A metal organic framework material ZnK-MOF, a preparation method and application thereof

Abstract

The application belongs to the technical field of catalyst materials, and relates to a metal organic framework material ZnK-MOF, a preparation method and application thereof, and a chemical general formula of the metal organic framework material ZnK-MOF is {(Me2NH2)·[ZnK(btda)2]·DMF} n ; wherein n is a polymerization degree of the metal organic framework material, and btda is benzothiophene dicarboxylic acid. The metal organic framework material ZnK-MOF provided by the application has a porous structure and contains two metal catalytic active centers of Zn and K, can efficiently activate an epoxide compound and an inert carbon dioxide molecule under mild conditions, and has the advantages of mild reaction conditions, high catalytic activity and good selectivity in a reaction of synthesizing a cyclic carbonate by catalyzing carbon dioxide conversion.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst materials, and relates to a metal organic framework material ZnK-MOF as well as a preparation method and application thereof. BACKGROUND

[0002] Since the industrial revolution, a large amount of emitted CO2 has led to serious environmental problems such as greenhouse effect intensification, seawater acidification and glacier melting. Converting CO2 into useful and high-value chemical products is one of important ways to reduce the content of carbon dioxide in the atmosphere. Among the chemical conversion ways of CO2, the ring addition reaction of CO2 and epoxide to generate cyclic carbonate is an atom-economic reaction meeting the requirements of green chemistry development, and thus has become a research hotspot of CO2 resource utilization. The obtained product cyclic carbonate can not only be used as an inert aprotic polar solvent, but also as a precursor of chemical products, and has wide application in the fields of chemical industry, medicine and polymer.

[0003] In the reaction of preparing cyclic carbonate by CO2 ring addition, a catalyst needs to be added to reduce the activation energy of the reaction because of the high stability of carbon dioxide and the difficulty in activating carbon dioxide. The catalysts currently used include homogeneous catalysts and heterogeneous catalysts. The homogeneous catalysts mainly include ionic liquids and organic catalysts, which have good catalytic performance but have the problem of difficult separation and recovery. The heterogeneous catalysts include metal organic frameworks and supported inorganic substances. The metal organic framework material as a new type of porous material has high porosity, high specific surface area and adjustable active sites, and exhibits high catalytic activity, high selectivity and easy regeneration in the process of the ring addition reaction of CO2 and epoxide, and has potential application value. However, the existing metal organic framework catalysts have the shortcomings of few active centers, low activity, poor recyclability and stability, and the reaction conditions are severe in the catalytic conversion, and additional solvents need to be added. SUMMARY

[0004] In view of the technical problems of poor catalyst activity and severe conversion conditions in the prior art, the application provides a metal organic framework material ZnK-MOF as well as a preparation method and application thereof. The material has a porous structure and contains two metal catalytic active centers of Zn and K, can efficiently activate epoxide and inert carbon dioxide molecules under mild conditions, and has the advantages of mild reaction conditions, high catalytic activity and good selectivity in the reaction of catalyzing the conversion of carbon dioxide to synthesize cyclic carbonate.

[0005] To achieve the above object, the technical scheme adopted by the application is as follows:

[0006] A metal organic framework material ZnK-MOF, a chemical general formula of the ZnK-MOF is:

[0007] {(Me2NH2)·[ZnK(btda)2]·DMF} n ;

[0008] Wherein, n is the degree of polymerization of the metal organic framework material, btda is benzothiophene dicarboxylic acid;

[0009] The structural formula of the benzothiophene dicarboxylic acid is as follows:

[0010]

[0011] Further limit, the ZnK-MOF is a crystal material, crystallographic data is: the crystal belongs to the orthorhombic system, the space group is Pna21; the cell parameters are: Alpha=90 degrees, beta=90 degrees, gamma=90 degrees, Z=2.

[0012] A preparation method of a metal organic framework material ZnK-MOF, comprising:

[0013] 1) Zn(NO3)2·6H2O, KCl, benzothiophene dicarboxylic acid ligand H2btda, N, N-dimethylformamide DMF and acetonitrile MeCN are mixed to obtain a mixture;

[0014] The mass ratio of the benzothiophene dicarboxylic acid ligand, Zn(NO3)2·6H2O and KCl is (2.1-4.1):(3-5):1; the volume ratio of the DMF and acetonitrile is (1-3):1; the mass ratio of the benzothiophene dicarboxylic acid ligand and DMF is 1:(8-12);

[0015] 2) The mixture is placed in a reaction kettle, heated to 115-125 DEG C, after the reaction is finished, cooling, and the yellow rod-shaped crystal is obtained by washing, filtering and drying, which is ZnK-MOF.

[0016] Further limit, in the step 2), the heating rate is 20 DEG C / h, and the reaction time is 48-72 h; the temperature is decreased to 30 DEG C, and the cooling rate is 5 DEG C / h.

