Preparation method and application of bismuth oxybromide loaded gold monatomic photocatalytic material

Abstract

The invention discloses a preparation method and application of a bismuth oxybromide supported gold monatomic photocatalytic material, and relates to the technical field of organic matter halogenation. In the photocatalytic material, the supported metal material is supported on the precursor in a monatomic form, and the metal material is uniformly dispersed in the monatomic form, so that the photocatalytic material shows excellent conversion rate and selectivity in a photocatalytic organic matter halogenation reaction. The invention also provides a preparation method and application of the photocatalytic material. According to the invention, gold single atoms are combined with a bismuth oxybromide photocatalytic material, so that the photocatalytic performance of the material is improved, the material shows excellent performance in photocatalytic toluene bromination, toluene can be rapidly halogenated, the reaction rate is relatively high, the selectivity is relatively high, the reaction conditions are mild, and environmental pollution and resource waste are not easy to cause.

Description

Technical Field

[0001] The present invention relates to the technical field of organic halogenation, and specifically relates to a preparation method and application of a bismuth oxybromide supported gold single-atom photocatalytic material. Background Art

[0002] Due to its high reactivity and wide range of chemical reactivity, benzyl bromide is an important organic intermediate in multiple fields, including chemical synthesis, pharmaceutical synthesis, materials science, etc. Its industrial applications cover aspects ranging from the synthesis of basic chemicals to the preparation of high-end drugs, providing important support for modern industry and scientific research. Therefore, the synthesis of benzyl bromide is of great significance. Traditional toluene bromination reactions usually rely on strong oxidants such as bromine chloride and hydrogen bromide, and often require high temperature and high pressure conditions to proceed effectively. These reactions are usually accompanied by side reactions, poor reaction selectivity, and harsh reaction conditions, which are prone to cause environmental pollution and resource waste. Therefore, developing an efficient, mild, and green catalyst to replace traditional brominating reagents has become an important research direction in the field of organic synthesis.

[0003] As a green chemical method, photocatalytic technology has received extensive attention in recent years. Photocatalytic reactions can utilize solar energy or visible light to drive chemical reactions under mild conditions, reduce energy consumption, and effectively avoid side reactions and environmental pollution commonly found in traditional methods. Semiconductor materials such as titanium dioxide (TiO2) as typical photocatalysts have been widely used in fields such as pollutant degradation, water treatment, and hydrogen production. However, titanium dioxide materials have a relatively large band gap, are mainly sensitive to ultraviolet light, and their photo-generated electrons and holes are prone to recombination, resulting in low catalytic efficiency. Therefore, how to improve the efficiency of photocatalysts and broaden their response to visible light has become an important topic in catalytic research.

[0004] Bismuth oxyhalide (Bi5O7Br) is a type of photocatalytic material with a relatively narrow bandgap, capable of absorbing light energy in the ultraviolet to visible light range, promoting the generation of photo-generated electrons and holes. Therefore, bismuth oxyhalide materials exhibit excellent catalytic performance in photocatalytic reactions, especially having high activity in the oxidation reaction of organic substances. However, the photocatalytic performance of bismuth oxyhalide is limited by the recombination of photo-generated carriers. Especially under visible light, the effective separation and migration of its photo-generated electrons and holes are poor, thus affecting the catalytic efficiency. To improve the photocatalytic performance of bismuth oxyhalide materials, single-atom catalysts (SACs) have become a research hotspot in catalysis in recent years. Gold (Au), as a noble metal element, has unique catalytic properties. Gold single-atom catalysts can effectively improve the selectivity and efficiency of catalytic reactions. Gold single atoms can enhance the performance of catalytic reactions by inducing local electric field effects, enhancing the separation of photo-generated carriers, and providing active sites. In addition, gold single atoms can optimize the catalytic process through the synergistic effect with the support material. Therefore, loading gold single atoms on photocatalytic materials, especially bismuth oxyhalide, can greatly improve its catalytic efficiency. The gold single-atom loaded bismuth oxyhalide composite material, as a novel photocatalyst, combines the good light absorption characteristics of bismuth oxyhalide and the excellent catalytic performance of gold single atoms, and has become a research hotspot in the field of photocatalysis. By loading gold single atoms on the surface of bismuth oxyhalide, the following advantages can be achieved: improving the separation efficiency of photo-generated carriers, reducing electron-hole recombination; enhancing the absorption ability of visible light, improving the photocatalytic activity of the catalyst; providing more catalytic sites in the reaction, improving the selectivity and efficiency of the reaction.

