Methods and applications for the preparation of cyclic carbonates by cycloaddition of CO2 with epoxides.

Abstract

This invention relates to the field of greenhouse gas control, and more particularly to a method and application for the cycloaddition reaction of CO2 with epoxides to prepare cyclic carbonates. The method includes: contacting epoxides and CO2 under the catalysis of a MOF material; the MOF material is obtained by: preparing a first mixed solution containing a neutral ligand, a hydrogen bond acceptor, and a hydrogen bond donor; preparing a second mixed solution containing a metal salt and a linker; mixing the second mixed solution with a regulator and the first mixed solution, followed by heat treatment to obtain the MOF material; the regulator includes at least one of a carboxylic acid and a carboxylate. The MOF material exhibits excellent catalytic activity and high thermal stability, and can significantly improve the conversion efficiency of reactants.

Description

Technical Field

[0001] This invention relates to the field of greenhouse gas control, and more particularly to a method and application for the preparation of cyclic carbonates by cycloaddition of CO2 with epoxides. Background Technology

[0002] Carbon dioxide (CO2) is a major component of greenhouse gases and is generally considered a key factor influencing global climate change. Despite considerable attention to CO2 emission control over the past few decades, anthropogenic CO2 emissions from fossil fuel combustion are higher than ever before, driven by energy demands for industrial development, economic growth, and daily life. Among technologies for reducing CO2 emissions, carbon capture and storage (CCS) is currently the most researched and widely considered an effective method for CO2 reduction. Post-combustion carbon capture (CCS) technology is more widely used in CCS because, compared to pre-combustion and in-combustion CCS, it can be implemented in existing plants by adding process units. Currently, post-combustion CCS primarily involves the physical and chemical adsorption of CO2 from flue gas, such as wet scrubbing with amine solutions. Converting the captured CO2 into high-value-added products is another solution for reducing CO2 emissions, such as synthesizing cyclic carbonates, dimethyl carbonate, and cyclic urea through chemical fixation.

[0003] The CO2 cycloaddition method, a commonly used approach for chemical CO2 fixation, is primarily based on acid-base catalysis and solid surface properties. In the presence of a catalyst, CO2 reacts with different epoxides to form cyclic carbonates. In recent years, metal-organic frameworks (MOFs) and their composites, as heterogeneous mesoporous catalytic materials, have exhibited more efficient catalytic properties in converting CO2 into other chemical substances than other solid catalysts due to the presence of acidic and basic sites on their surfaces. MOFs are coordination polymers self-assembled from oxygen- and nitrogen-containing polydentate organic ligands (mostly aromatic polyacids and polybases) and transition metal ions, possessing numerous characteristics such as porosity, large specific surface area, multiple metal sites, and acid-base catalytic performance. Zirconium-based MOFs, in particular, have been widely applied in practical production and daily life due to their excellent hydrophilicity and outstanding chemical and thermal stability in acidic and alkaline environments. Furthermore, the symmetry of zirconium-based MOFs allows them to be coordinated with various linkers and designed into various topologies, serving as heterogeneous catalysts in the CO2 chemical fixation process. Currently, common methods for synthesizing this type of MOF material include solvent evaporation diffusion, microwave-assisted synthesis, ionic liquid / supercritical CO2 emulsion method, metal-ligand-fragment co-assembly method, etc. However, these methods all require additional steps to remove the template, which leads to the destruction of the mesoporous structure of the material and the reduction of its acidic and basic sites, thereby affecting the catalytic performance of the MOF material. Summary of the Invention

[0004] This invention aims to at least partially address one of the technical problems in related technologies. To this end, this invention provides a method for preparing cyclic carbonates by the cycloaddition of CO2 with epoxides and its application. This method specifies a MOF material and uses it as a catalyst for the cycloaddition of CO2 with epoxides to prepare cyclic carbonates, which can significantly improve the conversion efficiency of the reactants.

[0005] Therefore, the first aspect of the present invention provides a method for preparing cyclic carbonates by cycloaddition of CO2 with epoxide, the method comprising: contacting epoxide and CO2 under the catalysis of MOF material;

[0006] The MOF material is obtained by the following method: preparing a first mixed solution containing a neutral ligand, a hydrogen bond acceptor, and a hydrogen bond donor;

[0007] Prepare a second mixed solution containing metal salt and binder;

[0008] The second mixed solution is mixed with a regulator and the first mixed solution, and then heat-treated to obtain the MOF material.

