Preparation method and application of amine-functionalized polyionic liquid-supported metal-organic framework catalyst

Abstract

The invention discloses a preparation method and application of a metal organic framework material catalyst supported by an amine functionalized polyionic liquid, and belongs to the field of green catalysis. The invention reacts the amine group on the amine functionalized ionic liquid with the chloromethyl group on MIL-101(Cr)-CH2Cl through a covalent bond, grafts the ionic liquid onto the MOF structure, introduces divinylbenzene, and performs a free radical polymerization reaction on the MOF surface. The prepared catalyst has the advantages of both MOF materials (Lewis acidic sites, high specific surface area) and ionic liquids (Lewis basic sites, nucleophilic reagent sites), realizes the advantage of 1+1>2, and the product separation is simple, and can efficiently and synergistically catalyze carbon dioxide and epoxides to synthesize cyclic carbonates.

Description

Technical Field

[0001] The invention belongs to the field of green catalytic synthesis, and specifically relates to a preparation method and application of an amine-functionalized polyionic liquid-loaded metal organic framework material catalyst. Background Art

[0002] Carbon dioxide (CO2) is the main greenhouse gas causing global warming and is a cheap, non-toxic and abundant C1 basic raw material. Among them, cyclic carbonates synthesized from CO2 and epoxides are one of the most promising strategies for utilizing CO2 as a carbon resource due to their 100% atom economy. They have been widely used as aprotic solvents, lithium battery electrolytes and intermediates for the synthesis of pharmaceutical products, which is in line with the perspectives of sustainable development and environmental protection.

[0003] As a homogeneous catalyst for the synthesis of cyclic carbonates, ionic liquids are environmentally friendly solvents with low vapor pressure, good solubility, high stability, and adjustable acidity. They show excellent catalytic activity in CO2 cycloaddition reactions. However, ionic liquids have the disadvantages of complex recovery process and high viscosity from the reaction system, which seriously hinders their industrial application. In order to overcome these shortcomings, ionic liquids are usually immobilized on different carriers, such as silica, molecular sieves, metal-organic framework materials (MOFs), etc., to obtain heterogeneous catalysts. For example, Niloufar Nokhodiyan Isfahani et al. published an article titled "Ionic Liquid Modification of Hierarchical ZSM-5 for Solvent-Free Insertion of CO2 to Epoxides" (Ind. Eng. Chem. Res, 2020, 59, 11970-11978) in which 1-(2-aminoethyl)-3-methylimidazolium bromide ionic liquid was introduced into h-ZSM-5 via a covalent bond. The catalyst can catalyze CO2 and 1,2-epoxyhexane at 2.4 MPa, 120°C, and 6 h, with a conversion rate of 94%. However, since h-ZSM-5 is used as a carrier, it has fewer active sites and a lower specific surface area, a large amount of catalyst is used, and the reaction conditions are harsh.

[0004] Metal-organic framework materials (MOFs) are a promising class of synthetic porous crystalline materials with the characteristics of regular structure, high porosity, large specific surface area, large adsorption capacity, easy functionalization, and more importantly, inherent Lewis acid sites. They are considered to be candidate materials for carbon capture, utilization and storage. By coupling ionic liquids and metal-organic framework materials, the materials can have the advantages of both ionic liquids and metal-organic framework materials. For example, Mehrnaz Bahadori et al. published an article titled "Ionic Liquid-Decorated MIL-101(Cr) via Covalent and Coordination Bonds for Efficient Solvent-Free CO2 Conversion and CO2 Capture at Low Pressure" (J. Phys. Chem. C, 2020, 124, 8716−8725). They introduced 1-(2-aminoethyl)-3-methylimidazolium bromide ionic liquid into MIL-101(Cr) through coordination bonds or covalent bonds. The two synthesized catalysts catalyzed CO2 and styrene oxidation at 2 MPa, 110°C, and 2 h, with conversion rates of 88% and 86%, respectively. However, the ionic liquid introduced through coordination bonds is easy to lose, and the ionic liquid introduced through covalent bonds is stable but has few active sites, resulting in low catalytic activity.

