S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material as well as preparation method and application thereof
By preparing the S-type covalent organic frame-carbon nitride nanosheet composite material, the heterojunction and built-in electric field are used to promote the separation of photogenerated electrons and holes, the problems of high cost and low efficiency of traditional photocatalysts in photocatalyst production of hydrogen peroxide are solved, and efficient and low-cost photocatalytic production is achieved.
Patent Information
- Application Number
- CN202510558371.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-29
- Publication Date
- 2025-08-01
AI Technical Summary
In the prior art, the method of photocatalyzing hydrogen peroxide production is expensive, has high energy consumption and is unfriendly in the environment. Traditional photocatalysts have limitations in charge separation efficiency and spectral response range.
By preparing the S-type covalent organic frame-carbon nitride nanosheet composite material, a heterojunction is formed with the carbon nitride nanosheets. The covalent organic frame is used as an oxidation photocatalyst and carbon nitride is used as a reducing photocatalyst. Combined with the built-in electric field and Fermi energy level differences, the separation of photogenerated electrons and holes is promoted and photocatalytic activity is enhanced.
It improves the efficiency of photocatalytic hydrogen peroxide production, increases the specific surface area and active sites, is simple to operate, is cheap to raw materials, and has good industrial production prospects.
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Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of photocatalytic material synthesis, and particularly relates to an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material, a preparation method thereof, and an application thereof. Background Art
[0002] Due to its excellent oxidizing property and the non-polluting decomposition products, hydrogen peroxide has significant advantages in industrial production and daily life fields. However, the traditional anthraquinone method for preparing hydrogen peroxide has disadvantages such as high cost, excessive energy consumption, and environmental unfriendliness. Therefore, the photocatalytic production of hydrogen peroxide technology with the advantages of low cost, high energy source, and environmental friendliness has come into people's view.
[0003] As an organic polymer semiconductor material, carbon nitride has advantages such as low cost, good chemical stability, and a suitable band gap (2.7 eV), and it has excellent visible light absorption performance in the visible light range. Covalent organic frameworks have advantages such as excellent structural designability, rich porosity, large specific surface area, and good crystallinity. Through precise design strategies, researchers can regulate key parameters such as its topological structure, pore size, and functional group distribution, endowing the material with a customizable energy band structure, high specific surface area, and rich active sites. The excellent structural designability enables covalent organic frameworks to break through the limitations of traditional photocatalysts in terms of charge separation efficiency, surface reaction kinetics, and spectral response range. In addition, the relatively negative conduction band position of carbon nitride also provides sufficient conditions for the oxygen reduction reaction to generate hydrogen peroxide, and it is expected to form an S-type heterojunction with covalent organic frameworks as a reducing semiconductor to solve the problem of low utilization rate of photo-generated carriers in single materials. Summary of the Invention
[0004] The technical problem to be solved by the present invention is to provide an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material, a preparation method thereof, and an application thereof in view of the above deficiencies existing in the prior art.
[0005] A preparation method of an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material includes the following steps: S1. Prepare carbon nitride nanosheets; S2. Disperse the carbon nitride nanosheets in an aqueous hydrochloric acid solution, stir ultrasonically at room temperature, and then successively perform filtration, washing, and freeze-drying treatments to obtain acidified carbon nitride nanosheets; S3. Preparation of covalent organic frameworks: Disperse phloroglucinol trialdehyde and 2,5-diaminobenzenesulfonic acid in a mixed solution of mesitylene and 1,4-dioxane, add an aqueous acetic acid solution, place the reaction system under oil bath conditions for reaction, and after the reaction is completed, wash and dry the reaction product to obtain covalent organic frameworks; S4. Preparation of covalent organic framework-carbon nitride nanosheet composite photocatalytic material: Ultrasonically disperse the covalent organic framework in absolute ethanol, add the carbon nitride nanosheets obtained in step S2, and then, after ultrasonic treatment, stirring, centrifugation and drying in sequence, obtain the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material.
