Co-CN photocatalyst based on ZIF-L derivative and preparation method and application thereof

Abstract

The application belongs to the technical field of photocatalytic material preparation, and particularly relates to a Co-CN photocatalyst based on ZIF-L derivation and a preparation method and application thereof. The application uses melamine, dimethyl imidazole and cobalt nitrate as raw materials, and utilizes water bath heating, program temperature control and vacuum calcination to synthesize a CN composite photocatalytic material modified by Co monatomic derived from zeolite imidazolate framework structure material (ZIF-L). The application has the advantages of simple process, convenient operation, low cost, non-toxicity, harmlessness, short reaction time and the like. The prepared photocatalytic material has excellent photocatalytic degradation performance on tetracycline in a water environment. When the photocatalytic material is applied to removal of tetracycline pollutants in water, the removal efficiency is improved while energy consumption and reaction cost are reduced, and the application is green, environmentally friendly and meets the environmental friendly requirements.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic material preparation technology, specifically relating to a ZIF-L-derived Co-CN photocatalyst, its preparation method, and its application. Background Technology

[0002] The increasingly serious environmental pollution problem severely hinders the green and sustainable development of modern society. In particular, the rapid economic growth and rapid urbanization and industrialization of recent decades have led to the discharge of large amounts of organic waste (such as dyes, pharmaceuticals, aromatic hydrocarbons, and other persistent organic compounds) into water bodies, seriously harming the ecological environment and human health. Furthermore, according to the "Global Antimicrobial Resistance Review" report, large amounts of antibiotics enter surface water bodies through effluent, thereby polluting groundwater and drinking water. When antibiotics in water reach a certain concentration, they will affect the dynamic balance of bacterial populations, promote the spread of antibiotic resistance, and lead to chronic poisoning and carcinogenic, teratogenic, and mutagenic effects in pathogenic bacteria, posing a potential threat to aquatic life and human health. If effective measures are not taken, by 2050, 10 million people worldwide will die annually as a result, with a GDP loss of $100 trillion. Therefore, developing highly efficient semiconductor photocatalysts and their practical application in water pollution treatment is a major current challenge.

[0003] The tertiary amine-linked tri-s-triazine framework structure and strong interlayer van der Waals forces in graphitic carbon nitride (g-C3N4, CN) endow it with excellent heat resistance and chemical stability. Furthermore, its suitable redox potential and simple preparation process make it an ideal candidate for degrading organic pollutants in environmental wastewater. However, single CN still suffers from problems such as rapid charge recombination and a limited number of catalytically active sites, leading to unsatisfactory photocatalytic degradation effects. In recent years, constructing CN-based composite systems has effectively improved the separation efficiency of photogenerated electron-hole pairs and enhanced catalytic activity, considered an effective way to improve the efficiency of semiconductor photocatalytic degradation. Composite catalysts such as CoZnAl-LDH / RGO / CN, ZnIn2S4 / CN, and Co3O4@Au / CN all exhibit strong photocatalytic activity. In addition, research on CN modification using metal single atoms has received widespread attention. Studies have shown that metal single atoms not only serve as reactive sites but also generate localized surface plasmon resonance effects, significantly improving visible light absorption and carrier separation efficiency, thus enhancing photocatalytic performance. However, to date, no research has been reported on CN composite photocatalysts modified with Co metal single atoms based on zeolite imidazole ester framework (ZIF-L) for wastewater treatment. Summary of the Invention

[0004] In view of this, in order to solve one of the above-mentioned technical problems, the present invention provides a ZIF-L-derived Co-CN photocatalyst, its preparation method, and its application. The present invention uses melamine, dimethylimidazole, and cobalt nitrate as raw materials, and utilizes water bath heating, programmed temperature-controlled vacuum calcination, and thermal shock methods to prepare and synthesize a single-atom Co-modified CN composite photocatalyst (Co-CN) with excellent performance. The synthesis process is simple and rapid, and the prepared Co-CN photocatalyst can remove tetracycline from wastewater under simulated sunlight and visible light of a fixed wavelength.