[0005] The Chinese invention patent document with publication number CN111036305A discloses a metal organic framework loaded with polyionic liquid, its preparation method and application. The ionic liquid is immobilized into the pores of MIL-101 through free radical polymerization. The obtained composite catalyst catalyzes CO2 and propylene oxide with a yield of 96% under the conditions of 1Mpa, 80°C and 3h. However, the introduction of polyionic liquid into the pores easily causes agglomeration and pore blocking, which is not conducive to the contact between the reactants and the active sites, resulting in low utilization of the active sites and reduced reaction efficiency. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method and application of an amine-functionalized polyionic liquid-supported metal organic framework material catalyst. The prepared catalyst has multiple active sites, simple product separation, and can efficiently catalyze carbon dioxide and epoxides to synthesize cyclic carbonates.

[0007] The technical solution of the present invention is: a technical solution of a method for preparing an amine-functionalized polyionic liquid-supported metal organic framework material catalyst, comprising the following steps:

[0008] (1) adding 1-vinyl imidazole or 1-allylimidazole and halogenated alkane to a first organic solvent, reacting at 70-90° C. for 12-24 hours under a nitrogen atmosphere; after the reaction, removing the solvent under reduced pressure, washing with ethyl acetate, and drying to obtain an ionic liquid with a halogen terminal;

[0009] (2) adding the halogen-terminated ionic liquid obtained in step (1) to the amino compound, reacting at 100 to 120° C. for 12 to 24 hours under a nitrogen atmosphere, cooling to room temperature, separating the solvent, washing with ethyl acetate, and drying to obtain an amine-functionalized ionic liquid;

[0010] (3) Adding the activated MIL-101(Cr)-CH2Cl and the amine-functionalized ionic liquid obtained in step (2) to a second organic solvent, reacting at 50-70°C for 24-48 hours, then adding divinylbenzene and an initiator, reacting at 70-90°C for 12-48 hours under a nitrogen atmosphere, separating the solvent, washing with DMF and ethanol in turn, and drying to obtain an amine-functionalized polyionic liquid-supported metal organic framework catalyst.

[0011] Furthermore, in step (1), the molar ratio of 1-vinylimidazole or 1-allylimidazole to halogenated alkane is 0.25 to 1:1; the halogenated alkane is 1,3-dibromopropane or 1,3-dichloropropane; the molar concentration of the halogenated alkane in the first organic solvent is 1 to 2 mol / L; and the first organic solvent is toluene or acetonitrile.

[0012] Furthermore, in step (2), the molar concentration of the halogen-terminated ionic liquid in the amine compound is 0.5 to 1 mol / L; and the amine compound is triethylenetetramine or tetraethylenepentamine.

[0013] Furthermore, in step (3), the mass concentration of the activated MIL-101(Cr)-CH2Cl in the second organic solvent is 5 to 10 g / L; the molar concentration of the amine-functionalized ionic liquid in the second organic solvent is 0.1 to 0.25 mol / L; the second organic solvent is ethanol or methanol; the molar ratio of the amine-functionalized ionic liquid to divinylbenzene is 1 to 2:1; the initiator is azobisisobutyronitrile or azobisisopropionitrile; and the initiator is 2% to 5% of the sum of the mass of the amine-functionalized ionic liquid and divinylbenzene.

[0014] The present invention also provides an application of the metal organic framework material catalyst supported by the amine functionalized polyionic liquid, wherein the catalyst is used to catalyze the synthesis of cyclic carbonates from carbon dioxide and epoxy compounds.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The present invention provides a method for preparing a metal organic framework catalyst supported by an amine functionalized polyionic liquid. First, the amino group on the amine functionalized ionic liquid is reacted with the chloromethyl group on the metal organic framework material (MIL-101(Cr)-CH2Cl) by a covalent bond method, and the ionic liquid is successfully grafted onto the metal organic framework material structure. Then, divinylbenzene is introduced by a free radical copolymerization method, so that the ionic liquid undergoes a free radical polymerization reaction on the surface of the metal organic framework material, thereby solving the problem that the polyionic liquid is easy to agglomerate and block the pores. The ionic liquid is not easy to lose, and can efficiently catalyze carbon dioxide and epoxy compounds to synthesize cyclic carbonates.