[0006] Further, in step S1, the steps for preparing the carbon nitride nanosheets are as follows: Calcinate, grind and disperse melamine in sequence, and then obtain the carbon nitride nanosheets by freeze-drying; Among them, the mass of the melamine is 5-10 mg; The calcination conditions are calcination at 500-600 °C for 2-4 h in an air atmosphere, and the heating rate is 5 °C / min; The dispersion is ultrasonic dispersion treatment, and the time condition for dispersion is 3-6 h; The time condition for freeze-drying is 24-36 h.
[0007] Further, in step S2, the mass of the carbon nitride nanosheets is 200-1000 mg; The concentration of the hydrochloric acid aqueous solution is 1-3 M; The time condition for ultrasonic stirring is 2-6 h.
[0008] Further, in step S3, in terms of molar ratio, phloroglucinol trialdehyde: 2,5-diaminobenzenesulfonic acid = 2:3; The volume ratio of mesitylene to 1,4-dioxane is 1:1; The concentration of the acetic acid aqueous solution is 6-12 M, and the volume is 0.3 mL; The temperature condition for the oil bath reaction is 80-120 °C, and the time condition is 48-72 h.
[0009] Further, in step S3, the washing process is to wash successively with tetrahydrofuran, N,N-dimethylformamide and ethanol.
[0010] Further, in step S4, in terms of mass ratio, carbon nitride nanosheets: covalent organic framework = 1-8:10; The time condition for ultrasonic treatment is 30-60 min; The time condition for stirring is 2-6 h.
[0011] The S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material obtained by the above preparation method.
[0012] The above-mentioned S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is composed of cross-linked carbon nitride nanosheets and covalent organic frameworks, wherein the carbon nitride nanosheets and the covalent organic frameworks form an S-type heterojunction.
[0013] For the above-mentioned S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material, the mass ratio of the carbon nitride nanosheets to the covalent organic frameworks is 1-4:5; the carbon nitride has a sheet-like structure.
[0014] Application of the above-mentioned S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in photocatalytic production of hydrogen peroxide.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material provided by the present invention, sulfonic acid groups are introduced into the covalent organic framework. The strong built-in electric field and closed hydrogen bond network constructed by the sulfonic acid groups promote the migration of charges and enhance the surface redox reaction. In addition, the covalent organic framework and the carbon nitride nanosheets are cross-linked to form a porous network, increasing the specific surface area of the composite material, increasing the number of photocatalytic reaction active sites, and further improving the efficiency of photocatalytic production of hydrogen peroxide.
[0016] 2. In the photocatalytic material of the present invention, the covalent organic framework and the carbon nitride nanosheets form an S-type heterojunction. The covalent organic framework serves as an oxidative photocatalyst, and the carbon nitride serves as a reductive photocatalyst. The reductive photocatalyst has a higher Fermi level than the oxidative photocatalyst. After the two are combined, due to the difference in Fermi level, electrons from the reductive photocatalyst are transferred to the oxidative photocatalyst. Driven by the band bending and the built-in electric field, photo-generated holes will accumulate in the valence band of the oxidative photocatalyst, while photo-generated electrons will remain in the conduction band of the reductive photocatalyst. Therefore, the S-type heterojunction can promote the separation of photo-generated electrons and holes and is suitable for photocatalytic production of hydrogen peroxide.
