Preparation method of BiOCl@MOFs core-shell structure photocatalyst

Abstract

This invention discloses a method for preparing a BiOCl@MOFs core-shell structured photocatalyst and its application, belonging to the field of photocatalytic materials technology. The method involves first preparing BiOCl by ultrasonically dispersing potassium chloride and bismuth nitrate pentahydrate with ethylene glycol and deionized water in a polytetrafluoroethylene-lined stainless steel high-pressure reactor at 160°C for 24 hours; then, dissolving the organic ligands and metal salts of MOFs in anhydrous ethanol, mixing them with the BiOCl dispersion, ultrasonically reacting them at 100°C and 520 rpm for 40 minutes, and repeating the process multiple times (LBL cycles 0-20 times) to obtain the BiOCl@MOFs core-shell structured photocatalyst. The MOFs can be selected from In-MOFs and HKUST-1. This preparation method employs a layer-by-layer self-assembly strategy, which can precisely control the number of layers in the core-shell structure. The prepared BiOCl@In-MOF and BiOCl@HKUST-1 core-shell photocatalysts exhibited superior catalytic performance compared to BiOCl alone and the corresponding MOF in the photocatalytic reduction of carbon dioxide, improving the carbon dioxide conversion rate and providing an effective catalyst for photocatalytic reduction of carbon dioxide. They have good application prospects in the fields of environmental protection and energy.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic materials technology, specifically relating to a method for preparing BiOCl@MOFs core-shell structured photocatalysts using a layer-by-layer self-assembly strategy. Background Technology

[0002] In recent years, global carbon dioxide emissions have continued to rise, causing serious environmental problems, making photocatalytic carbon dioxide reduction technology a research hotspot. BiOCl, as a promising photocatalyst, possesses certain photocatalytic activity due to its unique layered structure. However, BiOCl suffers from low electron-hole separation efficiency, hindering further improvement in its photocatalytic performance. Metal-organic frameworks (MOFs) possess advantages such as highly ordered porous structures, tunable chemical compositions, and high specific surface areas, showing promising application prospects in photocatalysis. Combining BiOCl with MOFs to construct a core-shell structure theoretically integrates the advantages of both, enhancing photocatalytic performance. However, in practical preparation, traditional methods struggle to precisely control key parameters of the core-shell structure, such as shell thickness and effective interfacial ratio, preventing the full realization of its advantages and limiting the development and application of this type of photocatalyst. Therefore, developing a preparation method capable of precisely controlling the core-shell structure is of significant practical importance. Summary of the Invention

[0003] 1. Purpose of the Invention: The purpose of this invention is to provide a method for preparing BiOCl@MOFs core-shell structured photocatalysts through a layer-by-layer self-assembly strategy, thereby achieving precise control of the core-shell structure, improving the separation efficiency of photogenerated carriers and the adsorption capacity of CO2, and thus significantly enhancing the performance of photocatalytic reduction of carbon dioxide, providing a more effective technical means to solve environmental problems.

[0004] 2. Technical Solution

[0005] Preparation of BiOCl@In-MOF core-shell structure

[0006] Synthesis of BiOCl: Bi(NO3)3·5H2O and KCl were dissolved in a 1:1 molar ratio in a mixed solvent of ethylene glycol / water (volume ratio 2:1), and the reaction was carried out at 200℃ for 24 h. After washing and drying, BiOCl nanosheets were obtained.

[0007] Layer-by-layer assembly: BiOCl was alternately immersed in H2BDC solution and In(NO3)3 solution, with a single immersion time of 40 min and a cycle number of 0-20 times. After drying, BiOCl@In-MOF was obtained.

[0008] Preparation of BiOCl@HKUST-1 core-shell structure

[0009] Synthesis of BiOCl: The synthesis method is the same as that of BiOCl in BiOCl@In-MOF.

[0010] Layer-by-layer assembly: BiOCl was alternately immersed in H3BTC solution and Cu(NO3)2 for 0-20 cycles, and then dried to obtain BiOCl@HKUST-1.

[0011] 3. Beneficial effects

[0012] This invention employs a layer-by-layer self-assembly strategy, using BiOCl as a precursor, to successfully synthesize BiOCl@In-MOF core-shell structures and BiOCl@HKUST-1 core-shell structures. This layer-by-layer self-assembly strategy allows for precise control of the thickness and composition of the MOF shells. Experiments show that the prepared BiOCl@In-MOF and BiOCl@HKUST-1 core-shell photocatalysts exhibit superior catalytic performance in the photocatalytic reduction of carbon dioxide compared to BiOCl alone and the corresponding MOFs, thus improving the carbon dioxide conversion rate and providing a more effective catalyst selection for the practical application of photocatalytic carbon dioxide reduction technology. Attached Figure Description

[0013] Figure 1 These are scanning electron microscope (SEM) images of BiOCl prepared according to embodiments of the present invention;

[0014] Figure 2 This is the X-ray powder diffraction (XRD) pattern of BiOCl prepared in the embodiments of the present invention;

[0015] Figure 3 This is a scanning electron microscope (SEM) image of the BiOCl@In-MOF core-shell structure prepared in the embodiments of the present invention;

[0016] Figure 4 This is the X-ray powder diffraction (XRD) pattern of the BiOCl@In-MOF core-shell structure prepared in the embodiments of the present invention;

[0017] Figure 5 These are the photocatalytic CO2 reduction performance diagrams of BiOCl, BiOCl@In-MOF, and In-MOF core-shell structures prepared in the embodiments of the present invention;

[0018] Figure 6 This is a scanning electron microscope (SEM) image of the BiOCl@HKUST-1 core-shell structure prepared in the embodiments of the present invention;

