A COF-C4N / NH2-Bi2O3 composite photocatalyst and its preparation method and application

Abstract

The application discloses a COF-C4N / NH2-Bi2O3 composite photocatalyst and a preparation method and application thereof, and belongs to the technical field of photocatalysts. The application prepares a composite catalyst COF-C4N / NH2-Bi2O3, and the preparation method is simple, efficient and easy to operate, and has practical application significance. The composite photocatalyst is prepared by in-situ growth of COF-C4N on the interface of Bi2O3 surface modified with amino groups, can effectively promote charge separation, significantly improves the photocatalytic degradation performance, and the degradation rate of 2-chlorophenol (2-cp) is 94.1% under xenon lamp (780nm>lambda>350nm) irradiation for 3.5h, and the maximum degradation rate constant is 0.1091min ‑1 , and the composite catalyst COF-C4N / NH2-Bi2O3 prepared by the application has excellent degradation stability.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of photocatalysts, in particular to a COF-C4N / NH2-Bi2O3 composite photocatalyst and a preparation method and application thereof. BACKGROUND

[0002] Chlorophenols are important chemical raw materials, are raw materials for industrial production, and have been widely used in commercial scale of herbicides, pharmaceutical intermediates, wood preservatives and pesticides. Chlorophenols have corrosive and toxic properties, are ubiquitous and accumulated in aquatic environments, and are harmful to human skin, eyes and respiratory systems, which prompts researchers to use solar-driven technology of high-efficiency photocatalysts for green remediation. Constructing a heterojunction photocatalyst system is one of the effective ways to realize solar-driven decomposition of chlorophenol pollutants, and effective light-induced charge separation is crucial for realizing high photocatalytic activity for degrading organic pollutants.

[0003] Covalent organic frameworks (COFs) are crystalline solids composed of strong covalent bonds connecting organic monomers, are porous framework materials, have the advantages of large specific surface area, low skeleton density, strong stability, programmable structure, high carrier transport rate and the like. The framework structure of COFs and the crystalline characteristics similar to nano-carbon materials can carry sufficient active sites and accurately control the coordination environment thereof.

[0004] Among many semiconductor metal oxides, beta-Bi2O3 exhibits high photocatalytic activity due to its narrow band gap, low energy level and good optical response characteristics. Can be used for degrading organic matter, but the catalytic degradation performance is poor. SUMMARY

[0005] The purpose of the present application is to provide a COF-C4N / NH2-Bi2O3 composite photocatalyst and a preparation method and application thereof, so as to solve the problems existing in the prior art.

[0006] To achieve the above purpose, the present application provides the following solutions:

[0007] The present application provides a composite photocatalyst for chlorophenol degradation, which is a COF-C4N / NH2-Bi2O3 composite photocatalyst.

[0008] The present application also provides a preparation method of the composite photocatalyst, comprising the following steps:

[0009] (1) dispersing amino surface modified NH2-Bi2O3, hexakishoxocyclohexane octahydrate and acetic acid in a mixed solution, and then adding triphenylene-2,3,6,7,10,11-hexamine hexahydrate and ultrasonic reaction;

[0010] (2) The dispersion liquid obtained in step (1) is degassed by freeze-thawing and dried by baking after nitrogen purging and vacuumizing, to obtain a crude product;

[0011] (3) The crude product is purified by filtration and washing, to obtain the composite photocatalyst.

[0012] Preferably, the amino surface-modified NH2-Bi2O3 is prepared by dispersing β-Bi2O3 in an ethanol solution of 3-aminopropyltriethylsilane for 30 min under ultrasonic irradiation, and then stirring for 24 h, and washing the dispersion with anhydrous ethanol and drying at 80 ℃ for 12 h.

[0013] Preferably, the ratio of the amino surface-modified NH2-Bi2O3, hexaketocyclohexane octahydrate and acetic acid is 100 mg:25 mg:0.5 mL.

[0014] Preferably, the mass ratio of the triphenylene-2,3,6,7,10,11-hexaamine hexahydrochloride to the amino-functionalized Bi2O3-NH2 is 25.5:100.

[0015] Preferably, the concentration of the acetic acid is 4 M.

[0016] Preferably, the mixed solution comprises mesitylene and 1,4-dioxane.

[0017] Preferably, the drying temperature is 150 ℃, and the drying time is 72 h.

[0018] Preferably, the filtration and washing are performed using tetrahydrofuran.