[0017] 3. In the preparation method of the present invention, the covalent organic framework-carbon nitride nanosheet composite photocatalytic material is prepared by a simple electrostatic self-assembly method. The operation of the present invention is simple, the raw materials are inexpensive, no complex equipment is required, and the product is safe and non-toxic. Therefore, it has good industrial production prospects. Description of the Drawings
[0018] Figure 1 It is a transmission electron microscope photograph of the carbon nitride nanosheet photocatalytic material prepared in Comparative Example 1 of the present invention; Figure 2 It is a transmission electron microscope photograph of the covalent organic framework-carbon nitride nanosheet composite photocatalytic material prepared in Example 1 of the present invention; Figure 3X-ray diffraction patterns of the materials prepared in Example 1 and Comparative Examples 1 and 2 of the present invention; Figure 4 UV-Vis diffuse reflectance absorption spectra of the materials prepared in Example 1 and Comparative Examples 1 and 2 of the present invention; Figure 5 Photocatalytic hydrogen peroxide production performance diagrams of the materials prepared in Example 1 and Comparative Examples 1 and 2 of the present invention. Detailed implementation manners
[0019] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings. For those not specified in the examples in terms of specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications. For the reagents or instruments not specified in terms of the manufacturer, they are all conventional products that can be obtained through commercial purchases.
[0020] The first object of the present invention is to provide an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material. This photocatalytic material forms an S-type heterojunction through electrostatic self-assembly between the covalent organic framework and the carbon nitride nanosheets. The mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1-8:10. Preferably, the mass ratio is 1-4:5. Among them, the covalent organic framework has sulfonic acid groups, and the carbon nitride nanosheets are in a sheet-like structure.
[0021] The second object of the present invention is to provide a preparation method for the above-mentioned S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material, and the steps are as follows: 1) Preparation of carbon nitride nanosheets: Add melamine to a covered crucible, and obtain a pale yellow solid after calcination using a muffle furnace. After thoroughly grinding the solid, disperse the above powder in deionized water, and after intense ultrasonic treatment, obtain carbon nitride nanosheets through freeze-drying.
[0022] In this step, the mass of the melamine is 5-10 mg; the calcination conditions of the muffle furnace are calcination at 500-600 °C for 2-4 h in an air atmosphere, and the heating rate is 5 °C / min; the ultrasonic time condition is 3-6 h. When the mass of melamine is too much, it may cause incomplete conversion to carbon nitride. Preferably, the mass of the melamine is 5-7 mg, the calcination conditions of the muffle furnace are 550-600 °C in an air atmosphere, the calcination time is 3-4 h, the ultrasonic time is 4-6 h, the ultrasonic power is 100-500 W, and the ultrasonic power density is 1-5 W / cm 2 .
[0023] 2) Preparation of acidified carbon nitride nanosheets: The prepared carbon nitride nanosheets were dispersed in an aqueous hydrochloric acid solution, sonicated and vigorously stirred at room temperature, with a stirring speed of 300 - 800 revolutions per minute. Subsequently, the excess aqueous hydrochloric acid solution was filtered off, and the sample was thoroughly washed with deionized water until neutral, and then freeze-dried to obtain acidified carbon nitride nanosheets.
[0024] In this step, the mass of the carbon nitride was 200 - 1000 mg, the concentration of the aqueous hydrochloric acid solution was 1 - 3 M, and the condition of the vigorous stirring time was 2 - 6 h. When the mass of the carbon nitride was too large, the acidification effect would decline, and the change in the Zeta potential on the surface of the carbon nitride was small. Preferably, the mass of the carbon nitride was 400 - 600 mg, the concentration of the aqueous hydrochloric acid solution was 1 - 2 M, and the condition of the vigorous stirring time was 4 - 6 h.
[0025] 3) Preparation of covalent organic frameworks: Phloroglucinol trialdehyde and 2,5-diaminobenzenesulfonic acid were dispersed in a mixed solution of mesitylene and 1,4-dioxane. After the monomers were fully dispersed, they were transferred to a reactor, an aqueous acetic acid solution was added, and then the reactor was frozen with liquid nitrogen, the device was evacuated and purged with nitrogen, and then the device was reacted under oil bath conditions. After the reaction was completed, the sample was washed successively with tetrahydrofuran, N,N-dimethylformamide and ethanol, and dried to obtain covalent organic frameworks.