[0017] Further limit, the benzothiophene dicarboxylic acid ligand H2btda is prepared by the following steps:

[0018] 1.1) under N2 atmosphere, add 3-methyl-4-nitrobenzoic acid methyl ester, N,N-dimethylformamide dimethyl acetal and N,N-dimethylformamide, heat to 130-150℃, react for 22-26h, after reaction, distill under reduced pressure to obtain brown-red solid, mark as product I; the amount ratio of 3-methyl-4-nitrobenzoic acid methyl ester, N,N-dimethylformamide dimethyl acetal and N,N-dimethylformamide is 5.4-6.0g:4.3-5g:120-130mL;

[0019] 1.2) mix product I, sodium periodate and 50% aqueous tetrahydrofuran solution, after stirring, suction filter, add ethyl acetate to the filtrate, wash, dry, distill under reduced pressure to obtain brown-black solid, separate by column chromatography to obtain yellowish solid, mark as product II; the amount ratio of product I, sodium periodate, aqueous tetrahydrofuran solution is 4.5-5g:11.5-13g:140-160mL;

[0020] 1.3) mix product II, K2CO3 and N,N-dimethylformamide, then add the mixed solution of mercaptoacetic acid methyl ester and N,N-dimethylformamide, after heating, add the obtained reaction solution to ice water mixture, suction filter to obtain yellow solid, mark as product III; the amount ratio of product II, K2CO3, N,N-dimethylformamide is 3.5-4g:2.5-2.77g:10-12mL; the amount ratio of mercaptoacetic acid methyl ester and N,N-dimethylformamide in the mixed solution is 1.9-2.1g:10mL; the amount ratio of product II and mercaptoacetic acid methyl ester is 1.7-2.1g:1g;

[0021] 1.4) add methanol, water and LiOH to product III in sequence, after constant temperature heating, adjust pH to 2-3 with HCl solution, suction filter to obtain white solid, which is benzo-thiophene dicarboxylic acid ligand H2btda; the amount ratio of product III, methanol, water and LiOH is 6.6-7.3g:60-80mL:30-40mL:3.4-3.8g.

[0022] Further limit, in step 1.1), the heating reflux condition is: temperature 130-150℃, time 23-25h; the reduced pressure distillation condition is: temperature 60-80℃, pressure 0.02-0.08MPa;

[0023] In step 1.2), the reduced pressure distillation condition is: temperature 35-40℃, pressure 0.02-0.08MPa; the column chromatography separation condition is: eluent is dichloromethane: petroleum ether solution with volume ratio of (2-3):1, collect yellowish solution;

[0024] The heating temperature in the step 1.3) is 50-60 DEG C, and the reaction time is 23-25 hours.

[0025] The heating temperature in the step 1.4) is 70-90 DEG C, and the reaction time is 3-5 hours.

[0026] Application of a metal organic framework material ZnK-MOF in catalyzing a carbon dioxide and an epoxide to perform a cycloaddition reaction to prepare a cyclic carbonate.

[0027] The application is that the carbon dioxide and the epoxide perform a cycloaddition reaction under the catalysis of ZnK-MOF and tetrabutylammonium bromide to obtain a cyclic carbonate.

[0028] The substance amount ratio of the ZnK-MOF catalyst, the tetrabutylammonium bromide and the epoxide is 1:(2-5):(190-210).

[0029] The cycloaddition reaction condition is that the pressure is 0.1-1.5 MPa, the temperature is 20-80 DEG C, and the time is 1-10 hours.

[0030] The epoxide is an epichlorohydrin, an epoxypropane, a 1,2-epoxybutane, a styrene oxide, an epoxypropyl phenyl ether, a n-butyl glycidyl ether or an allyl glycidyl ether.

[0031] The beneficial effects of the present application are:

[0032] 1. The metal organic framework material structure of the present application is {(Me2NH2)·[ZnK(btda)2]·DMF} n , has a porous structure and contains two metal catalytic active centers of Zn and K, has the characteristics of high catalytic performance and good selectivity, is easy to operate in regeneration, and the catalyst can be recycled.

[0033] 2. The metal organic framework material provided by the present application is used as a cycloaddition reaction catalyst, so that the carbon dioxide and the epoxide are converted into a cyclic carbonate by addition reaction, the reaction is mild at a temperature of 20-80 DEG C and a time of 1-10 hours, the catalytic yield reaches more than 57%, especially when the epichlorohydrin ring is catalyzed, the yield reaches 99%, and the catalyst has high catalytic activity and good selectivity.

[0034] 3. After the metal organic framework material of the present application is used as a catalyst, the product is centrifuged, filtered, vacuum dried, separated and regenerated into a catalyst, the separation method is simple, and after the regenerated catalyst is recycled for five times, the catalytic performance does not decrease obviously, and the catalyst can be recycled.