[0005] The above-mentioned objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for preparing a ZIF-L-derived Co-CN photocatalyst, the method comprising the following steps:

[0007] (1) After grinding the melamine evenly, place it in a programmed temperature muffle furnace and gradually increase the temperature. The gradual temperature increase is to first raise the temperature to 500-600 ℃, react at this temperature for 2-4 h, then raise the temperature in the muffle furnace by 50-100 ℃ and react for 1-2 h, and then naturally cool to room temperature to obtain CN sample.

[0008] (2) Mix dimethylimidazole, cobalt nitrate hexahydrate and methanol, and stir at room temperature to obtain a mixed solution;

[0009] (3) Transfer the CN sample prepared in step (1) to the mixed solution obtained in step (2), heat and stir until the methanol evaporates, and dry in a vacuum oven; place the obtained powder in a temperature-controlled tube furnace, calcine under vacuum conditions, and obtain a powder sample after the temperature in the tube furnace naturally cools to room temperature.

[0010] (4) The powdered sample obtained in step (3) is transferred to a thermal shock reactor, heated rapidly and then cooled rapidly to room temperature to obtain the Co-CN photocatalyst modified with a single Co atom.

[0011] Preferably, the gradient heating in step (1) involves first heating to 500 °C, reacting at that temperature for 2 h, and then heating the muffle furnace to 550 °C for another 2 h.

[0012] Further, in step (2), the ratio of dimethylimidazole, cobalt nitrate hexahydrate, and methanol is 0.13g - 0.39g: 0.0582g - 0.1746g: 50mL - 100mL.

[0013] The ratio of CN sample to mixed solution in step (3) is 0.25-0.75 g: 50-100 mL.

[0014] The heating and stirring in step (3) is water bath stirring at 60-70℃. The temperature conditions of the programmable temperature control tube furnace are to heat the tube furnace to 300-500℃ at a heating rate of 2.3℃ / min under vacuum conditions, and react at this temperature for 2-4 hours.

[0015] The temperature conditions of the thermal shock reactor in step (4) are as follows: the temperature is rapidly increased from 25°C to 100-300°C and then rapidly cooled to room temperature.

[0016] The present invention also provides a Co-CN photocatalyst prepared by the preparation method described above.

[0017] This invention also provides the application of the Co-CN photocatalyst described above in the field of tetracycline degradation in water.

[0018] Compared with the prior art, the beneficial effects of the present invention are:

[0019] This invention uses melamine, dimethylimidazole, and cobalt nitrate as raw materials to synthesize a CN composite photocatalyst material modified with a single Co atom derived from a zeolite imidazole ester framework material (ZIF-L) via water bath heating, programmed temperature control, and vacuum calcination. This invention offers advantages such as simple process, convenient operation, low cost, non-toxicity, and short reaction time. The prepared photocatalyst material exhibits excellent photocatalytic degradation performance of tetracycline in aquatic environments. Its application in the removal of tetracycline pollutants from water reduces energy consumption and reaction costs while improving removal efficiency, making it environmentally friendly and meeting environmental protection requirements. Attached Figure Description

[0020] Figure 1 These are the XRD patterns of the Co-CN catalysts prepared in Examples 1-3;

[0021] Figure 2 These are TEM images of pure CN and the Co-CN catalysts prepared in Examples 1-3; in the images, A is CN, B is 0.25-Co-CN, C is 0.5-Co-CN, D is 0.75-Co-CN, and E and F are magnified views of 0.5-Co-CN.

[0022] Figure 3 These are the solid-state ultraviolet absorption spectra of CN and the Co-CN catalysts prepared in Examples 1-3;

[0023] Figure 4 This is a diagram of a simulated wastewater treatment experimental setup;

[0024] Figure 5 The graph shows the catalytic performance of CN and Co-CN catalysts modified with different amounts of Co single atoms in natural river water for the degradation of tetracycline.

[0025] Figure 6 The graph shows the catalytic performance of CN and Co-CN catalysts modified with different amounts of Co single atoms in deionized water medium for the degradation of tetracycline.

