N-heterocyclic carbene silver catalyst based on MOF (Metal Organic Framework) as well as preparation method and application of N-heterocyclic carbene silver catalyst

Abstract

The invention belongs to the technical field of carbon dioxide catalysis, and discloses an N-heterocyclic carbene silver catalyst based on an MOF (Metal Organic Framework) as well as a preparation method and application of the N-heterocyclic carbene silver catalyst. The method comprises the following steps: 1) dispersing zirconium salt, a ligand I, a ligand II and an acid regulator in an organic solvent, and carrying out solvothermal reaction to obtain a perfluoroalkyl modified N-heterocyclic carbene-based organic metal framework material; and 2) reacting the perfluoroalkyl modified N-heterocyclic carbene organic metal framework material with silver salt in an organic solvent to obtain the MOF framework-based N-heterocyclic carbene silver catalyst, the ligand I is shown as a formula I, and the ligand II is shown as a formula II. The method is simple, and the catalyst shows high catalytic activity and stability when used for the reaction of carbon dioxide and alkynol, and also shows good catalytic performance in a thin carbon dioxide and humid environment. The catalyst is used for catalytic conversion of carbon dioxide. # imgabs0 #

Description

Technical Field

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

[0002] A large amount of carbon dioxide emitted during energy production, manufacturing, and transportation processes has caused serious environmental problems such as global warming and sea - level rise. To reduce the carbon dioxide content in the atmosphere, it is necessary to minimize emissions and convert it into useful compounds through chemical reactions. Currently, the methods for utilizing carbon dioxide are mainly divided into two categories: one is to directly reduce it to produce fuels such as carbon monoxide, methane, and methanol; the other is to react with organic substrates to produce high - value chemicals such as carboxylic acids and cyclic carbonates. However, due to the high thermodynamic and kinetic stability of carbon dioxide molecules, their chemical conversion requires the assistance of highly active 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 type of ligand known for its strong σ - coordination ability, and is widely used in the fields of catalysis, medicine, and materials science. Its excellent electron - donating ability enables it to directly coordinate with a variety of transition metals to form compounds with specific structures and functions, thus attracting much attention. In recent years, many nitrogen - heterocyclic metal 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, and it is difficult to recover the catalyst after the catalytic reaction, or the metal sites in the recovered catalyst are severely lost, resulting in a significant reduction in the catalyst activity (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 renowned for their porous structures and design diversity and are widely used in fields such as gas adsorption and catalysis. However, existing metal-organic framework materials often require high temperatures and high concentrations of carbon dioxide for catalytic carbon dioxide conversion and have insufficient tolerance to water. Summary of the Invention

[0005] To overcome the drawbacks and deficiencies of the prior art, the primary objective of the present invention is to provide a perfluoroalkylated N-heterocyclic carbene silver catalyst based on a MOF framework and a preparation method thereof. The present invention successfully prepares a catalyst modified with both perfluoroalkyl and N-heterocyclic metal carbene functional groups, and the preparation method is simple. The prepared catalyst has dual-functional catalytic sites, greatly enhancing the performance of the catalyst in absorbing and converting CO 2 .

[0006] Another objective of the present invention is to provide the application of the above-mentioned N-heterocyclic carbene silver catalyst. The N-heterocyclic carbene silver catalyst is used for the catalytic conversion of carbon dioxide, especially for catalyzing the reaction of carbon dioxide with alkynols. The present invention applies a perfluoroalkylated N-heterocyclic carbene silver catalyst based on a MOF framework to the reaction of CO 2 with alkynols to produce cyclic carbonates, which has a high yield at room temperature and normal pressure. Due to the dipole effect and hydrophobicity of fluorine atoms in the perfluoroalkyl group on the CO 2 molecule, the catalyst also has good catalytic effects in humid and low-concentration CO 2 simulated flue gas and has prospects for practical industrial applications.

[0007] The technical solution adopted by the present invention is as follows:

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

[0009] 1) Dispersing a zirconium salt, ligand I, ligand II, and an acid regulator in an organic solvent and performing a solvothermal reaction to obtain a perfluoroalkylated N-heterocyclic carbene-based organometallic framework material;

[0010] 2) Reacting the perfluoroalkylated N-heterocyclic carbene organometallic framework material with a silver salt in an organic solvent to obtain the perfluoroalkylated N-heterocyclic carbene silver catalyst based on a MOF framework.

