Biobr / t pbd-cof composite material and preparation method thereof

Abstract

This invention provides a BiOBr / TpBD-COF composite material and its preparation method. The BiOBr / TpBD-COF composite material is prepared by solvothermal generation of BiOBr nanosheets from Cs3Bi2Br9, followed by growth of the BiOBr nanosheets onto TpBD-COF. The TpBD-COF exhibits a flower-like structure with uniformly dispersed, sheet-like petals. The BiOBr nanosheets have a diameter of 63-93 nm and a thickness of 33-47 nm. The BiOBr / TpBD-COF composite material provided by this invention exhibits significantly improved photocatalytic performance, achieving a photocatalytic water splitting and hydrogen production rate of 16.17 mmol·g⁻¹. ‑1 ·h ‑1 It exhibits good cycle stability and is a highly efficient photocatalyst.

Description

Technical Field

[0001] This invention belongs to the field of environmental protection and energy materials, and more specifically, relates to a BiOBr / TpBD-COF composite material and its preparation method. Background Technology

[0002] With the rapid development of global industrialization, the energy crisis and environmental pollution are becoming increasingly serious. Photocatalysis, capable of converting inexhaustible solar energy into storable and transportable chemical fuels, is a promising strategy for addressing energy and environmental issues. Since Fujishima and Honda first reported TiO2 as a photocatalyst in 1972, many semiconductor photocatalysts have been explored, such as metal oxides, metal sulfides, and conjugated polymers. However, most of these photocatalysts suffer from inherent defects, including wide bandgap, photocorrosion, and limited visible light absorption.

[0003] In recent years, organic semiconductors have attracted widespread attention due to their structural diversity, tunable band gap, and strong light absorption capabilities. Covalent organic frameworks (COFs) are a novel class of porous organic crystalline materials, which can be used to synthesize COF-based photocatalysts with different structures and functions through different organic building blocks and connections. COFs are considered highly attractive photocatalysts due to their excellent molecular structure designability, π-π conjugated structure, abundant porosity, and large specific surface area, and have been applied to photocatalytic water splitting for hydrogen production. However, the strong electrostatic attraction of single-component COF materials leads to rapid recombination of photogenerated electrons and holes, reducing photocatalytic performance and thus greatly limiting their application range. Summary of the Invention

[0004] In view of the above, the present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a BiOBr / TpBD-COF composite material and its preparation method. The all-BiOBr / TpBD-COF composite material prepared by the method of the present invention not only significantly improves the photocatalytic water splitting hydrogen production rate, but also possesses excellent cycle stability, making it a highly efficient and stable photocatalyst. Furthermore, the preparation method has a simple process flow and is suitable for large-scale industrial production applications.

[0005] Therefore, in a first aspect, embodiments of the present invention provide a BiOBr / TpBD-COF composite material, wherein BiOBr nanosheets are generated from Cs3Bi2Br9 by a solvothermal method, and the BiOBr nanosheets are grown on TpBD-COF, wherein the TpBD-COF has a flower-like structure, and its petals have a sheet-like structure and are uniformly dispersed.

[0006] Preferably, the sheet-like BiOBr has a diameter of 63-93 nm and a thickness of 33-47 nm.

[0007] In a second aspect, embodiments of the present invention provide a method for preparing the BiOBr / TpBD-COF composite material provided in the first aspect above, the preparation method comprising:

[0008] Step S1, Preparation of TpBD-COF:

[0009] S1.1: After mixing trialdehyde phloroglucinol and benzidine, add mesitylene and 1,4-dioxane solvent, and sonicate for a certain time to obtain a uniformly dispersed mixture;

[0010] S1.2: Add acetic acid solution to the obtained mixture and sonicate for a certain time to completely dissolve it, thus obtaining a homogeneous solution;

[0011] S1.3: The homogeneous solution is rapidly frozen in a liquid nitrogen bath, and after three freezing, vacuum thawing, and degassing cycles, it is vacuum sealed and then kept warm in an oven for a certain period of time. The precipitate obtained from the reaction is washed multiple times to obtain a brownish-yellow product.

[0012] S1.4: Dry the brownish-yellow product for a certain period of time, then grind it to obtain TpBD-COF.

[0013] Step S2, Preparation of Cs3Bi2Br9:

[0014] S2.1: Cesium bromide and bismuth bromide were added to dimethyl sulfoxide (DMSO) respectively, and isopropanol was added while stirring continuously at room temperature. After stirring for a certain period of time, the yellow precipitate formed was collected by centrifugation.

[0015] S2.2: Wash the yellow precipitate three times with isopropanol, dry it for a certain period of time, and grind it to obtain Cs3Bi2Br9 powder.