[0035] 4. The metal organic framework material catalyst has a unique structure containing a channel and Lewis acid (Zn2+ , K + ), which can efficiently activate the epoxide compound and the inert carbon dioxide molecule, and make the catalytic process be carried out under mild and solvent-free conditions, and has good industrial application potential. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The coordination environment and three-dimensional structure diagram of the metal organic framework material prepared in Example 2 of the present application; 1 HNMR spectrum;

[0037] Figure 2 The coordination environment and three-dimensional structure diagram of the metal organic framework material prepared in Example 2 of the present application;

[0038] Figure 3 The infrared spectrum analysis diagram of the metal organic framework material prepared in Example 2 of the present application;

[0039] Figure 4 The X-ray powder diffraction spectrum diagram of the metal organic framework material prepared in Example 2 of the present application;

[0040] Figure 5 The thermogravimetric analysis diagram of the metal organic framework material prepared in Example 2 of the present application;

[0041] Figure 6 The nuclear magnetic hydrogen spectrum diagram of the metal organic framework material ZnK-MOF prepared in Example 8 of the present application catalyzing carbon dioxide and epichlorohydrin to generate cyclic carbonate;

[0042] Figure 7 The nuclear magnetic hydrogen spectrum diagram of the metal organic framework material ZnK-MOF prepared in Example 13 of the present application catalyzing carbon dioxide and propylene oxide to generate cyclic carbonate;

[0043] Figure 8 The nuclear magnetic hydrogen spectrum diagram of the metal organic framework material ZnK-MOF prepared in Example 14 of the present application catalyzing carbon dioxide and 1,2-epoxybutane to generate cyclic carbonate;

[0044] Figure 9 The nuclear magnetic hydrogen spectrum diagram of the metal organic framework material ZnK-MOF prepared in Example 15 of the present application catalyzing carbon dioxide and styrene oxide to generate cyclic carbonate;

[0045] Figure 10 The nuclear magnetic hydrogen spectrum diagram of the metal organic framework material ZnK-MOF prepared in Example 16 of the present application catalyzing carbon dioxide and epoxy propyl phenyl ether to generate cyclic carbonate;

[0046] Figure 11The 1H NMR spectrum of the metal-organic framework material ZnK-MOF prepared in Example 17 of this invention catalyzing the reaction of carbon dioxide with n-butyl glycidyl ether to form cyclic carbonates.

[0047] Figure 12 The 1H NMR spectrum of the metal-organic framework material ZnK-MOF prepared in Example 18 of this invention catalyzes the reaction of carbon dioxide with allyl glycidyl ether to form cyclic carbonates.

[0048] Figure 13 The results of five cycles of the reaction between the regenerated metal-organic framework material ZnK-MOF and epichlorohydrin to produce cyclic carbonates, as described in Example 19 of this invention. Detailed Implementation

[0049] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0050] This invention provides a metal-organic framework material ZnK-MOF, the structure of which is shown below.

[0051] {(Me2NH2)·[ZnK(btda)2]·DMF} n .

[0052] Wherein, n is the degree of polymerization of the metal-organic framework material, and btda is benzothiophene dicarboxylic acid, the structural formula of which is shown below.

[0053]

[0054] Metal-organic framework materials have a crystalline structure, and their crystallographic data are as follows: the crystal belongs to the orthorhombic crystal system, space group Pna21; unit cell parameters: α=90°, β=90°, γ=90°, Z=2.

[0055] This invention discloses a method for preparing a metal-organic framework material, comprising the following steps:

[0056] Zn(NO3)2·6H2O, KCl, benzothiophene dicarboxylic acid ligand, N,N-dimethylformamide (DMF) and acetonitrile (MeCN) were mixed and then placed in a polytetrafluoroethylene high-pressure reactor liner. The mixture was sealed, heated to a preset temperature, and reacted at a constant temperature for 48–72 hours. After cooling, the mixture was washed, filtered, and dried to obtain yellow rod-shaped crystals, which is the metal-organic framework material ZnK-MOF.

[0057] Preferably, the mass ratio of the benzothiophene dicarboxylic acid ligand to Zn(NO3)2.6H2O, KCl is (2.1-4.1):(3-5):1; the volume ratio of DMF to acetonitrile is (1-3):1; the mass ratio of the benzothiophene dicarboxylic acid ligand to DMF is 1:(8-12).

[0058] Preferably, the heating process comprises: increasing the temperature to a preset temperature at a heating rate of 20℃ / h; wherein the preset temperature is 115-125℃; and the cooling process comprises: decreasing the temperature from 115-125℃ to 30℃ at a cooling rate of 5℃ / h.

[0059] The application further provides a preparation process of the benzothiophene dicarboxylic acid ligand, and the specific steps are as follows.

[0060] Step 1: under N2 atmosphere, 3-methyl-4-nitrobenzoic acid methyl ester, N,N-dimethylformamide dimethyl acetal and N,N-dimethylformamide are added and heated to reflux; after the reaction, brown-red solid is obtained by reduced pressure distillation, and the brown-red solid is marked as product I.