[0017] (2) The method for preparing a metal organic framework material catalyst supported by an amine functionalized polyionic liquid provided by the present invention adopts a metal organic framework material as a carrier. Its high specific surface area increases the contact probability between the reaction substrate and the active sites, and the utilization rate of the catalyst active sites is high.

[0018] (3) The present invention provides a method for preparing a metal organic framework catalyst supported by an amine functionalized polyionic liquid, by using a metal organic framework material having a large number of Lewis acid sites (unsaturated Cr 3+ ), amine-functionalized ionic liquids have a large number of Lewis basic sites (imidazole ring, amine group) and nucleophilic sites (Br - or Cl - ), and a large number of secondary amine groups on the ionic liquid can also serve as hydrogen bond donors. The multiple active sites enable the catalyst to efficiently activate carbon dioxide and promote substrate ring opening.

[0019] (4) The amine-functionalized polyionic liquid-loaded metal organic framework catalyst provided by the present invention is used to catalyze the synthesis of cyclic carbonates from carbon dioxide and epoxy compounds. It is stable and not easy to decompose, and the product separation is simple. The catalytic yield of carbon dioxide and propylene oxide can reach more than 96%. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Scanning electron microscope (SEM) images of MIL-101(Cr)-CH2Cl (left) and Cat2 (right) in Example 2;

[0021] Figure 2 The infrared (FT-IR) spectra of MIL-101(Cr)-CH2Cl, N5-IL-2 and Cat2 in Example 2;

[0022] Figure 3 The nitrogen adsorption-desorption curves of MIL-101(Cr)-CH2Cl and Cat2 at 77K in Example 2;

[0023] Figure 4 XRD spectra of MIL-101(Cr)-CH2Cl and amine-functionalized polyionic liquid-supported metal organic framework catalysts obtained in Examples 1-4. DETAILED DESCRIPTION

[0024] The present invention will be further described below with reference to specific embodiments and drawings, but is not limited thereto.

[0025] Meanwhile, the experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available products unless otherwise specified.

[0026] In a specific embodiment of the present invention, the activated MIL-101(Cr)-CH2Cl used is prepared according to the following method:

[0027] A mixture of 1 g MIL-101, 1.9 g AlCl3·6H2O, 80 g nitromethane and 0.4 g methoxyacetyl chloride was heated at 100°C for 5 h and centrifuged. The green solid was treated with H2O at 100°C for 24 h, the H2O was removed by centrifugation, and then treated in THF at 67°C for 3 h. The THF was removed by centrifugation and the activated MIL-101(Cr)-CH2Cl was obtained. Example 1

[0028] (1) 0.01 mol of 1-vinylimidazole and 0.04 mol of 1,3-dibromopropane were added to 20 mL of acetonitrile and reacted at 80°C for 24 h under a nitrogen atmosphere. After the reaction, the solvent was removed under reduced pressure, and the oily liquid was washed three times with ethyl acetate to remove unreacted 1,3-dibromopropane, and then dried under vacuum at 40°C for 12 h to obtain an ionic liquid with a halogen terminal, namely IL-1.

[0029] (2) Add 0.01 mol of IL-1 obtained in step (1) to 10 mL of triethylenetetramine, react at 120° C. for 12 h under a nitrogen atmosphere; cool to room temperature, separate the solvent, wash the oily liquid three times with ethyl acetate to remove unreacted triethylenetetramine, and dry under vacuum at 40° C. for 12 h to obtain an amine-functionalized ionic liquid, namely N4-IL-1.

