A functionalized aldehyde monomer containing sulfur thiophene, DDA covalent organic framework material and its preparation method and application

Abstract

The present invention discloses a functionalized aldehyde monomer containing sulfur thiophene, a D-D-A covalent organic framework material, and its preparation method and application. The functionalized aldehyde monomer containing sulfur thiophene is based on a benzothiadiazole group as an electron acceptor; benzaldehyde is connected to the 4,7-position benzene ring to provide a reaction site for forming COFs, and an electron-rich sulfur thiophene group is connected to the 5,6-position benzene ring, which can effectively change the electronic structure and chemical properties of the COFs skeleton and more efficiently improve the photocatalytic performance. The monomer can be prepared in an organic solvent under alkaline conditions through thiol and halogen atoms, and the preparation process is simple and easy to prepare on a large scale. The covalent organic framework material prepared with the monomer has a D-D-A configuration, which is conducive to the effective separation of photogenerated charges and holes in photocatalysis, transfers more photogenerated charges to the active site, and gives it efficient photocatalytic hydrogen peroxide production performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of covalent organic framework functional materials, and specifically relates to a functionalized aldehyde monomer containing sulfur thiophene, a DDA covalent organic framework material, and a preparation method and application thereof. Background Art

[0002] Against the backdrop of the huge consumption of fossil fuels and increasingly serious environmental pollution, the development and utilization of sustainable energy, such as hydropower and solar energy, has become an urgent and pressing task. Photocatalysis, as a solar-based catalytic technology, can excite electrons and holes on the catalyst surface through irradiation with visible light and / or ultraviolet light, thereby initiating a series of chemical reactions. Hydrogen peroxide can be used as an environmentally friendly green oxidant and as a solar fuel in fuel cells, and has therefore attracted increasing attention. However, the current main industrial method for synthesizing hydrogen peroxide is the anthraquinone method, which has high energy consumption and high cost, and does not meet the requirements of green chemistry.

[0003] Photocatalytic hydrogen peroxide synthesis technology uses semiconductor materials to absorb solar energy and catalyze the reaction of water and oxygen. This synthesis method is environmentally friendly and sustainable, and has significant advantages over the traditional anthraquinone method for synthesizing hydrogen peroxide. Covalent organic frameworks (COFs) are excellent photocatalytic catalysts that can be used as photocatalytic catalysts to catalyze the synthesis of hydrogen peroxide. However, the photocatalysts have the disadvantages of weak oxygen adsorption and activation ability, low light response ability, and limited active sites; poor long-term photocatalytic stability; and the need for additional photosensitizers to assist photocatalysis. Therefore, the application of covalent organic frameworks in the green preparation of hydrogen peroxide through photocatalysis is limited. Summary of the Invention

[0004] Based on the above reasons, the first object of the present invention is to provide a functionalized aldehyde monomer containing sulfur thiophene; having an electron-rich thiophene group and a benzothiadiazole group as an electron acceptor, which is used to construct a covalent organic framework material, so that the framework material has a wider light absorption range and more efficient reaction activity.

[0005] The second object of the present invention is to provide a method for preparing a functionalized aldehyde monomer containing sulfur thiophene.

[0006] The third object of the present invention is to provide a DDA covalent organic framework material, in which the thiophene group serves as an electron-rich group and the pyrene group serves as an electron donor, and the benzothiadiazole group serves as an electron acceptor. The DDA configuration formed improves the photocatalytic reaction activity.

[0007] The fourth object of the present invention is to provide an application of the above-mentioned DDA covalent organic framework material, which is used for photocatalytic production of hydrogen peroxide catalyst, and the photocatalytic process is carried out continuously and efficiently.

[0008] The first object of the present invention can be achieved by adopting the following technical solutions:

[0009] A functionalized aldehyde monomer containing sulfur thiophene has a structure shown in Formula I:

[0010]

[0011] The second object of the present invention can be achieved by adopting the following technical solutions:

[0012] A method for preparing a functionalized aldehyde monomer containing sulfur thiophene, comprising reacting a structural compound represented by formula II with 2-thiophene thiol in the presence of a base to prepare the functionalized aldehyde monomer containing sulfur thiophene;

[0013]

[0014] Furthermore, the molar ratio of the compound represented by Formula II to 2-thiophenethiol is 1:(2-3).

[0015] Furthermore, the amount of the added base is 2-3 times the amount of the compound of the structure represented by Formula II.

