A covalent organic framework material with DDA configuration and its preparation method and application

Abstract

The invention discloses a covalent organic framework material with a D-D-A configuration and a preparation method and application thereof. The D-D-A covalent organic framework material comprises a functionalized aldehyde monomer containing sulfur-containing thiophene and a 1,3,6,8-tetra-(p-aminophenyl)-pyrene monomer connected by an imine bond; not only does it have a two-dimensional layered stacking structure with COFs characteristics, but it also has a strong π-π stacking between molecules caused by a highly conjugated rigid planar skeleton; it has a wide light absorption range and a narrow band gap; and the thiophene group and the pyrene unit are used as electron-donating groups together, and the benzothiadiazole unit is used as an electron-withdrawing group, and the thiophene unit and the pyrene unit are used as double electron-donating units, and the photogenerated electrons are enriched on the electron-withdrawing unit benzothiadiazole, effectively separating the charge from the hole, thereby improving the photocatalytic hydrogen peroxide production performance of the covalent organic framework material. The covalent organic framework material can be prepared by a solvent thermal reaction, and can be prepared on a large scale.

Description

Technical Field

[0001] The invention belongs to the technical field of covalent organic framework functional materials, and in particular relates to a covalent organic framework material with a DDA configuration, a preparation method and an application thereof. Background Art

[0002] Over the past century, with the growth of the global economy, we are inevitably faced with problems such as over-exploitation of fossil fuels, huge energy consumption in industrial processes, and increasingly serious environmental pollution. In this context, 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, has attracted widespread attention and research in solving environmental and energy problems. Through the irradiation of visible light and / or ultraviolet light, electrons and holes can be excited on the catalyst surface, 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 received increasing attention. Hydrogen peroxide has the characteristics of high energy density and easy transportation, and is currently widely used in sterilization, chemical synthesis, energy conversion, and fuel cells. However, the current main industrial synthesis method of hydrogen peroxide is the anthraquinone method, which has high energy consumption and high cost and does not meet the requirements of green chemistry. The photocatalytic synthesis of hydrogen peroxide technology is to prepare hydrogen peroxide by catalyzing water and oxygen by absorbing solar energy through semiconductor materials. This synthesis method has the advantages of environmental protection and sustainability, and has significant advantages over the traditional anthraquinone method for synthesizing hydrogen peroxide.

[0003] Covalent organic frameworks (COFs), as a new type of crystalline porous organic materials, have emerged in this context. Their unique structure not only has abundant surface active sites, but also has strong controllability, providing new possibilities for photocatalytic reactions. COFs are pure organic polymers with rich pore structures, clear two-dimensional or three-dimensional crystal structures, and are usually synthesized through reversible condensation reactions. Since Yaghi et al. first reported COFs in 2005, research on their preparation and application has developed rapidly. Compared with traditional materials, COFs have the characteristics of low density and high specific surface area, as well as regular pore structure, easy functional design and excellent photoelectric properties. These advantages, coupled with the chemical stability of COFs in aqueous media and even under harsh conditions, have gradually attracted attention and high attention in environmental applications. As an adaptable platform, COFs have gradually gained attention in the field of photocatalytic hydrogen peroxide production.

[0004] However, in the current photocatalytic synthesis of H2O2, photocatalysts have the disadvantages of weak oxygen adsorption and activation capabilities, low light response capabilities, and limited active sites. The photocatalytic performance of organic photocatalysts under natural light is low, and the long-term photocatalytic stability of photocatalyst materials is poor. In addition, the two-dimensional COF materials reported earlier mainly acted as the main framework, using their one-dimensional channels for mass transfer. However, due to the low efficiency of photogenerated electron-hole separation, additional photosensitizers can only be added to assist photocatalysis. These have restricted the practical application of organic photocatalysts in photocatalytic reactions. Summary of the invention

[0005] Based on the above reasons, the first object of the present invention is to provide a covalent organic framework material with a DDA configuration; the thiophene group is used as an electron-rich group and the pyrene group is used as an electron donor, and the benzothiadiazole group is used as an electron acceptor; a covalent organic framework material with a DDA configuration is formed. The introduction of the thiophene group effectively changes the electronic structure and chemical properties of the COF skeleton. The formed DDA configuration is conducive to enriching the photogenerated charges at the reaction site, so that more electrons participate in the photocatalytic reaction, and the covalent organic framework material has a wider light absorption range and more efficient reaction activity.