[0005] In the toluene bromination reaction, the gold single-atom loaded bismuth oxyhalide catalyst can not only achieve the reaction under mild visible light irradiation, but also effectively promote the generation of bromine radicals, thereby increasing the rate and selectivity of the bromination reaction. Therefore, developing this gold single-atom loaded bismuth oxyhalide photocatalyst can provide an efficient, green and visible-light-condition applicable catalytic system for the toluene bromination reaction. Summary of the Invention

[0006] To solve the above technical problems, the purpose of the present invention is to provide a preparation method and application of a bismuth oxybromide loaded with gold single atoms photocatalytic material, which combines gold single atoms with bismuth oxybromide photocatalytic material to improve the photocatalytic performance of the material, and exhibits excellent performance in photocatalytic toluene bromination, enabling toluene to be rapidly halogenated, with a relatively fast reaction rate, high selectivity, and mild reaction conditions, and is not likely to cause environmental pollution and waste of resources.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: A bismuth oxybromide supported gold single-atom photocatalytic material is provided, and the supported metal material is loaded onto the precursor in the form of single atoms, and the metal material is uniformly dispersed in the form of single atoms, showing excellent conversion rate and selectivity in the photocatalytic organic halogenation reaction.

[0008] Furthermore, the bismuth oxybromide supported gold single-atom photocatalytic material is a nanotube or nanosheet material, which has a large light absorption area in the photocatalytic reaction, thereby achieving higher electron transfer efficiency and photoelectric conversion efficiency.

[0009] Furthermore, the inner diameter of the nanotube of the bismuth oxybromide supported gold single-atom photocatalytic material is 5 nm, and the length is 5 - 50 nm.

[0010] The present invention also provides a preparation method of the above bismuth oxybromide supported gold single-atom photocatalytic material, including the following steps:

[0011] (1) Add bismuth salt, mannitol and polyvinylpyrrolidone into deionized water and mix evenly, then add bromide salt, adjust the pH and perform hydrothermal reaction, and then wash and dry in sequence to obtain a precursor material;

[0012] (2) Add the precursor material obtained in step (1) into deionized water and mix evenly, then add chloroauric acid and mix and stir. Wrap the reaction vessel with tin foil and punch holes at the top, irradiate with ultraviolet light, and then wash and dry in sequence to obtain the bismuth oxybromide supported gold single-atom photocatalytic material.

[0013] Furthermore, in step (1), the molar ratio of bismuth salt, mannitol and polyvinylpyrrolidone is 1:2 - 3:3 - 4.

[0014] Furthermore, in step (1), the molar ratio of bismuth salt, mannitol and polyvinylpyrrolidone is 1:2.5:3.6.

[0015] Furthermore, in step (1), the bromide salt is sodium bromide or potassium bromide; the bismuth salt is bismuth nitrate pentahydrate.

[0016] Furthermore, in step (1), adjust the pH to alkaline, place it in a reaction kettle and perform hydrothermal reaction at a temperature of 120 - 150 °C for 2 - 4 h.

[0017] Furthermore, in step (1), wash with deionized water and ethanol, and dry at a temperature of 60 °C for 10 h.

[0018] Furthermore, in step (2), the mass-volume ratio of the precursor material, chloroauric acid and deionized water is 100 mg:1.72 - 17.2 mg:30 - 50 mL.

[0019] Furthermore, in step (2), wash with deionized water and ethanol, and dry at a temperature of 60 °C for 6 h.

[0020] The present invention also provides the application of the above-mentioned bismuth oxybromide supported single-atom gold photocatalytic material in the preparation of organic halides.

[0021] The present invention has the following beneficial effects:

[0022] 1. The present invention synthesizes a single-atom gold supported bismuth oxybromide photocatalytic material through a hydrothermal method and a photochemical deposition method, which has better photocatalytic performance than other photocatalytic materials. The loading of single-atom gold can significantly enhance the light absorption ability of bismuth oxybromide, especially in the visible light range. This enhancement is attributed to the local surface plasmon resonance (LSPR) effect of single-atom gold, which synergistically acts with the photocatalytic activity of bismuth oxybromide, thereby improving the catalytic efficiency. A high reaction rate is shown in chemical reactions (such as photocatalytic bromination reactions).

[0023] 2. The combination of single-atom gold and bismuth oxybromide can effectively prevent the inactivation of the photocatalytic material during long-term reactions, ensuring the stability of the catalyst. This material can usually maintain a high activity during multiple catalytic cycles, making it more economical and environmentally friendly in industrial applications.

