Heterojunction catalysts, methods of making and use

Abstract

The application provides a heterojunction catalyst, a preparation method and application, and belongs to the technical field of organic chemistry. The preparation method of the heterojunction catalyst comprises the following steps: dispersing wide-bandgap metal oxide nanoparticles in a first solvent to obtain a first solution; dispersing a metal boride in a second solvent to obtain a second solution; adding the second solution into the first solution and performing heating treatment to obtain a heterojunction precursor; and performing calcination treatment on the heterojunction precursor under an inert atmosphere to obtain the heterojunction catalyst; and the band gap of the wide-bandgap metal oxide nanoparticles is greater than 3eV. The metal boride can absorb light energy and generate hot electrons, which can be effectively transferred to a reaction active site to activate reactants, and is conducive to subsequent application in the preparation of cyclic carbonates in an infrared spectrum.

Description

Technical Field

[0001] This invention relates to the field of organic chemistry, and in particular to a heterojunction catalyst, its preparation method, and its application. Background Technology

[0002] With societal development, the non-renewable nature of fossil fuels has driven humanity to seek alternative energy sources. The depletion of oil and fossil fuels has led to a continuous rise in emissions, primarily carbon dioxide, resulting in a greenhouse effect that has profoundly impacted the ecological environment and climate. Against the backdrop of optimizing ecological environment construction, exploring how to catalytically convert carbon dioxide, a C1 resource, into high-value-added multi-carbon chemicals presents a very attractive application prospect.

[0003] Among related technologies, fixing carbon dioxide into cyclic carbonates is a relatively green and atom-economical approach. However, the production of cyclic carbonates is subject to several thermodynamic limitations, as it often relies on thermal energy as an external energy source. Therefore, achieving carbon dioxide recovery and utilization, as well as conducting research to improve the reaction selectivity and yield of cyclic carbonates, is of great significance. Summary of the Invention

[0004] In view of this, in order to at least partially solve at least one of the aforementioned technical problems, the present invention provides a heterojunction catalyst, a preparation method thereof, and an application thereof.

[0005] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows:

[0006] According to one aspect of the present invention, a method for preparing a heterojunction catalyst is provided, comprising: dispersing wide-bandgap metal oxide nanoparticles in a first solvent to obtain a first solution; dispersing a metal boride in a second solvent to obtain a second solution; adding the second solution to the first solution and heating it to obtain a heterojunction precursor; calcining the heterojunction precursor under an inert atmosphere to obtain a heterojunction catalyst; wherein the bandgap of the wide-bandgap metal oxide nanoparticles is greater than 3 eV.

[0007] According to some embodiments of the present invention, metal borides are prepared by the following process: adding a metal salt to a third solvent and stirring to obtain a metal salt solution; adding a reducing agent to a fourth solvent and stirring to obtain a reducing agent solution; and adding the reducing agent solution dropwise to the metal salt solution while stirring to carry out a reduction reaction to obtain metal borides.

[0008] According to some embodiments of the present invention, the molar ratio of metal salt to reducing agent is 1:(2~6); the reduction reaction is carried out at room temperature for 0.5~6 h; the concentration of metal salt in the third solvent is 0.002~10 mol / L; the reducing agent includes sodium borohydride or potassium borohydride; the concentration of reducing agent in the fourth solvent is 0.05~5 mol / L; and the dropping rate is 0.1-2 mL / min.

[0009] According to some embodiments of the present invention, the wide-bandgap metal oxide nanoparticles include at least one of cerium dioxide, germanium dioxide, zirconium dioxide, titanium dioxide, tin dioxide, indium oxide, gallium oxide, and bismuth oxide; the metal salt includes nickel salt or iron salt; preferably, the metal salt includes at least one of nickel chloride hexahydrate, nickel sulfate hexahydrate, nickel bromide trihydrate, nickel nitrate hexahydrate, ferric nitrate nonahydrate, ferric chloride hexahydrate, and ferric bromide trihydrate.

[0010] According to some embodiments of the present invention, the diameter of the wide-bandgap metal oxide nanoparticles is 10~200 nm; the mass ratio of metal borides to wide-bandgap metal oxide nanoparticles is 1:(10~100).

[0011] According to some embodiments of the present invention, the temperature of the heat treatment is 100~120℃; the conditions for the calcination treatment are: heating from room temperature to 250~350℃ at a heating rate of 3~10℃ / min, and calcining at 250~350℃ for 0.5~6h.

[0012] According to another aspect of the present invention, a heterojunction catalyst is provided, which is prepared by the preparation method described above.