[0016] Furthermore, the reaction is carried out in an organic solvent, which is one or a combination of two or more of DMF, DMA, DMSO or dioxane; the molar volume ratio of the structural compound represented by formula II to the solvent is 1 mmol: (10-30) mL.

[0017] Furthermore, the reaction is carried out under an inert gas atmosphere; the reaction temperature is 20-60° C., and the reaction time is 20-120 min.

[0018] Furthermore, the reaction is completed including a purification step: using a silica gel chromatography column and a petroleum ether / ethyl acetate mixture with a volume ratio of 2:1 as an eluent.

[0019] Furthermore, the structural compound represented by formula II is prepared by using 4,7-dibromo-5,6-difluoro-benzothiadiazole and formylphenylboronic acid as raw materials in a Suzuki coupling reaction system.

[0020] Furthermore, the reaction was carried out in an inert gas atmosphere using a Suzuki coupling reaction system of tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system and a mixed solution of 1,4-dioxane and water as a solvent.

[0021] Furthermore, the molar ratio of tetrakis(triphenylphosphine)palladium(0) to potassium carbonate is 1:(30-100).

[0022] Furthermore, the volume ratio of 1,4-dioxane to water is (1-10):1.

[0023] Furthermore, the reaction temperature is 80-100° C., and the reaction time is 12-72 hours.

[0024] Furthermore, the molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to formylphenylboronic acid is 1:(2-3).

[0025] Furthermore, the molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to tetrakis(triphenylphosphine)palladium(0) is (10-40):1.

[0026] Furthermore, the molar volume ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to the solvent is 1 mmol:(10-20) mL.

[0027] The third object of the present invention can be achieved by adopting the following technical solutions:

[0028] A DDA covalent organic framework material is prepared by an ammonia-aldehyde condensation reaction of a functionalized aldehyde monomer containing sulfur-containing thiophene and 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene under solvent thermal conditions.

[0029] The fourth object of the present invention can be achieved by adopting the following technical solutions:

[0030] Application of DDA covalent organic framework materials as photocatalytic hydrogen peroxide production catalysts.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. A functionalized aldehyde monomer containing sulfur thiophene of the present invention has an electron-rich thiophene group and a benzothiadiazole group as an electron acceptor; the benzaldehyde connected to the 4 and 7 benzene rings of benzothiadiazole provides a reaction site for the formation of COFs, and the terphenyl structure is a rigid structure and a large conjugated structure, which can improve the photocatalytic and stability properties of the COFs material; and the introduction of the sulfur thiophene group connected to the 5 and 6 benzene rings can effectively change the electronic structure and chemical properties of the COFs skeleton, and more efficiently improve the photocatalytic performance.

[0033] 2. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene of the present invention is to react thiol with halogen atoms. The reaction can be carried out in an organic solvent under alkaline conditions; therefore, the preparation process is simple and can be easily prepared on a large scale.

[0034] 3. The DDA covalent organic framework material of the present invention has a DDA configuration. The introduction of the thiophene group effectively changes the electronic structure and chemical properties of the COF skeleton, which is beneficial to the effective separation of photogenerated charges and holes in photocatalysis, transfers more photogenerated charges to the active sites, and gives it efficient photocatalytic hydrogen peroxide production performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the H NMR spectrum of the functionalized aldehyde monomer containing sulfur-containing thiophene prepared in the present invention;

[0036] Figure 2 This is the NMR fluorine spectrum of the functionalized aldehyde monomer containing sulfur thiophene prepared in the present invention;

[0037] Figure 3 Solid UV-visible absorption spectra of BSZ-2F-2CHO and BSZ-2S-2CHO;

[0038] Figure 4 This is the tauc plot of BSZ-2F-2CHO;

[0039] Figure 5 This is the tauc plot of BSZ-2S-2CHO;

[0040] Figure 6 This is the solid UV-visible absorption spectrum of the DDA covalent organic framework material BSZ-2S-COF prepared by the present invention;

[0041] Figure 7 This is the tauc plot of the DDA covalent organic framework material BSZ-2S-COF;

[0042] Figure 8 X-ray powder diffraction patterns; a is the synthesized BSZ-2S-COF; b is the simulated AA stacking structure; c is the simulated AB stacking structure;

[0043] Figure 9 Schematic diagram of the simulated structure; a is a simulated AA stacking structure; b is a simulated AB stacking structure;

[0044] Figure 10 The photocatalytic performance diagram in water and water-benzyl alcohol systems;