[0019] Preferably, the purification is performed by Soxhlet extraction using tetrahydrofuran until the effluent liquid is colorless, and then drying the obtained solid product at 100 ℃ under vacuum for 24 h, to obtain the COF-C4N / NH2-Bi2O3 composite photocatalyst.

[0020] The application also provides use of the composite photocatalyst in preparing a product for degrading chlorophenol.

[0021] Preferably, the chlorophenol comprises 2-chlorophenol.

[0022] The application also provides a product for degrading chlorophenol, comprising the composite photocatalyst.

[0023] The application also provides a method for degrading chlorophenol, which uses the composite photocatalyst or the product to perform photocatalytic degradation treatment on chlorophenol in a water environment.

[0024] Based on the above technical solution, the application has the following technical effects:

[0025] The application prepares a composite catalyst COF-C4N / NH2-Bi2O3, and the preparation method is simple, efficient and easy to operate, and has practical application significance. The composite photocatalyst is prepared by in-situ growth of COF-C4N on the interface of the amino surface modified Bi2O3, which can effectively promote charge separation, thereby significantly improving the photocatalytic degradation performance. The degradation rate of 2-chlorophenol (2-cp) is 94.1% under xenon lamp (780nm>lambda>350nm) irradiation for 3.5h, and the maximum degradation rate constant is 0.1091min -1 , and the composite catalyst COF-C4N / NH2-Bi2O3 prepared by the application has excellent degradation stability. BRIEF DESCRIPTION OF DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0027] Figure 1 XRD patterns of COF-C4N, Bi2O3 and COF-C4N / NH2-Bi2O3;

[0028] Figure 2 Infrared spectra of COF-C4N, NH2-Bi2O3 and COF-C4N / NH2-Bi2O3;

[0029] Figure 3 UV-Vis absorption spectra of COF-C4N, Bi2O3 and COF-C4N / NH2-Bi2O3; wherein a is an absorption spectrum, and b is a band gap energy diagram;

[0030] Figure 4 Scanning electron microscope images and transmission electron microscope images of the COF-C4N / NH2-Bi2O3-2 composite catalyst; wherein a is a scanning electron microscope image of COF-C4N / NH2-Bi2O3-2, and b, c and d are transmission electron microscope images of COF-C4N / NH2-Bi2O3-2;

[0031] Figure 5 Electrochemical impedance diagrams of COF-C4N, Bi2O3 and COF-C4N / NH2-Bi2O3;

[0032] Figure 6Figure 4 is a degradation dynamic curve and a linear kinetic simulation curve of the photocatalytic degradation of o-chlorophenol by the composite photocatalyst COF-C4N / NH2-Bi2O3 under visible light; wherein a is the degradation dynamic curve, b is the linear kinetic simulation curve, and c is the degradation rate graph;

[0033] Figure 7 Figure 5 is a degradation dynamic curve and a linear kinetic simulation curve of the photocatalytic degradation of o-chlorophenol by the composite photocatalyst COF-C4N / NH2-Bi2O3 under full light range; wherein a is the degradation dynamic curve, b is the linear kinetic simulation curve, and c is the degradation rate graph;

[0034] Figure 8 Figure 6 is a degradation dynamic curve of the photocatalytic degradation of o-chlorophenol and other phenols by the composite photocatalyst COF-C4N / NH2-Bi2O3-2 under visible light; wherein a is a degradation dynamic curve of the photocatalytic degradation of o-chlorophenol and other phenols by the composite photocatalyst COF-C4N / NH2-Bi2O3-2 under visible light, and b is a degradation dynamic curve of the photocatalytic degradation of o-chlorophenol and other phenols by the composite photocatalyst COF-C4N / NH2-Bi2O3-2 under full light range.

[0035] Figure 9 Figure 7 is a photocatalytic degradation dynamic curve of the composite catalyst COF-C4N / NH2-Bi2O3-2 after 4 cycles. DETAILED DESCRIPTION

[0036] The following detailed description of various example embodiments of the application is not intended to limit the scope of the application, but rather to provide a detailed description of certain aspects, features and embodiments of the application.

[0037] It should be understood that the terms used herein are merely descriptive, but are not intended to limit the application. In addition, for numerical ranges in the present application, it should be understood that every intermediate value between the upper limit and the lower limit of the range is specifically disclosed. Each intermediate value within any stated value or stated range, as well as any other stated value or intermediate value within the stated range, is also included in the present application. The upper limit and the lower limit of these smaller ranges can be included or excluded independently.

[0038] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, the preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the content of the present specification will control.

[0039] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples given are exemplary only.

