bis(pinacol)boronic acid ester, 54 mg of 1,1-bis(diphenylphosphine)ferrocene palladium dichloride, and 10 mL of dioxane were added, followed by degassing three times with nitrogen. The mixture was then stirred at 80 °C for 24 h and allowed to cool naturally to room temperature. The mixture was extracted three times with saturated sodium chloride solution and ethyl acetate, and the organic phase was collected. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography, with the eluent consisting of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder. The reaction equation is:

[0044]

[0045] S3. Add 374.3 mg of [unspecified substance] to a 100 mL pressure tube. 200 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylindeneacetone)dipalladium(O), 10.8 mg of tritert-butylphosphine tetrafluoroborate, and 10 mL of tetrahydrofuran were mixed with 425 mg of potassium phosphate dissolved in 1 mL of water and added to a pressure tube. The mixture was then degassed three times with nitrogen and stirred at 80 °C for 24 h. After natural cooling to room temperature, the mixture was extracted with water, filtered, and dried to obtain a yellow powder, which was the crude product. The crude product was purified by silica gel chromatography. The eluent for silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1, yielding 260 mg of a yellow powder, 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-2-yl)phenyl)-6,7-dimethyl-[1,2,5]thiadiazo[3,4-g]quinoxaline, with a yield of 81.4%. The reaction equation is as follows:

[0046]

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

[0048] Add 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-tris(4-aminophenyl)benzene, and 600 μL of solvent (o-dichlorobenzene and n-butanol in a 1:1 volume ratio) to a 10 mL glass tube. After sonication for 1 min, add a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid. The volume was 0.12 mL. After sonication for 20 s, the glass tube was flash-frozen in a liquid nitrogen bath at 77 K. It was then thawed and degassed using a three-stage refrigeration pump, vacuum-sealed, and heated at 120 °C for 72 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 under vacuum at 120 °C for 24 h to obtain 22.1 mg of black powder, which was identified as a benzothiadiazole quinoxaline covalent organic framework material, denoted as COF-1. The reaction equation is as follows:

[0049]

[0050]

[0051] Example 2

[0052] The method for preparing an electron acceptor includes 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 to a 100 mL pressure tube. Degas the solution three times with nitrogen, then stir at 113 °C for 12 h and allow to cool naturally to room temperature. Extract the solution three times with saturated sodium chloride solution and ethyl acetate, collecting the organic phase. Dry the organic phase on anhydrous sodium sulfate and remove the solvent under vacuum to obtain the crude product. Purify the crude product using silica gel chromatography. The eluent for silica gel chromatography consists of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder.

[0054] S2. Add 400 mg of [unspecified substance] to a 100 mL pressure tube. 450 mg of bis(pinacol)boronic acid ester, 54 mg of 1,1-bis(diphenylphosphine)ferrocene palladium dichloride, and 10 mL of dioxane were added, followed by degassing three times with nitrogen. The mixture was then stirred at 80 °C for 24 h and allowed to cool naturally to room temperature. The mixture was extracted three times with saturated sodium chloride solution and ethyl acetate, and the organic phase was collected. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography, with the eluent consisting of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder.

[0055]

[0056] S3. Add 374.3 mg of [unspecified substance] to a 100 mL pressure tube. 200 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylindeneacetone)dipalladium(O), 10.8 mg of tritert-butylphosphine tetrafluoroborate, and 10 mL of tetrahydrofuran were mixed with 425 mg of potassium phosphate dissolved in 1 mL of water and added to a pressure tube. The mixture was then degassed three times with nitrogen and stirred at 80 °C for 24 h. After natural cooling to room temperature, the mixture was extracted with water, filtered, and dried to obtain a yellow powder, which was the crude product. The crude product was purified by silica gel chromatography. The eluent for silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1, yielding 260 mg of a yellow powder, 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-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 includes the following steps:

[0058] Add 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 (a 1:1 volume ratio of o-dichlorobenzene and n-butanol) to a 10 mL glass tube. After sonication for 1 min, add a 0.6 mol / L aqueous solution of trifluoroacetic acid and 6 mol / L acetic acid, with a total volume of 0.1 μL. 2 mL of the sample was sonicated for 20 seconds, then flash-frozen in a liquid nitrogen bath at 77 K. The sample was degassed using a three-stage cryogenic-thawing cycle, vacuum-sealed, and then heated at 120 °C for 3 days. After cooling to room temperature, a black precipitate was obtained. The precipitate was collected by suction filtration and thoroughly washed with anhydrous ethanol, tetrahydrofuran, and dichloromethane, respectively. The collected sample was then dried under vacuum at 120 °C for 24 h to obtain 22.1 mg of black powder, which is a benzothiadiazole quinoxaline covalent organic framework material, denoted as COF-2. The reaction equation is as follows:

[0059]

[0060] Example 3

[0061] The method for preparing an electron acceptor includes 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 to a 100 mL pressure tube. Degas the solution three times with nitrogen, then stir at 150 °C for 12 h and allow to cool naturally to room temperature. Extract the solution three times with saturated sodium chloride solution and ethyl acetate, collecting the organic phase. Dry the organic phase on anhydrous sodium sulfate and remove the solvent under vacuum to obtain the crude product. Purify the crude product using silica gel chromatography. The eluent for silica gel chromatography consists of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder.