[0045] Figure 11 Figure 2 is the structural diagram of the functionalized aldehyde monomer containing sulfur thiophene. DETAILED DESCRIPTION

[0046] The technical solutions of the present invention will be described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

[0047] In the prior art, DA-type covalent organic frameworks are typically constructed using a benzothiadiazole group as one of the monomers. To enhance the photocatalytic performance of these covalent organic frameworks, modifications are often made to the benzothiadiazole benzene ring. However, these modifications are limited to single atoms or simple groups, and fail to effectively enhance the photocatalytic activity of the covalent organic framework. Therefore, this application provides a DDA covalent organic framework material constructed using a functionalized aldehyde monomer containing sulfur thiophene, which exhibits efficient photocatalytic hydrogen peroxide production.

[0048] A functionalized aldehyde monomer containing sulfur thiophene has a structure shown in Formula I:

[0049]

[0050] A monomer having the structure shown in formula I, Figure 11 , with benzothiadiazole as the core, benzaldehyde is connected to the 4,7-position benzene rings, and the aldehyde group provides a reaction site for the formation of COFs; at the same time, the terphenyl structure connected by the three benzene rings is a rigid planar structure with a large conjugated structure, forming a highly conjugated rigid planar skeleton. The strong π-π stacking between molecules enhances the absorption of sunlight, shortens the band gap, and can improve the photocatalytic and stability properties of COFs materials. The thiothiophene connected to the 5,6-position benzene rings, the thiophene group as an electron-rich group, broadens the light absorption range of the monomer and shortens the band gap; the introduction of the thiophene group can effectively change the electronic structure and chemical properties of the COFs skeleton, and more efficiently improve the photocatalytic performance. Therefore, the functionalized aldehyde monomer containing thiothiophene of the structure shown in Formula I is an excellent monomer for organic framework materials.

[0051] A method for preparing a functionalized aldehyde monomer containing sulfur-thiophene, wherein a structural compound represented by Formula II reacts with 2-thiophenethiol in the presence of a base to prepare the functionalized aldehyde monomer containing sulfur-thiophene; the reaction process is as follows:

[0052]

[0053] In one embodiment, the thiol group in 2-thiophenethiol has strong nucleophilicity, and therefore can undergo a substitution reaction with a halogenated hydrocarbon under alkaline conditions. The reaction conditions are mild and the conversion rate is high to form a thioether compound. In this embodiment, the thiophene group is connected to the benzene ring of benzothiadiazole via a thioether bond.

[0054] In one embodiment, the alkali used in the reaction is one or a combination of two or more of sodium hydroxide, sodium carbonate, and potassium carbonate. The amount of the alkali added is 2-3 times the amount of the compound of formula II. Preferably, the alkali used in the reaction is potassium carbonate.

[0055] As one embodiment, in an alkaline environment, in order to avoid the hydrolysis of halogenated hydrocarbons, the solvent is an organic reagent, and the organic solvent is DMF, DMA, DMSO or dihydrogen sulfoxide. One or a combination of two or more of oxathiazolinone; The structural compound shown in formula II The molar volume ratio of the solvent is 1 mmol:(10-30) mL.

[0056] In one embodiment, the molar ratio of the compound of formula II to 2-thiophene thiol is 1:(2-3). The excess amount of 2-thiophene thiol allows the compound of formula II to react as completely as possible.

[0057] As one embodiment, the reaction is carried out under an inert gas atmosphere; the reaction temperature is 20-60° C., and the reaction time is 20-120 min.

[0058] In one embodiment, the inert gas atmosphere is formed by repeatedly evacuating the reactor and then filling it with inert gas after the reactants are added to the reactor; then, after bubbling the organic solvent under the inert gas to remove oxygen, the organic solvent is added to the reactor to form an inert gas atmosphere. The inert gas is argon, nitrogen, or a combination thereof; preferably, the inert gas is nitrogen.

[0059] In one embodiment, after the reaction is completed, purification is performed using silica gel column chromatography; the eluent is petroleum ether / ethyl acetate in a volume ratio of 2:1. Prior to column chromatography, the solvent is evaporated from the reaction solution. Furthermore, prior to evaporation, the solvent is evaporated by transferring the reaction solution through one or more of dichloromethane, chloroform, ethyl acetate, or acetone.

