Aza-cycloalkyl silver catalyst based on MOF framework and preparation method and application thereof

Abstract

The application belongs to the technical field of carbon dioxide catalysis, and discloses aza carbene silver catalyst based on MOF framework and a preparation method and application thereof. The method comprises the following steps: 1) dispersing zirconium salt, ligand I, ligand II and acid regulator in an organic solvent to perform a solvothermal reaction, and obtaining a perfluoroalkyl-modified aza carbene-based organic metal framework material; 2) reacting the perfluoroalkyl-modified aza carbene-based organic metal framework material with a silver salt in an organic solvent to obtain the aza carbene silver catalyst based on the MOF framework; the ligand I is formula I, and the ligand II is formula II. The method is simple, the catalyst has high catalytic activity and stability when used for the reaction of carbon dioxide and alkyne alcohol, and can also exhibit good catalytic performance in a dilute carbon dioxide and humid environment. The catalyst is used for the catalytic conversion of carbon dioxide.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalysts, and particularly relates to a nitrogen heterocyclic carbene silver catalyst based on a MOF framework and a preparation method and application thereof. BACKGROUND

[0002] The large amount of carbon dioxide emitted in the process of energy production, manufacturing and transportation has caused serious environmental problems such as global warming and sea level rise. In order to reduce the content of carbon dioxide in the atmosphere, it is necessary to minimize emissions and convert them into useful compounds through chemical reactions. At present, the methods for utilizing carbon dioxide mainly fall into two categories: one is to directly reduce it to generate carbon monoxide, methane, methanol and other fuels; the other is to react with organic substrates to generate carboxylic acids and cyclic carbonates and other high-value chemicals. However, due to the high thermodynamic and kinetic stability of carbon dioxide molecules, their chemical conversion needs to be assisted by high-activity catalysts (Das R, Nagaraja CM. Green Chemistry, 2021, 23, 5195; H.Y. Cui, Y.X. Zhang, C.S. Cao, T.D. Hu, Z.L. Wu, Chem. Eng. J. 2023, 451, 138764; Liu X, Zhu C, Li M, et al. Angewandte Chemie International Edition, 2024, e202412408.).

[0003] Nitrogen heterocyclic carbene (NHC) is a kind of ligand known for its strong σ-coordination ability, and is widely used in the fields of catalysis, medicine and material science. Its excellent electron-donating ability enables it to directly coordinate with various transition metals to form compounds with specific structures and functions, and thus it has attracted much attention. In recent years, many metal-nitrogen heterocyclic carbene (M-NHC) catalysts (such as Au-NHC, Ag-NHC and Cu-NHC) have been used for the catalytic conversion of carbon dioxide. However, most of these catalysts are homogeneous catalysts, which are difficult to recover after the catalytic reaction, or the metal sites are severely lost after recovery, resulting in a significant reduction in the activity of the catalysts (Moroni G, Bombonato E, Bonafè S, et al. ChemCatChem, 2024, e202301654; Beig N, Goyal V, Bansal R K. Beilstein Journal of Organic Chemistry, 2023, 19, 1408; Liu L C, Lin S, Xu K, et al. Advanced Science, 2024, 11, 2308710.).

[0004] Metal organic frameworks (MOFs) are known for their porous structure and design diversity, and are widely used in gas adsorption, catalysis and other fields. However, the existing metal organic framework materials often need high temperature and high concentration of carbon dioxide in catalyzing carbon dioxide conversion, and are not strong enough in water resistance. SUMMARY

[0005] In order to overcome the shortcomings and deficiencies of the prior art, the primary purpose of the present application is to provide a nitrogen heterocyclic carbene silver catalyst based on MOF framework and a preparation method thereof. The present application successfully prepares a catalyst modified with perfluoroalkyl and nitrogen heterocyclic metal carbene bifunctional groups, and the preparation method is simple, and the prepared catalyst has bifunctional catalytic sites, which greatly improves the performance of the catalyst in absorbing and converting CO2.