[0026] Figure 7 is Comparison chart of tetracycline degradation performance;

[0027] Figure 8 This is a comparison chart of water sample degradation under simulated sunlight; in the chart, a is the original river water sample, b is the water sample after 30 minutes of degradation, and c is the water sample after 60 minutes of degradation. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example

[0029] (1) Weigh 5 g of melamine and place it in an agate mortar. Grind it evenly and then transfer it to a crucible. Place it horizontally in a programmed temperature muffle furnace and heat the muffle furnace to 500 ℃ at a heating rate of 2.3 ℃ / min. React at this temperature for 2 h. Then heat the muffle furnace to 550 ℃ and react for 2 h. Allow it to cool naturally to room temperature to obtain the CN sample.

[0030] (2) Take 0.13 g of dimethylimidazole and 0.0582 g of cobalt nitrate hexahydrate into beakers, add 50 mL of methanol, and stir at room temperature until the solution turns blue;

[0031] (3) Take 0.25g of the CN sample prepared in step (1) and transfer it to the blue solution obtained in step (2). Stir in a water bath at 60 °C until the methanol evaporates to dryness. Continue drying in a vacuum oven at 60 °C. Place the obtained powder in a temperature-controlled tube furnace and heat the tube furnace to 300 °C at a heating rate of 2.3 °C / min under vacuum. React at this temperature for 2 h. Allow the temperature inside the tube furnace to cool naturally to room temperature to obtain a yellow powder sample.

[0032] (4) Take 0.25 g of the yellow powder sample obtained in step (3), transfer it to the thermal shock reactor, set the temperature to rise rapidly from 25°C to 100°C, and then cool it rapidly to room temperature. The resulting catalyst is recorded as 0.25-Co-CN. Example

[0033] (1) Weigh 5 g of melamine and place it in an agate mortar. Grind it evenly and then transfer it to a crucible. Place it horizontally in a programmed temperature muffle furnace and heat the muffle furnace to 500 ℃ at a heating rate of 2.3 ℃ / min. React at this temperature for 2 h. Then heat the muffle furnace to 550 ℃ and react for 2 h. Allow it to cool naturally to room temperature to obtain the CN sample.

[0034] (2) Weigh 0.26 g of dimethylimidazole and 0.1164 g of cobalt nitrate hexahydrate into a beaker, add 75 mL of methanol solvent, and stir at room temperature until the solution turns blue;

[0035] (3) Transfer 0.50 g of the CN sample prepared in step (1) to the blue solution obtained in step (2), stir in a water bath at 60 °C until the methanol evaporates to dryness, and then continue drying in a vacuum oven at 60 °C. Finally, place the obtained powder in a temperature-controlled tube furnace, heat the muffle furnace to 400 °C at a heating rate of 2.3 °C / min under vacuum, and react at this temperature for 3 h. After the temperature inside the tube furnace naturally cools to room temperature, a yellow powder sample is obtained.

[0036] (4) Take 0.25 g of the yellow powder obtained in step (3) and transfer it into a thermal shock reactor. Set the temperature to rise rapidly from 25°C to 200°C and then cool it rapidly to room temperature. Record the obtained catalyst as 0.50-Co-CN. Example

[0037] (1) Weigh 5 g of melamine and place it in an agate mortar. Grind it evenly and then transfer it to a crucible. Place it horizontally in a programmed temperature muffle furnace and heat the muffle furnace to 500 ℃ at a heating rate of 2.3 ℃ / min. React at this temperature for 2 h and then heat the muffle furnace to 550 ℃ for 2 h. After naturally cooling to room temperature, obtain the CN sample.

[0038] (2) Weigh 0.39 g of dimethylimidazole and 0.1746 g of cobalt nitrate hexahydrate into a beaker, add 100 mL of methanol solvent, and stir at room temperature until the solution turns blue.