[0016] Step S3, Preparation of BiOBr nanosheets:

[0017] S3.1: Disperse potassium bromide in deionized water and sonicate to obtain a homogeneous potassium bromide solution;

[0018] S3.2: Dissolve bismuth nitrate pentahydrate powder in ethylene glycol and stir for a certain time to obtain a homogeneous bismuth nitrate pentahydrate solution;

[0019] S3.3: The potassium bromide solution is added dropwise to the bismuth nitrate pentahydrate solution, and the mixture is stirred for a certain period of time to obtain a mixed solution;

[0020] S3.4: Transfer the mixed solution to a reaction vessel, heat for a certain time, centrifuge to collect the precipitate, wash it three times with deionized water and ethanol respectively, dry it for a certain time, and grind it to obtain BiOBr nanosheets.

[0021] Step S4, Preparation of BiOBr / TpBD-COF composite material:

[0022] S4.1: Cs3Bi2Br9 powder was mixed with monomeric trialdehyde phloroglucinol and benzidine, and then mesitylene and 1,4-dioxane solvent were added. After sonication for a certain time, a uniformly dispersed mixture was obtained.

[0023] S4.2: Add acetic acid solution to the mixture and sonicate for a period of time to completely dissolve it, thereby obtaining a homogeneous solution;

[0024] S4.3: The homogeneous solution is rapidly frozen in a liquid nitrogen bath, and after three freezing, vacuum thawing, and degassing cycles, it is vacuum sealed and then kept warm in an oven for a certain period of time. The precipitate obtained from the reaction is washed multiple times to obtain a brownish-yellow product.

[0025] S4.4: Dry the brownish-yellow product for a certain period of time, and then grind it to obtain the BiOBr / TpBD-COF composite material.

[0026] Preferably, in step S1.1, the molar ratio of the added trialdehyde phloroglucinol and benzidine is 1:(1.3-1.7), the volume ratio of the added mesitylene and 1,4-dioxane is 1:(0.8-1.2), the mass-to-volume ratio of the monomer mixture to the solvent is 41-58 mg / mL, and the ultrasonic time is 10-20 min; in step S1.2, the concentration of the acetic acid solution is 2-4 mol / L, the ultrasonic time is 5-10 min, and the mass-to-volume ratio of the monomer mixture to the acetic acid solution is 225-393 mg / mL.

[0027] Preferably, in step S1, in step S1.3, the heat preservation temperature is 100-140℃, the heat preservation time is 48-96h, and the detergent used for washing is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, dimethyl sulfoxide, or acetone, and the number of washing cycles is 6-10; in step S1.4, the drying method is one or more of forced air drying, vacuum drying, and spray drying, the drying temperature is 60-100℃, and the drying time is 10-14h.

[0028] Preferably, in step S2, the molar ratio of cesium bromide to bismuth bromide is 1:(1.3-1.7), the volume ratio of dimethyl sulfoxide to isopropanol is 1:(4-6), and the stirring time is 1-3 hours; the drying method is one or more of forced-air drying, vacuum drying, and spray drying, the drying temperature is 60-100°C, and the drying time is 10-14 hours.

[0029] Preferably, in step S3.2, the mass-to-volume ratio of bismuth nitrate pentahydrate to ethylene glycol is 19-32 mg / mL, the volume of ethylene glycol is 15-25 mL, and the stirring time is 10-20 min; in step S3.3, the molar ratio of potassium bromide to bismuth nitrate pentahydrate is 1:(0.8-1.2), and the stirring time is 10-30 min; in step S3.4, the heating temperature is 100-140℃, and the heating time is 4-8 h; the drying method is one or more of forced-air drying, vacuum drying, and spray drying, the drying temperature is 40-80℃, and the drying time is 10-14 h.

[0030] Preferably, in step S4.1, the mass percentage of the Cs3Bi2Br9 powder is 5%-20%; the molar ratio of the added trialdehyde phloroglucinol and benzidine is 1:(1.3-1.7); the volume ratio of the added mesitylene and 1,4-dioxane is 1:(0.8-1.2); and the ultrasonic time is 10-20 min. In step S4.2, the concentration of the acetic acid solution is 2-4 mol / L, and the ultrasonic time is 5-10 min. The mass-to-volume ratio of the monomer mixture to the acetic acid solution is 225-393 mg / mL.

[0031] Preferably, in step S4.3, the heat preservation temperature is 100-140℃, the heat preservation time is 48-96h, the detergent used for washing is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, dimethyl sulfoxide or acetone, and the number of washing cycles is 6-10.

[0032] Preferably, in step S4.4, the drying method is one or more of blower drying, vacuum drying, and spray drying, the drying temperature is 60-100℃, and the drying time is 10-14h.

