Preparation of sillen-aurivillius structure bismuth-based semiconductor material and application in photocatalytic co2 cycloaddition reaction

Abstract

The application belongs to the technical field of photocatalytic CO2 cycloaddition reaction, and particularly relates to a preparation method of a vacancy defect layered bismuth semiconductor material and application of the vacancy defect layered bismuth semiconductor material in photocatalytic CO2 cycloaddition reaction. The material is based on a bismuth semiconductor material with a Sillen-Aurivillius structure, and a defect site is constructed by vacancy regulation of the material. Low-valence metal ions exposed by the vacancy defect can be used as Lewis acid sites to adsorb and activate epoxides, and the defect site can promote separation of photo-generated carriers, thereby enhancing surface reaction kinetics and effectively improving photocatalytic activity of the material, and finally promoting photocatalytic CO2 cycloaddition reaction performance.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic CO2 cycloaddition reaction technology. More specifically, it relates to a method for preparing a Sillén-Aurivillius structure bismuth-based semiconductor material and its application in photocatalytic CO2 cycloaddition reaction. Background Technology

[0002] Bismuth-based semiconductor materials with a Sillén-Aurivillius structure are hybrid perovskite photocatalysts with a unique layered structure. They often exhibit excellent visible light response and suitable band structure, which can accelerate the transfer of photogenerated carriers and result in higher photocatalytic activity, making them a promising class of photocatalysts. Meanwhile, CO2 cycloaddition reactions are highly efficient and clean, with 100% atom utilization of the cyclic carbonate products and no byproducts. They are widely used in the pharmaceutical and fine chemical industries and are considered an ideal strategy for CO2 conversion. However, in practical applications, there are still problems such as harsh reaction conditions and relatively low catalytic performance. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the existing CO2 cycloaddition reaction conditions and low catalyst performance, and to provide a bismuth-based semiconductor material with a Sillén-Aurivillius structure that has mild reaction conditions, high catalytic efficiency and abundant Lewis acid sites.

[0004] The purpose of this invention is to provide a method for preparing and modifying layered bismuth-based semiconductor materials for the photocatalytic CO2 cycloaddition reaction.

[0005] Another objective of this invention is to provide the application of the layered bismuth semiconductor material in the photocatalytic CO2 cycloaddition reaction.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A defective layered bismuth semiconductor material for photocatalytic CO2 cycloaddition reaction is proposed, which is based on layered bismuth semiconductor material, and defect sites are designed through vacancy control to construct low-valence metal ions.

[0008] The layered bismuth-based semiconductor material in this invention is a hybrid perovskite photocatalyst with a Sillén-Aurivillius structure. Its crystal structure consists of alternating stacked layers of different ions: [Bi₂O₂], [MO₄], and [Cl]. This unique layered structure gives it excellent visible light absorption. Furthermore, the polarization fields present in the different ion layers and the permanent electric fields between the ion layers promote electron-hole pair separation during photoexcitation, thereby improving photocatalytic efficiency. In addition to relying on the material's unique layered structure, this invention also utilizes modulated defect sites and low-valence metal ions to increase substrate adsorption and activation sites, promoting photogenerated charge separation and significantly improving catalytic activity.

[0009] In addition, the present invention also provides a method for preparing the layered bismuth-based semiconductor material of the photocatalytic CO2 cycloaddition reaction, specifically including the following steps:

[0010] S1. Add the bismuth source and halogen source to a polar solvent, dissolve and mix them thoroughly, and then react completely at room temperature. After post-treatment, obtain the bismuth oxyhalide compound.

[0011] S2. Using the molten salt method, the bismuth oxyhalide compound obtained in step S1 and other solutes and fluxes are fully mixed in a certain proportion, calcined at a high temperature of 700-850℃ until the reaction is complete, and then post-treated to obtain bismuth semiconductor materials with a Sillén-Aurivillius structure.

[0012] S3. The layered bismuth semiconductor material obtained in step S2 is calcined in a reducing atmosphere at 500-600℃ until the reaction is complete, and then post-treated to obtain the final product.