[0009] The regulator includes at least one of carboxylic acid and carboxylate.

[0010] This invention synthesizes MOF materials based on a first mixed solution, which increases the number of acidic and basic sites on the surface of the synthesized MOF material. Compared with MOF materials synthesized by conventional methods, the MOF material synthesized by this invention exhibits two different acidic sites: weakly acidic and strongly acidic, while catalysts synthesized by conventional methods only have one strongly acidic site. The change in basic sites is the same as that of acidic sites, meaning that the MOF material synthesized by this invention has more basic sites on its surface. Therefore, it can serve as an effective catalyst for CO2 cycloaddition reactions, as the different types of acidic and basic sites on its surface can more easily catalyze the CO2 cycloaddition process. For example, it exhibits excellent catalytic activity in the CO2 cycloaddition reactions with epichlorohydrin and styrene oxide, with yields reaching 97% and 54%, respectively. Simultaneously, the MOF material used in this invention has a high diffusion rate for gas adsorption-desorption, thus being more conducive to CO2 cycloaddition reactions with different types and quantities of epoxides within different temperature ranges, thereby achieving higher efficiency in the chemical fixation of CO2 and its conversion into high-value-added products. Furthermore, the CO2 fixation method provided by this invention can chemically fix CO2 under relatively mild temperature and pressure conditions, without any solvent or external co-catalyst, which also demonstrates the superiority of this method.

[0011] According to an embodiment of the present invention, the neutral ligand includes one of magnesium nitrate hexahydrate, zinc nitrate hexahydrate, copper nitrate hexahydrate, and cobalt nitrate hexahydrate.

[0012] According to an embodiment of the present invention, the hydrogen bond acceptor includes one of choline chloride, glycine, fluorinated choline, acetylcholine chloride, and nitrate choline.

[0013] According to an embodiment of the present invention, the hydrogen bond donor includes one of urea, malic acid, oxalic acid, tartaric acid, benzoic acid, imidazole, and lactic acid.

[0014] According to an embodiment of the present invention, the molar ratio of the neutral ligand, hydrogen bond acceptor, and hydrogen bond donor is 1:2:1.

[0015] According to an embodiment of the present invention, the metal salt includes at least one of zirconium chloride, zinc nitrate, copper acetate, and ferric chloride.

[0016] According to embodiments of the present invention, the binder includes at least one selected from phthalic acid, 2-methylimidazole, 2,5-dihydroxyterephthalic acid, and tricarboxylic acid.

[0017] According to an embodiment of the present invention, the mass ratio of the metal salt to the binder is (1-2):(0.5-0.8).

[0018] According to an embodiment of the present invention, the first mixed solution, the regulator and the second mixed solution are mixed in a volume ratio of (1-5):(1-10):(50-100).

[0019] According to an embodiment of the present invention, the temperature of the heat treatment is 120-140°C.

[0020] According to an embodiment of the present invention, the heat treatment time is 18-24 hours.

[0021] According to an embodiment of the present invention, the contact is performed at 1.5-2 MPa.

[0022] According to an embodiment of the present invention, the contact is performed at 80-220°C.

[0023] A second aspect of the present invention provides an application of MOF material in the preparation of cyclic carbonates by cycloaddition of CO2 and epoxide, comprising: contacting epoxide and CO2 under the catalysis of the MOF material;

[0024] The MOF material is obtained by the following method: preparing a first mixed solution containing a neutral ligand, a hydrogen bond acceptor, and a hydrogen bond donor;

[0025] Prepare a second mixed solution containing metal salt and binder;

[0026] The second mixed solution is mixed with a regulator and the first mixed solution, and then heat-treated to obtain the MOF material.

[0027] The regulator includes at least one of carboxylic acid and carboxylate.

[0028] This invention synthesizes MOF materials based on a first mixed solution, which increases the number of acidic and basic sites on the surface of the synthesized MOF material. This allows it to serve as an effective catalyst for CO2 cycloaddition reactions, as the different types of acidic and basic sites on its surface more readily catalyze the CO2 cycloaddition process. Simultaneously, the MOF material used in this invention exhibits a high diffusion rate for gas adsorption-desorption, thus facilitating CO2 cycloaddition reactions with different types and quantities of epoxides within different temperature ranges. This results in more efficient chemical fixation of CO2, converting it into high-value-added products. Furthermore, this application allows for CO2 cycloaddition reactions to be carried out under relatively mild temperature and pressure conditions, completely without solvents and without the use of any external co-catalysts, offering significant advantages.