[0006] The second object of the present invention is to provide a method for preparing a covalent organic framework material having a DDA configuration.

[0007] The third object of the present invention is to provide an application of the above 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 covalent organic framework material with a DDA configuration has a structural unit shown in formula III:

[0010]

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

[0012] A method for preparing a covalent organic framework material having a DDA configuration, as shown in formula I The structural monomers are 1,3,6, Solvothermal reaction of 8-tetrakis-(p-aminophenyl)-pyrene with ammoniacal aldehyde Prepared by condensation reaction;

[0013]

[0014] Furthermore, the molar ratio of the structural monomer shown in Formula I to 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene is 1:(0.9-1.2).

[0015] Furthermore, the solvent for the solvothermal reaction is a mixed solvent of o-dichlorobenzene and n-butanol.

[0016] Furthermore, the volume ratio of o-dichlorobenzene to n-butanol is 1:(0.5-2).

[0017] Furthermore, the molar volume ratio of the structural monomer represented by Formula I and the solvent is 1 mmol: (10-50) mL.

[0018] Furthermore, acetic acid is used as a crystal form regulator in the reaction.

[0019] Furthermore, the concentration of the added acetic acid is 5-7 mol / L, and the amount of the added acetic acid is 5%-15% of the volume of the solvent.

[0020] Furthermore, the reaction conditions are: reacting at 100-140° C. for 12-96 hours.

[0021] Furthermore, after the reaction, solid-liquid separation is also included to purify the solid:

[0022] The 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.

[0023] Furthermore, the structural monomer shown in formula I is prepared by the following method:

[0024] The compound of the structure represented by formula II reacts with 2-thiophenethiol in the presence of a base to prepare the monomer of the structure represented by formula I;

[0025]

[0026] Furthermore, the compound of the structure shown in 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.

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

[0028] The DDA covalent organic framework material is used as a photocatalytic hydrogen peroxide production catalyst, and the photocatalytic reaction is carried out in water; or in a two-phase system of water-benzyl alcohol.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. The covalent organic framework material with DDA configuration of the present invention is formed by connecting the functionalized aldehyde monomer containing sulfur thiophene and the 1,3,6,8-tetra-(p-aminophenyl)-pyrene monomer through an imine bond. The COFs have a unique two-dimensional layered stacking structure with a highly conjugated rigid planar skeleton, resulting in strong π-π stacking between molecules, which enhances the absorption of sunlight and shortens the band gap. The thiophene unit and the pyrene unit act as double electron-donating units, enriching the photogenerated electrons on the electron-withdrawing unit benzothiadiazole, effectively separating the charge from the hole, thereby improving the photocatalytic hydrogen peroxide production performance of the covalent organic framework material.

[0031] 2. The preparation method of the DDA-configured covalent organic framework material of the present invention is prepared by solvent thermal reaction, the reaction is mature, the preparation process is simple, and it is easy to prepare on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The hydrogen nuclear magnetic spectrum of the functionalized aldehyde monomer containing sulfur thiophene prepared in the present invention;

[0033] Figure 2 The NMR fluorine spectrum of the functionalized aldehyde monomer containing sulfur thiophene prepared in the present invention;

[0034] Figure 3 Solid UV-visible absorption spectra of BSZ-2F-2CHO and BSZ-2S-2CHO;

[0035] Figure 4 This is the tauc plot of BSZ-2F-2CHO;

[0036] Figure 5 This is the tauc plot of BSZ-2S-2CHO;

[0037] Figure 6 The solid UV-visible absorption spectrum of the DDA covalent organic framework material BSZ-2S-COF prepared by the present invention;

[0038] Figure 7 This is the tauc plot of the DDA covalent organic framework material BSZ-2S-COF;

[0039] 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;

[0040] Fig. 9 Schematic diagram of the simulated structure; a is a simulated AA stacking structure; b is a simulated AB stacking structure;