[0013] Generally, Sillén-Aurivillius layered semiconductor materials are crystallized through high-temperature calcination. However, solid-state synthesis and calcination require high temperatures, resulting in large grain sizes and poor crystal morphology uniformity. Furthermore, the high temperatures cause halogen elements to evaporate, creating halogen defects. These halogen defects typically become recombination centers for photogenerated charge carriers, thus reducing the material's photocatalytic performance. This invention employs a molten salt method, significantly lowering the catalyst synthesis temperature. A reducing atmosphere is then provided to reduce and calcine the material, creating defect sites on the semiconductor surface and exposing low-valence metal ions as Lewis acid sites. These processes jointly promote the separation of photogenerated charges and the adsorption and activation of substrate molecules.

[0014] Further, in step S1, the bismuth source is bismuth nitrate, bismuth chloride, or bismuth bromide.

[0015] Furthermore, in step S1, the halogen source is selected from one or more of sodium chloride, potassium chloride, sodium bromide, potassium bromide, sodium iodide, and potassium iodide. Preferably, the halogen source is a chlorine source, i.e., potassium chloride.

[0016] Furthermore, in step S1, the polar solvent is ethylene glycol and deionized water.

[0017] Furthermore, in step S1, the reaction is carried out at room temperature for 30–150 min.

[0018] Furthermore, in step S1, the mass ratio of bismuth source to chlorine source is 13:2; the volume ratio of polar solvent to deionized water is 1:1.

[0019] Further, in step S1, the post-treatment is as follows: the solid obtained after the reaction is washed with deionized water 5 to 6 times, then washed with ethanol 2 to 3 times, and dried and activated at 50 to 70°C for 10 to 16 hours to obtain the final product.

[0020] Further, in step S2, the solute is selected from bismuth oxide, niobium oxide, tantalum oxide, antimony oxide, and the bismuth oxychloride compound obtained in step S1. Preferably, the solute is bismuth oxide, niobium oxide, and the bismuth oxychloride compound obtained in step S1.

[0021] Furthermore, in step S2, the flux is selected from sodium chloride, potassium chloride, and lithium chloride. Preferably, the flux is sodium chloride or potassium chloride.

[0022] Furthermore, in step S2, the mass ratio of the product to the flux is 0.54.

[0023] Furthermore, in step S2, the mass ratio of bismuth oxide, niobium oxide, and the bismuth oxychloride compound obtained in step S1 in the molten material is 3:1:2.

[0024] Furthermore, in step S2, the mass ratio of sodium chloride to potassium chloride in the flux is 1:1.

[0025] Preferably, in step S2, the high-temperature calcination reaction at 700–850°C lasts for 2–6 hours.

[0026] Further, in step S2, the post-treatment is as follows: the solid obtained after the reaction is washed with deionized water 5 to 8 times and dried in an oven at 60 to 80°C for 10 hours to obtain the final product.

[0027] Further, in step S3, the reducing atmosphere is selected from argon, carbon monoxide, hydrogen, and ammonia. Preferably, the reducing atmosphere is carbon monoxide. Further, a carbon source can be used to provide the CO atmosphere.

[0028] Furthermore, in step S3, calcination is carried out at 500–600°C under a reducing atmosphere for 2–8 hours. Preferably, calcination is performed in a muffle furnace.

[0029] Further, in step S3, the post-processing is as follows: the solid obtained after the reaction is ground 3 to 4 times to obtain the final product.

[0030] Therefore, the present invention also claims protection for the application of the layered bismuth semiconductor material for the photocatalytic CO2 cycloaddition reaction in the field of catalysts.

[0031] Furthermore, the catalyst photocatalyzes the cycloaddition reaction between CO2 and epoxides.

[0032] Furthermore, the photocatalytic cycloaddition reaction between CO2 and epoxides specifically includes the following steps:

[0033] The catalyst for the photocatalytic CO2 cycloaddition reaction, namely the layered bismuth semiconductor material, the co-catalyst, and the reaction substrate 1,2-epoxybutane, are mixed and carbon dioxide is introduced under light irradiation to carry out the cycloaddition reaction.

[0034] Preferably, the co-catalyst is tetrabutylammonium bromide.

[0035] More preferably, the reaction is carried out at a temperature below 60°C, the carbon dioxide pressure is 1 atm, and the reaction time is 4–12 h.