[0011] The ligand I is

[0012] Formula I:

[0013] The ligand II is

[0014] Formula II:

[0015] The zirconium salt is ZrCl4 , ZrOCl 2 , Zr(CH 3 COO) 4 , ZrO(NO 3 ) 2 at least one of

[0016] The acid regulator is at least one of glacial acetic acid and 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, and N,N-dimethylacetamide.

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

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

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

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

[0024] Ligand I is prepared by the following method:

[0025] S1. Under a protective atmosphere, using an organic solvent as the reaction medium, react 4-methoxycarbonylphenylboronic acid and methyl 4-methyl-3-bromobenzoate under the action of a catalyst and a basic compound to obtain a precursor P with a functionalized ligand of N-heterocyclic carbene 1 .

[0026] Precursor P 1 :

[0027]

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

[0029] S2. Using an organic solvent as the reaction medium, react the precursor P 1 with N-bromosuccinimide in a bromination reaction to obtain a precursor P with a functionalized ligand of N-heterocyclic carbene functional group. 2 ;

[0030] Precursor P 2 :

[0031]

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

[0033] S3. Using an organic solvent as the reaction medium, heat-react the precursor P 2 and N-isopropylimidazole, and then hydrolyze and acidify in a basic environment to obtain a ligand I with a functionalized N-heterocyclic carbene functional group.

[0034] Precursor P 2 The product of the reaction of precursor P and N-isopropylimidazole is

[0035]

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

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

[0038] Under a protective atmosphere, using an organic solvent as the reaction medium, react 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid with a perfluoro acid anhydride to obtain a perfluoroalkyl-modified functionalized ligand II.

[0039] The perfluoro acid anhydride is at least one of trifluoroacetic anhydride, pentafluoropropionic anhydride, and heptafluorobutyric anhydride. The organic solvent is CH3 In CN, the reaction temperature is 70 - 85 °C and the reaction time is 22 - 26 h.

[0040] The MOF framework-based N-heterocyclic carbene silver catalyst is prepared by the above method.

[0041] The N-heterocyclic carbene silver catalyst is used for the catalytic conversion of carbon dioxide, especially for catalyzing the reaction of carbon dioxide with alkynols. Specifically, it catalyzes the reaction of CO 2 with alkynols to form cyclic carbonates.

[0042] The alkynol is at least one of 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 3-ethyl-1-pentyn-3-ol, 3,4-dimethyl-1-pentyn-3-ol, 5-methylhex-1-yn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol.

[0043] An organic solvent such as N,N-dimethylformamide is added to the reaction. The reaction also adds a co-catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0044] The catalyst of the present invention also shows good catalytic performance for this reaction in a humid environment (for example, humidity ≤ 95%) and low-concentration CO 2 (volume concentration ≥ 13%).

[0045] The catalyst of the present invention has multi-functional catalytic sites. During the synthesis process, by adding ligands with different catalytic functional groups, a MOF framework-based N-heterocyclic carbene silver catalyst with dual-functional catalytic sites was synthesized, greatly improving the performance of the catalyst in absorbing and converting CO 2 Applying this perfluoroalkyl-modified MOF framework-based N-heterocyclic carbene silver catalyst to the reaction of CO with alkynols to form cyclic carbonates has a high yield at normal temperature and pressure. Due to the dipole effect and hydrophobicity of fluorine atoms in the perfluoroalkyl group on CO2 molecules, the catalyst also has good catalytic effects in humid and low-concentration CO 2 simulated flue gas, showing prospects for practical industrial applications. 2 Compared with the prior art, the beneficial effects of the present invention are as follows:

[0046] The MOF framework-based N-heterocyclic carbene silver catalyst of the present invention is simple to prepare. The prepared catalyst has dual catalytic functional groups and simultaneously has the functions of carbon dioxide adsorption and reaction. It shows high catalytic activity and stability when used in the reaction of carbon dioxide with alkynols. At the same time, it can also show good catalytic performance for this reaction in a harsh environment of thin carbon dioxide and humidity, showing prospects for practical industrial applications.