[0041] Fig.10The photocatalytic performance diagram in different systems of water and water-benzyl alcohol;

[0042] Fig.11 This is the structural diagram of the covalent organic framework material containing DDA. DETAILED DESCRIPTION

[0043] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only partial embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0044] At present, many functional COFs have been applied to the photocatalytic production of hydrogen peroxide and have made some progress. In order to improve the photocatalytic activity of organic photocatalysts with conjugated frameworks, various strategies have been proposed, such as expanding the light absorption range, designing organic-inorganic or organic-organic heterojunctions, constructing electron donor-acceptor (DA) or donor-π-acceptor (D-π-A) structures and enhancing hydrophilicity. Among these strategies, the construction of DA or D-π-A type polymer photocatalysts has attracted widespread attention because the intrinsic electron push-pull effect between the donor unit and the acceptor unit is conducive to photoinduced charge separation, thereby improving the photocatalytic activity of polymer photocatalysts.

[0045] By selecting appropriate functional units and incorporating them into the framework structure to regulate the physical and chemical properties of COFs, it is possible to control their energy bands and electronic structures at the molecular level, thereby increasing visible light absorption, promoting photogenerated electron-hole separation and transfer, and accelerating surface dynamics, thereby achieving the purpose of improving photocatalytic performance.

[0046] Therefore, the present application provides a functionalized aldehyde monomer containing sulfur thiophene to construct a DDA covalent organic framework material, which has efficient photocatalytic hydrogen peroxide production performance.

[0047] A functionalized aldehyde monomer containing sulfur thiophene has a structure shown in Formula I:

[0048]

[0049] The monomer of the structure shown in Formula I has benzothiazole as the core, and benzaldehyde is connected to the 4 and 7 benzene rings, where the aldehyde group provides a reaction site for the formation of COFs; at the same time, the terphenyl structure connected by three benzene rings is a rigid planar structure with a large conjugated structure, forming a highly conjugated rigid planar skeleton that leads to strong π-π stacking between molecules, which 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 and 6 benzene rings, 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.

[0050] A method for preparing a functionalized aldehyde monomer containing sulfur thiophene, wherein a compound having a structure shown in 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:

[0051]

[0052] As one embodiment, the thiol group in 2-thiophenethiol has strong nucleophilicity, so it can undergo substitution reaction with halogenated hydrocarbons under alkaline conditions, with mild reaction conditions and high conversion rate to form thioether compounds. In this embodiment, the thiophene group is connected to the benzene ring of benzothiadiazole through a thioether bond.

[0053] As one embodiment, the alkali 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 the structure shown in formula II. Preferably, the alkali in the reaction is potassium carbonate.

[0054] As one embodiment, in an alkaline environment, in order to avoid the hydrolysis of halogenated hydrocarbons, an organic reagent is selected as the solvent, and the organic solvent 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.

[0055] As 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.

[0056] 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.

[0057] As one embodiment, the inert gas atmosphere is that after the reactants are added to the reactor, the reactor is evacuated and filled with inert gas repeatedly; the organic 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 one or a combination of argon and nitrogen; preferably, the inert gas is nitrogen.

[0058] As one embodiment, after the reaction is completed, silica gel column chromatography is used for purification; the eluent is petroleum ether / ethyl acetate in a volume ratio of 2:1. Before column chromatography, the solvent is evaporated from the reaction solution, and further, before evaporation, the reaction solution is transferred through a combination of one or more of dichloromethane, chloroform, ethyl acetate or acetone to evaporate the solvent.

[0059] As one embodiment, the compound of the structure shown in 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; the reaction process is as follows:

[0060]

[0061] When 4,7-dibromo-5,6-difluoro-benzothiadiazole is used as the reaction raw material and formylphenylboronic acid, the reactivity of fluorine atoms is poor, and the reactivity of bromine is much higher than that of fluorine. Therefore, when there are bromine atoms at the 4 and 7 positions and fluorine atoms at the 5 and 6 positions at the same time, during the reaction, based on the reactivity and steric hindrance of halogen atoms, the coupling reaction occurs on the bromine atoms at the 4 and 7 positions, which results in the formation of the terphenyl structure shown in Formula II, and the two aldehyde groups at the para position provide reaction sites for the formation of COFs. The remaining unreacted fluorine atoms provide reaction sites for subsequent further modification.