[0036] Preferably, the illumination conditions use a xenon lamp as the light source, with a power of 300W and a full wavelength range.

[0037] More preferably, the mass ratio of the catalyst, co-catalyst and reaction substrate is 50:100:4400.

[0038] This invention has the following significant advantages:

[0039] Based on a bismuth-based semiconductor material with a Sillén-Aurivillius structure, this invention constructs defect sites by vacancy control of the material. As vacancy defects are generated, the exposed low-valence metal ions can be adsorbed and activated as Lewis acid sites. At the same time, these defect sites can promote the separation of photogenerated carriers, thereby enhancing surface reaction kinetics, effectively improving the photocatalytic activity of the material, and ultimately promoting the performance of photocatalytic CO2 cycloaddition reaction. Attached Figure Description

[0040] Figure 1 The XRD patterns are of Comparative Example 1 Bi4NbO8Cl, Example 1 Bi4NbO8Cl-500, Example 2 Bi4NbO8Cl-550, and Example 3 Bi4NbO8Cl-600 of this invention.

[0041] Figure 2 This is a SEM image of Bi4NbO8Cl obtained in Comparative Example 1 of this invention.

[0042] Figure 3 This is a SEM image of Bi4NbO8Cl-550 obtained in Example 2 of the present invention.

[0043] Figure 4 This is a TEM image of Bi4NbO8Cl obtained in Comparative Example 1 of this invention.

[0044] Figure 5 This is a TEM lattice pattern of Bi4NbO8Cl obtained in Comparative Example 1 of the present invention.

[0045] Figure 6 The EPR electron spin resonance spectra of Comparative Example 1 Bi4NbO8Cl and Example 2 Bi4NbO8Cl-550 are shown below.

[0046] Figure 7 The reaction performance diagrams are for Comparative Example 1 (Bi4NbO8Cl) and Example 2 (Bi4NbO8Cl-550) of this invention. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

[0048] Unless otherwise specified, all reagents and materials used in the following examples are commercially available.

[0049] Example 1. A layered bismuth-based semiconductor material Bi4NbO8Cl-500 for photocatalytic CO2 cycloaddition reaction

[0050] The preparation method of the layered bismuth-based semiconductor material specifically includes the following steps:

[0051] S1. Dissolve 4.85 g of bismuth nitrate pentahydrate and 0.7455 g of potassium chloride in 25 mL of ethylene glycol and 25 mL of deionized water, respectively. Then, slowly add the potassium chloride solution dropwise to the bismuth nitrate ethylene glycol solution at room temperature, and stir magnetically for 1 h. Wash the resulting suspension with deionized water, filter and collect, dry at 60 °C for 10 h, and label it as BiOCl.

[0052] S2. Using NaCl and KCl in a molar ratio of 1:1 as fluxes, and with a solute concentration of Bi4NbO8X / (Bi4NbO8X + flux) of 3.2 mol%, the flux was thoroughly mixed with Bi2O3, BiOCl, and Nb2O5 in a stoichiometric molar ratio of 3:2:1. The mixture was then placed in a muffle furnace and calcined at 750 °C for 4 hours, with a heating rate of 3 °C / min. -1After cooling at room temperature, the product was thoroughly washed with deionized water more than 5 times to remove the flux, and then dried at 60°C for 10 hours, labeled as Bi4NbO8Cl.

[0053] S3. Place 0.2g of Bi4NbO8Cl obtained in step S2 into a crucible, fill it with carbon powder to provide a CO atmosphere, and calcine it at 500℃ for 4h, with a heating rate of 5℃ / min. -1 After the reaction was complete, the sample was ground and collected, and labeled as Bi4NbO8Cl-500.

[0054] Example 2. A layered bismuth-based semiconductor material Bi4NbO8Cl-550 for photocatalytic CO2 cycloaddition reaction.

[0055] The preparation method of the layered bismuth-based semiconductor material specifically includes the following steps:

[0056] S1. Dissolve 4.85 g of bismuth nitrate pentahydrate and 0.7455 g of potassium chloride in 25 mL of ethylene glycol and 25 mL of deionized water, respectively. Then, slowly add the potassium chloride solution dropwise to the bismuth nitrate ethylene glycol solution at room temperature, and stir magnetically for 1 h. Wash the resulting suspension with deionized water, filter and collect, dry at 60 °C for 10 h, and label it as BiOCl.