[0040] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean inclusion, but not limited to, the listed material or list of materials.

[0041] The technical solutions of the present application, if not specifically stated, are the conventional solutions in the art, and the reagents or raw materials used, if not specifically stated, are purchased from commercial channels or are already disclosed.

[0042] Example 1

[0043] 1. Preparation of COF-C4N / NH2-Bi2O3 composite photocatalyst

[0044] 1.1 Bi2O3 was prepared by direct calcination method. 4 mmol of Bi(NO3)3·5H2O was dissolved in 20 mL of dilute nitric acid solution (1 M), and ultrasonic treatment was performed to make it clear. Then 6 mmol of sodium oxalate was added, and ultrasonic treatment was performed for 1 h. Then vacuum suction filtration was performed, and the filtered product was washed with distilled water and ethanol, and then vacuum dried at 60°C for 12 h to obtain a white powder. After drying, the sample was placed in a tube furnace, the heating rate was 10°C / min, and the temperature was raised to 270°C, and then kept in air for 4 h. After natural cooling, a bright yellow powder β-Bi2O3 was obtained.

[0045] 1.2 The β-Bi2O3 was dispersed in an ethanol solution of 3-aminopropyltriethylsilane for 30 min, and then stirred for 24 h. The dispersion was washed with anhydrous ethanol, and dried at 80°C for 12 h to obtain NH2-Bi2O3 after surface modification of the amino group.

[0046] 1.3 The amino surface modified NH2-Bi2O3 (100 mg) and 25 mg hexaketone cyclohexane octahydrate and 0.5 mL of 4M acetic acid were mixed and dispersed in a mixed solution of 1.5 mL mesitylene and 1.5 mL 1,4-dioxane, and then ultrasonicated (42 KHz) for 30 min and stirred (1000 R / min) for 2 h, after which 25.5 mg of triphenylene-2,3,6,7,10,11-hexaamine hexahydrochloride was added, and ultrasonicated (42 KHz) for 1 h. The dispersion was transferred to a PEX tube, and after nitrogen purging and vacuuming, degassing was performed using freeze-thaw, repeated three times; the degassed dispersion was placed in an oven at 150 °C and reacted for 72 h, and after the oven temperature returned to room temperature, the test tube was removed, and a crude reaction product was obtained; the crude reaction product was filtered and washed with tetrahydrofuran, and after natural air drying, a brown-black solid product was obtained; the solid product was subjected to Soxhlet extraction with tetrahydrofuran until the effluent liquid was colorless; the obtained solid product was vacuum dried at 100 °C for 24 h, and a COF-C4N / NH2-Bi2O3 composite photocatalyst (COF-C4N / NH2-Bi2O3-2) was obtained.

[0047] Comparative Example 1

[0048] The difference from Example 1 is that in step 1.3, the mass of the amino surface modified Bi2O3-NH2 is 50 mg, and the remaining steps are the same as Example 1, and finally a COF-C4N / NH2-Bi2O3 composite photocatalyst (COF-C4N / NH2-Bi2O3-1) is obtained.

[0049] Comparative Example 2

[0050] The difference from Example 1 is that in step 1.3, the mass of the amino surface modified Bi2O3-NH2 is 150 mg, and the remaining steps are the same as Example 1, and finally a COF-C4N / NH2-Bi2O3 composite photocatalyst (COF-C4N / NH2-Bi2O3-3) is obtained.

[0051] Example 2

[0052] 1. The COF-C4N / NH2-Bi2O3 composite photocatalysts COF-C4N / NH2-Bi2O3-1, COF-C4N / NH2-Bi2O3-2 and COF-C4N / NH2-Bi2O3-3 prepared in Example 1 and Comparative Examples 1-2 were subjected to XRD, infrared spectroscopy, UV-Vis absorption spectroscopy and electron microscopy analysis.

[0053] 2. Photocatalytic performance test:

[0054] To investigate the photocatalytic activity of the samples, phenol (cp), 2-chlorophenol (2-cp), 3-chlorophenol (3-cp), 4-chlorophenol (4-cp), and 2,4-dichlorophenol (2,4-dcp) were degraded under irradiation with a 300W xenon lamp (filter cutoff wavelength 420nm). 20mg of the synthesized sample was placed in 30mL of a 10ppm 2-cp reaction solution. The pH was not adjusted and the mixture was stirred in the dark for 30 minutes. After reaching adsorption equilibrium, the lamp was turned on and samples were collected every 30 minutes. The concentration of 2-cp was determined using a UV-visible spectrophotometer (UV-1200).