[0024] 3. The single-atom catalyst obtained in the present invention is a heterogeneous catalyst in the system, which can be recycled, has good cyclic economic benefits, high atomic utilization rate, and has great practical significance in industrial production based on the characteristics of good selectivity, high conversion rate, and good cyclic stability. Description of the Drawings

[0025] Figure 1 It is the transmission electron microscope image of the bismuth oxybromide supported single-atom gold photocatalytic material obtained in Example 1;

[0026] Figure 2 It is the AC-HAADF-STEM-EDS mapping image of the bismuth oxybromide material before and after loading single-atom gold;

[0027] Figure 3 It is the columnar diagram of the reaction conversion rate and selectivity of the single-atom gold supported bismuth oxybromide catalytic material for 5 cycles of bromotoluene;

[0028] Figure 4 It is the experimental result of the photocatalytic continuous flow system. Detailed Embodiments

[0029] The principles and features of the present invention are described below. The examples given are only used to explain the present invention and are not intended to limit the scope of the present invention. Those not specified in the examples are carried out according to conventional conditions or the conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0030] Example 1

[0031] A bismuth oxybromide supported gold single-atom photocatalytic material, and its preparation method includes the following steps:

[0032] (1) Bismuth nitrate pentahydrate, mannitol and polyvinylpyrrolidone are added to 30 mL of deionized water in a molar ratio of 1:2.5:3.6 and mixed evenly. Then, 2 M potassium bromide is added, the pH is adjusted to alkaline, and the mixture is placed in a reaction kettle and hydrothermally reacted at 140 °C for 3 h. It is washed with deionized water and ethanol and dried at 60 °C for 10 h to obtain a precursor material.

[0033] (2) 100 mg of the precursor material obtained in step (1) is added to 40 mL of deionized water and mixed evenly for 40 min. Then, 1.72 mg of chloroauric acid is added and stirred for 3 min. The beaker is wrapped with tin foil and 10 evenly distributed small holes are pricked at the top. It is irradiated with ultraviolet light for 10 min, washed with deionized water and ethanol, and dried at 60 °C for 6 h to obtain the bismuth oxybromide supported gold single-atom photocatalytic material.

[0034] The transmission electron microscope image of the bismuth oxybromide supported gold single-atom photocatalytic material obtained in Example 1 is as Figure 1 shown; while the AC-HAADF-STEM-EDS mapping images of the bismuth oxybromide material before and after loading gold single atoms are as Figure 2 shown; and the columnar diagram of the reaction conversion rate and selectivity of the bismuth oxybromide catalytic material loaded with gold single atoms in 5 cycles of bromotoluene experiments is as Figure 3 shown; based on the excellent photocatalytic reaction of bromotoluene of this material, an experiment on a photocatalytic continuous flow system is carried out, and the test results are as Figure 4 shown.

[0035] It can be seen from Figure 1 that a nanotube material with a length of about 5-10 nm is successfully synthesized, and no particles are observed on the surface.

[0036] It can be seen from Figure 2 that the bismuth oxybromide precursor has been successfully loaded with Au single atoms, and the Au, Bi, and Br elements are evenly distributed on the nanotubes.

[0037] It can be seen from Figure 3 that Au-BOB has excellent stability.

[0038] It can be seen from Figure 4 that the Au-BOB material shows excellent conversion rate and selectivity during continuous photocatalysis for 20 h.

[0039] Performance test:

[0040] Weigh 5 mg of the bismuth oxybromide-supported single-atom gold photocatalytic material (Au / BOB) obtained in Example 1, 0.5 mmol of toluene, and 6 mL of DCE and add them to a photocatalytic tube. Mix them evenly, stir for 30 min in a dark environment to achieve the adsorption-desorption equilibrium of the reaction substrates on the photocatalyst surface. Before the reaction starts, pass nitrogen to saturate and then carry out visible light irradiation. Sampling is carried out every 30 s. In order to detect the stability of the catalyst, a cyclic experiment is conducted. After 5 cycles, the catalyst still exhibits high catalytic performance and good stability.

[0041] Comparative Example 1

[0042] BOB catalyst without loading single-atom gold.

[0043] Comparative Example 2

[0044] Only chloroauric acid.

[0045] Comparative Example 3

[0046] Only Au nanoparticles.

[0047] Comparative Example 4

[0048] Use Au-M-A-LDH catalyst.