[0063] S2. Add 400 mg of [unspecified substance] to a 100 mL pressure tube. 470 mg of bis(pinacol)boronic acid ester, 54 mg of 1,1-bis(diphenylphosphine)ferrocene palladium dichloride, and 10 mL of dioxane were added, followed by degassing three times with nitrogen. The mixture was then stirred at 100 °C for 32 h and allowed to cool naturally to room temperature. The mixture was extracted three times with saturated sodium chloride solution and ethyl acetate, and the organic phase was collected. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography, with the eluent consisting of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder.

[0064]

[0065] S3. Add 374.3 mg of [unspecified substance] to a 100 mL pressure tube. 350.54 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylindeneacetone)dipalladium(O), 10.8 mg of tritert-butylphosphine tetrafluoroborate, and 10 mL of tetrahydrofuran were added to a pressure tube. 425 mg of potassium phosphate was dissolved in 1 mL of water. The solution was then added to the pressure tube and degassed three times with nitrogen. The mixture was stirred at 100 °C for 25 h and allowed to cool naturally to room temperature. Water was added for extraction, and the mixture was filtered and dried to obtain a yellow powder, which was the crude product. The crude product was purified by silica gel chromatography. The eluent for silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1, yielding 260 mg of a yellow powder, 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-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 includes the following steps:

[0067] Add 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-tris(4-aminophenyl)benzene, and 600 μL of solvent (o-dichlorobenzene and n-butanol in a 1:1 volume ratio) to a 10 mL glass tube. After sonication for 1 min, add a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid. The volume of the mixed aqueous solution was 0.12 mL. After sonication for 20 s, the glass tube was flash-frozen in a liquid nitrogen bath at 77 K. The tube was degassed using a three-stage cryogenic pump-thawing cycle, vacuum-sealed, and then heated at 140 °C for 76 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 under vacuum at 120 °C for 24 h to obtain 22.1 mg of black powder, which was identified as a benzothiadiazole quinoxaline covalent organic framework material.

[0068] Example 4

[0069] The preparation method of benzothiadiazole quinoxaline covalent organic framework material includes 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 to a 100 mL pressure tube. Degas the solution three times with nitrogen, then stir at 110 °C for 18 h and allow to cool naturally to room temperature. Extract the solution three times with saturated sodium chloride solution and ethyl acetate, collecting the organic phase. Dry the organic phase on anhydrous sodium sulfate and remove the solvent under vacuum to obtain the crude product. Purify the crude product using silica gel chromatography. The eluent for silica gel chromatography consists of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder.

[0071] S2. Add 400 mg of [unspecified substance] to a 100 mL pressure tube. 450 mg of bis(pinacol)boronic acid ester, 54 mg of 1,1-bis(diphenylphosphine)ferrocene palladium dichloride, and 10 mL of dioxane were added, followed by degassing three times with nitrogen. The mixture was then stirred at 120 °C for 28 h and allowed to cool naturally to room temperature. The mixture was extracted three times with saturated sodium chloride solution and ethyl acetate, and the organic phase was collected. The organic phase was dried over anhydrous sodium sulfate, and the solvent was removed under vacuum to obtain the crude product. The crude product was purified by silica gel chromatography, with the eluent consisting of dichloromethane and petroleum ether in a 2:1 volume ratio, yielding a white powder.

[0072]

[0073] S3. Add 374.3 mg of [unspecified substance] to a 100 mL pressure tube. 200 mg of 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, 9.8 mg of tris(dibenzylindeneacetone)dipalladium(O), 10.8 mg of tritert-butylphosphine tetrafluoroborate, and 10 mL of tetrahydrofuran were mixed with 425 mg of potassium phosphate dissolved in 1 mL of water and added to a pressure tube. The mixture was then degassed three times with nitrogen and stirred at 120 °C for 26 h. After natural cooling to room temperature, the mixture was extracted with water, filtered, and dried to obtain a yellow powder, which was the crude product. The crude product was purified by silica gel chromatography. The eluent for silica gel chromatography consisted of dichloromethane and ethyl acetate in a volume ratio of 30:1, yielding 260 mg of a yellow powder, 4,9-bis(4-(5,5-dimethyl-1,3-dioxane-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 includes the following steps:

[0075] Add 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 (a 1:1 volume ratio of o-dichlorobenzene and n-butanol) to a 10 mL glass tube. After sonication for 1 min, add a mixed aqueous solution of 0.6 mol / L trifluoroacetic acid and 6 mol / L acetic acid. The volume was 0.12 mL. After sonication for 20 s, the glass tube was flash-frozen in a liquid nitrogen bath at 77 K. The tube was degassed using a three-stage cryogenic pump-thawing cycle, 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 under vacuum at 120 °C for 24 h to obtain 22.1 mg of black powder, which was identified as a benzothiadiazole quinoxaline covalent organic framework material.