[0013] According to another aspect of the present invention, an application of infrared light-driven catalytic preparation of cyclic carbonates is provided, comprising: adding the heterojunction catalyst, quaternary ammonium salt co-catalyst, and epoxide as described above to a fifth solvent and stirring, introducing an inert gas to remove air from the fifth solvent to obtain a third solution; introducing carbon dioxide into the third solution and carrying out a catalytic reaction under infrared light irradiation and atmospheric pressure to obtain cyclic carbonates.

[0014] According to some embodiments of the present invention, infrared light is formed by attaching a CUT800 filter to a xenon lamp; the illuminance of the infrared light is 300-500 mW / cm². 2 The reaction time for the catalytic reaction is 8~24h.

[0015] According to some embodiments of the present invention, the quaternary ammonium salt co-catalyst includes tetrabutylammonium bromide; the added mass of the quaternary ammonium salt co-catalyst is 0.005~0.5g, and the volume of the epoxide is 0.02~0.5mL; the epoxide includes bromopropylene oxide.

[0016] Based on the above technical solution, the heterojunction catalyst, preparation method, and application provided by this invention utilize metal borides to absorb light energy. Because boron is doped within the metal lattice, the work function (the minimum energy required for electrons to escape from the crystal surface) decreases, which facilitates the escape of electrons from the metal boride surface, transforming them into excited electronic states (i.e., hot electrons), thereby initiating electron transitions while retaining metallic properties. Since the metal borides and wide-bandgap metal oxide nanoparticles carry opposite charges on their surfaces, electrostatic attraction occurs between them during mixing, promoting full contact between the metal borides and wide-bandgap metal oxide nanoparticles. Further calcination treatment allows chemical interactions to form between the metal borides and wide-bandgap metal oxide nanoparticles, creating an in-plane heterostructure with high catalytic activity, which facilitates efficient electron injection and transport. When this heterojunction catalyst is used for photocatalytic preparation of cyclic carbonates from carbon dioxide and epoxides, the metal boride in the heterojunction catalyst absorbs the energy of infrared light, efficiently transfers the hot electrons generated by photoexcitation and injects them into the conduction band of the wide-bandgap metal oxide nanoparticles, and stores them through redox ion pairs. The synthesis of infrared light-driven cyclic carbonates is achieved through the activation effect of these electrons on the epoxides. The synthesis process is simple and effective. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0018] Figure 1 A flowchart illustrating the preparation method of the heterojunction catalyst according to an embodiment of the present invention is shown;

[0019] Figure 2 The X-ray diffraction pattern of the heterojunction catalyst 1 of Example 1 of the present invention is shown; Figure 3 The X-ray diffraction pattern of the heterojunction catalyst 2 of Example 2 of the present invention is shown;

[0020] Figure 4 The 1H NMR spectrum of bromopropylene carbonate of Example 3 of the present invention is shown.

[0021] Figure 5 The 1H NMR spectrum of bromopropylene carbonate of Example 4 of the present invention is shown. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0023] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the invention. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the invention for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0024] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "comprising" as used herein indicates the presence of features, steps, or operations, but does not exclude the presence or addition of one or more other features.

[0025] When using expressions such as "at least one of A, B, and C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, and C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.). When using expressions such as "at least one of A, B, or C," the expression should generally be interpreted in accordance with the meaning commonly understood by a person skilled in the art (e.g., "a system having at least one of A, B, or C" should include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B, having A and C, having B and C, and / or having A, B, and C, etc.).

[0026] Currently, cyclic carbonates have been widely used and developed in the electronics industry, especially in the field of new energy vehicles, where they are increasingly demonstrating significant industrial value as excellent electrolytes for batteries and capacitors. However, traditional cyclic carbonate production methods still primarily rely on thermal energy as the external energy source, typically involving high-temperature and high-pressure reaction conditions. Related technologies also utilize ultraviolet and visible light as external energy sources to catalyze the conversion of carbon dioxide into cyclic carbonates. However, this limits the availability of ultraviolet and visible light, making it difficult to expand the utilization efficiency of sunlight and restricting its application in practical production.

[0027] In realizing the concept of this invention, it was discovered that, to solve the aforementioned problems, metal borides can be introduced into heterojunction catalysts. By using metal borides as light absorption and trapping centers, photons can be absorbed and hot electrons generated. Doping the metal lattice with boron alters the metal's electronic structure, facilitating the escape of electrons from the surface of the metal borides while retaining the metal's properties. This effectively expands the utilization efficiency of sunlight, reduces side reactions, and improves product selectivity. However, due to the low energy of infrared light, the recombination rate of photogenerated carriers is relatively high, making it difficult to achieve large-scale production of carbon dioxide catalytic conversion.