[0047] Description of the Drawings

[0048] Figure 1 1H NMR spectrum of ligand I in Example 1 1 ;

[0049] Figure 2 1H NMR spectrum of ligand II in Example 1 1 (a) and 19 19F NMR (b);

[0050] Figure 3 XRD spectra of the catalyst UiO-Ag-(BPDC-F 3 ) prepared in Example 1 and after 5 catalytic cycles;

[0051] Figure 4 SEM image of the catalyst UiO-Ag-(BPDC-F 3 ) prepared in Example 1;

[0052] Figure 5 Water contact angle test image of the catalyst UiO-Ag-(BPDC-F 3 ) prepared in Example 1;

[0053] Figure 6 Nitrogen adsorption test image of the catalyst UiO-Ag-(BPDC-F 3 ) prepared in Example 1;

[0054] Figure 7 Structure schematic diagram of the catalyst UiO-Ag-(BPDC-F 3 ) prepared in Example 1;

[0055] Figure 8 1H NMR spectrum of 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one in Application Example 1 1 ;

[0056] Figure 9 1H NMR spectrum of 4-ethyl-4-methyl-5-methylene-1,3-dioxolan-2-one in Application Example 2 1 ;

[0057] Figure 10 1H NMR spectrum of 4-isopropyl-4-methyl-5-methylene-1,3-dioxolan-2-one in Application Example 4 1 ;

[0058] Figure 11 1H NMR spectrum of 4-isobutyl-4-methyl-5-methylene-1,3-dioxolan-2-one in Application Example 5 1 ; Detailed Embodiments

[0059] The present invention will be further described in detail below in conjunction with specific embodiments, but the embodiments of the present invention are not limited thereto.

[0060] Embodiment 1

[0061] A preparation method of a nitrogen heterocyclic carbene silver catalyst based on a MOF framework includes the following steps:

[0062] 1) Synthesize the precursor P with a nitrogen heterocyclic carbene functionalized ligand 1

[0063] Reaction equation:

[0064]

[0065] Add 4-methoxycarbonylphenylboronic acid (2.763 g, 15.3 mmol), methyl 4-methyl-3-bromobenzoate (3.452 g, 15 mmol), cesium fluoride (4.50 g, 30 mmol), and tetrakis(triphenylphosphine)palladium (0.697 g, 0.60 mmol) to 150 mL of tetrahydrofuran, heat at 80 °C for 3 h under a nitrogen atmosphere; after the reaction is completed, filter the mixed solution to remove insoluble substances, and separate by column chromatography to obtain an orange-yellow solid P 1 , and the solid is dried overnight under high vacuum with a yield of 82%.

[0066] 2) Synthesize the precursor P with a nitrogen heterocyclic carbene functionalized ligand 2

[0067] Reaction equation:

[0068]

[0069] Dissolve the precursor P 1 (5.088 g, 17.8 mmol), N-bromosuccinimide (3.719 g, 20.9 mmol), and benzoyl peroxide (0.489 g, 2.02 mmol) in 100 mL of carbon tetrachloride, reflux and heat at 90 °C for 4 h; after the reaction is completed, filter the mixed solution to remove insoluble substances, and separate by column chromatography to obtain a yellow solid P 2 , and the solid is dried overnight under high vacuum with a yield of 68%.

[0070] 3) Synthesize the nitrogen heterocyclic carbene functionalized ligand, namely ligand I

[0071] Reaction equation:

[0072]

[0073] Dissolve the precursor P 2 (1.45 g, 4 mmol) in 45 mL of acetonitrile, add N-isopropylimidazole (970 μL, 8.8 mmol), heat at 60 °C for 2 h. After the reaction, concentrate the filtrate under reduced pressure to obtain a light yellow solid, which is dried overnight under high vacuum; add the obtained solid to the reaction vessel, dissolve it with 200 mL of 0.1 M lithium hydroxide solution (V 甲醇 :V 水 = 3:1), stir for 12 h. After concentrating the reaction solution under reduced pressure, dilute it with water, acidify it to pH = 3 - 4 with 1 M hydrobromic acid solution, filter to obtain a white solid, wash it with water, and dry it overnight under high vacuum to obtain a ligand functionalized with an N-heterocyclic carbene functional group, namely ligand I, with a yield of 92%.