[0060] As one embodiment, the compound of formula II is prepared by reacting 4,7-dibromo-5,6-difluoro-benzothiadiazole and formylphenylboronic acid as raw materials in a Suzuki coupling reaction system; the reaction process is as follows:

[0061]

[0062] Using 4,7-dibromo-5,6-difluoro-benzothiadiazole as the reactant with formylphenylboronic acid, the fluorine atom has a poor reactivity, while bromine is much more reactive than fluorine. Therefore, when bromine atoms are present at the 4,7 positions and fluorine atoms are present at the 5,6 positions simultaneously, the coupling reaction occurs at the bromine atoms at the 4,7 positions due to the reactivity of the halogen atoms and steric hindrance. This results in the formation of the terphenyl structure shown in Formula II. The two aldehyde groups at the para position provide reactive sites for the formation of COFs. The remaining unreacted fluorine atoms provide reactive sites for subsequent further modification.

[0063] As one embodiment, the Suzuki coupling reaction system is a tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system, a mixed solution of 1,4-dioxane and water is used as a solvent, and the reaction is carried out under an inert gas atmosphere.

[0064] The tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system allows for excellent coupling between bromine atoms and boronic acid groups, while the low reactivity of fluorine atoms prevents coupling with boronic acid. A mixed solution of 1,4-dioxane and water is a common solvent for this tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system, and an inert atmosphere is also a requirement for this system.

[0065] In one embodiment, the inert gas atmosphere is formed by repeatedly evacuating the reactor and then filling it with inert gas after the reactants are added to the reactor; the solvent is bubbled under the inert gas to remove oxygen and then added to the reactor to form an inert gas atmosphere. The inert gas is argon, nitrogen, or a combination thereof; preferably, the inert gas is nitrogen.

[0066] In one embodiment, the molar ratio of tetrakis(triphenylphosphine)palladium(0) to potassium carbonate is 1:(30-100).

[0067] As one embodiment, the volume ratio of 1,4-dioxane to water is (1-10):1.

[0068] As one embodiment, the reaction temperature is 80-100° C., and the reaction time is 12-72 hours.

[0069] In one embodiment, the molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to formylphenylboronic acid is 1:(2-3).

[0070] In one embodiment, the molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to tetrakis(triphenylphosphine)palladium(0) is (10-40):1.

[0071] In one embodiment, the molar volume ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to the solvent is 1 mmol:(10-20) mL.

[0072] As one embodiment, after the reaction is completed, a post-treatment step is included: washing with pure water, ethyl acetate and ethanol in sequence.

[0073] The present invention also provides a DDA covalent organic framework material, wherein the DDA covalent organic framework material has a structural unit shown in Formula III:

[0074]

[0075] The DDA covalent organic framework material of the present invention is a sulfur-containing thiophene covalent organic framework with a clear electron donor-donor-acceptor (DDA) configuration. A monomer of formula I containing sulfur-containing thiophene is connected to a 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene monomer via a Schiff base to form a main framework with high crystallinity and a DDA configuration and sulfur-containing thiophene. The thiophene group, as an electron-rich group, and the pyrene group both act as electron donors, and the benzothiadiazole group acts as an electron acceptor. The introduction of the thiophene group effectively changes the electronic structure and chemical properties of the COF skeleton, having a wide light absorption range. The resulting DDA configuration is conducive to enriching photogenerated charges at the reaction site, allowing more electrons to participate in the photocatalytic reaction and improving the photocatalytic hydrogen peroxide production performance.

[0076] The present invention also provides a method for preparing a DDA covalent organic framework material, which is prepared by an ammonia-aldehyde condensation reaction of the structural monomer represented by Formula I and 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene under solvent thermal conditions; the specific process is as follows:

[0077]

[0078] As one embodiment, the formation of a Schiff base by an ammonia-aldehyde condensation reaction is a commonly used method in the art for preparing COFs. The thiophene unit in the structural monomer represented by Formula I and the pyrene unit in the 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene monomer act as dual electron-donating units, enriching photogenerated electrons on the electron-withdrawing unit benzothiadiazole in the structural monomer represented by Formula I, effectively separating charges from holes, thereby improving the photocatalytic hydrogen peroxide production performance of COFs. Therefore, COFs prepared using these two as raw materials have excellent photocatalytic performance.

[0079] As one embodiment, the molar ratio of the structural monomer represented by Formula I to the 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene monomer is 1:(0.9-1.2).

[0080] As one embodiment, the solvent for the solvothermal reaction is a mixed solvent of o-dichlorobenzene and n-butanol, and the volume ratio of o-dichlorobenzene to n-butanol is 1:(0.5-2).