[0029] According to an embodiment of the present invention, the neutral ligand includes one of magnesium nitrate hexahydrate, zinc nitrate hexahydrate, copper nitrate hexahydrate, and cobalt nitrate hexahydrate.

[0030] According to an embodiment of the present invention, the hydrogen bond acceptor includes one of choline chloride, glycine, fluorinated choline, acetylcholine chloride, and nitrate choline.

[0031] According to an embodiment of the present invention, the hydrogen bond donor includes one of urea, malic acid, oxalic acid, tartaric acid, benzoic acid, imidazole, and lactic acid.

[0032] According to an embodiment of the present invention, the molar ratio of the neutral ligand, hydrogen bond acceptor, and hydrogen bond donor is 1:2:1.

[0033] According to an embodiment of the present invention, the metal salt includes at least one of zirconium chloride, zinc nitrate, copper acetate, and ferric chloride.

[0034] According to embodiments of the present invention, the binder includes at least one selected from phthalic acid, 2-methylimidazole, 2,5-dihydroxyterephthalic acid, and tricarboxylic acid.

[0035] According to an embodiment of the present invention, the mass ratio of the metal salt to the binder is (1-2):(0.5-0.8).

[0036] According to an embodiment of the present invention, the first mixed solution, the regulator and the second mixed solution are mixed in a volume ratio of (1-5):(1-10):(50-100).

[0037] According to an embodiment of the present invention, the temperature of the heat treatment is 120-140°C.

[0038] According to an embodiment of the present invention, the heat treatment time is 18-24 hours.

[0039] According to an embodiment of the present invention, the contact is performed at 1.5-2 MPa.

[0040] According to an embodiment of the present invention, the contact is performed at 80-220°C.

[0041] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0042] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0043] Figure 1 The NH3-TPD spectra of MOF materials synthesized by adding different volumes of the first mixed solution in Example 1 of the present invention are shown.

[0044] Figure 2 The CO2-TPD spectra of MOF materials synthesized by adding different volumes of the first mixed solution in Example 1 of the present invention are shown.

[0045] Figure 3 The time and TCD signal spectra of MOF materials synthesized by adding different volumes of the first mixed solution in Example 1 of the present invention are shown at 100°C.

[0046] Figure 4 This invention demonstrates the cycloaddition reaction of CO2 with epichlorohydrin catalyzed by the UiO-66 material, the functionalized UiO-66-F material, and the relineMgx5@UiO-66 material in Example 2 of this invention. 1 HNMR spectra. Figure (a) shows the UiO-66 material, the functionalized UiO-66-F material, and the cycloaddition reaction of CO2 with epichlorohydrin catalyzed by relineMgx5@UiO-66 material. 1 Comparison of HNMR spectra; (b) Figure shows reline Mg x5 @UiO-66 catalyzed cycloaddition reaction of CO2 with epichlorohydrin 1 HNMR spectrum;

[0047] Figure 5 This demonstrates that the MOF material synthesized by adding different volumes of a first mixed solution in Example 2 of the present invention catalyzes the cycloaddition reaction of CO2 with epichlorohydrin.1 HNMR spectrum;

[0048] Figure 6 This invention demonstrates the catalytic reaction of CO2 with styrene oxide cycloaddition using MOF materials synthesized by adding different volumes of a first mixed solution in Example 3 of this invention, as well as UiO-66 materials synthesized by conventional methods. 1 HNMR spectrum. Detailed Implementation

[0049] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0050] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0051] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0052] To facilitate understanding of the invention, certain technical and scientific terms are specifically defined below. Unless otherwise expressly defined elsewhere in this document, all other technical and scientific terms used herein have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0053] In this document, the terms “comprising” or “including” are open-ended expressions, meaning that they include the contents specified in this invention, but do not exclude other aspects.

[0054] In this document, the terms “optionally,” “optionally,” or “optionally” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0055] According to embodiments of the present invention, a first aspect of the present invention provides a method for preparing cyclic carbonates by cycloaddition of CO2 with an epoxide, the method comprising: contacting an epoxide and CO2 under the catalysis of an MOF material;

[0056] The MOF material is obtained by the following method: preparing a first mixed solution containing a neutral ligand, a hydrogen bond acceptor, and a hydrogen bond donor;

[0057] Prepare a second mixed solution containing metal salt and binder;

[0058] The second mixed solution is mixed with a regulator and the first mixed solution, and then heat-treated to obtain the MOF material.