[0049] Carry out the photocatalytic bromination reaction of toluene with the catalytic material obtained in Example 1 and the products obtained in Comparative Examples 1-4. And use the catalytic material obtained in Example 1 with reaction substrates toluene, o-dichlorobenzene, p-dichlorobenzene, and p-chloroaniline respectively. The results are shown in Table 1.

[0050] Table 1 Performance test of photocatalytic organic bromination reaction

[0051] Reaction time / min Conversion rate Selectivity Example 1 2 100％ 100％ Example 2 2 79.42％ 100％ Example 3 2 89.73％ 100％ Example 4 2 100％ 75.37％ Comparative example 1 10 - - Comparative example 2 2 100％ 100％ Comparative example 3 2 35.43％ 100％ Comparative example 4 10 - -

[0052] As can be seen from Table 1, when the bismuth oxybromide-supported single-atom gold photocatalytic material of the present invention is used for catalyzing the halogenation of organic compounds, the reaction rate is relatively fast, the conversion rate is high, and the selectivity is relatively high. While the reaction rates of the BOB catalyst without loading single-atom gold and the Au-M-A-LDH catalyst are relatively slow and require a long reaction time. Chloroauric acid and Au nanoparticles have a certain conversion rate in catalytic performance, but from the perspective of atomic utilization rate and economic benefits, their atomic utilization rate is relatively low. In addition, in this reaction system, chloroauric acid and Au nanoparticles belong to homogeneous catalysts, while the single-atom gold catalyst is a heterogeneous catalyst, enabling the catalyst to be recycled multiple times after the reaction, greatly improving the stability and recycling value of the catalyst. Therefore, in industrial applications, under the same Au content, the Au single-atom catalyst exhibits better utilization rate and greater application potential, and is expected to play an important role in catalyst cost control and sustainable development.

[0053] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A bismuth oxybromide-loaded gold single atom photocatalytic material, characterized in that: The loaded metal material is loaded onto the precursor in the form of single atoms, and the metal material is evenly dispersed in the form of single atoms, showing excellent conversion rate and selectivity in the photocatalytic organic halogenation reaction.

2. The method for preparing the bismuth oxybromide-supported gold single atom photocatalytic material according to claim 1, characterized in that: The following steps are involved: (1) adding bismuth salt, mannitol and polyvinyl pyrrolidone into deionized water and mixing them evenly, then adding bromide salt, adjusting the pH value and performing hydrothermal reaction, and then washing and drying in sequence to obtain a precursor material; (2) Add the precursor material obtained in step (1) into deionized water and mix well, then add chloroauric acid and mix and stir, wrap the reaction container with tin foil and pierce holes on the top, irradiate with ultraviolet light, and then wash and dry in sequence to obtain bismuth oxybromide loaded with gold single atom photocatalytic material.

3. The method for preparing the bismuth oxybromide-supported gold single-atom photocatalytic material according to claim 2, characterized in that: In step (1), the molar ratio of bismuth salt, mannitol and polyvinyl pyrrolidone is 1:2-3:3-4.

4. The method for preparing the bismuth oxybromide supported gold single atom photocatalytic material according to claim 2 or 3, characterized in that: In step (1), the molar ratio of bismuth salt, mannitol and polyvinyl pyrrolidone is 1:2.5:3.

6.

5. The method for preparing the bismuth oxybromide-supported gold single-atom photocatalytic material according to claim 2, characterized in that: In step (1), the bromine salt is sodium bromide or potassium bromide; and the bismuth salt is bismuth nitrate pentahydrate.

6. The method for preparing the bismuth oxybromide-supported gold single atom photocatalytic material according to claim 2, characterized in that: In step (1), the pH is adjusted to alkaline, and the mixture is placed in a reaction vessel and subjected to hydrothermal reaction at 120-150° C. for 2-4 hours.

7. The method for preparing the bismuth oxybromide-supported gold single atom photocatalytic material according to claim 2, characterized in that: In step (1), the product is washed with deionized water and ethanol and dried at 60° C. for 10 h.

8. The method for preparing the bismuth oxybromide-supported gold single atom photocatalytic material according to claim 2, characterized in that: In step (2), the mass volume ratio of the precursor material, chloroauric acid and deionized water is 100 mg: 1.72-17.2 mg: 30-50 mL.

9. The method for preparing the bismuth oxybromide-supported gold single atom photocatalytic material according to claim 2, characterized in that: In step (2), the product is washed with deionized water and ethanol and dried at 60° C. for 6 h.

10. Use of the bismuth oxybromide supported gold single atom photocatalytic material according to claim 1 in the preparation of organic halides.

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