[0081] As one embodiment, the molar volume ratio of the structural monomer represented by Formula I and the solvent is 1 mmol: (10-50) mL.

[0082] In one embodiment, acetic acid is used as a crystal form regulator in the reaction, the concentration of acetic acid added is 5-7 mol / L, and the amount of acetic acid added is 5%-15% of the volume of the solvent.

[0083] As one embodiment, the monomer of the structure shown in Formula I and 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene are dispersed in a solvent of o-dichlorobenzene and n-butanol, acetic acid is added, and then reacted in a closed environment. After the reaction is completed, solid-liquid separation is performed to obtain a DDA covalent organic framework material.

[0084] As one embodiment, the reaction conditions are: reaction at 100-140° C. for 12-96 hours.

[0085] As one embodiment, the reaction is carried out in a glass tube. After the materials are added into the glass tube, the glass tube is sealed with an oxyhydrogen flame and then heated.

[0086] In one embodiment, after solid-liquid separation, the solid is purified. In this embodiment, purification includes washing and / or Soxhlet extraction. The solvent used for washing is DMF and / or ethyl acetate; the solvent used for Soxhlet extraction is tetrahydrofuran.

[0087] As one embodiment, after solid-liquid separation, the powder sample is washed with DMF (5 mL×5) and ethyl acetate (5 mL×5), then Soxhlet extraction is performed in THF solution for 1-5 days, and vacuum drying is performed to obtain a DDA covalent organic framework material.

[0088] The present invention also provides an application of a DDA covalent organic framework material as a catalyst for photocatalytic hydrogen peroxide production.

[0089] As one embodiment, the photocatalytic reaction is carried out under visible light; in this embodiment, the visible light is provided by an LED lamp.

[0090] As one embodiment, the photocatalytic reaction is carried out in water; or in a two-phase system of water-benzyl alcohol.

[0091] The following is a further description with reference to specific embodiments.

[0092] Example 1 Preparation of the monomer having the structure shown in Formula II:

[0093] 0.758 mmol of 4,7-dibromo-5,6-difluoro-benzothiadiazole, 2.078 mmol of formylphenylboronic acid, 2.679 mmol of anhydrous potassium carbonate, and 0.046 mmol of tetrakis(triphenylphosphine)palladium(0) were weighed and added into a 25 ml two-necked round-bottom flask, and vacuum and nitrogen were repeatedly applied three times; 8 ml of 1,4-dioxane and 2 ml of pure water were added and nitrogen was bubbled for 3 minutes to remove oxygen; the mixture was placed in an oil bath at 100°C and reacted for 24 hours; after the reaction, the mixture was washed with pure water, ethyl acetate and ethanol in sequence, and dried in an oven at 70°C to obtain a monomer with the structure shown in formula II, named BSZ-2F-2CHO.

[0094] Example 2 Preparation of the monomer having the structure shown in Formula II:

[0095] 0.758 mmol of 4,7-dibromo-5,6-difluoro-benzothiadiazole, 2.274 mmol of formylphenylboronic acid, 2.28 mmol of anhydrous potassium carbonate, and 0.076 mmol of tetrakis(triphenylphosphine)palladium(0) were weighed and added into a 25 ml two-necked round-bottom flask, and vacuumed and filled with nitrogen three times. 13.8 ml of 1,4-dioxane and 1.4 ml of pure water were added, and the mixture was bubbled with nitrogen for 3 minutes to remove oxygen. The mixture was placed in an oil bath at 80°C and reacted for 72 hours. After the reaction, the mixture was washed with pure water, ethyl acetate, and ethanol in sequence, and dried in an oven at 70°C to obtain a monomer with the structure shown in formula II, named BSZ-2F-2CHO.

[0096] Example 3 Preparation of the monomer having the structure shown in Formula II:

[0097] 0.758 mmol of 4,7-dibromo-5,6-difluoro-benzothiadiazole, 1.516 mmol of formylphenylboronic acid, 1.9 mmol of anhydrous potassium carbonate, and 0.019 mmol of tetrakis(triphenylphosphine)palladium(0) were weighed and added into a 25 ml two-necked round-bottom flask, and vacuum and nitrogen were repeatedly applied three times; 3.79 ml of 1,4-dioxane and 3.79 ml of pure water were added and nitrogen was bubbled for 3 minutes to remove oxygen; the mixture was placed in an oil bath at 85°C for 12 hours; after the reaction, the mixture was washed with pure water, ethyl acetate and ethanol in sequence, and dried in an oven at 70°C to obtain a monomer with the structure shown in formula II, named BSZ-2F-2CHO.