[0059] The regulator includes at least one of carboxylic acid and carboxylate.

[0060] This method uses a specific approach to obtain a MOF material with a mesoporous structure and retains additional acidic and basic sites. It can be used as a heterogeneous mesoporous catalyst in the chemical fixation of CO2 process to carry out CO2 cycloaddition reaction with epoxides, thereby improving the conversion efficiency of epoxides into polycarbonates and cyclic carbonates.

[0061] Specifically, compared to MOF materials synthesized by conventional methods, the MOF materials obtained by the aforementioned method possess two types of sites (acidic and basic sites), and the number of these sites is increased, thus facilitating the cycloaddition reaction of CO2 more readily. Furthermore, by investigating the adsorption and desorption rates of gas on the MOF material surface, the activation state of the sites in the porous medium can be further determined. After gas molecules are adsorbed on the material surface, they are gradually released with increasing temperature. The MOF material synthesized in this invention exhibits a high diffusion rate for the gas adsorption-desorption process, thus being more conducive to CO2 cycloaddition reactions with different types and quantities of epoxides within different temperature ranges, thereby achieving CO2 chemical fixation with higher efficiency and converting it into high-value-added products. Simultaneously, the method provided by this invention enables the chemical fixation of CO2 under relatively mild temperature and pressure conditions, completely without solvents and without the use of any external co-catalysts, confirming the good catalytic activity of the catalyst used in this invention.

[0062] According to a specific embodiment of the present invention, the contact is carried out at 1.5-2 MPa and 80-220°C. This results in a high yield and a high conversion rate of the epoxide.

[0063] According to specific embodiments of the present invention, the epoxide includes at least one of epichlorohydrin, styrene oxide, propylene oxide, ethylene oxide, cyclohexene oxide, limonene oxide, or vinylcyclohexene oxide.

[0064] According to specific embodiments of the present invention, the types of neutral ligands, hydrogen bond acceptors, and hydrogen bond donors are not particularly limited, and those skilled in the art can select them as appropriate. As some specific examples, the neutral ligands include, but are not limited to, magnesium nitrate hexahydrate, zinc nitrate hexahydrate, copper nitrate hexahydrate, and cobalt nitrate hexahydrate; the hydrogen bond acceptors include, but are not limited to, choline chloride, glycine, fluorinated choline, acetylcholine chloride, and nitrate choline; and the hydrogen bond donors include, but are not limited to, urea, malic acid, oxalic acid, tartaric acid, benzoic acid, imidazole, and lactic acid.

[0065] According to a specific embodiment of the present invention, the molar ratio of the neutral ligand, hydrogen bond acceptor, and hydrogen bond donor is 1:2:1.

[0066] According to specific embodiments of the present invention, the types of metal salts and binders are not particularly limited, and those skilled in the art can choose them as appropriate. As some specific examples, the metal salts include, but are not limited to, zirconium chloride, zinc nitrate, copper acetate, ferric chloride, etc.; the binders include, but are not limited to, phthalic acid, 2-methylimidazole, 2,5-dihydroxyterephthalic acid, tricarboxylic acid, etc. Tricarboxylic acid should be understood as an organic acid whose molecular structure contains three carboxylic acids.

[0067] According to a specific embodiment of the present invention, the preparation of the second mixed solution is not particularly limited, and it can be obtained by dissolving a metal salt and a binding agent in a solvent. The type of solvent is not particularly limited, and includes, but is not limited to, dimethylformamide, etc.

[0068] According to specific embodiments of the present invention, the mass ratio of the metal salt to the binder is (1-2):(0.5-0.8). As some specific examples, the mass ratio of the metal salt to the binder can be 1:0.5, 1:0.8, 1.5:0.5, 1.7:0.8, 2:0.5, 2:0.8, etc.

[0069] According to specific embodiments of the present invention, the first mixed solution, the regulator, and the second mixed solution are mixed in a volume ratio of (1-5):(1-10):(50-100). As some specific examples, the volume ratio of the first mixed solution, the regulator, and the second mixed solution is 1:1:50, 1:1:75, 1:5:100, 2:7:75, 3:7:100, 5:10:100, etc.