[0062] 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 as a solvent, and the reaction is carried out under an inert gas atmosphere.

[0063] The tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system can make the bromine atom and the boronic acid group couple well, but the fluorine atom has low activity and does not undergo coupling reaction with boronic acid. A mixed solution of 1,4-dioxane and water is a commonly used solvent for the tetrakis(triphenylphosphine)palladium(0) and potassium carbonate catalyst system, and an inert gas atmosphere is also one of the requirements of this system.

[0064] As one embodiment, the inert gas atmosphere is that after the reactants are added to the reactor, the reactor is evacuated and filled with inert gas repeatedly; 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 one or a combination of argon and nitrogen; preferably, the inert gas is nitrogen.

[0065] As one embodiment thereof, the molar ratio of tetrakis(triphenylphosphine)palladium(0) to potassium carbonate is 1:(30-100).

[0066] As one embodiment, the volume ratio of 1,4-dioxane to water is (1-10):1.

[0067] As one embodiment, the reaction temperature is 80-100° C. and the reaction time is 12-72 hours.

[0068] As one embodiment thereof, the molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to formylphenylboronic acid is 1:(2-3).

[0069] As one embodiment, the molar ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to tetrakis(triphenylphosphine)palladium(0) is (10-40):1.

[0070] As one embodiment thereof, the molar volume ratio of 4,7-dibromo-5,6-difluoro-benzothiadiazole to the solvent is 1 mmol:(10-20) mL.

[0071] As one embodiment, after the reaction is completed, a post-treatment step is included: washing with pure water, ethyl acetate and ethanol in sequence.

[0072] 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:

[0073]

[0074] 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. The monomer of formula I structure containing sulfur-containing thiophene is connected with 1,3,6,8-tetra-(p-aminophenyl)-pyrene monomer through a Schiff base to form a main framework with high crystallinity and DDA configuration and sulfur-containing thiophene. The thiophene group as an electron-rich group and the pyrene group both serve as electron donors, and the benzothiadiazole group serves as an electron acceptor. The introduction of the thiophene group effectively changes the electronic structure and chemical properties of the COF skeleton, has a wider light absorption range, and the formed DDA configuration is conducive to enriching the photogenerated charge at the reaction site, so that more electrons participate in the photocatalytic reaction, and improve the photocatalytic hydrogen peroxide production performance.

[0075] The present invention also provides a method for preparing a DDA covalent organic framework material, wherein the structural monomer shown in formula I and 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene are subjected to an ammonia-aldehyde condensation reaction under solvent thermal conditions to prepare the material; the specific process is as follows:

[0076]

[0077] As one of the embodiments, the formation of Schiff base by ammonia aldehyde condensation reaction is a commonly used method for preparing COFs in the art. The thiophene unit in the structural monomer shown in Formula I and the pyrene unit in the 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene monomer serve as double electron-donating units, which enrich the photogenerated electrons on the electron-withdrawing unit benzothiazole in the structural monomer shown in Formula I, effectively separating the charge from the hole, thereby improving the photocatalytic hydrogen peroxide production performance of COFs. Therefore, COFs are prepared using the two as raw materials, and COFs have excellent photocatalytic performance.

[0078] 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).

[0079] 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).

[0080] As one embodiment, the molar volume ratio of the structural monomer represented by Formula I and the solvent is 1 mmol: (10-50) mL.

[0081] As one embodiment, acetic acid is used as a crystal form regulator in the reaction, the concentration of the added acetic acid is 5-7 mol / L, and the amount of the added acetic acid is 5%-15% of the volume of the solvent.

[0082] 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.

[0083] As one embodiment, the reaction conditions are: reacting at 100-140° C. for 12-96 hours.

[0084] 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.

[0085] As one embodiment, after the solid-liquid separation, the solid is purified. In this embodiment, the 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.

