Preparation method and application of thorium-based MOF material modified by ionic liquid

Abstract

The present invention discloses a preparation method and application of a thorium-based MOF material modified by an ionic liquid. The preparation method comprises the following steps: (1) reacting a water-soluble thorium salt with tetrakis[4-(4'-carboxylphenyl)phenyl]ethylene in the presence of an acidic regulator and a solvent to obtain a thorium-based MOF material; (2) reacting the thorium-based MOF material with an ionic liquid in the presence of a solvent to obtain an ionic liquid-modified thorium-based MOF material; the ionic liquid is a terminal halogenated 1-alkyl 3-methylimidazolium ionic liquid [MIM(CH2) n X]Y, wherein n=2-6, X is Cl, Br or I, and Y is Cl, Br or I. The thorium-based MOF material and the thorium-based MOF material modified by the above method both have stable crystalline structures. The thorium-based MOF material modified by the end-group halide ionic liquid exhibits excellent photocurrent response and has multiple active sites. It can be used as a photocatalyst to efficiently catalyze the reduction of carbon dioxide to carbon monoxide and methane, and exhibits good cyclic stability.

Description

Technical Field

[0001] The present invention relates to the technical field of photocatalysis, and in particular to a preparation method and application of an ionic liquid-modified thorium-based MOF material. Background Art

[0002] Photocatalytic carbon dioxide (CO2) reduction technology is a method that uses light energy to convert CO2 into useful chemicals and has broad application prospects. Photocatalytic CO2 reduction is usually carried out in the presence of a photocatalyst. Compared with traditional photocatalysts, metal-organic framework (MOFs)-based photocatalysts have the following advantages: (1) ultra-high specific surface area and adjustable pore structure, (2) easy functionalization of metal nodes and organic ligands, and (3) abundant pores that can accommodate functional guest substances. At present, in order to achieve efficient CO2 conversion, the surface chemical properties and structural characteristics of MOFs materials can be rationally designed and controlled to improve their catalytic activity and selectivity. For example, by introducing different metal ions and organic ligands, the charge transport properties and photocatalytic activity of MOFs materials can be regulated, thereby improving the efficiency and selectivity of the CO2 reduction reaction. In addition, by controlling the crystal structure and pore size of MOFs materials, their adsorption and mass transfer capabilities for CO2 molecules can be optimized, further enhancing the catalytic performance of the photocatalytic CO2 reduction reaction.

[0003] However, existing MOFs photocatalysts still generally suffer from a lack of surface active sites that are easily covered, and a narrow reaction space, resulting in low catalytic efficiency and poor stability when using MOFs as photocatalysts. Therefore, there is an urgent need for a MOF-based photocatalyst that can efficiently catalyze the reduction of CO2 and has good cyclic stability. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a preparation method and application of thorium-based MOF materials modified by ionic liquids, which uses water-soluble thorium salts and tetra[4-(4'-carboxyphenyl)phenyl]ethylene to form a thorium-based MOF material with a stable crystalline state under specific conditions, and uses a terminal halogenated 1-alkyl 3-methylimidazolium ionic liquid [MIM(CH2) n The above-mentioned thorium-based MOF material is further modified by X]Y (n is any integer from 2 to 6, X is Cl, Br or I, and Y is Cl, Br or I) to obtain an ionic liquid-modified thorium-based MOF material with a stable crystal structure and high photocatalytic performance, which can efficiently catalyze CO2 to produce carbon monoxide (CO) and methane (CH4).

[0005] Specifically, the present invention provides the following technical solutions:

[0006] The first aspect of the present invention provides a method for preparing an ionic liquid-modified thorium-based MOF material, comprising the following steps:

[0007] (1) reacting a water-soluble thorium salt with tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene in the presence of an acidic regulator and a solvent to obtain a thorium-based MOF material;

[0008] (2) The thorium-based MOF material prepared in step (1) is mixed with the ionic liquid [MIM(CH2) n X]Y reacts in the presence of a solvent to obtain an ionic liquid modified thorium-based MOF material; the ionic liquid [MIM(CH2) n The structure of X]Y is as follows:

[0009]

[0010] Wherein, n is any integer from 2 to 6;

[0011] X is Cl, Br or I;

[0012] Y is Cl, Br or I.