[0061] In this step, the amount ratio of 3-methyl-4-nitrobenzoic acid methyl ester, N,N-dimethylformamide dimethyl acetal and N,N-dimethylformamide is 5.4-6.0g:4.3-5g:120-130mL.

[0062] In this step, the heating reflux condition is: temperature 130-150℃, time 23-25h; and the reduced pressure distillation condition is: temperature 60-80℃, pressure 0.02-0.08MPa.

[0063] Step 2: the product I, sodium periodate and aqueous tetrahydrofuran solution are mixed, and after electric stirring, suction filtration is performed; then, ethyl acetate is added to the filtrate, washed, dried with anhydrous magnesium sulfate, and brown-black solid is obtained by reduced pressure distillation; the brown-black solid is separated by column chromatography to obtain yellowish solid, and the yellowish solid is marked as product II.

[0064] In this step, the amount ratio of the product I, sodium periodate, aqueous tetrahydrofuran solution is 4.5-5g:11.5-13g:140-160mL.

[0065] In this step, the reduced pressure distillation condition is: temperature 35-40℃, pressure 0.02-0.08MPa; and the column chromatography separation condition is: the eluent is a solution of dichloromethane: petroleum ether in a volume ratio of (2-3):1, and the yellowish solution is collected.

[0066] Step 3: The above product II, K2CO3 and DMF are mixed, then a mixed solution of methyl mercaptoacetate and DMF is added, and the solution is added into an ice water mixture, and a yellow solid is obtained by suction filtration, and the yellow solid is marked as product III.

[0067] In this step, the use amount ratio of product II, K2CO3 and N,N-dimethylformamide is 3.5-4 g: 2.5-2.77 g: 10-12 mL; the use amount ratio of methyl mercaptoacetate and N,N-dimethylformamide in the mixed solution is 1.9-2.1 g: 10 mL; and the use amount ratio of product II and methyl mercaptoacetate is 1.7-2.1 g: 1 g.

[0068] In this step, the heating temperature is 50-60 DEG C, and the reaction time is 23-25 h.

[0069] Step 4: Methanol, water and LiOH are added to the above product III, and after being heated and refluxed for a certain time, the pH is adjusted to pH=2-3 by using an HCl solution, and a white solid is obtained by suction filtration, and the white solid is the benzothiophene dicarboxylic acid ligand H2btda.

[0070] In this step, the use amount ratio of product III, methanol, water and LiOH is 6.6-7.3 g: 60-80 mL: 30-40 mL: 3.4-3.8 g.

[0071] In this step, the heating temperature is 70-90 DEG C, and the reaction time is 3-5 h.

[0072] The ZnK-MOF provided by the application is used as a catalyst in the reaction of converting CO2 and an epoxide into a cyclic carbonate.

[0073] In the reaction of converting CO2 and an epoxide, ZnK-MOF is used as a catalyst, and tetrabutylammonium bromide (TBAB) is used as a cocatalyst, so that the ring addition reaction of carbon dioxide and an epoxide is carried out to prepare a cyclic carbonate, and the reaction equation is as follows:

[0074]

[0075] The specific process of the reaction of converting CO2 and an epoxide into a cyclic carbonate is as follows:

[0076] In a high-pressure reaction kettle, an epoxide, a cocatalyst (tetrabutylammonium bromide, TBAB) and ZnK-MOF catalyst are added, the kettle cover is tightly screwed, CO2 gas is slowly filled into the reaction kettle, and the temperature is kept constant and stirred for a period of time. After the reaction is completed, the temperature is reduced to room temperature, and the selectivity and conversion rate of the target product are confirmed by nuclear magnetic hydrogen spectrum (H NMR). 1 H NMR).

[0077] The epoxide is epichlorohydrin, epoxypropane, 1,2-epoxybutane, styrene oxide, epoxypropyl phenyl ether, n-butyl glycidyl ether or allyl glycidyl ether.

[0078] In the reaction, the mass ratio of ZnK-MOF catalyst, tetrabutylammonium bromide and epoxide is 1:(2-5):(190-210).

[0079] Preferably, the mass ratio of ZnK-MOF, tetrabutylammonium bromide and epoxide is 1:5:200.

[0080] The cycloaddition reaction conditions are: pressure 0.1-1.5 MPa, temperature 20-80℃, time 1-10 h.

[0081] The technical solutions of the present application will be explained and described below with several specific examples, but the following examples cannot be regarded as limiting the protection technical solutions of the present application.

[0082] Example 1

[0083] In this embodiment, the synthesis of benzothiophene dicarboxylic acid ligand specifically includes the following steps.

[0084] Step 1: Under N2 atmosphere, 6.00 g of 3-methyl-4-nitrobenzoic acid methyl ester, 5.00 g of N,N-dimethylformamide dimethyl acetal and 130 mL of N,N-dimethylformamide are added, heated to reflux at 140℃ for 24 h. After the reaction, brown-red solid is obtained by distillation under reduced pressure, which is marked as product I, with a yield of 87.5%.