[0086] As one embodiment, after solid-liquid separation, the solid is washed with DMF (5 mL×5) and ethyl acetate (5 mL×5), and then Soxhlet extraction is performed in THF solution for 1-5 days. After vacuum drying, the DDA covalent organic framework material is obtained.

[0087] The present invention also provides an application of a DDA covalent organic framework material as a catalyst for photocatalytic production of hydrogen peroxide.

[0088] As one embodiment, the photocatalytic reaction is carried out under visible light; in this embodiment, the visible light is provided by an LED lamp.

[0089] As one embodiment, the photocatalytic reaction is carried out in water; or in a two-phase system of water-benzyl alcohol.

[0090] The following is a further description with reference to specific embodiments.

[0091] Example 1 Preparation of the monomer having the structure shown in Formula II:

[0092] Weigh 0.758mmol of 4,7-dibromo-5,6-difluoro-benzothiadiazole, 2.078mmol of formylphenylboronic acid, 2.679mmol of anhydrous potassium carbonate, and 0.046mmol of tetrakis(triphenylphosphine)palladium(0) into a 25ml two-necked round-bottom flask, and repeat vacuuming and nitrogen filling three times; add 8ml of 1,4-dioxane and 2ml of pure water, and bubble with nitrogen for 3min to remove oxygen; place in an oil bath at 100°C to react for 24h; after the reaction, wash with pure water, ethyl acetate and ethanol in turn, and dry in an oven at 70°C to obtain a monomer with the structure shown in formula II, named BSZ-2F-2CHO.

[0093] Example 2 Preparation of the monomer having the structure shown in Formula II:

[0094] Weigh 0.758mmol of 4,7-dibromo-5,6-difluoro-benzothiadiazole, 2.274mmol of formylphenylboronic acid, 2.28mmol of anhydrous potassium carbonate, and 0.076mmol of tetrakis(triphenylphosphine)palladium(0) into a 25ml two-necked round-bottom flask, and repeat the vacuum and nitrogen filling three times; add 13.8ml of 1,4-dioxane and 1.4ml of pure water, and bubble with nitrogen for 3min to remove oxygen; place in an oil bath at 80°C to react for 72h; after the reaction, wash with pure water, ethyl acetate and ethanol in turn, and dry in an oven at 70°C to obtain a monomer with the structure shown in formula II, named BSZ-2F-2CHO.

[0095] Example 3 Preparation of the structural monomer shown in Formula II:

[0096] Weigh 0.758mmol of 4,7-dibromo-5,6-difluoro-benzothiadiazole, 1.516mmol of formylphenylboronic acid, 1.9mmol of anhydrous potassium carbonate, and 0.019mmol of tetrakis(triphenylphosphine)palladium(0) into a 25ml two-necked round-bottom flask, and repeat vacuuming and nitrogen filling three times; add 3.79ml of 1,4-dioxane and 3.79ml of pure water, and bubble with nitrogen for 3min to remove oxygen; place in an oil bath at 85°C for 12h; after the reaction is completed, wash with pure water, ethyl acetate and ethanol in turn, and dry in an oven at 70°C to obtain a monomer with the structure shown in formula II, named BSZ-2F-2CHO.

[0097] Example 4 Preparation of the Monomer of the Structure Represented by Formula I

[0098] Weigh 0.263mmoL of BSZ-2F-2CHO, 0.788mmoL of 2-thiophenethiol, and 0.709mmoL of potassium carbonate, add them to a 10ml two-necked round-bottom flask, evacuate and fill with nitrogen three times; add 5mL of N,N-dimethylformamide to the flask after bubbling under nitrogen for 3min to remove oxygen, and stir the reaction at room temperature for 2h; after the reaction, transfer the reaction solution to a single-necked round-bottom flask with dichloromethane and evaporate the solution by rotary evaporator, purify the mixture by silica gel chromatography, use petroleum ether / ethyl acetate (2:1, v / v) as eluent, and obtain the structural monomer shown in formula I, named BSZ-2S-2CHO. The nuclear magnetic hydrogen spectrum is shown in Figure 1 As shown; NMR fluorine spectrum as Figure 2 shown.

[0099] The H-NMR spectrum data are: 1H 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).