[0028] Furthermore, to address the aforementioned issues, a chemical interaction was formed by tightly binding wide-bandgap metal oxide nanoparticles with metal borides. This enabled the prepared heterojunction catalyst to not only effectively absorb infrared light energy but also efficiently transfer and inject photoexcited hot electrons into the conduction band of the wide-bandgap metal oxide, where they are stored as redox ions. This facilitates the subsequent activation of epoxides using these hot electrons, enabling the efficient infrared-driven synthesis of cyclic carbonates.

[0029] Therefore, this invention combines the characteristics of metal borides absorbing and capturing photons and converting them into electrons with the redox ions of wide-bandgap metal oxide nanoparticles storing electrons, which helps to effectively inject and transport electrons. This enables the heterojunction catalyst to catalyze the preparation of cyclic carbonates from carbon dioxide and epoxides even under the driving force of low-energy infrared light, thus broadening the utilization efficiency of sunlight, reducing the occurrence of side reactions, and improving the reaction selectivity and yield of cyclic carbonates.

[0030] Figure 1 A flowchart illustrating the preparation method of the heterojunction catalyst according to an embodiment of the present invention is shown.

[0031] like Figure 1 As shown, the method includes steps S101 to S104.

[0032] In step S101, wide-bandgap metal oxide nanoparticles are dispersed in a first solvent to obtain a first solution.

[0033] In step S102, the metal boride is dispersed in a second solvent to obtain a second solution.

[0034] In step S103, the second solution is added to the first solution and heated to obtain the heterojunction precursor.

[0035] In step S104, the heterojunction precursor is calcined under an inert atmosphere to obtain a heterojunction catalyst.

[0036] According to some embodiments of the present invention, the band gap of the wide bandgap metal oxide nanoparticles is greater than 3 eV, for example, it can be 3.1 eV, 3.2 eV, 3.3 eV, 3.4 eV, 3.5 eV, 3.6 eV, 3.7 eV, 3.8 eV, 3.9 eV, 4.0 eV, 4.5 eV, 5.0 eV, 5.5 eV, 6.0 eV, etc.

[0037] According to some embodiments of the present invention, a first solvent is used to disperse and dissolve wide-bandgap metal oxide nanoparticles, and a second solvent is used to disperse and dissolve metal borides. Utilizing the opposite charge of the metal borides and wide-bandgap metal oxide nanoparticles, electrostatic attraction is formed during mixing. Heating promotes full contact between the two. Calcination of the resulting heterojunction precursor under an inert atmosphere facilitates chemical interaction and tight bonding between the metal borides and wide-bandgap metal oxide nanoparticles, thereby forming a heterojunction structure with high catalytic activity. This invention utilizes boron doping in the metal borides to absorb infrared light and reduce the energy required for the escape of hot electrons, which helps to absorb infrared light energy and generate hot electrons, thus broadening the utilization range of the solar spectrum. The tight bonding between the wide-bandgap metal oxide nanoparticles and the metal borides facilitates the efficient transfer and injection of hot electrons into the conduction band of the wide-bandgap metal oxide nanoparticles for storage. The wide-bandgap metal oxide nanoparticles serve as active sites for catalytic reactions. Utilizing these hot electrons to activate epoxides promotes the synthesis of cyclic carbonates, improves the reaction selectivity of cyclic carbonates, and enables practical large-scale production.

[0038] According to some embodiments of the present invention, the diameter of the wide-bandgap metal oxide nanoparticles is 10-200 nm, for example, 10 nm, 30 nm, 50 nm, 60 nm, 80 nm, 100 nm, 130 nm, 150 nm, 180 nm, or 200 nm. The mass ratio of metal borides to wide-bandgap metal oxide nanoparticles is 1:(10-100), for example, 1:10, 1:20, 1:30, 1:40, 1:50, 1:60, 1:70, 1:80, 1:90, or 1:100. If the mass ratio of metal borides to wide-bandgap metal oxide nanoparticles is too high, some metal borides will fail to form bonds, resulting in poor infrared light absorption of the final heterojunction catalyst; if the ratio is too low, the amount of wide-bandgap metal oxide nanoparticles added will be insufficient, providing fewer active sites for the catalytic reaction and reducing the catalytic activity.

[0039] According to some embodiments of the present invention, the heat treatment temperature is 100~120°C, for example, 100°C, 110°C, or 120°C. The heat treatment is to evaporate the solvent in the first and second solutions to obtain the heterojunction precursor. The calcination conditions are as follows: heating from room temperature to 250~350°C, for example, 250°C, 300°C, or 350°C, at a heating rate of 3~10°C / min, for example, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, or 10°C / min, and calcining at 250~350°C for 0.5~6 hours, for example, 0.5 hours, 2 hours, 3 hours, 5 hours, or 6 hours. The calcination treatment is to promote the tight bonding of the metal boride and the wide-bandgap metal oxide nanoparticles, forming a chemical interaction.