[0026] In this step, the molar ratio of phloroglucinol trialdehyde to 2,5-diaminobenzenesulfonic acid was 2:3. The volume ratio of mesitylene to 1,4-dioxane was 1:1, the volume and concentration of the aqueous acetic acid solution were 0.3 mL and 6 - 12 M respectively, the temperature condition of the oil bath reaction was 80 - 120 °C, and the time condition was 48 - 72 h. Preferably, the concentration of the aqueous acetic acid solution was 6 M, and the time condition of the oil bath reaction was 72 h.
[0027] 4) Preparation of covalent organic framework-carbon nitride nanosheet composite photocatalytic material: The covalent organic framework was ultrasonically dispersed in absolute ethanol, and then the acidified carbon nitride nanosheets were added to the above suspension. After ultrasonic treatment, stirring was continued to obtain a homogeneous suspension. Finally, the excess ethanol was removed by centrifugation, and the covalent organic framework-carbon nitride nanosheet composite photocatalytic material was obtained after vacuum drying.
[0028] In this step, the mass ratio of the acidified carbon nitride nanosheets to the covalent organic framework was 1 - 8:10, the ultrasonic treatment time condition was 30 - 60 min, and the stirring time condition was 2 - 6 h. Preferably, the mass ratio of the acidified carbon nitride nanosheets to the covalent organic framework was 1 - 4:5, the ultrasonic treatment time condition was 30 min, and the stirring time condition was 4 - 6 h.
[0029] The third object of the present invention is to provide the application of the above-mentioned covalent organic framework-carbon nitride nanosheet composite photocatalytic material in photocatalytic production of hydrogen peroxide.
[0030] Comparative Example 1 The preparation method of carbon nitride nanosheets is as follows: Melamine is added to a covered crucible and calcined in a muffle furnace at 600 °C for 3 h to obtain a pale yellow solid. After the solid is thoroughly ground, the above powder is dispersed in deionized water, and after intense ultrasonic treatment for 4 h, carbon nitride nanosheets are obtained by freeze-drying. Among them, the mass of the melamine is 5 mg.
[0031] Figure 1 This is the transmission electron microscope photograph of the carbon nitride nanosheet photocatalytic material prepared in Comparative Example 1. From Figure 1 it can be seen that the carbon nitride presents a special sheet-like structure.
[0032] Comparative Example 2 The preparation method of the covalent organic framework is as follows: Phloroglucinol trialdehyde and 2,5-diaminobenzenesulfonic acid are dispersed in a mixed solution of mesitylene and 1,4-dioxane; after the monomers are fully dispersed, they are transferred to a reactor, acetic acid aqueous solution is added, and then the reactor is frozen with liquid nitrogen, the device is evacuated and purged with nitrogen, and then the device is reacted in an oil bath at 80 °C for 72 h; after the reaction is completed, the sample is washed with tetrahydrofuran, N,N-dimethylformamide and ethanol, and dried to obtain the covalent organic framework; among them, the molar ratio of phloroglucinol trialdehyde to 2,5-diaminobenzenesulfonic acid is 2:3, the volume ratio of mesitylene to 1,4-dioxane is 1:1, and the volume and concentration of the acetic acid aqueous solution are 0.3 mL and 6 M respectively.
[0033] Example 1 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material includes the following steps: 1) Preparation of carbon nitride nanosheets: Melamine is added to a covered crucible and calcined in a muffle furnace at 600 °C for 3 h to obtain a pale yellow solid, and the heating rate is 5 °C / min; after the solid is thoroughly ground, the above powder is dispersed in deionized water, and after intense ultrasonic treatment for 4 h, carbon nitride nanosheets are obtained by freeze-drying. Among them, the mass of the melamine is 5 mg.
[0034] 2) Preparation of acidified carbon nitride nanosheets: The prepared carbon nitride nanosheets were dispersed in an aqueous hydrochloric acid solution, sonicated and vigorously stirred at room temperature for 4 h, and then the excess aqueous hydrochloric acid solution was filtered off. The sample was thoroughly washed with deionized water until neutral and freeze-dried for 24 h to obtain acidified carbon nitride nanosheets. Among them, the mass of the carbon nitride nanosheets was 500 mg, and the concentration of the aqueous hydrochloric acid solution was 1.5 M.