[0030] (3) 0.2 g of activated MIL-101(Cr)-CH2Cl and 0.005 mol of N4-IL-1 obtained in step (2) were added to 20 mL of ethanol and reacted at 70°C for 24 h. Then, 0.0025 mol of divinylbenzene and 3% of the sum of the mass of the amine-functionalized ionic liquid and divinylbenzene were added. The mixture was reacted at 80°C for 24 h under a nitrogen atmosphere. After separating the solvent, the solid was washed three times with DMF and ethanol respectively to remove the unreacted amine-functionalized ionic liquid, divinylbenzene and initiator, and then dried at 70°C in vacuum for 12 h to obtain an amine-functionalized polyionic liquid-supported metal organic framework catalyst, namely Cat1. Example 2

[0031] (1) 0.02 mol of 1-allylimidazole and 0.04 mol of 1,3-dibromopropane were added to 25 mL of toluene and reacted at 90°C for 24 h under a nitrogen atmosphere. After the reaction, the solvent was removed under reduced pressure, and the oily liquid was washed three times with ethyl acetate to remove unreacted 1,3-dibromopropane, and then dried under vacuum at 40°C for 12 h to obtain an ionic liquid with a halogen terminal, namely IL-2.

[0032] (2) Add 0.01 mol of IL-2 obtained in step (1) to 12.5 mL of tetraethylenepentamine, and react at 100° C. for 24 h under a nitrogen atmosphere; cool to room temperature, separate the solvent, wash the oily liquid three times with ethyl acetate to remove unreacted tetraethylenepentamine, and dry under vacuum at 40° C. for 12 h to obtain an amine-functionalized ionic liquid, namely N5-IL-2.

[0033] (3) 0.1 g of activated MIL-101(Cr)-CH2Cl and 0.003 mol of N5-IL-2 obtained in step (2) were added to 20 mL of ethanol and reacted at 60°C for 24 h. Then, 0.003 mol of divinylbenzene and 4% of the total mass of azobisisobutyronitrile of the amine-functionalized ionic liquid and divinylbenzene were added. The mixture was reacted at 90°C for 18 h under a nitrogen atmosphere. After separating the solvent, the solid was washed three times with DMF and ethanol respectively to remove the unreacted amine-functionalized ionic liquid, divinylbenzene and initiator, and then dried at 70°C in vacuum for 12 h to obtain an amine-functionalized polyionic liquid-supported metal organic framework catalyst, namely Cat2. Example 3

[0034] (1) 0.03 mol of 1-vinylimidazole and 0.04 mol of 1,3-dichloropropane were added to 30 mL of toluene and reacted at 80°C for 18 h under a nitrogen atmosphere. After the reaction, the solvent was removed under reduced pressure, and the oily liquid was washed three times with ethyl acetate to remove unreacted 1,3-dichloropropane, and then dried under vacuum at 40°C for 12 h to obtain an ionic liquid with a halogen terminal, namely IL-3.

[0035] (2) Add 0.01 mol of IL-3 obtained in step (1) to 20 mL of tetraethylenepentamine, and react at 110° C. for 18 h under a nitrogen atmosphere; cool to room temperature, separate the solvent, wash the oily liquid three times with ethyl acetate to remove unreacted tetraethylenepentamine, and dry under vacuum at 40° C. for 12 h to obtain an amine-functionalized ionic liquid, namely N5-IL-3.

[0036] (3) 0.2 g of activated MIL-101(Cr)-CH2Cl and 0.004 mol of N5-IL-3 obtained in step (2) were added to 20 mL of methanol and reacted at 60°C for 36 h. Then, 0.003 mol of divinylbenzene and 2% of the total mass of azobisisopropionitrile of the amine-functionalized ionic liquid and divinylbenzene were added. The mixture was reacted at 70°C for 18 h under a nitrogen atmosphere. After separating the solvent, the solid was washed three times with DMF and ethanol respectively to remove the unreacted amine-functionalized ionic liquid, divinylbenzene and initiator, and then dried at 70°C in vacuum for 12 h to obtain an amine-functionalized polyionic liquid-supported metal organic framework catalyst, namely Cat3. Example 4