[0039] (3) Transfer 0.75 g of CN sample prepared in step (1) to the blue solution obtained in step (2), stir in a water bath at 60 °C until the methanol evaporates, and then continue to dry in a vacuum oven at 60 °C; place the obtained powder in a temperature-controlled tube furnace, heat the muffle furnace to 500 °C at a heating rate of 2.3 °C / min under vacuum, and react at this temperature for 4 h. After the temperature inside the tube furnace naturally cools to room temperature, a yellow powder sample is obtained.

[0040] (4) Transfer 0.25 g of the yellow powder obtained in step (3) into a thermal shock reactor, set the temperature to rise rapidly from 25°C to 300°C, and then rapidly cool it to room temperature. The resulting catalyst is denoted as 0.75-Co-CN.

[0041] Figure 1 These are the XRD patterns of the Co-CN catalysts prepared in Examples 1-3; Figure 1 As shown, the characteristic peaks of the three composite photocatalysts prepared—0.25-Co-CN, 0.5-Co-CN, and 0.75-Co-CN—at 13.0° and 27.4° are consistent with the characteristic peak of CN. However, due to the relatively low content of single-atom Co, no characteristic diffraction peaks of single-atom Co were observed.

[0042] Figure 2 These are TEM images of pure CN and the Co-CN catalysts prepared in Examples 1-3; in the images, A is CN, B is 0.25-Co-CN, C is 0.5-Co-CN, and D is 0.75-Co-CN; E and F are magnified views of 0.5-Co-CN. Figure 2 As can be seen, pure CN exhibits an irregular blocky structure, and the morphology of the prepared Co-CN catalysts differs significantly from that of pure CN under TEM. Co-CN, on the other hand, has a relatively thin lamellar structure. Specifically, 0.5-Co-CN shows a distinct lamellar structure, with small bright white spots (Co metal single atoms) visible under further magnification. 0.75-Co-CN becomes slightly thicker and exhibits stacking. TEM characterization directly confirms the successful synthesis of Co single-atom modified CN.

[0043] Figure 3 These are the solid-state UV absorption spectra of CN and the Co-CN catalysts prepared in Examples 1-3; Figure 3 It can be seen that the light absorption edge of CN is at 450 nm, while the visible light absorption range of the Co-CN composite catalyst modified with Co single atoms is extended, indicating that the introduction of Co single atoms can enhance the visible light response range of CN and improve the light energy utilization rate. Example

[0044] In this embodiment, the catalytic performance of CN and Co-CN catalysts modified with different Co single atoms prepared in Examples 1-3 for the degradation of tetracycline was analyzed. Natural river water and deionized water were used as the analytical materials. CN and the Co-CN catalysts prepared in Examples 1-3 were respectively placed in... Figure 4 In the simulated wastewater treatment experimental setup shown, the performance of each catalyst was verified. Each catalyst was used at a dosage of 5 mg, and a concentration of 40 mg / L was prepared using natural river water as the water source. -1The tetracycline solution was irradiated with 450 nm visible light for 90 min. Figure 5 This diagram shows the catalytic performance of CN and Co-CN catalysts modified with different amounts of Co single atoms in natural river water for the degradation of tetracycline. Figure 5 It can be seen that CN has a tetracycline degradation rate of 29%, 0.25-Co-CN has a tetracycline degradation rate of 45%, 0.75-Co-CN has a tetracycline degradation efficiency of 36%, and 0.5-Co-CN has the best tetracycline degradation effect, reaching 62%. Example

[0045] In this embodiment, the amount of each catalyst is 10 mg, and a concentration of 20 mg / L is prepared using deionized water in the laboratory as the solvent. -1 The tetracycline solution was irradiated with 450 nm visible light for 60 min. Figure 6 This diagram shows the catalytic performance of CN and Co-CN catalysts modified with different amounts of Co single atoms in deionized water medium for the degradation of tetracycline. Figure 6 It can be seen that CN has a tetracycline degradation rate of 33%, 0.25-Co-CN has a tetracycline degradation rate of 50%, 0.75-Co-CN has a tetracycline degradation efficiency of 42%, and 0.5-Co-CN has the best tetracycline degradation effect, reaching 75%.