[0035] 3) Preparation of covalent organic frameworks: Phloroglucinol trialdehyde and 2,5-diaminobenzenesulfonic acid were dispersed in a mixed solution of mesitylene and 1,4-dioxane. After the monomers were fully dispersed, they were transferred to a reactor, an aqueous acetic acid solution was added, and then the reactor was frozen with liquid nitrogen, and the device was evacuated and purged with nitrogen. Subsequently, the device was reacted in an oil bath at 120 °C for 72 h. After the reaction was completed, the sample was washed with tetrahydrofuran, N,N-dimethylformamide, and ethanol and dried to obtain covalent organic frameworks. Among them, the molar ratio of phloroglucinol trialdehyde to 2,5-diaminobenzenesulfonic acid was 2:3, the volume ratio of mesitylene to 1,4-dioxane was 1:1, and the volume and concentration of the aqueous acetic acid solution were 0.3 mL and 6 M, respectively.
[0036] 4) Preparation of covalent organic framework-carbon nitride nanosheet composite photocatalytic material: The covalent organic framework was ultrasonically dispersed in absolute ethanol, and then acidified carbon nitride was added to the above suspension and sonicated for 30 min. The ultrasonic power was 300 W, and the ultrasonic power density was 3 W / cm 2 . After continuing to stir for 4 h under the condition that the stirring speed was 500 revolutions per minute, a uniform suspension was obtained. Finally, the excess ethanol was removed by centrifugation, and the covalent organic framework-carbon nitride nanosheet composite photocatalytic material was obtained after vacuum drying for 12 h. Among them, the mass ratio of the carbon nitride nanosheets to the covalent organic framework was 3:5.
[0037] Figure 2 This is the transmission electron microscope photograph of the covalent organic framework-carbon nitride nanosheet composite photocatalytic material prepared in Example 1. Figure 2 It can be clearly seen the carbon nitride and covalent organic framework components in the composite material. Among them, the covalent organic framework presents a rod shape, and the carbon nitride nanosheets present a sheet shape.
[0038] Figure 3 This is the X-ray diffraction pattern of the materials obtained in Example 1 (CG60), Comparative Example 1 (GCN), and Comparative Example 2 (COF). The characteristic diffraction peaks of carbon nitride and covalent organic frameworks simultaneously appear in the covalent organic framework-carbon nitride nanosheet composite photocatalytic material, confirming the successful synthesis of the composite material. (In the figure, the composite material is abbreviated as CG60, the carbon nitride nanosheets are abbreviated as GCN, and the covalent organic frameworks are abbreviated as COF) Figure 4 The UV-Vis diffuse reflectance absorption spectra of the materials obtained in Example 1 (CG60), Comparative Example 1 (GCN), and Comparative Example 2 (COF) are shown. It can be seen from the figure that after constructing the heterojunction photocatalyst with carbon nitride and covalent organic framework, the light absorption in the visible light region is enhanced.
[0039] Photocatalytic hydrogen peroxide production test: The photocatalytic hydrogen peroxide production experiment was carried out in a sealed 100 mL glass flask filled with oxygen. A 300 W xenon lamp with a wavelength range of 320 - 780 nm was used as the light source. First, 10 mg of the sample was dispersed in 40 mL of 10 vol% aqueous ethanol solution. Before irradiation, the suspension was purged with O2 for 30 min to achieve O2 saturation. During the photocatalytic hydrogen peroxide production process, 1 mL of the solution was extracted from the solution every 15 min and filtered through a 0.45 μm filter to obtain a transparent solution. Subsequently, 1 mL of 0.1 M potassium hydrogen phthalate and 1 mL of 0.4 M potassium iodide aqueous solution were added, and the mixture was allowed to stand for 30 min. The concentration of hydrogen peroxide was measured using a UV spectrophotometer.