[0033] The preparation method of the BiOBr / TpBD-COF composite material provided in this invention is simple to operate, low in cost, and has good reproducibility. Furthermore, the process flow is simple and suitable for large-scale industrial production. The BiOBr / TpBD-COF composite material prepared by this invention, by combining BiOBr and TpBD-COF materials, can improve the redox capacity, efficient separation and migration rate of photogenerated carriers, thereby significantly improving photocatalytic performance. The photocatalytic water splitting hydrogen production rate reaches 16.17 mmol·g⁻¹. -1 ·h -1 It exhibits good cycle stability and is a highly efficient photocatalyst. Attached Figure Description

[0034] Figure 1 This is a scanning electron microscope image of the TpBD-COF material prepared in Example 1 of this invention;

[0035] Figure 2 This is a scanning electron microscope image of the BiOBr material prepared in Example 1 of the present invention;

[0036] Figure 3 This is a scanning electron microscope image of the BiOBr / TpBD-COF composite material prepared in Example 1 of the present invention;

[0037] Figure 4 The attached diagram shows the nitrogen adsorption-desorption of the TpBD-COF, BiOBr materials, and BiOBr / TpBD-COF composite materials prepared in Example 1 of this invention.

[0038] Figure 5 The powder X-ray diffraction patterns of the TpBD-COF, BiOBr materials and BiOBr / TpBD-COF composite materials prepared in Example 1 of this invention are shown below.

[0039] Figure 6 Fourier transform infrared spectra of the TpBD-COF, BiOBr materials and BiOBr / TpBD-COF composite materials prepared in Example 1 of this invention;

[0040] Figure 7 The UV-Vis diffuse reflectance spectra of the TpBD-COF, BiOBr materials, and BiOBr / TpBD-COF composite materials prepared in Example 1 of this invention are shown below.

[0041] Figure 8 The fluorescence spectra of the TpBD-COF, BiOBr materials, and BiOBr / TpBD-COF composite materials prepared in Example 1 of this invention are shown below.

[0042] Figure 9The graphs show the photocatalytic water splitting hydrogen production rates of the TpBD-COF and BiOBr materials prepared in Example 1 and the BiOBr / TpBD-COF composite materials prepared in Examples 1-4 of this invention.

[0043] Figure 10 The image shows the photocatalytic hydrogen production cycle stability of the BiOBr / TpBD-COF composite material prepared in Example 1 of this invention. Detailed Implementation

[0044] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0045] The following disclosure provides numerous different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples. Such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. Additionally, examples of various specific processes and materials are provided, but those skilled in the art will recognize the reusability of other processes and / or the use of other materials.

[0046] The purpose of this invention is to provide a BiOBr / TpBD-COF composite material and its preparation method. Specifically, the first aspect of this invention provides a BiOBr / TpBD-COF composite material, which is obtained by solvothermal growth of more stable BiOBr (bismuth oxybromide) nanosheets from Cs3Bi2Br9 (cesium tribismuth dibromonin) onto TpBD-COF. The TpBD-COF material exhibits a flower-like structure, with its petals being plate-like and uniformly dispersed. The plate-like BiOBr has a diameter of 63-93 nm and a thickness of 33-47 nm.

[0047] The BiOBr / TpBD-COF composite material provided in this embodiment combines BiOBr and TpBD-COF materials, which can improve the redox capacity, efficient separation and migration rate of photogenerated carriers, thereby significantly improving photocatalytic performance. The photocatalytic water splitting hydrogen production rate reaches 16.17 mmol·g -1 ·h -1 It exhibits good cycle stability and is a highly efficient photocatalyst.

[0048] A second aspect of the present invention provides a method for preparing a BiOBr / TpBD-COF composite material, the method comprising the following steps:

[0049] Step S1: Preparation of TpBD-COF:

[0050] S1.1: After mixing trialdehyde phloroglucinol and benzidine, add mesitylene and 1,4-dioxane solvent, and sonicate for a certain time to obtain a uniformly dispersed mixture;

[0051] The molar ratio of the added trialdehyde phloroglucinol and benzidine is 1:(1.3-1.7); the volume ratio of the added mesitylene and 1,4-dioxane is 1:(0.8-1.2); the mass-volume ratio of the monomer mixture to the solvent can be 41-58 mg / mL; and the ultrasonic time can be 10-20 min.

[0052] S1.2: Add acetic acid solution to the obtained mixture and sonicate for a certain time to completely dissolve it, thus obtaining a homogeneous solution;

[0053] The concentration of the acetic acid solution can be 2-4 mol / L, and the ultrasonic time can be 5-10 min; the mass-to-volume ratio of the monomer mixture to the acetic acid solution can be 225-393 mg / mL; and the volume of the acetic acid solution can be 0.8-1.2 mL.