[0006] Another purpose of the present application is to provide the application of the above-mentioned nitrogen heterocyclic carbene silver catalyst. The nitrogen heterocyclic carbene silver catalyst is used for catalytic conversion of carbon dioxide, especially catalyzing the reaction of carbon dioxide and alkyne alcohol. The present application applies the perfluoroalkyl modified nitrogen heterocyclic carbene silver catalyst based on MOF framework to the reaction of CO2 and alkyne alcohol to generate cyclic carbonate, and has a high yield at normal temperature and pressure. Due to the dipole effect of fluorine atoms in perfluoroalkyl on CO2 molecules and the hydrophobicity, the catalyst also has good catalytic effect in humid and low-concentration CO2 simulated flue gas, and has practical industrial application prospect.

[0007] The technical scheme adopted by the present application is:

[0008] A preparation method of a nitrogen heterocyclic carbene silver catalyst based on MOF framework, comprising the following steps:

[0009] 1) dispersing zirconium salt, ligand I, ligand II and acid regulator in an organic solvent to perform solvothermal reaction, and obtaining perfluoroalkyl modified nitrogen heterocyclic carbene based organic metal framework material;

[0010] 2) reacting the perfluoroalkyl modified nitrogen heterocyclic carbene based organic metal framework material with silver salt in an organic solvent to obtain the nitrogen heterocyclic carbene silver catalyst based on MOF framework.

[0011] The ligand I is

[0012] Formula I:

[0013] The ligand II is

[0014] Formula II:

[0015] The zirconium salt is at least one of ZrCl4, ZrOCl2, Zr(CH3COO)4 and ZrO(NO3)2,

[0016] The acid regulator is at least one of glacial acetic acid, benzoic acid.

[0017] The molar ratio of the zirconium salt, ligand I and ligand II is 1: (0.4-0.6): (0.4-0.6).

[0018] The molar ratio of the zirconium salt and the acid regulator is 1: (10-50).

[0019] The organic solvent in step 1) is at least one of N, N-dimethylformamide, N, N-diethylformamide, N, N-dibutylformamide, N, N-dimethylacetamide.

[0020] The temperature of the solvothermal reaction is 110-130℃, and the reaction time is 20-30h.

[0021] The silver salt in step 2) is at least one of silver nitrate, silver trifluoroacetate; the organic solvent is at least one of methanol, tetrahydrofuran, acetonitrile, dichloromethane.

[0022] The molar ratio of the mass of the perfluoroalkyl-modified nitrogen heterocyclic carbene organometallic framework material to the silver salt is 10mg: (0.005-0.15) mmol. The molar volume ratio of the silver salt to the organic solvent is (0.001-0.03) mmol: 1mL.

[0023] The reaction time in step 2) is 8-15h; the reaction temperature is 15-30℃.

[0024] The ligand I is prepared by the following method:

[0025] S1, under a protective atmosphere, 4-methoxycarbonyl phenylboronic acid and 4-methyl-3-bromobenzoic acid are reacted in an organic solvent as a reaction medium in the presence of a catalyst and a basic compound to obtain a precursor P of a nitrogen heterocyclic carbene functionalized ligand 1 .

[0026] Precursor P 1 :

[0027]

[0028] The basic compound in step S1 is CsF cesium fluoride, cesium carbonate, and the catalyst is tetrakis triphenylphosphine palladium. The organic solvent in step S1 is at least one of tetrahydrofuran, N, N-dimethylformamide. The reaction temperature is 70-90℃, and the reaction time is 2-4h.

[0029] S2, precursor P 1Bromination reaction with N-bromosuccinimide to obtain precursor P 2 ;

[0030] Precursor P 2 :

[0031]

[0032] The organic solvent in step S2 is at least one of carbon tetrachloride and benzene. The reaction temperature is 70-90℃, and the reaction time is 4-6h. An initiator is added to the reaction.

[0033] S3, in an organic solvent as a reaction medium, precursor P 2 and N-isopropyl imidazole are heated to react, then hydrolyzed in an alkaline environment, and acidified to obtain ligand I with aza carbene functional group.

[0034] Precursor P 2 and N-isopropyl imidazole to obtain

[0035]

[0036] The organic solvent in step S3 is CH3CN, the reaction temperature is 45-65℃, and the reaction time is 1.5-3h. The hydrolysis uses a mixed solvent of methanol and water, the volume ratio of methanol to water in the mixed solvent is (2.5-3.5):1, the base used in the alkaline environment is at least one of lithium hydroxide, sodium hydroxide, and potassium hydroxide, and the hydrolysis reaction time is 10-13h. The acid used for acidification is at least one of hydrobromic acid, hydrochloric acid, and glacial acetic acid. Acidification refers to adjusting the pH to 3-4 with acid.