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

[0075] Reaction equation:

[0076]

[0077] Dissolve 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid (128 mg, 0.5 mmol) in 3.5 mL of acetonitrile, add trifluoroacetic anhydride (70 μL, 0.5 mmol), reflux at 80 °C for 24 h under a nitrogen atmosphere. After the reaction, centrifuge to obtain a yellow solid, wash it with acetonitrile, and dry it overnight under high vacuum, with a yield of 67%.

[0078] 5) Synthesis of N-heterocyclic carbene-based metal-organic framework

[0079] Dissolve 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) in 10 mL of N,N-dimethylformamide, and ultrasonicate for 10 minutes to dissolve them thoroughly. Heat the mixed solution in an oven at 120 °C for 24 h. After the reaction is cooled, centrifuge to obtain a precipitate, wash it three times with N,N-dimethylformamide, soak the solid in methanol for 3 days, change the solvent every 24 h, and then dry it overnight under high vacuum to obtain the metal-organic framework material UiO-NHC-(BPDC-F 3 ).

[0080] 6) Synthesis of N-heterocyclic carbene silver catalyst based on MOF framework

[0081] Dissolve 60 mg of the metal-organic framework material UiO-NHC-(BPDC-F 3) 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, the obtained silver nitrate solution was added to the MOF suspension, stirred at room temperature overnight, and after the reaction was completed, centrifuged to obtain a white solid, which was washed with acetonitrile and dried under high vacuum overnight to obtain the catalyst UiO-Ag-(BPDC-F 3 ).

[0082] Figure 1 is the ligand Ⅰ in Example 1 1 H NMR spectrum; Figure 2 is the ligand II in Example 1 1 HNMR spectra and 19 FNMR.

[0083] Figure 3 The catalyst UiO-Ag-(BPDC-F 3 ) and the XRD patterns of UiO-67 after 5 catalytic cycles compared with the simulated ones. It can be seen that UiO-Ag-(BPDC-F 3 ) has similar characteristic peaks to those of simulated UiO-67, indicating that UiO-Ag-(BPDC-F 3 ) was successfully prepared and its structural morphology remained unchanged after 5 catalytic cycles. Figure 4 The catalyst UiO-Ag-(BPDC-F 3 ) SEM image, we can see that UiO-Ag-(BPDC-F 3 ) The crystals are regular octahedrons, which is consistent with the crystal morphology of UiO-67. Figure 5 The catalyst UiO-Ag-(BPDC-F 3 ) water contact angle test diagram, it can be seen that the water contact angle is 72.8°, showing good hydrophobicity. Figure 6 The catalyst UiO-Ag-(BPDC-F 3 ) nitrogen adsorption test diagram, we can see that UiO-Ag-(BPDC-F 3 ) has the characteristics of type I adsorption, which is consistent with UiO-67.

[0084] Application Example 1

[0085] Catalytic CO 2 Cyclization reaction with 2-methyl-3-butyn-2-ol:

[0086] 2-Methyl-3-butyn-2-ol (145 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F prepared in Example 1 3)(10 mg, 0.03 mmol), 1,8-diazabicyclo[5.4.0]undec-7-ene (as a cocatalyst, which removes the H on the -OH of the substrate during the reaction) (30 μL, 0.2 mmol) and 2 mL of N,N-dimethylformamide were added to a Schlenk tube. After evacuation, a CO 2 balloon was put on it. The reaction was stirred at room temperature for 8 h, centrifuged, and the upper clear liquid was collected. It was extracted three times with ether and 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] Catalyze the cyclization reaction of CO 2 with 3-methyl-1-pentyn-3-ol:

[0091] 3-Methyl-1-pentyn-3-ol (170 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F prepared in Example 1 3 )(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 were added to a Schlenk tube. After evacuation, a CO 2 balloon was put on it. The reaction was stirred at room temperature for 8 h, centrifuged, and the upper clear liquid was collected. It was extracted three times with ether and rotary evaporated under reduced pressure to obtain the target product 4-ethyl-4-methyl-5-methylene-1,3-dioxolan-2-one with a yield of 99%.