[0070] According to specific embodiments of the present invention, the modifier includes at least one of carboxylic acids and carboxylates, including, but not limited to, formic acid, formate, and propionate. The modifier generates bonding defects on the surface of the MOF material and helps the first mixed solution establish additional connections with the metal nodes.

[0071] According to specific embodiments of the present invention, the temperature and time of the heat treatment are not particularly limited, and those skilled in the art can select them as appropriate. As some specific examples, the temperature of the heat treatment is 120-140°C, and the time of the heat treatment is 18-24 hours.

[0072] According to a specific embodiment of the present invention, the preparation method of the MOF material further includes: mixing the second mixed solution with a regulator and the first mixed solution, and then performing heat treatment, washing, activation and drying to obtain the MOF material.

[0073] Specifically, the washing method is not particularly limited and can be carried out using ethanol or dimethylformamide.

[0074] Specifically, the activation method is not particularly limited and can be achieved by placing the sample in acetone to remove the suspending solvent and simultaneously activate the product. Typically, after the MOF material synthesis process is completed, some unreacted metal ions and organic linkers remain in its structure. To remove these unreacted organic linkers, acetone can be used to activate the final MOF product. After activation, the product can be washed with methanol and then dried to obtain the MOF material.

[0075] According to an embodiment of the present invention, a second aspect of the present invention provides the application of MOF material in the preparation of cyclic carbonates by cycloaddition of CO2 and epoxide, comprising: contacting epoxide and CO2 under the catalysis of the MOF material;

[0076] The MOF material is obtained by the following method: preparing a first mixed solution containing a neutral ligand, a hydrogen bond acceptor, and a hydrogen bond donor;

[0077] Prepare a second mixed solution containing metal salt and binder;

[0078] The second mixed solution is mixed with a regulator and the first mixed solution, and then heat-treated to obtain the MOF material.

[0079] The regulator includes at least one of carboxylic acid and carboxylate.

[0080] The MOF material used in this application is the same as the MOF material used in the aforementioned method. For specific details, please refer to the above, and it will not be repeated here.

[0081] The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0082] Example 1

[0083] In this embodiment, MOF materials were synthesized using different volumes of the first mixed solution, as detailed below:

[0084] (1) Magnesium nitrate hexahydrate (Mg(NO3)3·6H2O), choline chloride, and urea were added to a beaker in a molar ratio of 1:2:1. The beaker was placed in an oven preheated to 100°C and allowed to stand until it became a liquid. The three liquids were mixed on a magnetic stirrer, and then the solution was heated until it became a clear, transparent liquid without any bubbles. A magnesium-based eutectic solvent (i.e., the first mixed solution) was thus prepared and named relineMg.

[0085] (2) At room temperature, 1.06 g of zirconium chloride and 0.67 g of phthalic acid were dissolved in 50 mL of dimethylformamide and stirred on a magnetic stirrer for 10 min to obtain a second mixed solution.

[0086] (3) Add 5 mL of formic acid to the second mixed solution, stir for 10 min, and sonicate for 30 min to make all components completely and evenly distributed in the solution;

[0087] (4) Add 1 mL, 2 mL, 3 mL and 5 mL of relineMg to the mixed solution respectively, stir on a magnetic stirrer for 30 min and sonicate for 45 min to completely disperse the added components.

[0088] (5) Place the mixture in a 100 mL autoclave lined with Teflon, heat to 120 °C, and maintain for 24 hours;

[0089] (6) After the reaction is complete, wash the mixture several times with hot ethanol and then several times with hot dimethylformamide solvent;

[0090] (7) The sample was placed in 30 mL of acetone and left to stand overnight to remove the suspended solvent and activate the product. After activation, it was washed three times with methanol and dried under vacuum at 80 °C overnight to obtain the heterogeneous mesoporous catalyst relineMg@UiO-66 synthesized with the assistance of different concentrations of relineMg.

[0091] The prepared MOF materials were named relineMg. x1 @UiO-66、relineMg x2 @UiO-66、relineMg x3 @UiO-66、relineMg x5 @UiO-66, where x1 = 1 mL relineMg, x2 = 2 mL relineMg, and so on.