[0037] The ligand II is prepared by the following method:

[0038] Under a protective atmosphere, 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid and perfluoro anhydride are reacted in an organic solvent as a reaction medium to obtain perfluoroalkyl-modified functional ligand II.

[0039] The perfluoro anhydride is at least one of trifluoroacetic anhydride, pentafluoropropionic anhydride, and heptafluorobutyric anhydride. The organic solvent is CH3CN, the reaction temperature is 70-85℃, and the reaction time is 22-26h.

[0040] The aza carbene silver catalyst based on the MOF framework is prepared by the above method.

[0041] The aza carbene silver catalyst is used for catalytic conversion of carbon dioxide, especially for catalyzing the reaction of carbon dioxide with alkyne alcohol, and specifically for catalyzing the reaction of CO2 with alkyne alcohol to generate cyclic carbonate.

[0042] The alkyne alcohol is at least one of 2-methyl-3-butyne-2-ol, 3-methyl-1-pentyn-3-ol, 3-ethyl-1-pentyn-3-ol, 3,4-dimethyl-1-pentyn-3-ol, 5-methylhex-1-yne-3-ol, and 3,5-dimethyl-1-hexyn-3-ol.

[0043] An organic solvent, such as N,N-dimethylformamide, is added to the reaction.

[0044] The catalyst of the present application also exhibits good catalytic performance for the reaction in a humid (for example, humidity ≤ 95%) and low-concentration CO2 (volume concentration ≥ 13%) environment.

[0045] The catalyst of the present application has multiple functional catalytic sites. In the synthesis process, by adding ligands with different catalytic functional groups, a MOF framework-based azolide silver catalyst with double functional catalytic sites is synthesized, which greatly improves the performance of the catalyst in absorbing and converting CO2. The perfluoroalkyl-modified MOF framework-based azolide silver catalyst is applied to the reaction of CO2 and alkyne alcohol to generate cyclic carbonate, and has a high yield at normal temperature and pressure. Due to the dipole effect of the fluorine atoms in the perfluoroalkyl group on the CO2 molecule and the hydrophobicity, the catalyst also has good catalytic effect in a humid and low-concentration CO2 simulated flue gas, and has practical industrial application prospects.

[0046] Compared with the prior art, the present application has the following beneficial effects:

[0047] The MOF framework-based azolide silver catalyst of the present application is simple to prepare, and the prepared catalyst has double catalytic functional groups and simultaneously has the functions of carbon dioxide adsorption and reaction. When used for the reaction of carbon dioxide and alkyne alcohol, the catalyst exhibits high catalytic activity and stability, and also exhibits good catalytic performance for the reaction in a harsh environment of thin carbon dioxide and humidity, and has practical industrial application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 The H NMR spectrum of ligand II in Example 1 is shown in Figure 2. 1 The H NMR spectrum of ligand II in Example 1 is shown in Figure 2.

[0049] Figure 2 The H NMR spectrum of ligand II in Example 1 is shown in Figure 2. 1 The H NMR spectrum of ligand II in Example 1 is shown in Figure 2. 19 The F NMR of ligand II in Example 1 is shown in Figure 3.

[0050] Figure 3XRD pattern of the catalyst UiO-Ag-(BPDC-F3) prepared for example 1 and after 5 catalytic cycles;

[0051] Figure 4 SEM image of the catalyst UiO-Ag-(BPDC-F3) prepared for example 1 ;

[0052] Figure 5 Water contact angle test image of the catalyst UiO-Ag-(BPDC-F3) prepared for example 1 ;

[0053] Figure 6 Nitrogen adsorption test image of the catalyst UiO-Ag-(BPDC-F3) prepared for example 1 ;

[0054] Figure 7 Structural schematic of the catalyst UiO-Ag-(BPDC-F3) prepared for example 1 ;

[0055] Figure 8 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ; 1 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ;

[0056] Figure 9 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ; 1 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ;

[0057] Figure 10 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ; 1 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ;

[0058] Figure 11 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1 ; 1 HNMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolane-2-one for application example 1. DETAILED DESCRIPTION

[0059] The application will be further described in conjunction with specific examples, but the embodiments of the application are not limited thereto.