[0085] Step 2: 5.00 g of the above product I, 13.00 g of sodium periodate and 150 mL of 50% tetrahydrofuran aqueous solution are mixed, stirred for 4 h, then filtered, and ethyl acetate is added to the filtrate, washed, dried with anhydrous magnesium sulfate, distilled under reduced pressure at a temperature of 40℃ and a pressure of 0.05 MPa to obtain brown-black solid, which is separated by silica gel column chromatography, using a solution of dichloromethane: petroleum ether with a volume ratio of 2:1 as eluent, and collecting the yellowish solution, then rotary evaporation to obtain yellowish solid, which is marked as product II, with a yield of 83.0%.

[0086] Step 3: 4.00 g of the above product II, 2.77 g of K2CO3 and 10 mL of DMF are mixed, then 2.10 g of mercaptoacetic acid methyl ester and 10 mL of DMF are added, stirred at a temperature of 50℃ for 24 h, and the resulting solution is added to an ice water mixture, then filtered to obtain yellow solid, which is marked as product III, with a yield of 91.0%.

[0087] Step 4: Take 7.34 g of the product III, add 80 mL of methanol, 40 mL of water and 3.78 g of LiOH, heat to 80℃ for 4 h, adjust the pH to pH = 2-3 with HCl solution, and filter to obtain a white solid, which is the benzothiophene dicarboxylic acid ligand H2btda, with a yield of 98.0%.

[0088] Example 2

[0089] The preparation method of the metal organic framework material provided in the embodiment comprises the following steps.

[0090] Take 0.0595 g of Zn(NO3)2·6H2O, 0.0149 g of KCl and 0.0444 g of the benzothiophene dicarboxylic acid ligand H2btda prepared in the implementation 1, mix 4 mL of N,N-dimethylformamide DMF and 2 mL of acetonitrile MeCN, and then add them into a polytetrafluoroethylene inner liner of a 25 mL high-pressure reaction kettle, seal, place in an oven, heat to 120℃ at a heating rate of 20℃ / h, keep the temperature constant for 72 h, then cool to 30℃ at a cooling rate of 5℃ / h, wash with DMF for three times, filter, and dry to obtain yellow rod-shaped crystals, which are the metal organic framework material ZnK-MOF.

[0091] In the embodiment, the yield of the ZnK-MOF is 45.20% based on the metal Zn.

[0092] Examples 3-7

[0093] The preparation methods of the metal organic framework material ZnK-MOF provided in Examples 3-7 are the same as that in Example 2, except that the amounts of the materials and the reaction parameters are different, and refer to Table 1 for details.

[0094] Table 1: Preparation parameter table of Examples 2-7

[0095]

[0096]

[0097] In order to illustrate the characteristics of the prepared benzothiophene dicarboxylic acid ligand H2btda and the metal organic framework material ZnK-MOF, the following experiments are performed.

[0098] Experiment 1: H2btda molecular structure characterization

[0099] The molecular structure of the benzothiophene dicarboxylic acid ligand H2btda is characterized, and the white solid prepared in Step 4 of Example 1 is subjected to 400Hz 1 H NMR test with deuterated DMSO as the solvent, and the results are shown in the following Figure 1 Figure.

[0100] Referring to Figure 1 , the benzothiophene dicarboxylic acid ligand 1 The H NMR spectrum has an absorption peak at a chemical shift of 2.51 ppm, which is the solvent peak of deuterated DMSO. b (single peak, 8.28 ppm) is the hydrogen on the thiophene ring, and the absorption peaks at c (single peak, 8.65 ppm), d (doublet, 8.15 ppm), and e (doublet, 8.55 ppm) are the magnetic resonance absorption peaks of four H atoms on the aromatic ring with different chemical environments. Due to the active hydrogen atoms on the carboxyl group, rapid proton exchange can occur between deuterated DMSO, so it is not detected in the hydrogen spectrum, but from the hydrogen spectrum data, it can be inferred that the benzothiophene skeleton exists, and there is no other impurity, and it can be determined that the synthesized substance is H2btda.

[0101] Experiment 2 ZnK-MOF crystal structure

[0102] Take the metal-organic framework material ZnK-MOF prepared in Example 2, use the German Bruker X-ray single crystal diffractometer, use Mo-Kα The target is the radiation source for diffraction data collection and analysis. Structure analysis and refinement are performed using the SHELXS-2013 and SHELXL-2013 programs in Olex2. All non-hydrogen atoms are determined using difference Fourier synthesis, and anisotropic refinement is performed to determine the crystal structure of the metal-organic framework material ZnK-MOF, and the results are shown in Figure 2 ; Figure 2 (a) is a structural diagram of the coordination environment of the metal ion of ZnK-MOF, Figure 2 (b) is a three-dimensional structural diagram of ZnK-MOF.