[0037] (1) 0.04 mol of 1-allylimidazole and 0.04 mol of 1,3-dichloropropane were added to 40 mL of acetonitrile and reacted at 70°C for 12 h under a nitrogen atmosphere. After the reaction, the solvent was removed under reduced pressure, and the oily liquid was washed three times with ethyl acetate to remove unreacted 1,3-dichloropropane, and then dried under vacuum at 40°C for 12 h to obtain an ionic liquid with a halogen terminal, namely IL-4.

[0038] (2) Add 0.01 mol of IL-4 obtained in step (1) to 15 mL of triethylenetetramine, and react at 120° C. for 18 h under a nitrogen atmosphere; cool to room temperature, separate the solvent, wash the oily liquid three times with ethyl acetate to remove unreacted triethylenetetramine, and dry under vacuum at 40° C. for 12 h to obtain an amine-functionalized ionic liquid, namely N4-IL-4.

[0039] (3) 0.15 g of activated MIL-101(Cr)-CH2Cl and 0.002 mol of N4-IL-4 obtained in step (2) were added to 20 mL of methanol and reacted at 50°C for 48 h. Then, 0.002 mol of divinylbenzene and 5% of the sum of the mass of the amine-functionalized ionic liquid and divinylbenzene were added. The mixture was reacted at 80°C for 12 h under a nitrogen atmosphere. After separating the solvent, the solid was washed three times with DMF and ethanol respectively to remove the unreacted amine-functionalized ionic liquid, divinylbenzene and initiator, and then dried at 70°C in vacuum for 12 h to obtain an amine-functionalized polyionic liquid-supported metal organic framework catalyst, namely Cat4. Example 5

[0040] Study on the Catalytic Performance of Cat1-Cat4 in Synthesis of Cyclic Carbonates from Carbon Dioxide and Propylene Oxide

[0041] 50 mg of catalyst and 0.01 mol of propylene oxide were added to a 15 mL stainless steel autoclave equipped with a magnetic rod, and the reaction was stirred at 1 MPa and 60°C for 6 h. After the reaction was completed, the temperature was cooled in an ice-water bath, and the excess carbon dioxide was slowly released. Ethanol and an appropriate amount of biphenyl (internal standard for chromatographic analysis) were added to the liquid after the reaction, and the solid catalyst was separated by centrifugation. The liquid sample was analyzed by gas chromatography (GC-2030) equipped with a PEG column (30 m*0.32 mm*0.5 um), and the yield of propylene carbonate was shown in Table 1.

[0042] Comparative Example 1

[0043] The only difference from Example 5 is that the catalyst is MIL-101(Cr)-CH2Cl of Example 1, and other conditions remain unchanged. The yield of propylene carbonate is 13%. Comparative Example 2

[0044] Study on the Catalytic Performance of Cat2 in Synthesis of Cyclic Carbonates from Carbon Dioxide and Other Epoxides

[0045] The only difference from Example 5 is that propylene oxide is adjusted to other epoxy compounds, the catalyst is Cat2, and other conditions remain unchanged. The conversion rate of cyclic carbonate is shown in Table 2.

[0046]

[0047] SEM characterization of MIL-101(Cr)-CH2Cl (left) and Cat2 (right) in Example 2 (Attached Figure 1 ), the results show that the introduction of ionic liquid does not cause significant changes in the material morphology.

[0048] The MIL-101(Cr)-CH2Cl, N5-IL-2 and Cat2 in Example 2 were characterized by infrared spectroscopy (see Appendix). Figure 2 ), the results show that 1568cm -1 The peak at 1128 cm-1 can be attributed to the stretching vibration peak of the C=N bond on the imidazole ring in the ionic liquid. -1 The peak at can be attributed to the stretching vibration peak of the CN bond on the aminoalkyl chain, indicating that the ionic liquid was successfully introduced into MIL-101(Cr)-CH2Cl.