[0040] Among them, the hydrogen peroxide production activity of the photocatalyst was calculated by the following formula:
[0041] Figure 5 The performance comparison diagram of photocatalytic hydrogen peroxide production of the materials obtained in Example 1 (CG60), Comparative Example 1 (GCN), and Comparative Example 2 (COF) is shown. It can be seen from the figure that the covalent organic framework-carbon nitride nanosheet composite photocatalyst exhibits the best performance, and the hydrogen peroxide production rate is 1.15 mmol g −1 h −1 。
[0042] Example 2 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences, and other preparation conditions are the same: In step 1), the material was calcined in a muffle furnace for 6 h and ultrasonically treated for 6 h.
[0043] In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5, the ultrasonic power is 100 W, and the ultrasonic power density is 1 W / cm 2 。
[0044] Example 3 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences, and other preparation conditions are the same: In step 1), the material is calcined in a muffle furnace at 550 °C for 2 h; In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5, the ultrasonic power is 500 W, and the ultrasonic power density is 5 W / cm 2 .
[0045] Example 4 The preparation method of the present S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 2), the mass of the carbon nitride is 600 mg; the concentration of the hydrochloric acid aqueous solution is 1 M.
[0046] In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5, the ultrasonic power is 500 W, and the ultrasonic power density is 5 W / cm 2 , and the stirring speed is 800 revolutions per minute.
[0047] Example 5 The preparation method of the present S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 2), the mass of the carbon nitride is 400 mg; the concentration of the hydrochloric acid aqueous solution is 1 M.
[0048] In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5, the ultrasonic power is 100 W, and the ultrasonic power density is 1 W / cm 2 , and the stirring speed is 800 revolutions per minute.
[0049] Example 6 The preparation method of the present S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 2), the mass of the carbon nitride is 600 mg; the concentration of the hydrochloric acid aqueous solution is 1 M.
[0050] In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5, the ultrasonic power is 100 W, and the ultrasonic power density is 1 W / cm 2 , and the stirring speed is 100 revolutions per minute.
[0051] Example 7 The preparation method of the present S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 3), the temperature condition of the oil bath reaction is 80 °C.
[0052] In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5.
[0053] Example 8 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences: In step 3), the concentration of the acetic acid aqueous solution is 12 M; In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5.
[0054] Example 9 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences: In step 3), the time of the oil bath reaction is 48 h; In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5.
[0055] Example 10 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences: In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5.
[0056] Example 11 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences: In step 3), the temperature condition of the oil bath reaction is 80 °C; In step 4), the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 2:5.
[0057] Example 12 The preparation method of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material in this example is the same as that in Example 1 except for the following differences: In step 4), the vigorous stirring time is 6 h, the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 2:5, and the stirring speed is 800 revolutions per minute.
[0058] Example 13 The preparation method of this S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 4), the vigorous stirring time is 6 h, the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 4:5, and the stirring speed is 100 revolutions per minute.
[0059] Example 14 The preparation method of this S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 2), the mass of the carbon nitride is 600 mg; the concentration of the hydrochloric acid aqueous solution is 1 M; In step 3), the time of the oil bath reaction is 48 h; In step 4), the vigorous stirring time is 6 h, and the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 1:5.
[0060] Example 15 The preparation method of this S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 2), the mass of the carbon nitride is 600 mg; the concentration of the hydrochloric acid aqueous solution is 1 M; In step 3), the time of the oil bath reaction is 48 h; In step 4), the vigorous stirring time is 6 h, and the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 2:5.
[0061] Example 16 The preparation method of this S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material is the same as that of Example 1 except for the following differences, and other preparation conditions are the same: In step 2), the mass of the carbon nitride is 600 mg; the concentration of the hydrochloric acid aqueous solution is 1 M; In step 3), the time of the oil bath reaction is 48 h; In step 4), the vigorous stirring time is 6 h, and the mass ratio of the carbon nitride nanosheets to the covalent organic framework is 4:5.