[0060] Example 1

[0061] A method for preparing a MOF framework-based azolide silver catalyst, comprising the following steps:

[0062] 1) Synthesis of precursor P with azolide functionalized ligand 1

[0063] Reaction equation:

[0064]

[0065] To precursor P (5.088 g, 17.8 mmol), N-bromosuccinimide (3.719 g, 20.9 mmol), and dibenzoyl peroxide (0.489 g, 2.02 mmol) were dissolved in 100 mL of carbon tetrachloride and heated at 90 °C under reflux for 4 h; after the reaction was completed, the mixture was filtered to remove the insoluble material and separated by column chromatography to obtain yellow solid P 1 , which was dried under high vacuum overnight, with a yield of 68%.

[0066] 2) Synthesis of precursor P 2

[0067] Reaction equation:

[0068]

[0069] To precursor P 1 (5.088 g, 17.8 mmol), N-bromosuccinimide (3.719 g, 20.9 mmol), and dibenzoyl peroxide (0.489 g, 2.02 mmol) were dissolved in 100 mL of carbon tetrachloride and heated at 90 °C under reflux for 4 h; after the reaction was completed, the mixture was filtered to remove the insoluble material and separated by column chromatography to obtain yellow solid P 2 , which was dried under high vacuum overnight, with a yield of 68%.

[0070] 3) Synthesis of ligand I

[0071] Reaction equation:

[0072]

[0073] To precursor P 2 (1.45 g, 4 mmol) was dissolved in 45 mL of acetonitrile, N-isopropylimidazole (970 μL, 8.8 mmol) was added, and heated at 60 °C for 2 h; after the reaction was completed, the filtrate was concentrated under reduced pressure to obtain a light yellow solid, which was dried under high vacuum overnight; the obtained solid was added to a reaction vessel, and 200 mL of 0.1 M lithium hydroxide solution (V 甲醇 :V 水= 3: 1) was dissolved, stirred for 12 h, the resulting solution was concentrated under reduced pressure, diluted with water, acidified with 1 M hydrogen bromide solution to pH = 3-4, filtered to obtain white solid, washed with water, dried under high vacuum overnight to obtain ligand I with aza-cyclo-carbene functional group, yield 92%.

[0074] 4) Synthesis of perfluoroalkyl-modified functionalized ligand, ligand II

[0075] Reaction equation:

[0076]

[0077] 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid (128 mg, 0.5 mmol) was dissolved in 3.5 mL of acetonitrile, trifluoroacetic anhydride (70 μL, 0.5 mmol) was added, and the reaction was refluxed at 80 °C under a nitrogen atmosphere for 24 h. After the reaction was completed, a yellow solid was obtained by centrifugal separation, washed with acetonitrile, and dried under high vacuum overnight to obtain a yield of 67%.

[0078] 5) Synthesis of aza-cyclo-carbene-based organometallic framework

[0079] Zirconium tetrachloride (70 mg, 0.30 mmol), ligand I (66.8 mg, 0.15 mmol), ligand II (52.9 mg, 0.15 mmol), and glacial acetic acid (515 μL, 8.58 mmol) were dissolved in 10 mL of N,N-dimethylformamide and ultrasonically dissolved for 10 min. The mixed solution was heated in an oven at 120 °C for 24 h. After the reaction was cooled, the precipitate was obtained by centrifugal separation, washed with N,N-dimethylformamide three times, immersed in methanol for 3 days, changed the solvent every 24 h, and then dried under high vacuum overnight to obtain the metal-organic framework material UiO-NHC-(BPDC-F3).

[0080] 6) Synthesis of aza-cyclo-carbene-based silver catalyst based on a MOF framework

[0081] The metal-organic framework material UiO-NHC-(BPDC-F3) (60 mg) was dispersed in 2 mL of anhydrous acetonitrile, added to a reaction vessel, and stirred to obtain a MOF suspension; silver nitrate (10.2 mg, 0.06 mmol) was dissolved in 2 mL of anhydrous acetonitrile, and the resulting silver nitrate solution was added to the MOF suspension, which was stirred at room temperature overnight. After the reaction was completed, a white solid was obtained by centrifugal separation, washed with acetonitrile, and dried under high vacuum overnight to obtain the catalyst UiO-Ag-(BPDC-F3).

[0082] Figure 1 Synthesis of ligand I in Example 1 1 H NMR spectrum; Figure 2The ligand II in Example 1 1 HNMR spectrum and 19 FNMR.