[0054] S1.3: The homogeneous solution is rapidly frozen in a liquid nitrogen bath, and after three freezing, vacuum thawing, and degassing cycles, it is vacuum sealed and then kept warm in an oven for a certain period of time. The precipitate obtained from the reaction is washed multiple times to obtain a brownish-yellow product.

[0055] The heat preservation temperature can be 100-140℃, the heat preservation time can be 48-96h, the detergent used for washing can be one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, dimethyl sulfoxide or acetone, and the number of washing cycles can be 6-10.

[0056] S1.4: Dry the brownish-yellow product for a certain period of time, then grind it to obtain TpBD-COF.

[0057] The drying method can be one or more of the following: forced air drying, vacuum drying, and spray drying; the drying temperature can be 60-100℃; and the drying time can be 10-14h.

[0058] Step S2, Preparation of Cs3Bi2Br9:

[0059] S2.1: Cesium bromide (CsBr) and bismuth bromide (BiBr3) were added to dimethyl sulfoxide (DMSO) respectively. Isopropanol was added while stirring continuously at room temperature. After stirring for a certain period of time, the yellow precipitate formed was collected by centrifugation.

[0060] The molar ratio of cesium bromide to bismuth bromide is 1:(1.3-1.7), the volume ratio of dimethyl sulfoxide to isopropanol is 1:(4-6), and the stirring time can be 1-3 hours.

[0061] S2.2: Wash the yellow precipitate three times with isopropanol, dry it for a certain period of time, and grind it to obtain Cs3Bi2Br9 powder.

[0062] The drying method can be one or more of the following: forced air drying, vacuum drying, and spray drying; the drying temperature can be 60-100℃; and the drying time can be 10-14h.

[0063] Step S3, Preparation of BiOBr nanosheets:

[0064] S3.1: Disperse potassium bromide in deionized water and sonicate to obtain a homogeneous potassium bromide solution;

[0065] S3.2: Dissolve bismuth nitrate pentahydrate powder in ethylene glycol and stir for a certain time to obtain a homogeneous bismuth nitrate pentahydrate solution;

[0066] The mass-to-volume ratio of bismuth nitrate pentahydrate to ethylene glycol can be 19-32 mg / mL; the volume of ethylene glycol is 15-25 mL; and the stirring time is 10-20 min.

[0067] S3.3: The potassium bromide solution is added dropwise to the bismuth nitrate pentahydrate solution, and the mixture is stirred for a certain period of time to obtain a mixed solution;

[0068] The molar ratio of potassium bromide to bismuth nitrate pentahydrate is 1:(0.8-1.2), and the stirring time can be 10-30 min.

[0069] S3.4: Transfer the mixed solution to a reaction vessel, heat for a certain time, centrifuge to collect the precipitate, wash it three times with deionized water and ethanol respectively, dry it for a certain time, and grind it to obtain BiOBr nanosheets.

[0070] The heating temperature can be 100-140℃, and the heating time can be 4-8h; the drying method can be one or more of the following: forced air drying, vacuum drying, and spray drying; the drying temperature can be 40-80℃, and the drying time can be 10-14h.

[0071] Step S4, Preparation of BiOBr / TpBD-COF composite material:

[0072] S4.1: Cs3Bi2Br9 powder was mixed with trialdehyde phloroglucinol and benzidine, then mesitylene and 1,4-dioxane solvent were added, and the mixture was sonicated for a certain time to obtain a uniformly dispersed mixture.

[0073] The Cs3Bi2Br9 powder comprises 5%-20% by mass; the molar ratio of the trialdehyde phloroglucinol to benzidine is 1:(1.3-1.7); the volume ratio of the mesitylene to 1,4-dioxane is 1:(0.8-1.2); the mass-volume ratio of the monomer mixture to the solvent is 41-58 mg / mL; and the ultrasonic time can be 10-20 min.

[0074] S4.2: Add acetic acid solution to the mixture and sonicate for a period of time to completely dissolve it, thereby obtaining a homogeneous solution;

[0075] The acetic acid solution has a concentration of 2-4 mol / L and an ultrasonic time of 5-10 min; the mass-to-volume ratio of the monomer mixture to the acetic acid solution is 225-393 mg / mL; and the volume of the acetic acid solution is 0.8-1.2 mL.

[0076] S4.3: The homogeneous solution is rapidly frozen in a liquid nitrogen bath, and after three freezing, vacuum thawing, and degassing cycles, it is vacuum sealed and then kept warm in an oven for a certain period of time. The precipitate obtained from the reaction is washed multiple times to obtain a brownish-yellow product.

[0077] The heat preservation temperature can be 100-140℃, the heat preservation time can be 48-96h, the detergent used for washing can be one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, dimethyl sulfoxide or acetone, and the number of washing cycles can be 6-10.

[0078] S4.4: Dry the brownish-yellow product for a certain period of time, and then grind it to obtain the BiOBr / TpBD-COF composite material.