[0049] For MIL-101(Cr)-CH2Cl and Cat2 in Example 2, nitrogen adsorption and desorption tests were performed at 77K (see attached). Figure 3 ), according to the IUPAC nomenclature, the nitrogen adsorption-desorption isotherm is a type I curve, and the specific surface area of ​​MIL-101(Cr)-CH2Cl is 1896m 2 / g, after the introduction of ionic liquid, the specific surface area of ​​Cat2 is 1273m 2 / g.

[0050] XRD characterization was performed on the MIL-101(Cr)-CH2Cl and amine functionalized polyionic liquid supported metal organic framework catalysts in Examples 1-4 (see Appendix). Figure 4 ), the results show that the catalyst structure remains intact with the introduction of ionic liquid.

[0051] For those skilled in the art, any technical solution formed by equivalent transformation or equivalent replacement according to the above description and conception should fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing an amine-functionalized polyionic liquid-supported metal organic framework catalyst, characterized in that: The following steps are involved: (1) adding 1-vinyl imidazole or 1-allylimidazole and halogenated alkane to a first organic solvent, reacting at 70-90° C. for 12-24 hours under a nitrogen atmosphere; after the reaction, removing the solvent under reduced pressure, washing with ethyl acetate, and drying to obtain an ionic liquid with a halogen terminal; (2) adding the halogen-terminated ionic liquid obtained in step (1) to the amino compound, reacting at 100 to 120° C. for 12 to 24 hours under a nitrogen atmosphere, cooling to room temperature, separating the solvent, washing with ethyl acetate, and drying to obtain an amine-functionalized ionic liquid; (3) adding the activated MIL-101(Cr)-CH2Cl and the amine-functionalized ionic liquid obtained in step (2) to a second organic solvent, reacting at 50-70°C for 24-48 hours, then adding divinylbenzene and an initiator, reacting at 70-90°C for 12-48 hours under a nitrogen atmosphere, separating the solvent, washing with DMF and ethanol in turn, and drying to obtain an amine-functionalized polyionic liquid-supported metal organic framework catalyst; In the step (3), the mass concentration of the activated MIL-101(Cr)-CH2Cl in the second organic solvent is 5 to 10 g / L; the molar concentration of the amine-functionalized ionic liquid in the second organic solvent is 0.1 to 0.25 mol / L; the second organic solvent is ethanol or methanol; the molar ratio of the amine-functionalized ionic liquid to divinylbenzene is 1 to 2:1; the initiator is azobisisobutyronitrile or azobisisopropionitrile; and the initiator is 2% to 5% of the sum of the mass of the amine-functionalized ionic liquid and divinylbenzene.

2. The method for preparing the amine-functionalized polyionic liquid-supported metal organic framework catalyst according to claim 1, characterized in that: In the step (1), the molar ratio of 1-vinylimidazole or 1-allylimidazole to halogenated alkane is 0.25 to 1:1; and the halogenated alkane is 1,3-dibromopropane or 1,3-dichloropropane.

3. The method for preparing the amine-functionalized polyionic liquid-supported metal organic framework catalyst according to claim 1, characterized in that: In the step (1), the molar concentration of the halogenated alkane in the first organic solvent is 1 to 2 mol / L; the first organic solvent is toluene or acetonitrile.

4. The method for preparing the amine-functionalized polyionic liquid-supported metal organic framework catalyst according to claim 1, characterized in that: In the step (2), the molar concentration of the halogen-terminated ionic liquid in the amino compound is 0.5 to 1 mol / L; the amino compound is triethylenetetramine or tetraethylenepentamine.

5. An application of an amine-functionalized polyionic liquid-supported metal organic framework catalyst prepared by the preparation method according to claim 1, characterized in that: Amine-functionalized polyionic liquid-supported metal-organic framework catalysts were used to catalyze the synthesis of cyclic carbonates from carbon dioxide and epoxides.

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