[0040] According to some embodiments of the present invention, the wide-bandgap metal oxide nanoparticles include at least one of cerium dioxide, germanium dioxide, zirconium dioxide, titanium dioxide, tin dioxide, indium oxide, gallium oxide, and bismuth oxide. Other types of wide-bandgap metal oxide nanoparticles may also be selected as needed. It is worth noting that the type of wide-bandgap metal oxide nanoparticles affects their solubility and dispersibility in the first solvent, and careful selection of the type of wide-bandgap metal oxide nanoparticles is necessary.

[0041] According to some specific embodiments of the present invention, the preparation method of the heterojunction catalyst may specifically include: in step S101, dispersing wide-bandgap metal oxide nanoparticles in a first solvent, and then uniformly dispersing them by ultrasound to obtain a first solution. In step S102, dispersing a metal boride in a second solvent, and then uniformly dispersing it by ultrasound to obtain a second solution. The first solvent and the second solvent are respectively selected from at least one of water, methanol, and ethanol; the first solvent and the second solvent may be the same or different. In step S103, the second solution is slowly added dropwise to the first solution at a dropping rate of 0.5~10 mL / min, for example, 0.5 mL / min, 1 mL / min, 3 mL / min, 5 mL / min, 7 mL / min, 9 mL / min, or 10 mL / min. Controlling the dropping rate within the above range aims to improve the dispersion uniformity of the wide-bandgap metal oxide nanoparticles and the metal boride, and to avoid agglomeration. In step S104, an inert atmosphere is used, such as a nitrogen atmosphere, an argon atmosphere, or a mixture thereof. For example, programmed heating can be used to raise the temperature during calcination.

[0042] According to some embodiments of the present invention, metal borides are prepared by the following process: adding a metal salt to a third solvent and stirring to obtain a metal salt solution; adding a reducing agent to a fourth solvent and stirring to obtain a reducing agent solution; and adding the reducing agent solution dropwise to the metal salt solution while stirring to carry out a reduction reaction, thereby obtaining the metal borides. By doping boron into the metal lattice through the reduction process, hot electrons are more easily emitted from the metal borides, enabling the prepared heterojunction catalyst to not only effectively absorb infrared light energy through the doped boron, but also, due to the presence of the metal, facilitate the transfer of photoexcited hot electrons.

[0043] According to some embodiments of the present invention, the molar ratio of metal salt to reducing agent is 1:(2~6), for example, it can be 1:2, 1:3, 1:4, 1:5 or 1:6. When the molar ratio of metal salt to reducing agent is within the above range, the reducing agent is in the range of excess addition, which can fully reduce the metal salt without wasting resources due to excessive addition of reducing agent.

[0044] The reduction reaction is carried out at room temperature for a time of 0.5–6 h, for example, 0.5 h, 2 h, 3 h, 5 h, or 6 h. The concentration of the metal salt in the third solvent is 0.002–10 mol / L, for example, 0.002 mol / L, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, or 10 mol / L. The reducing agent includes sodium borohydride or potassium borohydride, preferably sodium borohydride. The concentration of the reducing agent in the fourth solvent is 0.05–5 mol / L, for example, 0.05 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, or 5 mol / L. The dropping rate should be 0.1-2 mL / min, for example, 0.1 mL / min, 0.5 mL / min, 1 mL / min, 1.5 mL / min, or 2 mL / min. Controlling the dropping rate within this range helps prevent the reduction reaction from becoming too vigorous and causing other side reactions.

[0045] According to some embodiments of the present invention, the metal salt includes nickel salts or iron salts; preferably, it specifically includes at least one of nickel chloride hexahydrate, nickel sulfate hexahydrate, nickel bromide trihydrate, nickel nitrate hexahydrate, ferric nitrate nonahydrate, ferric chloride hexahydrate, and ferric bromide trihydrate. During the experiments related to the present invention, it was found that when the aforementioned nickel or iron salts are used as the metal salt, the prepared metal boride exhibits relatively better absorption of infrared light and transfer of hot electrons.

[0046] According to some embodiments of the present invention, the selection range of the third solvent and the fourth solvent is the same as that of the first solvent and the second solvent described above, and will not be repeated here.