[0019] Figure 7 This is the X-ray powder diffraction (XRD) pattern of the BiOCl@HKUST-1 core-shell structure prepared in the embodiments of the present invention;

[0020] Figure 8 The graph shows the photocatalytic reduction performance of CO2 by the BiOCl, BiOCl@HKUST-1 and HKUST-1 core-shell photocatalysts prepared in the embodiments of the present invention. Detailed Implementation

[0021] Example 1: Preparation of BiOCl@In-MOF core-shell structure

[0022] Bi(NO3)3·5H2O and KCl were dissolved in an ethylene glycol / water mixed solvent (volume ratio 2:1) at a 1:1 molar ratio, and the mixture was solvothermal reacted at 200℃ for 24 h. After washing and drying, BiOCl nanosheets were obtained. Then, the precursor BiOCl was alternately impregnated in H2BDC solution and In(NO3)3 solution for 40 min each time, with 10 cycles. After drying, BiOCl@In-MOF core-shell structures were obtained. Figure 1 and Figure 2 The SEM and XRD of BiOCl in this embodiment are respectively obtained by... Figure 2 The X-ray diffraction pattern can identify the phase of the synthesized sample as BiOCl; Figure 3 and Figure 4 The images show the SEM and XRD patterns of the BiOCl@In-MOF core-shell structure in this embodiment. The X-ray powder diffraction peak positions of the BiOCl@In-MOF core-shell photocatalyst match those of BiOCl and In-MOF, proving that the BiOCl@In-MOF material has been successfully synthesized.

[0023] Example 2: Preparation of BiOCl@HKUST-1 core-shell structure

[0024] The precursor BiOCl was alternately immersed in H3BTC solution and Cu(NO3)2 solution for 40 min each time, with 15 cycles. After drying, the BiOCl@HKUST-1 core-shell structure was obtained. Figure 6 and Figure 7 The images show the SEM and XRD patterns of the BiOCl@core-shell structure in this embodiment. The X-ray powder diffraction peak positions of the BiOCl@HKUST-1 core-shell photocatalyst match those of BiOCl and HKUST-1, proving that the BiOCl@HKUST-1 material has been successfully synthesized.

[0025] Application Example 1

[0026] In this embodiment, a 300W xenon lamp was used as the light source. 5mg of photocatalysts BiOCl, BiOCl@In-MOF, In-MOF and 300μL of water were added to a CO2-filled, sealed quartz reactor and the reaction was carried out under light for 10 hours.

[0027] Application Example 2

[0028] In this embodiment, a 300W xenon lamp was used as the light source. 5mg of photocatalysts BiOCl, BiOCl@HKUST-1, HKUST-1 and 300μL of water were added to a CO2-filled sealed quartz reactor and the reaction was carried out under light for 10h.

[0029] Figure 5 The graphs show the photocatalytic CO2 reduction performance of BiOCl, BiOCl@In-MOF, and In-MOF. The core-shell structure of BiOCl@In-MOF exhibits the best photocatalytic CO2 reduction performance.

[0030] Figure 8 The graphs show the photocatalytic CO2 reduction performance of BiOCl, BiOCl@HKUST-1, and HKUST-1. The core-shell structure of BiOCl@HKUST-1 exhibits the best photocatalytic CO2 reduction performance.

Claims

1. A method for preparing a BiOCl@MOFs core-shell structured photocatalyst, characterized in that, Includes the following steps: (a) Synthesis of BiOCl: Weigh potassium chloride (KCl) and bismuth nitrate pentahydrate (Bi(NO3)3·5H2O), and transfer them to a stainless steel high-pressure reactor lined with polytetrafluoroethylene (PTFE); add ethylene glycol and deionized water, and ultrasonically disperse to form a homogeneous solution; heat the reactor to 160℃ and maintain the reaction for 24 hours; after the reaction is completed, allow it to cool naturally to room temperature, wash and dry to obtain BiOCl; (b) Synthesis of BiOCl@MOF core-shell structures: Weigh out the organic ligands and metal salts of MOFs and dissolve them in anhydrous ethanol; The BiOCl obtained in step (a) was dispersed in anhydrous ethanol, and the above organic ligand solution was added. The mixture was then ultrasonically dispersed to form a homogeneous solution. The reaction was carried out under certain temperature and stirring conditions. After the reaction was completed, the sample was washed and dried to obtain the BiOCl@MOFs core-shell structured photocatalyst.

2. The preparation method according to claim 1, characterized in that, The MOFs are In-MOF and HKUST-1.

3. The preparation method according to claim 1, characterized in that, In the synthesis of BiOCl, the molar ratio of potassium chloride to bismuth nitrate pentahydrate is 1:1, and the volume ratio of ethylene glycol to deionized water is 2:

1.

4. The preparation method according to claim 1, characterized in that, In the synthesis of the BiOCl@MOFs core-shell structure, the molar ratio of organic ligands to metal salts is adjusted according to the specific chemical composition of the MOFs.

5. The preparation method according to claim 1, characterized in that, In the synthesis of the BiOCl@MOFs core-shell structure, the reaction temperature was 100℃, the stirring speed was 520rpm, and the reaction time was 40 minutes.

6. The preparation method according to claim 1, characterized in that, In the synthesis of the BiOCl@MOFs core-shell structure, a layer-by-layer self-assembly strategy was adopted, and the thickness of the MOFs shell was controlled through multiple wetting processes.

7. The preparation method according to claim 1, characterized in that, The LBL cycle is repeated 10-15 times.

8. The preparation method according to claim 1, characterized in that, The BiOCl@MOFs core-shell structured photocatalyst is used for the photocatalytic reduction of carbon dioxide.

9. A BiOCl@MOFs core-shell structured photocatalyst, characterized in that, It is prepared by the method described in any one of claims 1-8.

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