[0092] In addition, UiO-66 metal-organic framework materials (i.e., Parent@UiO-66, Parent UiO-66, or UiO-66 material) were prepared using a conventional method. Specifically, 0.67 g of phthalic acid and 1.06 g of ZrCl4 were dissolved in 50 mL of dimethylformamide and 5 mL of formic acid. The mixture was stirred on a magnetic stirrer for 10 minutes, followed by ultrasonic dispersion for 30 minutes. After ultrasonic treatment, the mixture was placed in a 100 mL autoclave and heated to 120 °C for 24 hours. After cooling to room temperature, the product was washed three times with dimethylformamide. To activate the sample and remove unreacted dimethylformamide from its structure, the white solid powder was placed in 30 mL of acetone overnight, then washed several times with methanol and dried under vacuum at 80 °C.

[0093] Since the acidic and basic sites on the surface of the catalytic materials are crucial to the chemical fixation of CO2, the five catalytic materials synthesized in this example were analyzed using NH3-TPD and CO2-TPD methods. x1 @UiO-66、relineMg x2 @UiO-66、relineMg x3 @UiO-66、relineMg x5 The Lewis acid and Bronsted basic sites of @UiO-66 and Parent@UiO-66 were analyzed, and the intensity of the acid and basic sites was calculated using the integrated area of ​​the peaks, thereby identifying the catalytic activity level of the catalytic material.

[0094] In similar studies, acidic sites are mainly divided into three groups of peaks: weak acid (50–100℃), moderate acid (150–200℃), and strong acid (320–500℃). However, in this embodiment, to more accurately obtain peak areas by grouping, the acidic sites in the NH3-TPD analysis results are divided into two groups of peaks: weak to moderate acid (50–320℃) and strong acid (320–400℃), as shown below. Figure 1 As shown in the spectrum, the peaks indicate that the acidic sites in the MOF material are closely related to the concentration of the eutectic solvent (i.e., the first mixed solution). With increasing temperature, the integrated peak area shifts to the right and increases in size, while the peak intensity gradually increases with the addition of the first mixed solution. The high peak intensity of the catalytic material indicates the presence of numerous acidic sites, which may be due to the presence of Mg on the porous material surface. 2+ and Zr 2+ This is due to the presence of metal sites. Compared to UiO-66 metal-organic framework materials (Parent@UiO-66) synthesized by conventional methods, the relineMg in this example... x1 @UiO-66、relineMg x2@UiO-66、relineMg x3 @UiO-66、relineMg x5 @UiO-66 material exhibits two distinct TPD peaks (weakly acidic and moderately acidic) across different temperature ranges, while UiO-66 material displays only one strongly acidic peak. The presence of multiple acidic / basic sites on the material surface can enhance site availability, indicating that relineMg... x1 @UiO-66、relineMg x2 @UiO-66、relineMg x3 @UiO-66、relineMg x5 @UiO-66 materials are more likely to catalyze the cycloaddition process of CO2.

[0095] Figure 2 Corresponding to the CO2-TPD spectrum, different base sites of varying intensities were also divided into two groups: weakly basic (50–177 °C) and moderately strong basic (177–500 °C). The results show that, compared to UiO-66 metal-organic framework materials synthesized by conventional methods, the relineMg@UiO-66 material in this embodiment exhibits significantly higher basicity and a markedly higher number of basic sites. Furthermore, with increasing amounts of the first mixed solution, the CO2-TPD spectrum showed a similar pattern to the NH3-TPD spectrum, with both peak intensity and area increasing, indicating an increase in the number of basic sites on its surface. The increase in peak intensity and area may be due to the increase in nitrogen and oxygen atoms in its structure, resulting in a greater number of basic groups and sites.

[0096] Furthermore, NH3-TPD analysis helps determine the rate of gas adsorption-desorption in catalytic materials as the experimental temperature increases. Studying the rates of gas adsorption and desorption on the MOF surface helps determine the activation state of the porous medium, where gas molecules are tightly bound and released with increasing temperature. Figure 3 It can be seen that within 60 minutes of the experiment, as the amount of the first mixed solution increased (from 1 mL to 5 mL), relineMg... x5 @UiO-66 can reach its maximum peak within 10 minutes. This indicates that relineMg x5 @UiO-66 has the highest gas diffusion rate and strong catalytic active sites, which is more conducive to CO2 cycloaddition reactions with different amounts of epoxides in different temperature ranges, thereby converting CO2 into higher-yield value-added products through chemical fixation.