[0083] Figure 3 Figure 1 is an XRD pattern of the product catalyst UiO-Ag-(BPDC-F3) obtained in Example 1 and simulated UiO-67, which shows that the UiO-Ag-(BPDC-F3) has similar characteristic peaks to the simulated UiO-67, indicating that the UiO-Ag-(BPDC-F3) is successfully prepared and maintains the structural morphology unchanged after 5 catalytic cycles. Figure 4 Figure 2 is a SEM image of the product catalyst UiO-Ag-(BPDC-F3) obtained in Example 1, which shows that the UiO-Ag-(BPDC-F3) crystals exhibit a regular octahedron, consistent with the crystal morphology of UiO-67. Figure 5 Figure 3 is a water contact angle test image of the product catalyst UiO-Ag-(BPDC-F3) obtained in Example 1, which shows that the water contact angle is 72.8°, showing good hydrophobicity. Figure 6 Figure 4 is a nitrogen adsorption test image of the product catalyst UiO-Ag-(BPDC-F3) obtained in Example 1, which shows that the UiO-Ag-(BPDC-F3) has the characteristics of type I adsorption, consistent with UiO-67.

[0084] Application Example 1

[0085] Catalyzing the cyclization reaction of CO2 and 2-methyl-3-butyn-2-ol:

[0086] A Schlenk tube was charged with 2-methyl-3-butyn-2-ol (145 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F3) prepared in Example 1 (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (as a cocatalyst, which removes H on the substrate-OH during the reaction) (30 μL, 0.2 mmol) and 2 mL N,N-dimethylformamide, vacuumed and then a CO2 balloon was attached, stirred at room temperature for 8 h, centrifuged, and the supernatant was collected. Extracted with diethyl ether three times, rotary evaporated under reduced pressure to obtain the target product 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, with a yield of 99%.

[0087] Reaction equation:

[0088]

[0089] Application Example 2

[0090] Catalyzing the cyclization reaction of CO2 and 3-methyl-1-pentyn-3-ol:

[0091] Into a Schlenk tube was added 3-methyl-1-pentyn-3-ol (170 μL, 2 mmol), catalyst UiO-Ag-(BPDC-F3) prepared in Example 1 (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol) and 2 mL of N,N-dimethylformamide. After vacuuming, a CO2 balloon was attached and the reaction was stirred at room temperature for 8 h. The supernatant was collected after centrifugation. The target product 4-ethyl-4-methyl-5-methylene-1,3-dioxolan-2-one was obtained with a yield of 99% after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0092] Reaction equation:

[0093]

[0094] Application Example 3

[0095] Cyclization of CO2 with 3-ethyl-1-pentyn-3-ol:

[0096] Into a Schlenk tube was added 3-ethyl-1-pentyn-3-ol (195 μL, 2 mmol), catalyst UiO-Ag-(BPDC-F3) prepared in Example 1 (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol) and 2 mL of N,N-dimethylformamide. After vacuuming, a CO2 balloon was attached and the reaction was stirred at room temperature for 8 h. The supernatant was collected after centrifugation. The target product 4,4-diethyl-5-methylene-1,3-dioxolan-2-one was obtained with a yield of 68% after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0097] Reaction equation:

[0098]

[0099] Application Example 4

[0100] Cyclization of CO2 with 3,4-dimethyl-1-pentyn-3-ol:

[0101] Into a Schlenk tube was added 3,4-dimethyl-1-pentyn-3-ol (260 μL, 2 mmol), catalyst UiO-Ag-(BPDC-F3) prepared in Example 1 (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol), and 2 mL N,N-dimethylformamide. After vacuuming, a CO2 balloon was attached and the reaction was stirred at room temperature for 8 h. The supernatant was collected after centrifugation. The target product 4-isopropyl-4-methyl-5-methylene-1,3-dioxolan-2-one was obtained in 99% yield after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0102] Reaction equation:

[0103]

[0104] Application Example 5

[0105] Cyclization of CO2 with 5-methylhex-1-yn-3-ol:

[0106] Into a Schlenk tube was added 5-methylhex-1-yn-3-ol (220 μL, 2 mmol), catalyst UiO-Ag-(BPDC-F3) prepared in Example 1 (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol), and 2 mL N,N-dimethylformamide. After vacuuming, a CO2 balloon was attached and the reaction was stirred at room temperature for 8 h. The supernatant was collected after centrifugation. The target product 4-isobutyl-4-methyl-5-methylene-1,3-dioxolan-2-one was obtained in 94% yield after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0107] Reaction equation:

[0108]

[0109] Application Example 6

[0110] Cyclization of simulated humid flue gas with 2-methyl-3-butyne-2-ol:

[0111] Into a Schlenk tube was added 2-methyl-3-butyne-2-ol (145 μL, 2 mmol), catalyst UiO-Ag-(BPDC-F3) prepared in Example 1 (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol), and 2 mL N,N-dimethylformamide. After vacuuming, a simulated humid flue gas (V CO2 :V N2= 13:87) balloon, drop several drops of water into the balloon, stir the reaction at room temperature for 8 h, centrifuge, collect the supernatant. Extract with diethyl ether three times, rotary evaporation under reduced pressure to obtain the target product, the yield is 63%.

[0112] Reaction equation:

[0113]

[0114] Comparative Example 1

[0115] Using 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid instead of ligand II in Example 1, the preparation of the MOF framework-based azolide silver catalyst includes the following steps:

[0116] 1) Synthesis of azolide-based organometallic framework

[0117] Dissolve zirconium tetrachloride (70 mg, 0.30 mmol), ligand I (66.8 mg, 0.15 mmol), 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid (38.6 mg, 0.15 mmol) and glacial acetic acid (515 μL, 8.58 mmol) in 10 mL of N,N-dimethylformamide, and ultrasonic for 10 minutes to fully dissolve; the mixed solution is heated in an oven at 120°C for 24 h, and the precipitate is separated by centrifugation after the reaction is cooled, washed with N,N-dimethylformamide three times, and the solid is soaked in methanol for 3 days, changing the solvent every 24 h, and then dried under high vacuum overnight to obtain the desolvated metal organic framework material UiO-NHC-(BPDC-NH2).

[0118] 2) Synthesis of MOF framework-based azolide silver catalyst

[0119] Dissolve 60 mg of the metal organic framework material synthesized in step 1) in 2 mL of anhydrous acetonitrile and add to a round-bottom flask for stirring. Dissolve silver nitrate (10.2 mg, 0.06 mmol) in 2 mL of anhydrous acetonitrile, and add the obtained silver nitrate solution to the MOF suspension, and stir at room temperature overnight; after the reaction is completed, separate the white solid by centrifugation, wash with acetonitrile, and dry under high vacuum overnight.

[0120] Application: catalyzing the cyclization reaction of CO2 and 2-methyl-3-butyn-2-ol:

[0121] A Schlenk tube was charged with 2-methyl-3-butyn-2-ol (145 μL, 2 mmol), catalyst prepared in step 2) (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol) and 2 mL of N,N-dimethylformamide, evacuated and charged with a CO2 balloon, stirred at room temperature for 8 h, centrifuged and the supernatant was collected. The product was extracted with diethyl ether three times and evaporated under reduced pressure to give the target product 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one in 60% yield.

[0122] Comparative Example 2

[0123] An imidazolium-based MOF framework catalyst was prepared by replacing ligand II in Example 1 with 4,4-biphenyldicarboxylic acid, comprising the following steps:

[0124] 1) Synthesis of imidazolium-based MOF framework

[0125] Zirconium tetrachloride (70 mg, 0.30 mmol), ligand I (66.8 mg, 0.15 mmol), 4,4-biphenyldicarboxylic acid (38.6 mg, 0.15 mmol), and glacial acetic acid (515 μL, 8.58 mmol) were dissolved in 10 mL of N,N-dimethylformamide and sonicated for 10 min to ensure complete dissolution; the mixed solution was heated in an oven at 120 °C for 24 h. After the reaction was cooled, the precipitate was separated by centrifugation and washed with N,N-dimethylformamide three times. The solid was soaked in methanol for 3 days, changing the solvent every 24 h, and then dried under high vacuum overnight to give the desolvated metal-organic framework material UiO-NHC-BPDC.

[0126] 2) Synthesis of imidazolium-based MOF framework silver catalyst

[0127] The metal-organic framework material synthesized in step 1) (60 mg) was dispersed in 2 mL of anhydrous acetonitrile and added to a round-bottom flask with stirring; silver nitrate (10.2 mg, 0.06 mmol) was dissolved in 2 mL of anhydrous acetonitrile, and the resulting silver nitrate solution was added to the MOF suspension, which was stirred at room temperature overnight. After the reaction was completed, the white solid was separated by centrifugation and washed with acetonitrile and dried under high vacuum overnight.