[0062] For those not mentioned above, the prior art shall apply.
[0063] Although some specific embodiments of the present invention have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and not for limiting the scope of the present invention. Those skilled in the technical field to which the present invention pertains can make various modifications or supplements to the described specific embodiments or use similar means for substitution, but will not deviate from the direction of the present invention or exceed the scope defined by the appended claims. Those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. made to the above embodiments based on the technical essence of the present invention should all be included within the protection scope of the present invention.
Claims
1. A preparation method of an S-shaped covalent organic framework-carbon nitride nanosheet composite photocatalytic material, characterized in that, It includes the following steps: S1. Prepare carbon nitride nanosheets; S2. Disperse the carbon nitride nanosheets in an aqueous hydrochloric acid solution, perform ultrasonic stirring at room temperature, and then successively perform filtration, washing, and freeze-drying treatments to obtain acidified carbon nitride nanosheets; S3. Preparation of covalent organic frameworks: Disperse phloroglucinol trialdehyde and 2,5-diaminobenzenesulfonic acid in a mixed solution of mesitylene and 1,4-dioxane, add an aqueous acetic acid solution, place the reaction system under oil bath conditions for reaction, and after the reaction ends, wash and dry the reaction product to obtain covalent organic frameworks; S4. Prepare a covalent organic framework-carbon nitride nanosheet composite photocatalytic material: Ultrasonically disperse the covalent organic framework in absolute ethanol, add the carbon nitride nanosheets obtained in step S2, and then successively perform ultrasonic treatment, stirring, centrifugation, and drying to prepare an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material.
2. The preparation method of an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 1, characterized in that, In step S1, the steps for preparing carbon nitride nanosheets are as follows: Calcinate melamine, then grind and disperse it, and finally perform freeze-drying to obtain carbon nitride nanosheets; Among them, the mass of the melamine is 5-10 mg; The calcination conditions are calcination at 500-600 °C for 2-4 h in an air atmosphere, and the heating rate is 5 °C / min; The dispersion is ultrasonic dispersion treatment, and the dispersion time condition is 3-6 h; The freeze-drying time condition is 24-36 h.
3. The preparation method of an S-shaped covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 1, characterized in that, In step S2, the mass of the carbon nitride nanosheets is 200-1000 mg; The concentration of the aqueous hydrochloric acid solution is 1-3 M; The ultrasonic stirring time condition is 2-6 h.
4. The preparation method of an S-shaped covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 1, characterized in that, In step S3, in terms of molar ratio, phloroglucinol trialdehyde:2,5-diaminobenzenesulfonic acid = 2:3; The volume ratio of the mesitylene to the 1,4-dioxane is 1:1; The concentration of the aqueous acetic acid solution is 6-12 M, and the volume is 0.3 mL; The temperature condition of the oil bath reaction is 80-120 °C, and the time condition is 48-72 h.
5. The preparation method of an S-shaped covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 1, characterized in that, In step S3, the washing process is to wash successively with tetrahydrofuran, N,N-dimethylformamide, and ethanol.
6. The preparation method of an S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 1, characterized in that, In step S4, in terms of mass ratio, carbon nitride nanosheets:covalent organic framework = 1-8:10; The ultrasonic treatment time condition is 30-60 min; The stirring time condition is 2-6 h.
7. An S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material obtained by the preparation method according to any one of claims 1-6.
8. The S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 7, wherein This composite photocatalytic material is composed of carbon nitride nanosheets and covalent organic frameworks crosslinked with each other, wherein the carbon nitride nanosheets and the covalent organic frameworks form an S-type heterojunction.
9. The S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 8, characterized in that, The mass ratio of the carbon nitride nanosheets to the covalent organic frameworks is 1-4:5; the carbon nitride has a flaky structure.
10. Application of the S-type covalent organic framework-carbon nitride nanosheet composite photocatalytic material according to claim 9 in photocatalytic production of hydrogen peroxide.