[0100] Example 5 Preparation of the Monomer of the Structure Represented by Formula I

[0101] 0.263 mmol / L BSZ-2F-2CHO, 0.526 mmol / L 2-thiophenethiol, and 0.526 mmol / L potassium carbonate were weighed and added to a 10 ml two-necked round-bottom flask, and vacuumed and filled with nitrogen three times; 2.63 mL of 1,4-dioxane was added to the flask after bubbling under nitrogen for 3 min to remove oxygen, and stirred at 60° C. for 20 min; 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, and the mixture was purified by silica gel chromatography using petroleum ether / ethyl acetate (2:1, v / v) as an eluent to obtain a monomer of the structure shown in formula I, named BSZ-2S-2CHO.

[0102] Example 6 Preparation of the Monomer of the Structure Represented by Formula I

[0103] 0.263 mmol / L BSZ-2F-2CHO, 0.658 mmol / L 2-thiophenethiol, and 0.789 mmol / L 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 min to remove oxygen, and the mixture was stirred and reacted at 20° C. for 2 h. 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 of the structure shown in formula I, which was named BSZ-2S-2CHO.

[0104] Example 7 Preparation of COFs

[0105] 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), 0.5 ml of o-dichlorobenzene, 0.5 ml of n-butanol and 0.1 ml of 6M acetic acid aqueous solution were added, and 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, and then naturally cooled to room temperature; the powder was collected by suction filtration, and the powder sample was washed with DMF (5 mL×5) and THF (5 mL×5), and 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.

[0106] Example 8 Preparation of COFs

[0107] 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), 0.32 ml of o-dichlorobenzene, 0.16 ml of n-butanol and 0.072 ml of 7M acetic acid aqueous solution were added, and the mixture was then ultrasonically treated for 10 min; the glass tube was sealed with an oxyhydrogen flame and heated in an oven at 100°C for 96 h, and then naturally cooled to room temperature; the powder was collected by suction filtration, the powder sample was washed with DMF (5 mL×5) and THF (5 mL×5), and then Soxhlet extracted in THF solution for 3 days and dried in vacuum to obtain a DDA covalent organic framework material named BSZ-2S-COF.

[0108] Example 9 Preparation of COFs

[0109] 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 5M acetic acid aqueous solution were added, and the mixture was then ultrasonically treated for 10 min; the glass tube was sealed with an oxyhydrogen flame and heated in an oven at 140°C for 140 h, and then naturally cooled to room temperature; the powder was collected by filtration, and the powder sample was washed with DMF (5 mL×5) and THF (5 mL×5), and 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.

[0110] Test example:

[0111] (1) BSZ-2F-2CHO, BSZ-2S-2CHO and BSZ-2S-COF were subjected to solid UV-visible light absorption test. The UV absorption spectra of BSZ-2F-2CHO and BSZ-2S-2CHO are shown in Figure 3 As shown; the UV absorption spectrum of BSZ-2S-COF is as follows Figure 6 As shown; the tauc plot of BSZ-2F-2CHO is as follows 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.

[0112] 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 = 2.34 eV; while BSZ-2F-2CHO has good light absorption before 475 nm. Figure 5 The band gap Eg = 2.62 eV was calculated from the Tauc plot. 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 narrower.

[0113] BSZ-2S-COF has a DDA configuration in the main framework and the introduction of thiophene groups, so the absorption range is extended 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.

[0114] (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.

[0115] from Figure 8 The results of X-ray powder diffraction test show that the diffraction spectrum of the synthesized BSZ-2S-COF is highly consistent with the X-ray powder diffraction of the 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 Fig. 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.

[0116] Test example:

[0117] In order to study the photocatalytic performance of BSZ-2S-COF powder in producing hydrogen peroxide, 3 mg of BSZ-2S-COF powder sample was evenly dispersed in 20 mL of deionized water as a photocatalyst, and the system was sealed after oxygen was passed through for 30 minutes. LED lamp was used as a visible light source, and 1 mL of the reaction solution was taken after 1 hour of photocatalytic experiment, and the filtrate was obtained by passing through a 0.22 μm filter.