[0047] According to some specific embodiments of the present invention, in the preparation process of metal borides: when adding the metal salt to the third solvent and stirring, adding the reducing agent to the fourth solvent and stirring, and mixing and stirring the reducing agent solution and the metal salt solution, magnetic stirring or mechanical stirring can be selected as needed. The stirring speed can be, for example, 300~1600 r / min, such as 500 r / min, 600 r / min, 800 r / min, 1000 r / min, 1400 r / min, or 1500 r / min. During the reduction reaction, the reaction solution composed of the reducing agent solution and the metal salt solution is transferred to a glass container, such as a beaker, a three-necked flask, or a flask. The ratio of the reaction solution to the solvent in the glass container is 1:4~1:10 to avoid a vigorous reduction reaction and splashing of the reaction solution out of the glass container, thus preparing a precipitate. The precipitate is then separated, washed, dried, and ground sequentially to obtain metal borides. For example, it can be centrifuged at 10,000 to 14,000 r / min for 2 to 10 min, washed three times with water and ethanol solutions respectively, dried at 60 to 100°C for 8 to 20 h, and then ground to obtain metal borides.

[0048] According to another aspect of the present invention, a heterojunction catalyst is provided, which is prepared by the above-described preparation method.

[0049] According to some embodiments of the present invention, this heterojunction catalyst can absorb the energy of infrared light, efficiently transfer and inject the photoexcited hot electrons into the conduction band of wide-bandgap metal oxide nanoparticles, and store them through redox ion pairs. The wide-bandgap metal oxide nanoparticles provide active sites for catalytic reactions, facilitating their subsequent application in infrared photodriven catalytic preparation of cyclic carbonates.

[0050] According to another aspect of the present invention, an application of infrared light-driven catalytic preparation of cyclic carbonates is provided, comprising: adding the above-mentioned heterojunction catalyst, quaternary ammonium salt co-catalyst, and epoxide to a fifth solvent and stirring, introducing an inert gas to remove air from the fifth solvent to obtain a third solution; introducing carbon dioxide into the third solution and carrying out a catalytic reaction under infrared light irradiation and atmospheric pressure to obtain cyclic carbonates.

[0051] According to some embodiments of the present invention, the metal boride in the heterojunction catalyst can absorb infrared light and generate hot electrons that are injected into the semiconductor conduction band of the wide-bandgap metal oxide nanoparticles. The wide-bandgap metal oxide nanoparticles serve as active sites for the catalytic reaction, transferring the hot electrons stored in the redox ion pairs in the conduction band to the epoxide, thereby activating the epoxide and achieving efficient synthesis of cyclic polycarbonates. Conducting the reaction at atmospheric pressure reduces operating costs while maintaining the feasibility of the reaction. Adding a quaternary ammonium salt co-catalyst helps stabilize intermediates in the catalytic reaction, lowers the activation energy, and improves reaction efficiency.

[0052] According to some embodiments of the present invention, the fifth solvent may be, for example, N,N-dimethylformamide. N,N-dimethylformamide has good solubility and can dissolve the reactants, which helps to ensure uniform dispersion during the reaction process and avoids agglomeration. Preferably, the volume of N,N-dimethylformamide is 1 to 5 mL. The inert gas is at least one of nitrogen and argon.

[0053] According to some embodiments of the present invention, infrared light is generated by attaching a CUT800 filter to a xenon lamp. The CUT800 filter is capable of filtering out the spectrum below 800 nm while retaining the spectrum above 800 nm. The illuminance of the infrared light is 300-500 mW / cm². 2 For example, it could be 300mW / cm 2 350mW / cm 2 400mW / cm 2 450mW / cm 2 Or 500mW / cm 2 By using lower-energy infrared light, this invention not only expands the utilization efficiency of sunlight but also reduces side reactions, improves product selectivity, and highlights its industrial potential. This invention combines a light-harvesting center and a catalytic reaction center, leveraging their synergistic effect to facilitate the large-scale production of carbon dioxide through catalytic conversion. The reaction time for the catalytic reaction is 8–24 hours, for example, 8 hours, 10 hours, 15 hours, 20 hours, or 24 hours.

[0054] According to some embodiments of the present invention, the quaternary ammonium salt co-catalyst comprises tetrabutylammonium bromide. The mass of the quaternary ammonium salt co-catalyst added is 0.005~0.5 g, for example, 0.005 g, 0.1 g, 0.2 g, 0.3 g, 0.4 g, or 0.5 g. The volume of the epoxide is 0.02~0.5 mL, for example, 0.1 mL, 0.2 mL, 0.3 mL, 0.4 mL, or 0.5 mL. The epoxide comprises brominated propylene oxide. During the experiments related to the present invention, it was found that when reactants within the above-mentioned range are used in the reaction process, the cyclic carbonates prepared exhibit better selectivity and higher yield.