[0079] The drying method can be one or more of the following: forced air drying, vacuum drying, and spray drying; the drying temperature can be 60-100℃; and the drying time can be 10-14h.

[0080] The preparation method of the BiOBr / TpBD-COF composite material provided in this invention is simple to operate, low in cost, and has good reproducibility. Furthermore, the process flow is simple and suitable for large-scale industrial production. The BiOBr / TpBD-COF composite material prepared by this invention, by combining BiOBr and TpBD-COF materials, can improve the redox capacity, efficient separation and migration rate of photogenerated carriers, thereby significantly improving photocatalytic performance. The photocatalytic water splitting hydrogen production rate reaches 16.17 mmol·g⁻¹. -1 ·h -1 It exhibits good cycle stability and is a highly efficient photocatalyst.

[0081] The following detailed description, in conjunction with some specific embodiments, further illustrates the specific process and effects of the preparation method of the BiOBr / TpBD-COF composite material of the present invention, but does not limit the scope of protection of the present invention.

[0082] Example 1

[0083] This embodiment provides a method for preparing BiOBr / TpBD-COF composite material, the preparation method including the following steps:

[0084] Step S1, Preparation of TpBD-COF:

[0085] S1.1: First, mix 126 mg of trialdehyde phloroglucinol and 166 mg of benzidine monomer in a 100 mL Parker heat pipe, add 3 mL of mesitylene and 3 mL of 1,4-dioxane mixed solvent, and sonicate for 15 min to obtain a uniformly dispersed mixture.

[0086] S1.2: Add 1 mL of 3 mol / L acetic acid solution to the obtained mixture, and sonicate for 5 min to completely dissolve it, thus obtaining a homogeneous solution;

[0087] S1.3: The homogeneous solution was rapidly frozen in a liquid nitrogen bath at 77K, and after three freezing, vacuum thawing, and degassing cycles, it was vacuum sealed and then kept in an oven at 120℃ for 72h. The precipitate obtained from the reaction was washed three times each with N,N-dimethylformamide and acetone to obtain a brownish-yellow product.

[0088] S1.4: The brownish-yellow product is dried under vacuum at 80°C for 12 hours and then ground to obtain TpBD-COF powder.

[0089] Step S2, Preparation of Cs3Bi2Br9:

[0090] S2.1: Add 415.6 mg CsBr and 583.2 mg BiBr3 to 40 mL of dimethyl sulfoxide (DMSO), add 200 mL of isopropanol while stirring continuously at room temperature, continue stirring for 2 h, and collect the yellow precipitate formed by centrifugation at 6000 rpm for 5 min.

[0091] S2.2: The yellow precipitate was washed three times with isopropanol, dried under vacuum at 80°C for 12 hours, and then ground to obtain Cs3Bi2Br9 powder.

[0092] Step S3, Preparation of BiOBr nanosheets:

[0093] S3.1: Disperse 119.1 mg of potassium bromide in 10 mL of deionized water and sonicate to obtain a homogeneous potassium bromide solution;

[0094] S3.2: Dissolve 485.3 mg of bismuth nitrate pentahydrate powder in 20 mL of ethylene glycol and stir for 15 min to obtain a homogeneous bismuth nitrate pentahydrate solution;

[0095] S3.3: Add the potassium bromide solution dropwise to the bismuth nitrate pentahydrate solution and continue stirring for 20 minutes to obtain a mixed solution;

[0096] S3.4: Transfer the mixed solution to a 50 mL reaction vessel, heat at 120 °C for 6 h, centrifuge at 6000 rpm for 5 min to collect the precipitate, wash three times with deionized water and ethanol respectively, dry under vacuum at 60 °C for 12 h, and grind to obtain BiOBr nanosheets.

[0097] Step S4, Preparation of BiOBr / TpBD-COF composite material:

[0098] S4.1: Mix 32.4 mg Cs3Bi2Br9 powder with 126 mg trialdehyde phloroglucinol and 166 mg benzidine in a Parker heat pipe, add 3 mL of mesitylene and 3 mL of 1,4-dioxane mixed solvent, and sonicate for 15 min to obtain a uniformly dispersed mixture;

[0099] S4.2: Add 1 mL of 3 mol / L acetic acid solution to the mixture and sonicate for 5 min to completely dissolve it, obtaining a homogeneous solution;

[0100] S4.3: The homogeneous solution was rapidly frozen in a liquid nitrogen bath at 77K, and after three freezing, vacuum thawing, and degassing cycles, it was vacuum sealed and then kept in an oven at 120℃ for 72h. The precipitate obtained from the reaction was washed three times each with N,N-dimethylformamide and acetone to obtain a brownish-yellow product.