[0055] The pollutant removal rate calculation formula is:

[0056] Removal rate (%) = (1-C t / C0)×100%;

[0057] Among them, C t is the pollutant concentration at time t, and C0 is the initial pollutant concentration.

[0058] 3. Result analysis:

[0059] 3.1 XRD spectra of COF-C4N, Bi2O3 and COF-C4N / NH2-Bi2O3-2 Figure 1 As shown in the figure, the characteristic diffraction peaks of Bi2O3 at 28.05°, 32.75°, and 46.25° correspond to the (201)(220)(222) crystal planes of Bi2O3, which correspond to the standard card. This proves that the tetragonal phase of Bi2O3 was successfully synthesized. COF-C4N / NH2-Bi2O3-2 shows the (001) crystal plane corresponding to the diffraction peak of COF-C4N at 27°, and the (201) crystal plane represented by Bi2O3 at 28.05°, which proves the successful synthesis of the composite material.

[0060] 3.2 Infrared spectra of COF-C4N, NH2-Bi2O3 and Bi2O3 / COF-C4N-2 Figure 2 As shown in the figure, it can be observed that 3421.84cm -1 、2850cm -1 、1620cm -1 、1450cm -1 and 1310cm -1 The vibration peaks at 3415 cm-1 in NH2-Bi2O3 correspond to NH, CH, CC, C=C and CH3 in COF-C4N, respectively. -1 ,1664cm -1The vibration peak of COF-C4N and Bi2O3 is retained in the COF-C4N / NH2-Bi2O3 material, and the vibration peak of NH is weakened, which proves that COF-C4N / NH2-Bi2O3-2 is successfully synthesized.

[0061] 3.3 UV-Vis absorption spectra of COF-C4N, Bi2O3 and COF-C4N / NH2-Bi2O3 are shown in Figure 3. Figure 3 As shown in the figure, Bi2O3 can absorb some visible light. The COF-C4N / NH2-Bi2O3 composite photocatalyst has the mixed absorption characteristics of COF-C4N and Bi2O3, which enhances visible light absorption and broadens the visible light absorption range. Calculations show that all composite photocatalysts have smaller band gaps, indicating that the synthesized composite photocatalyst absorbs visible light more efficiently than pure Bi2O3.

[0062] 3.4Scanning electron microscope images and transmission electron microscope images of COF-C4N / NH2-Bi2O3-2 composite catalyst are shown in Figure 3. Figure 4 As shown in Figure (a), it can be clearly seen that COF-C4N is distributed on the flaky Bi2O3. (b)-(d) are transmission electron microscope images of the composite material COF-C4N / NH2-Bi2O3-2. The interface between Bi2O3 and COF-C4N is clear, and there is interfacial interaction, which helps electrons to transmit between the two, proving that the composite material was successfully synthesized.

[0063] 3.5 The electrochemical impedance spectroscopy of COF-C4N, Bi2O3 and COF-C4N / NH2-Bi2O3 is shown in Figure 2. Figure 5 As shown in the figure, compared with pure COF-C4N and Bi2O3 electrodes, the arc radius of the EIS curve of the COF-C4N / NH2-Bi2O3-2 electrode is smaller, indicating that the formation of the composite photocatalyst COF-C4N / NH2-Bi2O3 heterojunction can effectively enhance electronic conductivity, accelerate charge transfer, and thus improve the photocatalytic performance.

[0064] 3.6 The degradation dynamic curve of o-chlorophenol by composite photocatalyst COF-C4N / NH2-Bi2O3 under visible light and the kinetic linear simulation curve are as follows Figure 6 As shown in the figure, the composite photocatalyst COF-C4N / NH2-Bi2O3-2 sample has the highest photocatalytic activity. After irradiation with a xenon lamp (780nm>λ>420nm) for 3.5h, the degradation rate of 2-cp can reach 71.4%, which is 1.79 times that of pure Bi2O3. In addition, by using the first-order reaction kinetic equation ln(C tThe fitting of degradation 2-cp kinetic curves of different samples can obtain the rate constant k value. The maximum degradation rate constant of 2-cp on the COF-C4N / NH2-Bi2O3-2 sample is 0.0054 min -1 , which is 2.84 times of pure Bi2O3. These results all show that the composite of COF-C4N / NH2-Bi2O3 heterojunction can effectively improve the photocatalytic degradation performance.