[0098] Example 4 Preparation of the Monomer of Formula I

[0099] Weigh 0.263 mmol of BSZ-2F-2CHO, 0.788 mmol of 2-thiophene thiol, and 0.709 mmol of potassium carbonate, add them to a 10 ml two-necked round-bottom flask, evacuate and fill with nitrogen three times; add 5 mL of N, N-dimethylformamide to the flask after bubbling under nitrogen for 3 minutes to remove oxygen, and stir at room temperature for 2 hours; after the reaction, transfer the reaction solution to a single-necked round-bottom flask with dichloromethane and evaporate the solution by rotary evaporation. Purify the mixture by silica gel chromatography using petroleum ether / ethyl acetate (2:1, v / v) as eluent to obtain the structural monomer shown in Formula I, named BSZ-2S-2CHO. The H NMR spectrum is shown in Figure 1. Figure 1 As shown; the NMR fluorine spectrum is as shown Figure 2 shown.

[0100] The H-NMR spectrum data are: 1 H NMR (400MHz, DMSO-d6) δ10.11(s,2H),8.00(d,J=8.2Hz,4H),7.64(d,J=8.1Hz,4H),7 .50(dd,J=5.3,1.2Hz,2H), 6.83(dd,J=5.3,3.6Hz,2H), 6.68(dd,J=3.6,1.2Hz,2H).

[0101] Example 5 Preparation of the Monomer of the Structure Represented by Formula I

[0102] 0.263 mmol of BSZ-2F-2CHO, 0.526 mmol of 2-thiophenethiol, and 0.526 mmol of potassium carbonate were weighed and added to a 10 ml two-necked round-bottom flask, and vacuumed and filled with nitrogen were repeated three times; 2.63 mL of 1,4-dioxane was bubbled under nitrogen for 3 minutes to remove oxygen and then added to the flask, and stirred at 60° C. for 20 minutes; after the reaction, the reaction solution was transferred to a single-necked round-bottom flask with dichloromethane and the solution was evaporated and removed by a rotary evaporator. The mixture was purified by silica gel chromatography using petroleum ether / ethyl acetate (2:1, v / v) as an eluent to obtain a monomer represented by formula I, named BSZ-2S-2CHO.

[0103] Example 6 Preparation of the Monomer of Formula I

[0104] 0.263 mmol of BSZ-2F-2CHO, 0.658 mmol of 2-thiophenethiol, and 0.789 mmol of potassium carbonate were weighed and added to a 10 ml two-necked round-bottom flask, and the mixture was evacuated and filled with nitrogen three times. 7.89 mL of DMA was added to the flask after bubbling under nitrogen for 3 minutes to remove oxygen, and the mixture was stirred at 20°C for 2 hours. After the reaction, the reaction solution was transferred to a single-necked round-bottom flask with dichloromethane and the solution was evaporated and removed by rotary evaporation. The mixture was purified by silica gel chromatography using petroleum ether / ethyl acetate (2:1, v / v) as eluent to obtain a monomer represented by formula I, named BSZ-2S-2CHO.

[0105] Example 7 Preparation of COFs

[0106] 48 μmol of BSZ-2S-2CHO and 48 μmol of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene were weighed into a glass tube (8×150 mm), and 0.5 ml of o-dichlorobenzene, 0.5 ml of n-butanol, and 0.1 ml of 6 M acetic acid aqueous solution were added. The mixture was then ultrasonically treated for 10 min. The glass tube was sealed with an oxyhydrogen flame and heated in an oven at 120°C for 72 h, then naturally cooled to room temperature. The powder was collected by filtration, washed with DMF (5 mL×5) and THF (5 mL×5), then Soxhlet extracted in THF solution for 3 days, and dried in a vacuum to obtain a DDA covalent organic framework material named BSZ-2S-COF.

[0107] Example 8 Preparation of COFs

[0108] 48 μmol of BSZ-2S-2CHO and 43.2 μmol of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene were weighed into a glass tube (8×150 mm), and 0.32 ml of o-dichlorobenzene, 0.16 ml of n-butanol, and 0.072 ml of 7 M aqueous acetic acid were added. The mixture was then sonicated for 10 min. The glass tube was sealed with an oxyhydrogen flame and heated in an oven at 100°C for 96 h, then naturally cooled to room temperature. The powder was collected by filtration, washed with DMF (5 mL×5) and THF (5 mL×5), then Soxhlet extracted in THF solution for 3 days, and dried in a vacuum to obtain a DDA covalent organic framework material named BSZ-2S-COF.