[0101] S4.4: The brownish-yellow product is dried under vacuum at 80°C for 12 hours and then ground to obtain the BiOBr / TpBD-COF composite material (named 10% BiOBr / TpBD-COF).

[0102] Figure 1 This is a scanning electron microscope (SEM) image of the TpBD-COF material prepared in step S1 of this embodiment. From... Figure 1 It can be seen that TpBD-COF has a flower-like structure, and its petals are plate-like and evenly distributed.

[0103] Figure 2 This is a scanning electron microscope (SEM) image of the BiOBr material prepared in step S3 of Example 1 of this embodiment. From... Figure 2 As can be seen, BiOBr nanomaterials are obtained by the aggregation of nanosheets, with a diameter of about 78 nm, a thickness of about 40 nm, and a rough surface.

[0104] Figure 3 This is a scanning electron microscope (SEM) image of the BiOBr / TpBD-COF composite material prepared in step S4 of Example 1. Figure 4 As can be seen, sheet-like BiOBr grows on the flower-like TpBD-COF surface, thus synthesizing a BiOBr / TpBD-COF composite material.

[0105] Figure 4 The accompanying diagram shows the nitrogen adsorption-desorption of the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials prepared in Example 1. N2 adsorption and desorption experiments were conducted on the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials obtained in Example 1 at 77 K. The specific surface areas of the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials were 213.9 m², respectively. 2 ·g -1 213.9m 2 ·g -1 and 239.9m 2 ·g -1 According to BET results, TpBD-COF has a large specific surface area, which can provide many active sites, thus promoting photocatalytic hydrogen production. The BiOBr / TpBD-COF composite material has a slightly larger specific surface area than TpBD-COF, and can also provide more active sites, making it even more conducive to photocatalytic hydrogen production.

[0106] Figure 5The powder X-ray diffraction patterns are shown for the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials prepared in Example 1. TpBD-COF exhibits XRD diffraction peaks at 3.4° and 5.9°, which can be attributed to its (100) and (200) crystal planes, respectively. The small, broad peak at 27.4° corresponds to the (001) crystal plane and can be attributed to the π-π interlayer stacking of TpBD-COF. Furthermore, the BiOBr nanomaterial exhibits high crystallinity, with peaks at 10.9°, 25.1°, 31.7°, 32.2°, 39.4°, 46.2°, and 57.1°, respectively, belonging to the (001), (101), (102), (110), (112), (200), and (212) crystal planes of BiOBr. The above diffraction peaks were observed in the BiOBr / TpBD-COF composite material, indicating that the BiOBr / TpBD-COF composite material was successfully synthesized by the solvothermal method.

[0107] Figure 6 The Fourier transform infrared spectra of the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials prepared in Example 1 are shown. The BiOBr / TpBD-COF composite material exhibits similar characteristic absorption peaks to TpBD-COF, at 1567 and 1250 cm⁻¹. -1 Two distinct peaks appeared at this point, which are attributed to the C=C and CN stretching bands, respectively.

[0108] Figure 7 The images show the UV-Vis diffuse reflectance spectra of the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials prepared in Example 1. The BiOBr / TpBD-COF composite material has similar absorption peak positions to TpBD-COF, with the absorption edge of the BiOBr / TpBD-COF composite material around 615 nm, resulting in a band gap of 2.02 eV. The BiOBr nanosheets have an absorption edge around 440 nm and a band gap of 2.82 eV.

[0109] Figure 8 The images show the fluorescence spectra of the TpBD-COF, BiOBr, and BiOBr / TpBD-COF composite materials prepared in Example 1. At an excitation wavelength of 350 nm, the PL peak intensity of the BiOBr / TpBD-COF composite material is the weakest compared to TpBD-COF and BiOBr, indicating that the introduction of BiOBr effectively suppresses the recombination of photogenerated charges in the BiOBr / TpBD-COF composite material, thus facilitating the migration of photogenerated carriers.

[0110] Example 2

[0111] The difference between Example 2 and Example 1 lies only in step S4. In step S4, 15.4 mg of Cs3Bi2Br9 powder, 126 mg of trialdehyde-based phloroglucinol, and 166 mg of benzidine monomer are mixed in a Parker heat pipe. 3 mL of mesitylene and 3 mL of 1,4-dioxane mixed solvent are added, and the mixture is sonicated for 15 min to obtain a uniformly dispersed mixture. 1 mL of a 3 mol / L acetic acid solution is added to the resulting mixture, and the mixture is sonicated for 5 min to completely dissolve it. The resulting uniform solution is rapidly frozen in a 77 K liquid nitrogen bath. After three freezing-evacuation-thawing cycles and degassing, the mixture is vacuum-sealed and then kept in a 120 °C oven for 72 h. The resulting precipitate is washed three times each with N,N-dimethylformamide and acetone to obtain a brownish-yellow product. The brownish-yellow product is then vacuum-dried at 80 °C for 12 h and ground to obtain the BiOBr / TpBD-COF composite material (named 5% BiOBr / TpBD-COF).