[0046] Depend on Figure 5 , Figure 6 The test results show that water quality has a certain impact on the degradation effect of the catalyst. River water contains more impurities and is relatively difficult to treat. However, the catalyst provided by this invention still has a high catalytic degradation effect on tetracycline. In particular, compared with CN, the degradation efficiency of tetracycline solution prepared by deionized water in the laboratory is more than doubled. Example

[0047] In this embodiment, natural river water was used as the sample. After static filtration to remove suspended solids and insoluble impurities, a concentration of 40 mg / L was prepared. -1 A tetracycline solution was prepared and irradiated with 5 mg of catalyst under simulated full-spectrum sunlight for 60 min. The degradation performance of tetracycline in water under CN, 0.5-Co-CN catalyst, and no catalyst conditions was analyzed. Figure 7 is Comparison chart of tetracycline degradation performance. (From...) Figure 7 As can be seen, the degradation rate of 0.5-Co-CN is 51%, and the degradation rate of CN for tetracycline is 24%. In the absence of a catalyst, tetracycline is hardly removed, indicating that tetracycline is very stable in nature. The 0.5-Co-CN provided by this invention has excellent tetracycline degradation performance.

[0048] Figure 8This is a comparison chart of water sample degradation under simulated sunlight; in the chart, a is the original river water sample, b is the water sample after 30 minutes of degradation, and c is the water sample after 60 minutes of degradation. Figure 8 As can be seen, after irradiation with visible light for 30 minutes, the solution color lightened significantly, and after 60 minutes of degradation, the solution became almost colorless. This confirms that the prepared photocatalyst Co-CN has excellent catalytic removal effect under simulated sunlight.

[0049] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a ZIF-L-derived Co-CN photocatalyst, characterized in that, The preparation method includes the following steps: (1) After grinding the melamine evenly, place it in a programmed temperature muffle furnace and gradually increase the temperature. The gradual temperature increase is to first raise the temperature to 500-600 ℃, react at this temperature for 2-4 h, then raise the temperature in the muffle furnace by 50-100 ℃ and react for 1-2 h, and then naturally cool to room temperature to obtain CN sample. (2) Mix dimethylimidazole, cobalt nitrate hexahydrate and methanol, and stir at room temperature to obtain a mixed solution; (3) Transfer the CN sample prepared in step (1) to the mixed solution obtained in step (2), heat and stir until the methanol evaporates, and dry in a vacuum oven; place the obtained powder in a temperature-controlled tube furnace, calcine under vacuum conditions, and obtain a powder sample after the temperature in the tube furnace naturally cools to room temperature. (4) The powdered sample obtained in step (3) is transferred to a thermal shock reactor, rapidly heated and then rapidly cooled to room temperature to obtain the Co-CN photocatalyst modified with a single Co atom; the ratio of dimethylimidazole, cobalt nitrate hexahydrate and methanol in step (2) is 0.13 g - 0.39 g: 0.0582 g - 0.1746 g: 50 mL - 100 mL; the ratio of CN sample to mixed solution in step (3) is 1.5 g: 200 mL - 300 mL; the temperature conditions of the thermal shock reactor in step (4) are rapidly increased from 25℃ to 100-300℃ and then rapidly cooled to room temperature.

2. The preparation method according to claim 1, characterized in that, The gradient heating in step (1) involves first heating to 500℃, reacting at that temperature for 2 hours, and then heating the muffle furnace to 550℃ for another 2 hours.

3. The preparation method according to claim 1, characterized in that, The heating and stirring in step (3) is water bath stirring at 60-70℃. The temperature conditions of the programmable temperature control tube furnace are to heat the tube furnace to 300-500℃ at a heating rate of 2.3℃ / min under vacuum conditions, and react at this temperature for 2-4 hours.

4. The Co-CN photocatalyst prepared by the preparation method according to any one of claims 1-3.

5. The application of the Co-CN photocatalyst according to claim 4 in the field of antibiotic degradation in water.

6. The application of the Co-CN photocatalyst according to claim 4 in the field of tetracycline degradation in water.

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