[0103] As can be seen from Figure 2 , ZnK-MOF is a material with channels.

[0104] Experiment 3 ZnK-MOF infrared spectrum

[0105] Take the metal-organic framework material ZnK-MOF prepared in Example 2, and test it on the Bruker infrared spectrometer VERTEX 70 in the range of 4000-500 cm -1 , and the results are shown in Figure 3 .

[0106] Referring to Figure 3 , the peak of ZnK-MOF at 1658 cm -1 is the C=O stretching vibration peak of the carboxyl group, indicating that the ligand benzothiophene dicarboxylic acid is coordinated with the metal ion.

[0107] Experiment 4 ZnK-MOF X-ray powder diffraction pattern (PXRD)

[0108] The metal organic framework material ZnK-MOF prepared in Example 2 was ground into powder and tested for X-ray powder diffraction pattern on a Bruker D8 instrument. During the test, Cu-Ka radiation was used with a tube voltage of 40 kV and a tube current of 30 mA. The test results are shown in Figure 2. As the incident light source, the 2 theta angle scanning range was set to 5-50°, the instrument working voltage was 40 kV, and the working current was 30 mA. The test results are shown in Figure 2. Figure 4

[0109] Referring to Figure 2, the obtained PXRD is basically consistent with the peak position of the single crystal simulation data, indicating that the ZnK-MOF has high phase purity. Figure 4 Experiment 5 Thermogravimetric curve of ZnK-MOF

[0110] The metal organic framework material ZnK-MOF prepared in Example 2 was tested for thermal stability in the range of 25-600°C on a Mettler Toledo TGA / DSC1 analyzer. The results are shown in Figure 3.

[0111] Figure 5 Referring to Figure 3, it can be observed that the ZnK-MOF has no weight loss below 110°C, indicating that the compound has high thermal stability. With the increase of temperature, the DMF molecules in the pores and the dimethylamine ions (Me2NH2 + ) after the decomposition of DMF are lost successively in the temperature ranges of 140°C-220°C and 200°C-320°C, respectively. With the continuous increase of temperature, the compound rapidly loses weight, indicating that the structure of ZnK-MOF collapses.

[0112] Figure 5 Example 8

[0113] Performance research of ZnK-MOF in catalyzing the cycloaddition reaction of CO2 and epichlorohydrin

[0114] ZnK-MOF catalyzing the cycloaddition reaction of CO2 and epichlorohydrin

[0115] 33.2 mg (0.05 mmol) of ZnK-MOF (prepared in Example 2), 10 mmol of epichlorohydrin (ECH) and 80.6 mg (0.25 mmol) of a co-catalyst tetrabutylammonium bromide TBAB were weighed into a 25 mL reaction kettle and the kettle cover was tightened. CO2 gas was slowly filled into the reaction kettle so that the pressure was 1 MPa, and the temperature was kept at 60°C. After stirring for 5 h, the reaction was completed, the temperature was lowered to room temperature, and then the remaining CO2 was slowly discharged. The obtained liquid was a cyclic carbonate.

[0116] ​​​The obtained liquid was subjected to hydrogen nuclear magnetic resonance spectrum test to analyze the structure of the product, and the yield was calculated to be 99%.

[0117] The synthesized cyclic carbonate 1 The H NMR spectrum is shown in Figure 6 .

[0118] Examples 9-12

[0119] The experiments of the ZnK-MOF catalyzed CO2 and epichlorohydrin cycloaddition reaction described in Examples 9-12 are basically the same as those of Example 8, except that the ratio of ZnK-MOF, co-catalyst tetrabutylammonium bromide TBAB and epichlorohydrin (ECH) is different, see Table 2 for details.

[0120] At the same time, the obtained liquid was subjected to hydrogen nuclear magnetic resonance spectrum test to analyze the structure of the product, and the yield of the cyclic carbonate was calculated, see Table 2 for calculation results.

[0121] Table 2 Experimental parameters and results of ZnK-MOF catalyzed CO2 and epichlorohydrin cycloaddition reaction

[0122] Example 9 Example 10 Example 11 Example 12 ZnK-MOF 0.05 mmol 0.05 mmol 0.05 mmol 0.05 mmol TBAB 0.10 mmol 0.15 mmol 0.20 mmol 0.25 mmol ECH 10 mmol 10 mmol 10 mmol 10.5 mmol Cyclic carbonate yield 35％ 62％ 83％ 90％

[0123] From Table 2 and the results of Example 8, it can be determined that in the ZnK-MOF catalyzed CO2 and epichlorohydrin cycloaddition reaction, when the molar ratio of ZnK-MOF, tetrabutylammonium bromide, epoxide is 1:5:200 (Example 8), the yield of cyclic carbonate can reach up to 99%, and the catalyst activity is good.