[0112] Example 3

[0113] The difference between Example 3 and Example 1 lies only in step S4. In step S4, 51.5 mg of Cs3Bi2Br9 powder, 126 mg of trialdehyde-based phloroglucinol, and 166 mg of benzidine monomer are mixed in a Parker heat pipe. 3 mL of mesitylene and 3 mL of 1,4-dioxane mixed solvent are added, and the mixture is sonicated for 15 min to obtain a uniformly dispersed mixture. 1 mL of a 3 mol / L acetic acid solution is added to the resulting mixture, and the mixture is sonicated for 5 min to completely dissolve it. The resulting uniform solution is rapidly frozen in a 77 K liquid nitrogen bath. After three freezing-evacuation-thawing cycles and degassing, the mixture is vacuum-sealed and then kept in a 120 °C oven for 72 h. The resulting precipitate is washed three times each with N,N-dimethylformamide and acetone to obtain a brownish-yellow product. The brownish-yellow product is then vacuum-dried at 80 °C for 12 h and ground to obtain the BiOBr / TpBD-COF composite material (named 15% BiOBr / TpBD-COF).

[0114] Example 4

[0115] The difference between Example 4 and Example 1 lies only in step S4. In step S4, 73 mg of Cs3Bi2Br9 powder, 126 mg of trialdehyde-based phloroglucinol, and 166 mg of benzidine monomer are mixed in a Parker heat pipe. 3 mL of mesitylene and 3 mL of 1,4-dioxane mixed solvent are added, and the mixture is sonicated for 15 min to obtain a uniformly dispersed mixture. 1 mL of a 3 mol / L acetic acid solution is added to the resulting mixture, and the mixture is sonicated for 5 min to completely dissolve it. The resulting homogeneous solution is rapidly frozen in a 77 K liquid nitrogen bath. After three freezing-evacuation-thawing cycles and degassing, the mixture is vacuum-sealed and then kept in a 120 °C oven for 72 h. The resulting precipitate is washed three times each with N,N-dimethylformamide and acetone to obtain a brownish-yellow product. This brownish-yellow product is then vacuum-dried at 80 °C for 12 h and ground to obtain the BiOBr / TpBD-COF composite material (named 20% BiOBr / TpBD-COF).

[0116] The photocatalytic performance differences between the TpBD-COF and BiOBr materials prepared in Example 1 and the BiOBr / TpBD-COF composite materials prepared in Examples 1-4 were compared: 10 mg of powder samples (TpBD-COF and BiOBr materials prepared in Example 1 and the BiOBr / TpBD-COF composite materials prepared in Examples 1-4), 0.95 g of ascorbic acid, and 3% Pt were dispersed in 100 mL of aqueous solution. After ultrasonic dispersion for 30 min, the samples were placed in a photocatalytic reaction vessel and continuously stirred. The circulating cooling water temperature was maintained at 6 °C, and a 300 W xenon lamp with a 420 nm cutoff filter was used as the light source for continuous illumination. Pt deposition was performed under illumination for 30 min, followed by evacuation using a vacuum pump until the reaction system was in a near-vacuum state (P ≤ 1.0 kPa). Every 1 h, gas was extracted from the reaction vessel using an autosampler and sent to a gas chromatograph. The gas chromatograph detected the gas in real time online, and the reaction products and their amounts were determined based on the peak position and peak area. After 4 hours of testing, the hydrogen production instrument and xenon lamp were turned off, and the reaction ended.

[0117] Figure 9 The graph shows the photocatalytic water splitting hydrogen production rate of the TpBD-COF and BiOBr materials prepared in Example 1, and the BiOBr / TpBD-COF composite materials prepared in Examples 1-4. Figure 9 As can be seen, under the same illumination conditions, the photocatalytic water splitting hydrogen production rates of the materials show significant differences. Specifically, the hydrogen production rate of pure TpBD-COF is 5.18 mmol·g⁻¹. -1 ·h -1BiOBr materials generally exhibit no hydrogen production performance, but when TpBD-COF is loaded with BiOBr, the hydrogen production rate of the BiOBr / TpBD-COF composite material is significantly improved. In particular, the hydrogen production rate of the composite material in Example 1 reaches a maximum of 16.17 mmol·g. -1 ·h -1 The performance is 3.1 times that of pure TpBD-COF material, demonstrating excellent photocatalytic hydrogen production performance. The photocatalytic water splitting hydrogen production rates of the BiOBr / TpBD-COF composite materials prepared in Examples 1-4 are shown in Table 1 below:

[0118] Table 1: Photocatalytic water splitting hydrogen production rate of BiOBr / TpBD-COF composite materials with different mass percentages

[0119]

[0120]

[0121] In addition, the BiOBr / TpBD-COF composite material sample prepared in Example 1 was repeated four times in the above photocatalytic water splitting hydrogen production experiment, and its cycle stability was as follows: Figure 10 As shown in the figure. The results show that the photocatalytic hydrogen production performance of the BiOBr / TpBD-COF composite material did not decrease significantly, indicating that the BiOBr / TpBD-COF composite material has good cycle stability.