[0055] According to some specific embodiments of the present invention, the preparation process of cyclic carbonates may specifically include: dispersing a heterojunction catalyst, a quaternary ammonium salt co-catalyst, and an epoxide in N,N-dimethylformamide, and subjecting the mixture to ultrasonic treatment to obtain a uniformly dispersed solution. The ultrasonic power may be, for example, 40-100 kHz, and the ultrasonic treatment time may be, for example, 5-60 min. The obtained mixed solution is transferred to a quartz tube bottle, sealed, and an inert gas may be introduced into the mixed solution at a rate of 10-100 mL / min to remove air from the N,N-dimethylformamide, resulting in a third solution. Carbon dioxide gas may be introduced into the quartz tube at a rate of 10-100 mL / min, while maintaining the outlet gas from the injection needle to maintain atmospheric pressure inside the quartz tube. The gas exchange time may be 1-10 min. The injection needles at the inlet and outlet are removed sequentially, and a balloon filled with carbon dioxide, with a volume of 50-100 mL, is connected to the quartz tube. Under magnetic stirring conditions of 600~1400 r / min, the quartz tube is irradiated with infrared light to carry out the catalytic reaction. The reaction solution is centrifuged at a rate of 10000~14000 r / min for 1~20 min to obtain the supernatant, which is the cyclic carbonate. The yield of the cyclic carbonate is 70~95%.

[0056] According to some embodiments of the present invention, the atom utilization rate in the reaction for preparing cyclic carbonates reaches 100%, the reaction steps are simple, and the cost is low.

[0057] The present invention will be further illustrated below through embodiments, accompanying drawings, and related test experiments and results. In the following detailed description, numerous specific details are set forth for ease of explanation to provide a comprehensive understanding of the embodiments of the present invention. However, it will be apparent that one or more embodiments may be practiced without these specific details. Moreover, the details in the following embodiments can be arbitrarily combined to form other feasible embodiments without conflict.

[0058] It should be noted that the specific embodiments described below are merely illustrative examples, and the scope of protection of this invention is not limited thereto. The chemicals and raw materials used in the following embodiments are all commercially available or prepared using recognized processing methods. Nuclear magnetic resonance spectroscopy detection uses proton NMR with tetrachloroethane as an internal standard.

[0059] Example 1:

[0060] Preparation process of heterojunction catalyst 1 composed of nickel boride and cerium dioxide:

[0061] 1 mmol of nickel nitrate hexahydrate was added to 50 mL of deionized water and magnetically stirred at 800 rpm until completely dissolved. 2 mmol of sodium borohydride was added to 10 mL of deionized water and magnetically stirred at 600 rpm until completely dissolved. The sodium borohydride solution was then added to the nickel nitrate solution at a rate of 2 mL / min and magnetically stirred at 1400 rpm to obtain the reaction solution.

[0062] The reaction solution was transferred to a 100 mL beaker and stirred at room temperature for 2 hours to obtain a precipitate. The precipitate was centrifuged at 14000 r / min for 1 minute, washed three times with water and ethanol respectively, dried in a vacuum drying oven at 80 °C for 8 hours, and ground in an agate mortar to obtain the nickel boride precursor.

[0063] 100 mg of commercially available cerium dioxide nanoparticles with a particle size of 200 nm were dispersed in deionized water; 5 mg of nickel boride precursor was dispersed in deionized water and ultrasonicated to ensure uniform dispersion. The precursor was then added to an ethanol solution of titanium dioxide at a rate of 2 mL / min. The reaction system was then heated to 105 °C, and the solvent was evaporated to obtain the heterojunction precursor.

[0064] The heterojunction precursor was placed in a tube furnace and calcined at 300°C for 2 hours under a nitrogen atmosphere. The temperature was then programmed to rise at a rate of 5°C / min to prepare heterojunction catalyst 1.

[0065] Figure 2 The X-ray diffraction pattern of the heterojunction catalyst 1 of Example 1 of the present invention is shown.

[0066] like Figure 2 As shown, the heterojunction catalyst 1 prepared from nickel boride and wide-bandgap metal oxide exhibits high purity, and no other impurity peaks were detected.

[0067] Example 2:

[0068] Preparation process of heterojunction catalyst 2 composed of nickel boride and titanium dioxide:

[0069] 10 mmol of nickel nitrate hexahydrate was added to 500 mL of deionized water and magnetically stirred at 1000 rpm until completely dissolved. 30 mmol of sodium borohydride was added to 300 mL of deionized water and magnetically stirred at 500 rpm until completely dissolved. The sodium borohydride solution was then added to the nickel nitrate solution at a rate of 5 mL / min and magnetically stirred at 1000 rpm to obtain the reaction solution.