[0092] Reaction equation:

[0093]

[0094] Application Example 3

[0095] Catalyze the cyclization reaction of CO 2 with 3-ethyl-1-pentyn-3-ol:

[0096] 3-Ethyl-1-pentyn-3-ol (195 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F prepared in Example 1 3 )(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 were added to a Schlenk tube. After evacuation, a CO 2The balloon was stirred at room temperature for 8 h, centrifuged, and the supernatant was collected. It was extracted three times with ether and rotary evaporated under reduced pressure to obtain the target product 4,4-diethyl-5-methylene-1,3-dioxolan-2-one with a yield of 68%.

[0097] Reaction equation:

[0098]

[0099] Application Example 4

[0100] Catalytic CO 2 Cyclization reaction with 3,4-dimethyl-1-pentyn-3-ol:

[0101] 3,4-Dimethyl-1-pentyn-3-ol (260 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F prepared in Example 1 3 )(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 were added to a Schlenk tube. After evacuation, a CO 2 balloon was attached, and the reaction was stirred at room temperature for 8 h, centrifuged, and the supernatant was collected. It was extracted three times with ether and rotary evaporated under reduced pressure to obtain the target product 4-isopropyl-4-methyl-5-methylene-1,3-dioxolan-2-one with a yield of 99%.

[0102] Reaction equation:

[0103]

[0104] Application Example 5

[0105] Catalytic CO 2 Cyclization reaction with 5-methylhex-1-yn-3-ol:

[0106] 5-Methylhex-1-yn-3-ol (220 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F prepared in Example 1 3 )(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 were added to a Schlenk tube. After evacuation, a CO 2 balloon was attached, and the reaction was stirred at room temperature for 8 h, centrifuged, and the supernatant was collected. It was extracted three times with ether and rotary evaporated under reduced pressure to obtain the target product 4-isobutyl-4-methyl-5-methylene-1,3-dioxolan-2-one with a yield of 94%.

[0107] Reaction equation:

[0108]

[0109] Application Example 6

[0110] Catalyze the cyclization reaction of simulated wet flue gas and 2-methyl-3-butyn-2-ol:

[0111] Add 2-methyl-3-butyn-2-ol (145 μL, 2 mmol), the catalyst UiO-Ag-(BPDC-F prepared in Example 1 3 )(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 into a Schlenk tube. After evacuation, attach a simulated wet flue gas (V CO2 :V N2 = 13:87) balloon. Drop a few drops of water into the balloon and stir the reaction at room temperature for 8 h. Centrifuge and collect the supernatant. Extract with ether three times and rotary evaporate under reduced pressure to obtain the target product with a yield of 63%.

[0112] Reaction equation:

[0113]

[0114] Comparative Example 1

[0115] Replace ligand II in Example 1 with 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid. The preparation of the N-heterocyclic carbene silver catalyst based on the MOF framework includes the following steps:

[0116] 1) Synthesize the N-heterocyclic carbene-based metal-organic 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 sonicate for 10 minutes to dissolve them fully; heat the mixed solution in an oven at 120 °C for 24 h. After the reaction cools, centrifuge to separate the precipitate, wash it three times with N,N-dimethylformamide, soak the solid in methanol for 3 days, change the solvent every 24 h, and then dry it overnight under high vacuum to obtain the desolvated metal-organic framework material UiO-NHC-(BPDC-NH 2 ).

[0118] 2) Synthesize the N-heterocyclic carbene silver catalyst based on the MOF framework

[0119] Disperse 60 mg of the metal-organic framework material synthesized in step 1) in 2 mL of anhydrous acetonitrile, and add it to a round-bottom flask and stir. 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. Stir overnight at room temperature; after the reaction is completed, centrifuge to obtain a white solid, wash it with acetonitrile, and dry it overnight under high vacuum.

[0120] Application: Catalyze CO 2 Cyclization reaction with 2-methyl-3-butyn-2-ol:

[0121] Add 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 into a Schlenk tube, evacuate it and then put on a CO 2 balloon, stir the reaction at room temperature for 8 h, centrifuge, and collect the supernatant. Extract it three times with ether, and rotary evaporate under reduced pressure to obtain the target product 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one with a yield of 60%.