[0124] Example 13

[0125] In this example, the epoxide is propylene oxide, and ZnK-MOF is used to catalyze the CO2 and propylene oxide cycloaddition reaction. The process of the addition reaction is the same as that of Example 8.

[0126] The obtained liquid was subjected to hydrogen nuclear magnetic resonance spectrum test to analyze the structure of the product, and the yield was calculated to be 58%.

[0127] The synthesized cyclic carbonate 1 The H NMR spectrum is shown in Figure 7 .

[0128] Example 14

[0129] In this example, the epoxide is 1.2-epoxybutane, and ZnK-MOF is used to catalyze the CO2 and 1.2-epoxybutane cycloaddition reaction. The process of the addition reaction is the same as that of Example 8.

[0130] The obtained liquid was subjected to hydrogen nuclear magnetic resonance spectrum test to analyze the structure of the product, and the yield was calculated to be 58%.

[0131] Synthesized cyclic carbonate 1 The H NMR spectrum is shown in Figure 8

[0132] Example 15

[0133] In this example, the epoxide is styrene oxide, and ZnK-MOF is used to catalyze the cycloaddition reaction of CO2 and styrene oxide. The process of the cycloaddition reaction is the same as that of Example 8.

[0134] The obtained liquid is subjected to H NMR test to analyze the structure of the product, and the yield is calculated to be 65%.

[0135] Synthesized cyclic carbonate 1 The H NMR spectrum is shown in Figure 9

[0136] Example 16

[0137] In this example, the epoxide is propylene glycidyl ether, and ZnK-MOF is used to catalyze the cycloaddition reaction of CO2 and propylene glycidyl ether. The process of the cycloaddition reaction is the same as that of Example 8.

[0138] The obtained liquid is subjected to H NMR test to analyze the structure of the product, and the yield is calculated to be 67%.

[0139] Synthesized cyclic carbonate 1 The H NMR spectrum is shown in Figure 10

[0140] Example 17

[0141] In this example, the epoxide is n-butyl glycidyl ether, and ZnK-MOF is used to catalyze the cycloaddition reaction of CO2 and n-butyl glycidyl ether. The process of the cycloaddition reaction is the same as that of Example 8.

[0142] The obtained liquid is subjected to H NMR test to analyze the structure of the product, and the yield is calculated to be 90%.

[0143] Synthesized cyclic carbonate 1 The H NMR spectrum is shown in Figure 11

[0144] Example 18

[0145] In this example, the epoxide is allyl glycidyl ether, and ZnK-MOF is used to catalyze the cycloaddition reaction of CO2 and allyl glycidyl ether. The process of the cycloaddition reaction is the same as that of Example 8.

[0146] The obtained liquid is subjected to H NMR test to analyze the structure of the product, and the yield is calculated to be 86%.​​​​

[0147] Synthetic cyclic carbonate 1 HNMR spectrum is shown in Figure 12

[0148] Cyclic performance test of example 19

[0149] The cyclic regeneration ability of the catalyst is an important indicator for evaluating the performance of the catalyst, so the metal organic framework material ZnK-MOF is subjected to cyclic catalysis test.

[0150] The cyclic catalysis experiment is specifically:

[0151] (1) After the completion of the catalytic reaction of example 8, the product after catalysis is centrifuged, filtered and vacuum dried to obtain the regenerated catalyst ZnK-MOF.

[0152] (2) Selecting epichlorohydrin as the catalytic substrate, using the regenerated catalyst ZnK-MOF obtained in step (1), the CO2 and epichlorohydrin cycloaddition reaction is carried out under the action of the regenerated catalyst ZnK-MOF and the cocatalyst tetrabutylammonium bromide TBAB according to the operation method of example 8.

[0153] (3) Repeat steps (1) and (2) and carry out 5 cycles of reaction under the same conditions, and the results are shown in Figure 13

[0154] As can be seen from Figure 13 , with the increase of the number of cycles, the catalytic performance of the catalyst does not decrease obviously, which shows that the catalyst ZnK-MOF material has good regeneration and cyclic properties.

[0155] Finally, it is pointed out that the above content is only for explaining the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification according to the technical idea of the present application, or equivalent substitution of part of the technical features, is within the protection scope of the claims of the present application.​​

Claims

1. A metal-organic framework material ZnK-MOF, characterized in that, The general chemical formula of ZnK-MOF is: {(Me2NH2)·[ZnK(btda)2]·DMF} n ; Wherein, n is the degree of polymerization of the metal-organic framework material, and btda is benzothiophene dicarboxylic acid; The structural formula of the benzothiophene dicarboxylic acid is shown below:

2. The metal-organic framework material ZnK-MOF according to claim 1, characterized in that, The ZnK-MOF is a crystalline material, and its crystallographic data are as follows: the crystal belongs to the orthorhombic crystal system, space group Pna21; unit cell parameters: α=90°, β=90°, γ=90°, Z=2.