[0070] The reaction solution was transferred to a 5000 mL beaker and stirred at room temperature for 4 hours to obtain a precipitate. The precipitate was centrifuged at 12000 r / min for 10 minutes, washed three times with water and ethanol respectively, dried in a vacuum drying oven at 85 °C for 16 hours, and ground in an agate mortar to obtain the nickel boride precursor.

[0071] 200 mg of commercially available titanium dioxide nanoparticles with a particle size of 20 nm were dispersed in ethanol.

[0072] 20 mg of nickel boride precursor was dispersed in ethanol and sonicated to ensure uniform dispersion. It was then added to an ethanol solution of titanium dioxide at a rate of 1 mL / min. The reaction system was then heated to 80 °C, and the solvent was evaporated to obtain the heterojunction precursor.

[0073] The heterojunction precursor was placed in a tube furnace and calcined at 250°C for 1 h under a nitrogen atmosphere. The temperature was then programmed to rise at a rate of 3°C / min to prepare the heterojunction catalyst 2.

[0074] Figure 3 The X-ray diffraction pattern of the heterojunction catalyst 2 of Example 2 of the present invention is shown. Figure 3 As shown, the heterojunction catalyst 2 prepared from nickel boride and wide-bandgap metal oxide exhibits high purity, and no other impurity peaks were detected.

[0075] Example 3:

[0076] Using the heterojunction catalyst 1 prepared in Example 1 as a catalyst, the preparation process of synthesizing bromopropylene carbonate from carbon dioxide and bromopropylene oxide under infrared light driving is as follows:

[0077] 0.02 g of the heterojunction catalyst 1 prepared in Example 1, 5 mg of tetrabutylammonium bromide and 0.05 mL of bromopropylene oxide were added to 2 mL of N,N-dimethylformamide and sonicated at 100 kHz for 30 min to obtain a uniformly dispersed mixed solution.

[0078] The mixed solution was transferred to a specially made 10 mL quartz tube bottle, and the quartz tube was sealed with a rubber stopper. Argon gas was then introduced into the quartz tube at a rate of 10 mL / min using a syringe to remove the air dissolved in N,N-dimethylformamide, thereby obtaining the reaction solution.

[0079] High-purity carbon dioxide gas was introduced into the reaction solution at a rate of 10 mL / min, while one of the venting needles was kept in place to maintain the reaction system at atmospheric pressure. The gas exchange time was maintained at 5 min. The venting needles were then removed from both the inlet and outlet, and a balloon filled with 20 mL of carbon dioxide was connected to the quartz tube.

[0080] The quartz tube reaction system was stirred with a magnetic stirrer at a speed of 1400 r / min and a stirring rate of 500 mW / cm². 2 The xenon lamp was irradiated with infrared light, which was obtained by attaching a CUT800 filter to the xenon lamp. The reaction time was 20 hours. After the reaction, the lamp was centrifuged at 14000 r / min for 3 min, and the supernatant was taken as the product bromopropylene carbonate.

[0081] Figure 4 The 1H NMR spectrum of cyclic carbonate 1 from Example 3 of the present invention is shown. Figure 4 As shown, tetrachloroethane was used as an internal standard, and the yield of the product was analyzed by nuclear magnetic resonance hydrogen spectroscopy. The selectivity of infrared light-driven catalysis of carbon dioxide and bromopropylene oxide to synthesize bromopropylene carbonate was 100%, with no peaks of other byproducts detected. The yield of bromopropylene carbonate was 93%.

[0082] Example 4:

[0083] Using the heterojunction catalyst 2 prepared in Example 2 as a catalyst, the preparation process of synthesizing bromopropylene carbonate from carbon dioxide and bromopropylene oxide under infrared light driving is as follows:

[0084] 0.3 g of the heterojunction catalyst 2 prepared in Example 2, 50 mg of tetrabutylammonium bromide and 0.2 Mlde of bromopropylene oxide were added to 20 mL of N,N-dimethylformamide and sonicated at 80 kHz for 50 min to obtain a uniformly dispersed mixed solution.

[0085] The mixed solution was transferred to a specially made 50 mL quartz tube bottle, and the quartz tube was sealed with a rubber stopper. Nitrogen gas was then introduced into the quartz tube at a rate of 20 mL / min using a syringe to remove the air dissolved in N,N-dimethylformamide, thereby obtaining the reaction solution.