[0118] 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 is as follows: Fig.10 shown.

[0119] Therefore, under pure water conditions and oxygen, the photocatalytic hydrogen peroxide production rate (ORR) is 628.52 μmol g -1 h -1 .

[0120] When H2O2 is generated in the 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 min. Other reaction conditions and detection conditions are the same; the yield of hydrogen peroxide is as follows Fig.10 shown.

[0121] The photocatalytic hydrogen peroxide production rate (ORR) was 4130.63 μmol g -1 h -1 , which is 6.6 times higher than that of pure water. In the benzyl alcohol-water two-phase system, benzyl alcohol acts as a sacrificial agent; and BSZ-2S-COF powder has good dispersibility in benzyl alcohol, which can better expose the catalytic sites, and the generated H2O2 can be transferred to the water phase in time to avoid further degradation.

[0122] In summary, the present invention synthesizes a DDA covalent organic framework material, which contains a functionalized aldehyde monomer containing sulfur thiophene and a 1,3,6,8-tetra-(p-aminophenyl)-pyrene monomer connected by an imine bond. Not only does it have a two-dimensional layered stacking structure with COFs characteristics, but also has a strong π-π stacking between molecules caused by a highly conjugated rigid planar skeleton; it has a wide light absorption range and a narrow band gap; and the thiophene group and the pyrene unit act as electron-donating groups together, and the benzothiadiazole unit acts as an electron-withdrawing group. The thiophene unit and the pyrene unit act as double electron-donating units, enriching the photogenerated electrons on the electron-withdrawing unit benzothiadiazole, effectively separating the charge from the hole, thereby improving the photocatalytic hydrogen peroxide production performance of BSZ-2S-COF.

[0123] The above-mentioned 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 substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. Application of a covalent organic framework material having a DDA configuration as a photocatalytic hydrogen peroxide production catalyst, characterized in that: The photocatalytic reaction is carried out in water; or in a two-phase system of water-benzyl alcohol; The method for preparing the covalent organic framework material with a DDA configuration is prepared by carrying out an ammonia-aldehyde condensation reaction between the structural monomer shown in formula I and 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene under solvent thermal conditions; Acetic acid is used as a crystal form regulator in the reaction.

2. The use of the covalent organic framework material with DDA configuration according to claim 1 as a photocatalytic hydrogen peroxide production catalyst, characterized in that: The molar ratio of the structural monomer shown in formula I to 1,3,6,8-tetrakis-(p-aminophenyl)-pyrene is 1:(0.9-1.2).

3. The use of the covalent organic framework material with DDA configuration according to claim 1 as a photocatalytic hydrogen peroxide production catalyst, characterized in that: The solvent for the solvothermal reaction is a mixed solvent of o-dichlorobenzene and n-butanol; The volume ratio of o-dichlorobenzene to n-butanol is 1:(0.5-2); The molar volume ratio of the structural monomer shown in Formula I and the solvent is 1 mmol:(10-50) mL.

4. The use of the covalent organic framework material with DDA configuration according to claim 1 as a photocatalytic hydrogen peroxide production catalyst, characterized in that: The concentration of added acetic acid is 5-7 mol / L; The amount of acetic acid added is 5%-15% of the solvent volume.

5. The use of the covalent organic framework material with DDA configuration according to claim 1 as a photocatalytic hydrogen peroxide production catalyst, characterized in that: The reaction conditions are: reaction at 100-140°C for 12-96h.

6. The use of the covalent organic framework material with DDA configuration according to claim 1 as a photocatalytic hydrogen peroxide production catalyst, characterized in that: After the reaction, solid-liquid separation is also included to purify the solid: The 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.

7. The use of the covalent organic framework material with DDA configuration according to claim 1 as a photocatalytic hydrogen peroxide production catalyst, characterized in that: The structural monomer shown in formula I is prepared by the following method: The compound of the structure represented by formula II reacts with 2-thiophenethiol in the presence of a base to prepare the monomer of the structure represented by formula I; 8. The use of the covalent organic framework material with DDA configuration as a photocatalytic hydrogen peroxide production catalyst according to claim 7, characterized in that: The structural compound shown in 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.

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