[0122] In summary, the preparation method of the BiOBr / TpBD-COF composite material provided in this invention is simple to operate, low in cost, and has good reproducibility. Furthermore, the process flow is simple and suitable for large-scale industrial production. The BiOBr / TpBD-COF composite material prepared by this invention, by combining BiOBr and TpBD-COF materials, can improve the redox capacity of the composite material, the efficient separation and migration rate of photogenerated carriers, thereby significantly improving photocatalytic performance. The photocatalytic water splitting hydrogen production rate reaches 16.17 mmol·g⁻¹. -1 ·h -1 It exhibits good cycle stability and is a highly efficient photocatalyst.

[0123] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0124] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for preparing a BiOBr / TpBD-COF composite material, characterized in that, The preparation method includes: Step S1, Preparation of Cs3Bi2Br9: S1.1: Cesium bromide and bismuth bromide were added to dimethyl sulfoxide, and isopropanol was added while stirring continuously at room temperature. After stirring for a certain period of time, the yellow precipitate was collected by centrifugation. S1.2: The yellow precipitate was washed three times with isopropanol, dried for a certain period of time, and then ground to obtain Cs3Bi2Br9 powder; Step S2, Preparation of BiOBr / TpBD-COF composite material: S2.1: Cs3Bi2Br9 powder was mixed with monomeric trialdehyde phloroglucinol and benzidine, and then mesitylene and 1,4-dioxane solvent were added. After sonication for a certain time, a uniformly dispersed mixture was obtained. S2.2: Add acetic acid solution to the mixture and sonicate for a period of time to completely dissolve it, thereby obtaining a homogeneous solution; S2.3: The homogeneous solution is rapidly frozen in a liquid nitrogen bath, and after three freezing, vacuum thawing, and degassing cycles, it is vacuum sealed and then kept warm in an oven for a certain period of time. The precipitate obtained from the solvothermal reaction is washed multiple times to obtain a brownish-yellow product. S2.4: Dry the brownish-yellow product for a certain period of time, and then grind it to obtain the BiOBr / TpBD-COF composite material.

2. The preparation method of the BiOBr / TpBD-COF composite material according to claim 1, characterized in that, In step S1, the molar ratio of cesium bromide to bismuth bromide is 1:(1.3-1.7), the volume ratio of dimethyl sulfoxide to isopropanol is 1:(4-6), and the stirring time is 1-3 h; the drying method is one or more of forced air drying, vacuum drying, and spray drying, the drying temperature is 60-100 ℃, and the drying time is 10-14 h.

3. The method for preparing the BiOBr / TpBD-COF composite material according to claim 1, characterized in that, In step S2.1, the mass percentage of the Cs3Bi2Br9 powder is 5%-20%; the molar ratio of the added trialdehyde phloroglucinol and benzidine is 1:(1.3-1.7); the volume ratio of the added mesitylene and 1,4-dioxane is 1:(0.8-1.2); and the ultrasonic time is 10-20 min. In step S2.2, the concentration of the acetic acid solution is 2-4 mol / L, and the ultrasonic time is 5-10 min; the mass-to-volume ratio of the mixture to the acetic acid solution is 225-393 mg / mL.

4. The method for preparing the BiOBr / TpBD-COF composite material according to claim 1, characterized in that, In step S2.3, the heat preservation temperature is 100-140℃, the heat preservation time is 48-96 h, and the detergent used for washing is one or a combination of N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylformamide, dimethyl sulfoxide or acetone, and the number of washing cycles is 6-10.

5. The method for preparing the BiOBr / TpBD-COF composite material according to claim 1, characterized in that, In step S2.4, the drying method is one or more of the following: forced air drying, vacuum drying, and spray drying; the drying temperature is 60-100℃; and the drying time is 10-14h.

6. A BiOBr / TpBD-COF composite material prepared by any one of the preparation methods according to claims 1-5, characterized in that, The BiOBr / TpBD-COF composite material is obtained by generating BiOBr nanosheets from Cs3Bi2Br9 via a solvothermal method, and then growing the BiOBr nanosheets on TpBD-COF. The TpBD-COF has a flower-like structure with petals that are plate-like and uniformly dispersed. The BiOBr nanosheets have a diameter of 63-93 nm and a thickness of 33-47 nm.

Images