[0122] Comparative Example 2

[0123] Replace ligand II in Example 1 with 4,4-biphenyldicarboxylic acid. The preparation of the N-heterocyclic carbene silver catalyst based on the MOF framework includes the following steps:

[0124] 1) Synthesize N-heterocyclic carbene-based metal-organic framework

[0125] Dissolve 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) in 10 mL of N,N-dimethylformamide, and ultrasonicate for 10 minutes to dissolve it completely; heat the mixed solution in an oven at 120 °C for 24 h. After the reaction cools down, centrifuge to obtain a precipitate, wash it three times with N,N-dimethylformamide, soak the solid in methanol for 3 days, change the solvent every 24 h, and then dry it overnight under high vacuum to obtain the desolvated metal-organic framework material UiO-NHC-BPDC.

[0126] 2) Synthesize the N-heterocyclic carbene silver catalyst based on the MOF framework

[0127] Disperse 60 mg of the metal-organic framework material synthesized in step 1) in 2 mL of anhydrous acetonitrile, add it to a round-bottom flask and stir; dissolve silver nitrate (10.2 mg, 0.06 mmol) in 2 mL of anhydrous acetonitrile, add the resulting silver nitrate solution to the MOF suspension, stir overnight at room temperature, after the reaction is completed, centrifuge to obtain a white solid, wash it with acetonitrile, and dry it overnight under high vacuum.

[0128] Application: Catalyzing CO 2 Cyclization reaction with 2-methyl-3-butyn-2-ol

[0129] Add 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 to a Schlenk tube, evacuate it and then put on a CO 2 balloon, stir the reaction at room temperature for 8 h, centrifuge, and collect the supernatant. Extract it three times with ether, and rotary evaporate under reduced pressure to obtain the target product 4,4-dimethyl-5-methylene-1,3-dioxolan-2-one with a yield of 53%.

[0130] Comparative Example 3

[0131] Use the metal-organic framework material UiO-NHC-(BPDC-F 3 (prepared in step 5 of Example 1) to catalyze the cyclization reaction of CO 2 with 2-methyl-3-butyn-2-ol:

[0132] Add 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 to a Schlenk tube, evacuate it and then put on a CO 2 balloon, stir the reaction at room temperature for 8 h, centrifuge, and collect the supernatant. Extract it three times with ether, and rotary evaporate under reduced pressure. No target product was detected.

[0133] Comparative Example 4

[0134] Perform the cyclization reaction of CO without using a catalyst 2 with 2-methyl-3-butyn-2-ol:

[0135] 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 were added to a Schlenk tube. After evacuation, a CO2 balloon was put on, and the reaction was stirred at room temperature for 8 h. Then, it was centrifuged, and the supernatant was collected. It was extracted three times with diethyl ether and rotary evaporated under reduced pressure. The target product was not detected.

[0136] Figure 7 Catalyst UiO-Ag-(BPDC-F prepared in Example 1 3 ) Structural schematic diagram;

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

[0138] Figure 9 1H NMR spectrum of 4-ethyl-4-methyl-5-methylene-1,3-dioxolan-2-one in Application Example 2 1 ;

[0139] Figure 10 1H NMR spectrum of 4-isopropyl-4-methyl-5-methylene-1,3-dioxolan-2-one in Application Example 4 1 ;

[0140] Figure 11 1H NMR spectrum of 4-isobutyl-4-methyl-5-methylene-1,3-dioxolan-2-one in Application Example 5 1 ;

Claims

1. A method for preparing a nitrogen heterocyclic carbene silver catalyst based on a MOF framework, characterized in that: The following steps are involved: 1) dispersing zirconium salt, ligand I, ligand II and an acid regulator in an organic solvent, and performing a solvothermal reaction to obtain a perfluoroalkyl-modified nitrogen heterocyclic carbene-based organic metal framework material; 2) reacting a perfluoroalkyl-modified nitrogen heterocyclic carbene metal organic framework material with a silver salt in an organic solvent to obtain a nitrogen heterocyclic carbene silver catalyst based on the MOF framework; The ligand I is The ligand II is The molar ratio of the zirconium salt, ligand I and ligand II is 1:(0.4-0.6):(0.4-0.6); The temperature of the solvent thermal reaction in step 1) is 110-130° C. and the reaction time is 20-30 h; 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 nitrogen heterocyclic 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 to 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 nitrogen heterocyclic carbene organic metal framework material to the silver salt is 10 mg: (0.005-0.15) mmol; The reaction time in step 2) is 8 to 15 hours; the reaction temperature is 15 to 30°C.