[0086] High-purity carbon dioxide gas was introduced into the reaction solution at a rate of 20 mL / min, while one of the venting needles was kept in place to maintain the reaction system at atmospheric pressure. The gas exchange time was maintained at 10 min. The venting needles were then removed from both the inlet and outlet, and a balloon filled with 100 mL of carbon dioxide was connected to the quartz tube.

[0087] The quartz tube reaction system was stirred with a magnetic stirrer at a speed of 1200 r / min and a strength of 400 mW / cm². 2The xenon lamp was irradiated with infrared light, which was obtained by attaching a CUT800 filter to the xenon lamp. The reaction time was 16 hours. After the reaction, the product was centrifuged at 12000 r / min for 10 min, and the supernatant was collected to obtain bromopropylene carbonate.

[0088] Figure 5 The 1H NMR spectrum of bromopropylene carbonate from Example 4 of this invention is shown. Figure 5 As shown, tetrachloroethane was used as an internal standard, and the yield of the product was analyzed by nuclear magnetic resonance hydrogen spectroscopy. The selectivity of infrared light-driven catalysis of carbon dioxide and brominated propylene oxide to synthesize bromopropylene carbonate was 100%, with no peaks of other byproducts detected. The yield of the product bromopropylene carbonate was 85%.

[0089] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An application of infrared photocatalytic preparation of cyclic carbonates, comprising: The heterojunction catalyst, quaternary ammonium salt co-catalyst, and epoxide were added to N,N-dimethylformamide and stirred. An inert gas was introduced to remove air from the N,N-dimethylformamide to obtain a third solution. Carbon dioxide is introduced into the third solution, and a catalytic reaction is carried out under infrared light irradiation and normal pressure to obtain cyclic carbonates; The heterojunction catalyst was prepared by the following method: Wide-bandgap metal oxide nanoparticles are dispersed in a first solvent to obtain a first solution; The metal boride is dispersed in a second solvent to obtain a second solution; The second solution is added to the first solution and heated to obtain a heterojunction precursor. The heterojunction precursor was calcined under an inert atmosphere to obtain the heterojunction catalyst. The calcination treatment conditions are as follows: heating from room temperature to 250~350℃ at a heating rate of 3~10℃ / min, and calcining at 250~350℃ for 0.5~6h; The wide bandgap metal oxide nanoparticles have a bandgap greater than 3 eV; the wide bandgap metal oxide nanoparticles include at least one of cerium dioxide, germanium dioxide, zirconium dioxide, titanium dioxide, tin dioxide, indium oxide, gallium oxide, and bismuth oxide; the metal borides are nickel boride or iron boride.

2. The application according to claim 1, wherein, The metal boride is prepared by the following process: The metal salt is added to the third solvent and stirred to obtain a metal salt solution; The reducing agent is added to the fourth solvent and stirred to obtain a reducing agent solution; The reducing agent solution is added dropwise to the metal salt solution while stirring to carry out the reduction reaction, thereby obtaining the metal boride.

3. The application according to claim 2, wherein, The molar ratio of the metal salt to the reducing agent is 1:(2~6). The reduction reaction is carried out at room temperature for 0.5 to 6 hours. The concentration of the metal salt in the third solvent is 0.002~10 mol / L; The reducing agent includes sodium borohydride or potassium borohydride; The concentration of the reducing agent in the fourth solvent is 0.05~5 mol / L; The dropwise addition rate is 0.1-2 mL / min.

4. The application according to claim 2, wherein, The metal salts include nickel salts or iron salts.

5. The application according to claim 2, wherein, The metal salt includes at least one of nickel chloride hexahydrate, nickel sulfate hexahydrate, nickel bromide trihydrate, nickel nitrate hexahydrate, ferric nitrate nonahydrate, ferric chloride hexahydrate, and ferric bromide trihydrate.

6. The application according to claim 1, wherein, The diameter of the wide-bandgap metal oxide nanoparticles is 10~200nm; The mass ratio of the metal boride to the wide-bandgap metal oxide nanoparticles is 1:(10~100).

7. The application according to claim 1, wherein, The temperature of the heat treatment is 100~120℃.

8. The application according to claim 1, wherein, The infrared light is formed by attaching a CUT800 filter to the xenon lamp; The infrared light intensity is 300-500 mW / cm². 2 The reaction time for the catalytic reaction is 8-24 hours.

9. The application according to claim 1, wherein, The quaternary ammonium salt co-catalyst includes tetrabutylammonium bromide; the added mass of the quaternary ammonium salt co-catalyst is 0.005~0.5g, and the volume of the epoxide is 0.02~0.5mL; the epoxide includes bromopropylene oxide.

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