[0109] Example 9 Preparation of COFs

[0110] 48 μmol of BSZ-2S-2CHO and 57.6 μmol of 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene were weighed in a glass tube (8×150 mm), 0.8 ml of o-dichlorobenzene, 1.6 ml of n-butanol, and 0.12 ml of a 5 M aqueous acetic acid solution were added, and the mixture was then sonicated for 10 min. The glass tube was sealed with an oxyhydrogen flame and heated in an oven at 140°C for 140 h, then naturally cooled to room temperature. The powder was collected by filtration, washed with DMF (5 mL×5) and THF (5 mL×5), then Soxhlet extracted in THF solution for 3 days, and dried in a vacuum to obtain a DDA covalent organic framework material named BSZ-2S-COF.

[0111] Test example:

[0112] (1) BSZ-2F-2CHO, BSZ-2S-2CHO and BSZ-2S-COF were subjected to solid UV-visible absorption test. The UV absorption spectra of BSZ-2F-2CHO and BSZ-2S-2CHO are shown in Figure 2. Figure 3 As shown; the UV absorption spectrum of BSZ-2S-COF is as shown Figure 6 As shown; the tauc plot of BSZ-2F-2CHO is as shown Figure 4 As shown; the tauc plot of BSZ-2S-2CHO is as follows Figure 5 As shown; the tauc plot of BSZ-2S-COF is as follows Figure 7 shown.

[0113] from Figure 3 The absorption spectrum test results show that the absorption range of BSZ-2F-2CHO and BSZ-2S-2CHO has expanded to the visible light region, and the absorption range of the monomer BSZ-2S-2CHO has become wider after the introduction of the thiophene group, and it has good absorption of light before 575nm. Figure 4 The band gap of BSZ-2S-2CHO is calculated from the Tauc plot to be Eg = 2.34eV; while BSZ-2F-2CHO has good light absorption before 475nm. Figure 5 The band gap Eg is calculated from the Tauc plot to be 2.62 eV. It can be seen that the absorption range of BSZ-2F-2CHO is wider than that of BSZ-2S-2CHO, and the band gap is smaller.

[0114] BSZ-2S-COF has a DDA structure in the main framework and the introduction of thiophene groups, which extends the absorption range to the visible region and has good light absorption ability, such as Figure 6 As shown, it has good absorption of light before 600nm. Figure 7 The band gap Eg = 2.16 eV was calculated from the Tauc plot.

[0115] (2) X-ray powder diffraction test was performed on the covalent organic framework material BSZ-2S-COF. Figure 8 As shown; wherein a is the X-ray powder diffraction pattern of the prepared BSZ-2S-COF covalent organic framework material; b is the simulated AA stacking model; c is the simulated AB stacking model.

[0116] from Figure 8 The results of X-ray powder diffraction test show that the diffraction spectrum of synthesized BSZ-2S-COF is highly consistent with the X-ray powder diffraction of AA stacking structure simulated by Materials Studio software in terms of peak position, indicating that the synthesized BSZ-2S-COF is a two-dimensional layered structure of AA stacking, such as Figure 9 It can also be seen from the diffraction spectrum that the diffraction peak of BSZ-2S-COF is strong and sharp, proving that the synthesized covalent organic framework BSZ-2S-COF has high crystallinity.

[0117] Test example:

[0118] To investigate the photocatalytic performance of BSZ-2S-COF powder for hydrogen peroxide production, a 3 mg sample of BSZ-2S-COF powder was uniformly dispersed in 20 mL of deionized water. After a 30-minute oxygen flow, the system was sealed. An LED light was used as the visible light source. After one hour of photocatalytic activity, 1 mL of the reaction solution was collected and filtered through a 0.22 μm filter to obtain the filtrate.

[0119] The content of H2O2 was quantified by iodine titration. 1 mL of the reaction filtrate was mixed with 2 mL of potassium iodide solution (0.4 mol / L) and 2 mL of potassium hydrogen phthalate solution (0.1 mol / L). After 30 min, the absorbance at 350 nm was measured by UV spectrophotometer. The yield of hydrogen peroxide was as follows: Figure 10 shown.