[0057] S2. Using NaCl and KCl in a molar ratio of 1:1 as fluxes, and with a solute concentration of Bi4NbO8X / (Bi4NbO8X + flux) of 3.2 mol%, the flux was thoroughly mixed with Bi2O3, BiOCl, and Nb2O5 in a stoichiometric molar ratio of 3:2:1. The mixture was then placed in a muffle furnace and calcined at 750 °C for 4 hours, with a heating rate of 3 °C / min. -1 After cooling at room temperature, the product was thoroughly washed with deionized water more than 5 times to remove the flux, and then dried at 60°C for 10 hours, labeled as Bi4NbO8Cl.

[0058] S3. Place 0.2g of Bi4NbO8Cl obtained in step S2 into a crucible, fill it with carbon powder to provide a CO atmosphere, and calcine it at 550℃ for 4h, with a heating rate of 5℃ / min. -1 After the reaction was complete, the sample was ground and collected, and labeled as Bi4NbO8Cl-550.

[0059] Example 3. A layered bismuth-based semiconductor material Bi4NbO8Cl-600 for photocatalytic CO2 cycloaddition reaction.

[0060] The preparation method of the layered bismuth-based semiconductor material specifically includes the following steps:

[0061] S1. Dissolve 4.85 g of bismuth nitrate pentahydrate and 0.7455 g of potassium chloride in 25 mL of ethylene glycol and 25 mL of deionized water, respectively. Then, slowly add the potassium chloride solution dropwise to the bismuth nitrate ethylene glycol solution at room temperature, and stir magnetically for 1 h. Wash the resulting suspension with deionized water, filter and collect, dry at 60 °C for 10 h, and label it as BiOCl.

[0062] S2. Using NaCl and KCl in a molar ratio of 1:1 as fluxes, and with a solute concentration of Bi4NbO8X / (Bi4NbO8X + flux) of 3.2 mol%, the flux was thoroughly mixed with Bi2O3, BiOCl, and Nb2O5 in a stoichiometric molar ratio of 3:2:1. The mixture was then placed in a muffle furnace and calcined at 750 °C for 4 hours, with a heating rate of 3 °C / min. -1 After cooling at room temperature, the product was thoroughly washed with deionized water more than 5 times to remove the flux, and then dried at 60°C for 10 hours, labeled as Bi4NbO8Cl.

[0063] S3. Place 0.2g of Bi4NbO8Cl obtained in step S2 into a crucible, fill it with carbon powder to provide a CO atmosphere, and calcine it at 600℃ for 4h, with a heating rate of 5℃ / min. -1 After the reaction was complete, the sample was ground and collected, and labeled as Bi4NbO8Cl-600.

[0064] Comparative Example 1. Layered Bismuth Semiconductor Material Bi4NbO8Cl

[0065] The preparation method of the layered bismuth-based semiconductor material specifically includes the following steps:

[0066] S1. Dissolve 4.85 g of bismuth nitrate pentahydrate and 0.7455 g of potassium chloride in 25 mL of ethylene glycol and 25 mL of deionized water, respectively. Then, slowly add the potassium chloride solution dropwise to the bismuth nitrate ethylene glycol solution at room temperature, and stir magnetically for 1 h. Wash the resulting suspension with deionized water, filter and collect, dry at 60 °C for 10 h, and label it as BiOCl.

[0067] S2. Using NaCl and KCl in a molar ratio of 1:1 as fluxes, and with a solute concentration of Bi4NbO8X / (Bi4NbO8X + flux) of 3.2 mol%, the flux was thoroughly mixed with Bi2O3, BiOCl, and Nb2O5 in a stoichiometric molar ratio of 3:2:1. The mixture was then placed in a muffle furnace and calcined at 750 °C for 4 hours, with a heating rate of 3 °C / min. -1 After cooling at room temperature, the product was thoroughly washed with deionized water more than 5 times to remove the flux, and then dried at 60°C for 10 hours, labeled as Bi4NbO8Cl.