[0128] Application: catalyzing the cyclization of CO2 with 2-methyl-3-butyn-2-ol

[0129] A Schlenk tube was charged with 2-methyl-3-butyn-2-ol (145 μL, 2 mmol), the catalyst prepared in Step 2) (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol), and 2 mL of N,N-dimethylformamide, evacuated and fitted with a CO2 balloon, and stirred at room temperature for 8 h. The upper clear liquid was collected by centrifugation. The target product, 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one, was obtained in 53% yield after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0130] Comparative Example 3

[0131] The catalytic cyclization of CO2 with 2-methyl-3-butyn-2-ol was performed using the metal-organic framework material UiO-NHC-(BPDC-F3) prepared in Step 5 of Example 1 without Ag catalytic sites:

[0132] A Schlenk tube was charged with 2-methyl-3-butyn-2-ol (145 μL, 2 mmol), UiO-NHC-BPDC (10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol), and 2 mL of N,N-dimethylformamide, evacuated and fitted with a CO2 balloon, and stirred at room temperature for 8 h. The upper clear liquid was collected by centrifugation. The target product was not detected after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0133] Comparative Example 4

[0134] The catalytic cyclization of CO2 with 2-methyl-3-butyn-2-ol was performed without a catalyst:

[0135] A Schlenk tube was charged with 2-methyl-3-butyn-2-ol (145 μL, 2 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (30 μL, 0.2 mmol), and 2 mL of N,N-dimethylformamide, evacuated and fitted with a CO2 balloon, and stirred at room temperature for 8 h. The upper clear liquid was collected by centrifugation. The target product was not detected after extraction with diethyl ether three times and rotary evaporation under reduced pressure.

[0136] Figure 7 Structure of the catalyst UiO-Ag-(BPDC-F3) prepared for Example 1;

[0137] Figure 8 Application of 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one prepared in Example 1 1 H NMR spectrum;

[0138] Figure 9For the application of 4-ethyl-4-methyl-5-methylene-1,3-dioxolane-2-one in Example 2 1 HNMR spectrum;

[0139] Figure 10 For the application of 4-isopropyl-4-methyl-5-methylene-1,3-dioxolane-2-one in Example 4 1 HNMR spectrum;

[0140] Figure 11 For the application of 4-isobutyl-4-methyl-5-methylene-1,3-dioxolane-2-one in Example 5 1 HNMR spectrum.

Claims

1. A method for preparing a MOF framework based silver catalyst of azaheterocyclic carbene, characterized in that: The method comprises the following steps: 1) dispersing a zirconium salt, a ligand I, a ligand II and an acid regulator in an organic solvent to perform a solvothermal reaction, and obtaining a perfluoroalkyl-modified azacyclic carbene-based organic metal framework material; 2) reacting the perfluoroalkyl-modified azacyclic carbene-based organic metal framework material with a silver salt in an organic solvent to obtain the azacyclic carbene silver catalyst based on the MOF framework; The ligand I is The ligand II is The molar ratio of the zirconium salt, the ligand I and the ligand II is 1:(0.4-0.6):(0.4-0.6); The temperature of the solvothermal reaction in step 1) is 110-130℃, and the reaction time is 20-30h; The organic solvent in step 1) is at least one of N,N-dimethylformamide, N,N-diethylformamide, N,N-dibutylformamide and N,N-dimethylacetamide; The silver salt in step 2) is at least one of silver nitrate and silver trifluoroacetate.

2. The method for preparing the azacyclic carbene silver catalyst based on the MOF framework according to claim 1, characterized in that: The zirconium salt is at least one of ZrCl4, ZrOCl2, Zr(CH3COO)4 and ZrO(NO3)2; The acid regulator is at least one of glacial acetic acid and benzoic acid; The molar ratio of the zirconium salt and the acid regulator is 1:(10-50); The organic solvent in step 2) is at least one of methanol, tetrahydrofuran, acetonitrile and dichloromethane; The molar ratio of the mass of the perfluoroalkyl-modified azacyclic carbene-based organic metal framework material to the silver salt is 10mg:(0.005-0.15)mmol; The reaction time in step 2) is 8-15h, and the reaction temperature is 15-30℃.