3. A method for preparing the metal-organic framework material ZnK-MOF as described in claim 2, characterized in that, The preparation method includes: 1) Mix Zn(NO3)2·6H2O, KCl, benzothiophene dicarboxylic acid ligand H2btda, N,N-dimethylformamide DMF and acetonitrile MeCN to obtain a mixture; The mass ratio of the benzothiophene dicarboxylic acid ligand H2btda, Zn(NO3)2·6H2O, and KCl is (2.1–4.1):(3–5):1; the volume ratio of DMF to MeCN is (1–3):1; and the mass ratio of the benzothiophene dicarboxylic acid ligand H2btda to DMF is 1:(8–12). 2) Place the mixture in a reaction vessel, heat it to 115℃~125℃, cool it down after the reaction is complete, and wash, filter and dry it to obtain yellow rod-shaped crystals, which is ZnK-MOF.

4. The preparation method according to claim 3, characterized in that, In step 2), the heating rate is 20℃ / h, and the reaction time is 48h to 72h; the temperature is lowered to 30℃, and the cooling rate is 5℃ / h.

5. The preparation method according to claim 4, characterized in that, The benzothiophene dicarboxylic acid ligand H2btda was prepared by the following steps: 1.1) Under N2 atmosphere, methyl 3-methyl-4-nitrobenzene, N,N-dimethylformamide dimethyl acetal and N,N-dimethylformamide were added, heated to 130℃~150℃, and reacted for 22h~26h. After the reaction, the product was distilled under reduced pressure to obtain a brownish-red solid, which was designated as product I. The ratio of methyl 3-methyl-4-nitrobenzene, N,N-dimethylformamide dimethyl acetal, and N,N-dimethylformamide is 5.4–6.0 g: 4.3–5 g: 120–130 mL. 1.2) Mix the above product I, sodium periodate and 50% tetrahydrofuran aqueous solution, stir, filter, add ethyl acetate to the filtrate, wash, dry, and distill under reduced pressure to obtain a brownish-black solid, which is separated by column chromatography to obtain a pale yellow solid, denoted as product II. The ratio of product I, sodium periodate, and tetrahydrofuran aqueous solution is 4.5–5 g: 11.5–13 g: 140–160 mL; 1.3) Mix the above product II, K2CO3 and N,N-dimethylformamide, then add a mixed solution of methyl mercaptoacetate and N,N-dimethylformamide, heat the mixture and add the resulting reaction solution to an ice-water mixture, filter to obtain a yellow solid, which is denoted as product III; The ratio of product II, K2CO3, and N,N-dimethylformamide is 3.5–4 g: 2.5–2.77 g: 10–12 mL. In the mixed solution, the mass-to-volume ratio of methyl mercaptoacetate and N,N-dimethylformamide is 1.9–2.1 g: 10 mL; The ratio of product II to methyl mercaptoacetate is 1.7–2.1 g: 1 g; 1.4) Add methanol, water and LiOH to product III in sequence, heat at a constant temperature, adjust the pH to 2-3 with HCl solution, filter to obtain a white solid, which is benzothiophene dicarboxylic acid ligand H2btda. The ratio of product III, methanol, water and LiOH is 6.6-7.3g: 60-80mL: 30-40mL: 3.4-3.8g.

6. The preparation method according to claim 5, characterized in that, In step 1.1), the heating reflux conditions are: temperature 130℃~150℃, time 23h~25h; the vacuum distillation conditions are: temperature 60℃~80℃, pressure 0.02MPa~0.08MPa. In step 1.2), the vacuum distillation conditions are: temperature 35-40℃, pressure 0.02-0.08MPa; the column chromatography separation conditions are: the eluent is a solution of dichloromethane and petroleum ether in a volume ratio of (2-3):1, and the pale yellow band solution is collected. In step 1.3), the heating temperature is 50℃~60℃, and the reaction time is 23h~25h. In step 1.4), the heating temperature is 70℃~90℃ and the reaction time is 3h~5h.

7. The application of the metal-organic framework material ZnK-MOF as described in claim 1 in the catalytic cycloaddition reaction of carbon dioxide with epoxides to prepare cyclic carbonates.

8. The application according to claim 7, characterized in that, The application involves the cycloaddition reaction of carbon dioxide and epoxides under the catalysis of ZnK-MOF and tetrabutylammonium bromide to obtain cyclic carbonates. The molar ratio of the ZnK-MOF catalyst, tetrabutylammonium bromide, and epoxide is 1:(2-5):(190-210); The cycloaddition reaction conditions are: pressure 0.1 MPa to 1.5 MPa, temperature 20℃ to 80℃, and time 1 h to 10 h.

9. The application according to claim 8, characterized in that, The epoxide is epichlorohydrin, propylene oxide, 1,2-epoxybutane, styrene oxide, glycidyl ether, n-butyl glycidyl ether, or allyl glycidyl ether.

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