[0068] Experimental Example 1. X-ray Powder Diffraction Analysis

[0069] The crystal structures of the materials obtained in Comparative Example 1 and Examples 1-3 of this invention were characterized using a Bruker SmartLab powder diffractometer (Germany). The operating conditions were: voltage 40 kV and current 30 mA; Cu-Kα radiation was used for scanning within a range of 10–80° at twice the diffraction angle; and the scanning speed was 10° / min. The results are shown in [reference needed]. Figure 1 .

[0070] As shown in the figure, the diffraction peak positions of the synthesized Bi4NbO8Cl and Bi4NbO8Cl-550 are consistent with those of the JCPDS standard card (PDF#84-0843), indicating that the synthesized Bi4NbO8Cl series structures have good crystallinity and that the crystal structure of Bi4NbO8Cl remains stable after the generation of defect vacancies.

[0071] Experimental Example 2. Scanning Electron Microscopy Characterization

[0072] The morphology of Comparative Example 1 and Example 2 of this invention was characterized using a Hitachi SU8010 ultra-high resolution field emission scanning electron microscope (USA). The accelerating voltage was 10 kV and the current was 10 mA. Gold sputtering pretreatment was required before testing. The results are shown in [reference needed]. Figures 2-3 .

[0073] As shown in the figure, the Bi4NbO8Cl in Comparative Example 1 has a relatively regular plate-like morphology with a length and width of approximately 1.7 μm and 145 nm, respectively, with a smooth surface and edges, and good crystallinity. Example 2 shows no significant difference in morphology from Comparative Example 1.

[0074] Experimental Example 3. Transmission Electron Microscopy Characterization

[0075] The morphology of the composite material of Comparative Example 1 of this invention was characterized using a high-resolution transmission electron microscope (HR-TEM, JEM-2100F, JEOL) with an accelerating voltage of 200 kV. The results are shown in [reference needed]. Figures 4-5 .

[0076] Bi4NbO8Cl was observed to have a plate-like structure with clearly visible lattice fringes. The interplanar spacing was measured to be 0.388 nm, corresponding to the (110) interplanar spacing of Bi4NbO8Cl, indicating that Bi4NbO8Cl exposes the (001) crystal plane.

[0077] Experimental Example 4. Characterization of Electron Spin Resonance Spectroscopy

[0078] The materials obtained in Comparative Example 1 and Example 2 of this invention were characterized using an electron spin resonance spectrometer (A300-10 / 12) from Bruker GmbH, Germany. See the results below. Figure 6 .

[0079] As shown in the figure, the presence of oxygen vacancy defects in the catalyst was detected using electron spin resonance spectroscopy. The symmetric ESR signal centered at g = 2.003 is a typical characteristic of oxygen vacancies. Bi4NbO8Cl-550 exhibits a high signal, indicating that a large number of oxygen vacancies were formed during the calcination reaction due to the presence of a reducing atmosphere. Introducing oxygen vacancies into Bi4NbO8Cl can reduce the band gap of the catalyst, expand the light absorption range, maximize the utilization of sunlight, and thus promote the photocatalytic reaction process.

[0080] Experimental Example 5. Catalytic Performance Test of Photocatalytic CO2 Cycloaddition Reaction with Epoxides

[0081] 1. Comparative experiment on photocatalytic CO2 cycloaddition reaction using the materials in the examples and comparative examples as catalysts.

[0082]

[0083] 50 mg of the materials obtained in Examples 1-3 and Comparative Example 1 were respectively placed in a 50 mL quartz reactor with 0.3 mmol of tetrabutylammonium bromide as a co-catalyst and 5 mL of 1,2-epoxybutane as a substrate. The quartz reactor was evacuated to a vacuum state and then purged with CO2 2-3 times. Afterwards, CO2 was purged to maintain a pressure of 1 atm. A constant temperature circulator (model CC-1008E) was used to maintain the reaction at 25°C or 60°C. The quartz reactor was then irradiated with a 300W xenon lamp for 4 hours. After the reaction was complete, the quartz reactor was removed, and 0.25 mmol of dodecane was added as an internal standard and mixed thoroughly. The mixture was then filtered through a 0.22 μm organic filter membrane to remove insoluble matter, and the reaction solution was transferred to a chromatographic vial. Gas chromatography was performed using an Agilent GC-6890N. The test results are shown in Table 1 and... Figure 7 As shown.