3. The method of claim 1, wherein the MOF framework-based catalyst is prepared by the following steps: (1) preparing a MOF framework; (2) introducing a silver source into the MOF framework; and (3) introducing a nitrogen heterocyclic compound into the MOF framework. The ligand I is prepared by the following method: S1, under a protective atmosphere, 4-methoxycarbonylphenylboronic acid and 4-methyl-3-bromobenzoic acid methyl ester are reacted in the presence of a catalyst and a basic compound in an organic solvent to obtain a precursor P of a ligand functionalized with a nitrogen heterocyclic carbene functional group 1 ; Precursor P 1 : S2, the precursor P is functionalized with a nitrogen heterocyclic carbene functional group by bromination reaction with N-bromosuccinimide 1 ; and S3, the precursor P is functionalized with a nitrogen heterocyclic carbene functional group by bromination reaction with N-bromosuccinimide 2 ; and S3, the precursor P is functionalized with a nitrogen heterocyclic carbene functional group by bromination reaction with N-bromosuccinimide Precursor P 2 : S3, heating reaction of precursor P with organic solvent as reaction medium 2 and N-isopropylimidazole, then hydrolysis in alkaline environment, acidification, to obtain ligand I with azepine carbene functional group. Precursor P 2 and the product of the reaction of N-isopropylimidazole 4. The method for preparing the nitrogen heterocyclic carbene silver catalyst based on the MOF framework according to claim 3, characterized in that: The basic compound in step S1 is at least one of cesium fluoride and cesium carbonate; the catalyst is tetrakis(triphenylphosphine)palladium; the organic solvent in step S1 is at least one of tetrahydrofuran and N,N-dimethylformamide; the reaction temperature is 70-90℃, and the reaction time is 2-4h; The organic solvent in step S2 is at least one of carbon tetrachloride and benzene; the reaction temperature is 70-90℃, the reaction time is 4-6h; and an initiator is added in the reaction, and the initiator is dibenzoyl peroxide; The organic solvent in step S3 is CH3CN, the reaction temperature is 45-65℃, the reaction time is 1.5-3h; the solvent used in the hydrolysis is a mixed solvent of methanol and water, the volume ratio of methanol to water in the mixed solvent is (2.5-3.5):1, the base used is at least one of lithium hydroxide, sodium hydroxide and potassium hydroxide, the hydrolysis reaction time is 10-13h; the acid used in the acidification is at least one of hydrobromic acid, hydrochloric acid and glacial acetic acid; and the acidification refers to adjusting the pH to 3-4 by using an acid.

5. The method for preparing the nitrogen heterocyclic carbene silver catalyst based on the MOF framework according to claim 1, characterized in that: The ligand II is prepared by the following method: Under a protective atmosphere, 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid and perfluoroanhydride are reacted in an organic solvent as a reaction medium to obtain the perfluoroalkyl-modified functionalized ligand II. The perfluoro acid anhydride is trifluoroacetic anhydride; The organic solvent is acetonitrile, the reaction temperature is 70-85℃, and the reaction time is 22-26h.

6. A MOF framework-based azolide silver catalyst obtained by the preparation method of any one of claims 1-5.

7. Use of a MOF framework based azaheterocyclic carbene silver catalyst according to claim 6, characterized in that: The MOF framework-based azolide silver catalyst is used for catalytic conversion of carbon dioxide.

8. Use according to claim 7, characterized in that: The MOF framework-based azolide silver catalyst is used for catalyzing reaction of carbon dioxide and alkyne alcohol.

9. Use according to claim 8, characterized in that: The MOF framework-based azolide silver catalyst is used for catalyzing reaction of CO2 and alkyne alcohol to generate cyclic carbonate.

10. Use according to claim 9, characterized in that: The alkyne alcohol is at least one of 2-methyl-3-butyne-2-ol, 3-methyl-1-pentyne-3-ol, 3-ethyl-1-pentyne-3-ol, 3,4-dimethyl-1-pentyne-3-ol, 5-methylhex-1-yne-3-ol, and 3,5-dimethyl-1-hexyne-3-ol; The catalyst is added with a cocatalyst 1,8-diazabicyclo[5.4.0]undec-7-ene during catalysis; Humidity is ≤95%, and the volume concentration of CO2 is ≥13%.

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