[0065] 3.7 The degradation dynamic curve of the composite photocatalyst COF-C4N / NH2-Bi2O3 in the full light range and the kinetic linear simulation curve of photocatalytic degradation of o-chlorophenol are as shown in Figure 7 , wherein the photocatalytic activity of the composite photocatalyst COF-C4N / NH2-Bi2O3-2 sample is the highest, and the degradation rate of 2-cp reaches 94.1% after 3.5h of xenon lamp (780nm>λ>350nm) irradiation, and the maximum degradation rate constant is 0.1091 min -1 .

[0066] 3.8 The degradation dynamic curve of the composite photocatalyst COF-C4N / NH2-Bi2O3-2 in the visible light range (780nm>λ>420nm) and the degradation dynamic curve of the composite photocatalyst COF-C4N / NH2-Bi2O3-2 in the full light range (780nm>λ>350nm) photocatalytic degradation of o-chlorophenol and other phenols are as shown in Figure 8 , and the results show that the composite photocatalyst COF-C4N / NH2-Bi2O3-2 has different degrees of degradation on cp, 3-cp, 4-cp, 2, 4-dcp, and the degradation effect on 2-cp and 2, 4-dcp is the best, and the degradation effect on other phenols is the second.

[0067] 3.9 The photocatalytic degradation dynamic curve of the composite catalyst COF-C4N / NH2-Bi2O3-2 is as shown in Figure 9 , and the loss of the sample after 4 cycles is very small, which shows that the composite catalyst COF-C4N / NH2-Bi2O3-2 prepared by the present application has excellent degradation stability.

[0068] In summary, the present application prepares a composite catalyst COF-C4N / NH2-Bi2O3-2, and the preparation method is simple, efficient and easy to operate, and has practical application significance. The composite photocatalyst prepared by in-situ growth of COF-C4N on the interface of the amino surface modified Bi2O3 can effectively promote charge separation, thereby significantly improving the photocatalytic degradation performance, and the degradation rate of 2-cp reaches 94.1% after 3.5h of xenon lamp (780nm>λ>350nm) irradiation, and the maximum degradation rate constant is 0.1091 min-1 The composite catalyst COF-C4N / NH2-Bi2O3-2 prepared by the application has excellent degradation stability.

[0069] Obviously, the above embodiments of the application are merely exemplary and are not intended to limit the embodiments of the application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. It is not necessary or possible to exhaust all the embodiments. Any modification, equivalent replacement and improvement made within the spirit and principle of the application shall be included in the protection scope of the claims of the application.

Claims

1. A composite photocatalyst for the degradation of chlorophenol, characterized in that: The composite photocatalyst is a COF-C4N / NH2-Bi2O3 composite photocatalyst; The preparation method thereof comprises the following steps: (1) dispersing amino-surface-modified NH2-Bi2O3, hexaketone cyclohexane octahydrate, and acetic acid in a mixed solution, ultrasonically stirring, and then adding triphenylene-2,3,6,7,10,11-hexamine hexahydrochloride for ultrasonic reaction; (2) The dispersion obtained in step (1) was purged with nitrogen and vacuumed, and then degassed and dried by freeze-thaw to obtain a crude product; (3) The crude product is filtered, washed and purified to obtain the composite photocatalyst.

2. The composite photocatalyst according to claim 1, characterized in that The preparation method of the amino surface-modified NH2-Bi2O3 is as follows: dispersing β-Bi2O3 in an ethanol solution of 3-aminopropyltriethylsilane and ultrasonicating for 30 minutes, then stirring for 24 hours, washing the dispersion with anhydrous ethanol, and drying at 80°C for 12 hours.

3. The composite photocatalyst according to claim 1, characterized in that The ratio of the amino-surface-modified NH2-Bi2O3, hexaketone cyclohexane octahydrate and acetic acid is 100 mg:25 mg:0.5 mL.

4. The composite photocatalyst according to claim 3, characterized in that The mass ratio of the triphenylene-2,3,6,7,10,11-hexamine hexahydrochloride to the amino-surface-modified NH2-Bi2O3 is 25.5:

100.

5. Use of the composite photocatalyst according to claim 1 in preparing a product for degrading chlorophenol.

6. The use according to claim 5, characterized in that The chlorophenol includes 2-chlorophenol.

7. A product for degrading chlorophenol, characterized in that: Comprising the composite photocatalyst according to claim 1.

8. A method for degrading chlorophenol, characterized in that: The composite photocatalyst according to claim 1 or the product according to claim 7 is used to photocatalytically degrade chlorophenol in an aqueous environment.

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