3. The method for preparing the nitrogen heterocyclic carbene silver catalyst based on the MOF framework according to claim 1, characterized in that: The ligand I is prepared by the following method: S1. Under a protective atmosphere, using an organic solvent as a reaction medium, 4-methoxycarbonylphenylboronic acid and methyl 4-methyl-3-bromobenzoate are reacted in the presence of a catalyst and an alkaline compound to obtain a precursor P having a functionalized ligand with a nitrogen heterocyclic carbene functional group. 1 ; Precursor P 1 : S2, using an organic solvent as a reaction medium, 1 Bromination reaction with N-bromosuccinimide gives the precursor P with nitrogen heterocyclic carbene functional ligand. 2 ; Precursor P 2 : S3, using an organic solvent as a reaction medium, 2 It is heated to react with N-isopropylimidazole, and then hydrolyzed and acidified in an alkaline environment to obtain ligand Ⅰ functionalized with a nitrogen heterocyclic carbene functional group; Precursor P 2 The product of the reaction with N-isopropylimidazole is 4. The method for preparing the nitrogen heterocyclic carbene silver catalyst based on the MOF framework according to claim 3, characterized in that: The alkaline compound in step S1 is one or more of cesium fluoride or cesium carbonate; the catalyst is tetrakistriphenylphosphine palladium; the organic solvent in step S1 is at least one of tetrahydrofuran and N,N-dimethylformamide; the reaction temperature is 70-90° C., and the reaction time is 2-4 hours; In step S2, the organic solvent is at least one of carbon tetrachloride and benzene; the reaction temperature is 70-90° C., the reaction time is 4-6 hours; the initiator added to the reaction is dibenzoyl peroxide; The organic solvent in step S3 is CH3CN, the reaction temperature is 45-65°C, and the reaction time is 1.5-3h; the solvent used for the hydrolysis is a mixed solvent of methanol and water, the volume ratio of methanol: 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, 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 using acid to adjust pH=3-4.

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 protective atmosphere, with an organic solvent as the reaction medium, 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid and perfluoroanhydride are reacted to obtain a perfluoroalkyl-modified functionalized ligand II; The perfluoroanhydride is at least one of trifluoroacetic anhydride, pentafluoropropionic anhydride and heptafluorobutyric anhydride; The organic solvent is acetonitrile, the reaction temperature is 70-85° C., and the reaction time is 22-26 hours.

6. A nitrogen heterocyclic carbene silver catalyst based on a MOF framework obtained by the preparation method according to any one of claims 1 to 5.

7. The use of the nitrogen heterocyclic carbene silver catalyst based on the MOF framework according to claim 6, characterized in that: The nitrogen heterocyclic carbene silver catalyst based on the MOF framework is used for catalytic conversion of carbon dioxide.

8. The use according to claim 7, characterized in that: The nitrogen heterocyclic carbene silver catalyst based on the MOF framework is used to catalyze the reaction of carbon dioxide and alkynol.

9. The use according to claim 8, characterized in that: The nitrogen heterocyclic carbene silver catalyst based on the MOF framework is used to catalyze the reaction of CO2 and alkynol to generate cyclic carbonate.

10. The use according to claim 9, characterized in that: The alkynol is at least one of 2-methyl-3-butyn-2-ol, 3-methyl-1-pentyn-3-ol, 3-ethyl-1-pentyn-3-ol, 3,4-dimethyl-1-pentyn-3-ol, 5-methylhex-1-yn-3-ol, and 3,5-dimethyl-1-hexyn-3-ol; The co-catalyst 1,8-diazabicyclo[5.4.0]undec-7-ene is added during the catalysis; Humidity ≤95%, CO2 volume concentration ≥13%.

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