[0084] Table 1 Comparison of photocatalytic CO2 cycloaddition reactions with different catalysts

[0085]

[0086] As shown in the table, when only the co-catalyst tetrabutylammonium bromide is added (without adding any catalyst as the control group), the formation rate of the cyclic carbonate product is only 4210.4 μmol g. -1 h -1 When the layered bismuth semiconductor material of Comparative Example 1 is used alone, it exhibits a certain catalytic efficiency, but the effect is limited. However, the introduction of defect vacancies can effectively improve the product yield. Among them, Bi4NbO8Cl-550 shows the best catalytic performance, with a product formation rate of 9224.5 μmol g. -1 h -1 .

[0087] 2. Substrate expansion catalytic experiments of the material obtained in Example 2

[0088]

[0089] 50 mg of Bi4NbO8Cl-550 obtained in Example 2, 0.3 mmol of tetrabutylammonium bromide co-catalyst, 5 mL of N,N-dimethylformamide (an aprotic polar solvent), and 0.25 mmol of the epoxy derivatives with different substituents shown in Table 2 were placed in 50 mL quartz reactors. The quartz reactors were evacuated and then purged with CO2 2-3 times, followed by CO2 purging to maintain a pressure of 1 atm. The reaction was maintained at 60 °C using a constant temperature circulator (model CC-1008E), and then the quartz reactors were irradiated under a 300 W xenon lamp for 12 h. After the reaction was complete, the quartz reactors were removed, and the resulting solution was extracted with a 1:1 mixture of ethyl acetate and water. The insoluble matter was filtered off using a 0.22 μm organic filter membrane, and the reaction solution was transferred to a chromatographic vial. The products in the upper ethyl acetate layer were detected by gas chromatography (Agilent GC-6890N). The test results are shown in Table 2.

[0090] Table 2. Results of experimental substrate expansion for CO2 cycloaddition reaction catalysis

[0091]

[0092] As can be seen from the table, the material obtained by this invention can undergo cycloaddition reactions with a variety of epoxy compounds CO2, and has good substrate extensibility.

[0093] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The application of a layered bismuth-based semiconductor material Bi4NbO8Cl in the photocatalytic cycloaddition reaction of CO2 with epoxides, characterized in that, Based on the Sillén-Aurivillius structure bismuth-based semiconductor material, oxygen vacancies and low-valence metal ions generated in a reducing atmosphere promote the separation of photogenerated carriers and the adsorption and activation of epoxides, thereby improving the photocatalytic CO2 cycloaddition reaction performance; the preparation method of the layered bismuth-based semiconductor material Bi4NbO8Cl specifically includes the following steps: S1. Add the bismuth source and halogen source to a polar solvent, dissolve and mix them thoroughly, and then react completely at room temperature. After post-treatment, obtain a bismuth oxyhalide compound. The halogen source is selected from one or both of sodium chloride and potassium chloride. S2. Using the molten salt method, the bismuth oxyhalide compound obtained in step S1 and other solutes and fluxes are thoroughly mixed in a certain proportion at 700~850°C. o After complete high-temperature calcination and post-processing, a bismuth-based semiconductor material with a Sillén-Aurivillius structure is obtained; the other solutes are bismuth oxide and niobium oxide. S3. The bismuth-based semiconductor material with the Sillén-Aurivillius structure obtained in step S2 is calcined under a reducing atmosphere at 550 °C. o After C reacts completely, post-processing is performed to obtain the final product.

2. The application according to claim 1, characterized in that, In step S1, the bismuth source is bismuth nitrate, bismuth chloride, or bismuth bromide.

3. The application according to claim 1, characterized in that, In step S2, the flux is selected from one or more of sodium chloride, potassium chloride, and lithium chloride.

4. The application according to claim 1, characterized in that, In step S3, the reducing atmosphere is selected from one or both of carbon monoxide and hydrogen.

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