[0076] Examples 1-4 of this invention all yielded benzothiadiazole quinoxaline covalent organic framework materials with excellent photocatalytic performance. The following research uses the benzothiadiazole quinoxaline covalent organic framework materials obtained in Examples 1 and 2 as examples. Specific research methods and results are shown below:

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

[0078] Figure 2 The solid-state nuclear magnetic resonance spectrum also verified its structural information. According to Figure 2The chemical shifts at δ158 ppm in COF-1 and δ161 ppm in COF-2 are attributed to imine carbons, respectively. The COF-1 peaks at δ152 ppm and δ148 ppm, and the COF-2 peaks at δ152 ppm and δ148 ppm, are attributed to benzothiadiazole and quinoxaline units, respectively. The broad peaks at δ110.01–δ140.23 in both benzothiadiazole and quinoxaline covalent organic framework materials belong to carbons of the benzene ring.

[0079] Figure 3 The results show that the synthesized benzothiadiazole quinoxaline covalent organic framework materials exhibit extremely high crystallinity. This means that their crystal structure is highly ordered, possessing good crystallinity and thus better stability and catalytic activity. Figure 4 This is a simulated structural diagram of a benzothiadiazole quinoxaline covalent organic framework material. Figure 4 This further confirms Figure 3 .

[0080] Figure 5 The results showed that the synthesized benzothiadiazole quinoxaline covalent organic framework material had a high specific surface area and porosity.

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

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

[0083] The following describes the photocatalytic reaction of anisole to sulfoxide using COF-1 from Example 1 and COF-2 from Example 2. The procedure was as follows: 0.3 mmol of anisole, 10 mg of benzothiadiazole quinoxaline covalent organic framework material, and 3 mL of solvent ethanol were placed together in a quartz tube and mixed. The benzothiadiazole quinoxaline covalent organic framework material was selected from COF-1 or COF-2. Then, under an oxygen atmosphere, the reaction was carried out using light with a power density of 1800 W / m². 2 The photocatalytic experiment was conducted by irradiating the sample with a 910W blue LED lamp, with the LED emission wavelength being 460nm. The reaction process was monitored by thin-layer chromatography and proton nuclear magnetic resonance spectroscopy. The yield results of photocatalytic production of sulfoxide from anisole are shown in Table 1.

[0084] Table 1. Photocatalytic production of sulfoxide from anisole.

[0085]

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

[0087] Those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims and their equivalents, this 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 an electron acceptor according to claim 1, characterized in that, Includes the following steps: Using p-bromobenzaldehyde, 2,2-dimethyl-1,3-propanediol, and the catalyst p-toluenesulfonic acid monohydrate as raw materials, an acetal reaction was carried out under an inert atmosphere to obtain... ； by , Using bis(pinacol)boronic acid ester and catalyst 1,1-bis(diphenylphosphine)ferrocene palladium dichloride as raw materials, a Miyaura boronic acid esterification reaction was carried out under an inert atmosphere to obtain... ； by , Using 4,9-dibromo-6,7-dimethyl-[1,2,5]thiadiazole[3,4-G]quinoxaline, tris(dibenzylindeneacetone)dipalladium as catalyst, tritert-butylphosphine tetrafluoroborate, and potassium phosphate as pH adjuster as raw materials, a Suzuki-Miyaura coupling reaction was carried out under an inert atmosphere to obtain... .

3. The method for preparing an electron acceptor according to claim 2, characterized in that, The conditions for the Suzuki-Miyaura coupling reaction are: stirring at 80℃~120℃ for 24h~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 2~2.2:

1.

5. A benzothiadiazole quinoxaline covalent organic framework material, obtained from the electron acceptor as described in claim 1, characterized in that, The structural formula of the benzothiadiazole quinoxaline covalent organic framework material is as follows: or 。 6. A method for preparing the benzothiadiazole quinoxaline covalent organic framework material according to claim 5, characterized in that, It is prepared by a Schiff base reaction of an electron acceptor and an electron donor, wherein the electron donor is selected from... or 。 7. The method for preparing the benzothiadiazole quinoxaline 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: Using a mixture of trifluoroacetic acid and acetic acid as the raw material, the mixture was flash-frozen in a liquid nitrogen bath at 77 K, degassed, sealed, and then heated at 120℃~150℃ for 72h~76h to obtain a benzothiadiazole quinoxaline covalent organic framework material.

8. The method for preparing the benzothiadiazole quinoxaline covalent organic framework material according to claim 6, characterized in that, and The molar ratio is 3:2~2.

6. and The molar ratio is 2~2.6:

1.

9. The application of the benzothiadiazole quinoxaline covalent organic framework material according to claim 5 in the preparation of photocatalytic materials.

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