[0097] Example 2

[0098] This embodiment uses relineMg x5@UiO-66 catalyzes the cycloaddition reaction of CO2 with epichlorohydrin, as detailed below:

[0099] (1) For the 25mL stainless steel autoclave equipment with external temperature controller and magnetic stirrer, use pure CO2 gas (99.99%) to purify it 3 to 5 times to remove residual air or other gases in the equipment;

[0100] (2) Without adding any external solvents and co-catalysts, UiO-66 material, functionalized UiO-66-F material and relineMgx5@UiO-66 material synthesized in Example 1 were placed into reaction vessels respectively, and 30 mmol of epichlorohydrin was added.

[0101] The functionalized UiO-66-F material uses formic acid (F) as a modifier to generate more open metal sites or missing connection defects, thereby enabling the MOF material to react more effectively with epoxides. Its preparation method is as follows:

[0102] 1.06 g ZrCl4 and 0.67 g phthalic acid were dissolved in 50 mL dimethylformamide and stirred on a magnetic stirrer for 30 min. Then, 5 mL formic acid was added, and the mixture was stirred for 10 min, followed by sonication for 30 min. After complete dissolution, the mixture was added to a 100 mL Teflon-lined autoclave and heated in an oven at 120 °C for 24 h. Before cooling the mixture to room temperature, it was washed three times with dimethylformamide and then suspended in 30 mL acetone overnight to remove excess dimethylformamide. Subsequently, it was washed with methanol and vacuum dried overnight at 80 °C in a vacuum oven to obtain the UiO-66-F material.

[0103] (3) Seal the reactor and pressurize it to the target pressure within a fixed time. Use an external magnetic stirrer to mix the gas and solid phases at a speed of 600 rpm and heat it to 100°C with the help of an external heating controller.

[0104] (4) The reaction time lasted for 12 hours. After the experiment was completed, the reaction temperature was cooled to room temperature, the unreacted CO2 gas was slowly discharged, and the mixture was filtered to obtain the target product after cycloaddition.

[0105] In this embodiment, the catalytic efficiency of three different catalysts in step (2) for the cycloaddition reaction of CO2 with epichlorohydrin at 100°C and 2 MPa was first compared, and the product's... 1 HNMR spectrum as follows Figure 4As shown in the figure, DMSO is the NMR solvent used in the NMR test. Compared with other MOF materials, the product exhibited a higher intensity peak under the catalysis of relineMgx5@UiO-66 material, while the product peak intensities of the other two MOF catalytic materials were lower. This indicates that the method proposed in this invention can improve the rate of conversion of CO2 and epichlorohydrin to cyclic carbonates. Table 1 shows the catalytic yield of the product in this example, where relineMg@UiO-66 has the highest catalytic yield of 97% compared with other MOF materials, while UiO-66 material has the lowest catalytic yield of 26%. The results show that the catalyst provided by this invention exhibits higher catalytic performance in the cycloaddition reaction of CO2 and epichlorohydrin.

[0106] Table 1

[0107]

[0108] Secondly, this embodiment also compared the catalytic performance of MOF materials synthesized from different amounts of the first mixed solution on the cycloaddition reaction of CO2 and epichlorohydrin, such as... Figure 5 As shown, under relatively low temperature and pressure conditions (100℃, 2MPa), MOF materials prepared with different amounts of the first mixed solution exhibited excellent performance and high conversion rates in the CO2 cycloaddition reaction with epichlorohydrin. Meanwhile, relineMg... x5 @UiO-66 exhibits a higher intensity peak associated with the product (cyclic carbonate) compared to materials synthesized with low solution addition, indicating the highest conversion rate.

[0109] Finally, this embodiment also tested relineMg under a constant temperature of 100°C. x5 @UiO-66's catalytic performance in the cycloaddition reaction of epichlorohydrin and CO2 under different pressure conditions was tested. Under pressures of 1 MPa to 2 MPa, relineMg... x5 @UiO-66 exhibited excellent catalytic activity for the quantitative CO2 cycloaddition of epichlorohydrin. It was also found that the yield of the chemical cycloaddition reaction increased with increasing applied pressure, as shown in Table 2. x5 @UiO-66 exhibited the highest catalytic yield (97%) at 100°C and 2 MPa pressure; under the same isothermal condition of 100°C, the lowest catalytic yield (64%) was observed at 1 MPa pressure. The catalytic yield of the catalyst used in this example is higher than that of any other MOF material reported to date. In terms of the percentage yield of MOF materials in the absence of a co-catalyst and under completely solvent-free conditions, relineMg currently ranks first. x5 The @UiO-66 catalytic material exhibits quite high catalytic activity.