[0120] Therefore, under pure water and oxygen conditions, the photocatalytic hydrogen peroxide production rate (ORR) was 628.52 μmol g -1 h -1 .

[0121] When H2O2 is generated in a benzyl alcohol-water two-phase system, 3 mg of BSZ-2S-COF powder sample is dispersed in 10 mL of deionized water and 10 mL of benzyl alcohol as a photocatalyst, and the system is sealed after oxygen is passed through for 30 minutes. Other reaction conditions and detection conditions are the same; the yield of hydrogen peroxide is as follows Figure 10 shown.

[0122] The photocatalytic hydrogen peroxide production rate (ORR) was 4130.63 μmol g -1 h -1 , 6.6 times higher than in pure water. In the benzyl alcohol-water two-phase system, benzyl alcohol acts as a sacrificial agent. Furthermore, the BSZ-2S-COF powder has good dispersibility in benzyl alcohol, which better exposes catalytic sites. The generated H2O2 can be promptly transferred to the aqueous phase, preventing further degradation.

[0123] In summary, the present invention synthesizes a functionalized aldehyde monomer containing sulfur thiophene, and the introduction of the thiophene group broadens the light absorption range of the monomer and narrows the band gap; it is used as one of the monomers to construct a covalent organic framework material COFs, wherein the thiophene group and the pyrene unit in another amino monomer serve as electron-donating groups, and the benzothiadiazole unit in the aldehyde monomer serves as an electron-withdrawing group, and the two are connected by an imine bond to form a covalent organic framework material BSZ-2S-COF with a DDA configuration; the two-dimensional layered stacking structure has a highly conjugated rigid planar skeleton resulting in strong π-π stacking between molecules; it has a wide light absorption range and a narrow band gap; the thiophene unit and the pyrene unit serve as dual electron-donating units, enriching photogenerated electrons on the electron-withdrawing unit benzothiadiazole, effectively separating charges and holes, thereby improving the photocatalytic hydrogen peroxide production performance of BSZ-2S-COF.

[0124] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A functionalized aldehyde monomer containing sulfur thiophene, characterized in that: Having the structure shown in formula I:

2. A method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 1, characterized in that: The structural compound represented by formula II reacts with 2-thiophenethiol in the presence of a base to prepare the functionalized aldehyde monomer containing sulfur-containing thiophene; 3. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 2, characterized in that: The molar ratio of the compound represented by formula II to 2-thiophenethiol is 1:(2-3); The amount of the added base is 2-3 times the amount of the compound represented by formula II; The reaction is carried out in an organic solvent, which is one or a combination of two or more of DMF, DMA, DMSO or dioxane; the molar volume ratio of the compound represented by Formula II to the solvent is 1 mmol: (10-30) mL; The reaction was carried out under an inert gas atmosphere; The reaction temperature is 20-60°C and the reaction time is 20-120 minutes.

4. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 2, wherein: The reaction was completed and a purification step was performed using a silica gel column with a petroleum ether / ethyl acetate mixture having a volume ratio of 2:1 as the eluent.

5. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 2, characterized in that: The structural compound represented by formula II is prepared by using 4,7-dibromo-5,6-difluoro-benzothiadiazole and formylphenylboronic acid as raw materials in a Suzuki coupling reaction system.

6. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 5, characterized in that: The Suzuki coupling reaction system is a tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system, a mixed solution of 1,4-dioxane and water is used as a solvent, and the reaction is carried out under an inert gas atmosphere.

7. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 6, characterized in that: The molar ratio of tetrakis(triphenylphosphine)palladium(0) and potassium carbonate is 1:(30-100); The volume ratio of 1,4-dioxane and water is (1-10):1; The reaction temperature is 80-100°C and the reaction time is 12-72h.

8. The method for preparing a functionalized aldehyde monomer containing sulfur thiophene according to claim 6, characterized in that: The molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole and formylphenylboronic acid is 1:(2-3); The molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to tetrakis(triphenylphosphine)palladium(0) is (10-40):1; The molar volume ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to the solvent is 1 mmol:(10-20) mL.

9. A DDA covalent organic framework material, characterized in that The sulfur-containing thiophene functionalized aldehyde monomer according to any one of claims 1 to 8 is prepared by an ammonia-aldehyde condensation reaction with 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene under solvent thermal conditions.

10. Use of the DDA covalent organic framework material according to claim 9 as a catalyst for photocatalytic hydrogen peroxide production.

Images