[0110] Table 2

[0111]

[0112] Example 3

[0113] This embodiment uses relineMg x5 @UiO-66 catalyzes the cycloaddition reaction of CO2 with styrene oxide, as detailed below:

[0114] (1) For the 25mL stainless steel autoclave equipment with external temperature controller and magnetic stirrer, use pure CO2 gas (99.99%) to purify it 3 to 5 times to remove residual air or other gases in the equipment;

[0115] (2) Without adding any external solvents and co-catalysts, the UiO-66 material and the relineMg synthesized in Example 1 were used. x5 @UiO-66 materials were placed into reaction vessels, and then 30 mmol of styrene oxide was added;

[0116] (3) Seal the reactor and pressurize it to the target pressure within a fixed time. Use an external magnetic stirrer to mix the gas and solid phases at a speed of 600 rpm and heat it to 100°C with the help of an external heating controller.

[0117] (4) The reaction time lasted for 12 hours. After the experiment was completed, the reaction temperature was cooled to room temperature, the unreacted CO2 gas was slowly discharged, and the mixture was filtered to obtain the target product after cycloaddition.

[0118] from Figure 6 It can be seen that when UiO-66 is used as a catalyst for the CO2 cycloaddition reaction with styrene oxide, almost no target product, styrene carbonate, is formed. However, when relineMg is used... x5 When @UiO-66 is used as a heterogeneous catalyst, 1 The HNMR spectrum showed some small peaks, which are related to the products of the cycloaddition reaction of CO2 with styrene oxide. Therefore, it can be concluded that under the same temperature and pressure conditions, relineMg... x5 @UiO-66 exhibits superior catalytic performance for styrene oxide compared to UiO-66 materials synthesized using conventional methods. In this embodiment, different pressures were applied to the reaction vessel to observe changes in the material's catalytic performance. The yield also tended to increase with increasing pressure. Under conditions of 100°C and 2 MPa, the catalytic yield of the styrene oxide and CO2 cycloaddition reaction reached a maximum of 54%, as detailed in Table 3.

[0119] Table 3

[0120]

[0121] These results indicate that the method for catalytic cycloaddition reaction of CO2 provided by the present invention can carry out CO2 cycloaddition reaction with different epoxides under relatively mild temperature and pressure conditions, and chemically fix CO2 into products with high added value, such as polycarbonate and cyclic carbonates.

[0122] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0123] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A MOF material catalyst, characterized in that, The MOF material catalyst is prepared by the following method: A first mixed solution containing a neutral ligand, a hydrogen bond acceptor, and a hydrogen bond donor is prepared, wherein the molar ratio of the neutral ligand, the hydrogen bond acceptor, and the hydrogen bond donor is 1:2:1, the neutral ligand is magnesium nitrate hexahydrate, the hydrogen bond acceptor is choline chloride, and the hydrogen bond donor is urea. A second mixed solution containing a metal salt and a binder is prepared, wherein the mass ratio of the metal salt to the binder is (1-2):(0.5-0.8), the metal salt is zirconium chloride, and the binder is phthalic acid; The second mixed solution is mixed with a regulator and the first mixed solution, and then heat-treated to obtain the MOF material. The regulator is selected from at least one of formic acid, formate, and propionate.

2. The MOF material catalyst according to claim 1, characterized in that, The first mixed solution, the regulator, and the second mixed solution are mixed in a volume ratio of (1-5):(1-10):(50-100).

3. The MOF material catalyst according to claim 1, characterized in that, The heat treatment temperature is 120-140℃.

4. The MOF material catalyst according to claim 1, characterized in that, The heat treatment time is 18-24 hours.

5. A method for preparing cyclic carbonates by cycloaddition of CO2 with epoxides, characterized in that, The method comprises: contacting epoxide and CO2 under the catalytic action of the MOF material catalyst of claim 1; the contact is carried out at 1.5-2 MPa; The epoxide is selected from epichlorohydrin and styrene oxide.

6. The method according to claim 5, characterized in that, The contact is carried out at 80-220°C.

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