[0013] Furthermore, in step (1), the water-soluble thorium salt is thorium nitrate and / or thorium nitrate hydrate.

[0014] Furthermore, in step (1), the molar ratio of the water-soluble thorium salt to tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene is (2.0-2.1):(0.9-1.0).

[0015] Furthermore, in step (1), the acidic regulator is hydrochloric acid, nitric acid, formic acid, acetic acid, etc., and the reaction pH is adjusted to 3-5.

[0016] Furthermore, the solvent is N,N-dimethylformamide (DMF) or a mixed solvent of DMF and water.

[0017] Furthermore, in step (1), the reaction temperature is 80-100° C., and the reaction time is 48 h-72 h.

[0018] Furthermore, in step (1), the chemical formula of the thorium-based MOF material is Th2(C 54 H 32 O8)2(H2O)4,C 54 H 32 O8 is a tetravalent anionic ligand of tetra[4-(4'-carboxyphenyl)phenyl]ethylene; the thorium-based MOF material belongs to the monoclinic system, the space group is C2 / m, and the unit cell parameters are α=γ=90°, β=105.213(5)°, Z=4.

[0019] Furthermore, in step (2), the thorium-based MOF material and the ionic liquid [MIM ​​(CH2) n The mass ratio of X]Y is (1-1.5):(10-15).

[0020] Furthermore, in step (2), the ionic liquid can be prepared by the following preparation method: reacting 1-methylimidazole with a halogenated alkane at 60-70°C for 50-70min, cooling to room temperature (20-30°C), washing the product with a solvent (such as ethyl acetate), and drying it in vacuo at 80-100°C; the halogenated alkane can be 1,4-dichlorobutane, 1,4-dibromobutane, 1,4-diiodobutane, 1,2-dibromoethane, 1,3-dibromopropane, 1,5-dibromopentane or 1,6-dibromohexane.

[0021] Furthermore, in step (2), the solvent is a mixed solvent of acetonitrile and DMF.

[0022] Furthermore, in step (2), the reaction temperature is 60-70°C and the reaction time is 24h-48h.

[0023] Furthermore, in step (2), the BET specific surface area of ​​the thorium-based MOF material modified by the ionic liquid is 120-200 m 2 ·g -1 , pore volume is 0.054-0.1022cm 3 ·g -1 , the pore size is 2.34-5.51nm.

[0024] Furthermore, step (2) further comprises the steps of filtering, washing and vacuum drying the reaction product using a mixed solvent of acetonitrile and DMF; the vacuum drying temperature is 100-120°C.

[0025] The second aspect of the present invention provides an ionic liquid-modified thorium-based MOF material prepared by the preparation method described in the first aspect.

[0026] A third aspect of the present invention provides an application of an ionic liquid-modified thorium-based MOF material as a photocatalyst in a photocatalytic CO2 reduction reaction.

[0027] Furthermore, the thorium-based MOF material modified with ionic liquid is placed in a photocatalytic reactor with water and a sacrificial agent, and CO2 is introduced under light-proof conditions and subjected to light treatment, whereby CO2 is reduced to generate CO and CH4.

[0028] Furthermore, the CO yield reached 60.82±0.50 μmol·g -1 ·h -1The CH4 yield reached 23.75±0.20μmol·g -1 ·h -1 , μmol·g -1 ·h -1 It is a commonly used unit for expressing catalyst yield, where μmol is the amount of product, g is the mass of the catalyst, and h is the reaction time, which is used to reflect the product yield per unit catalyst per unit time.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention provides an ionic liquid-modified thorium-based MOF. The preparation method is simple, and the thorium-based MOF has a stable crystalline structure and exhibits excellent photocurrent response. The structural features such as multiple active sites formed by the metal and ionic liquid and a large specific surface area enable it to exhibit excellent catalytic performance in the photocatalytic reduction of CO2. When used as a photocatalyst for the photocatalytic reduction of CO2, the yield of the reduced product CO can reach 60.82±0.50μmol·g -1 ·h -1 The CH4 yield reached 23.75±0.20μmol·g -1 ·h -1 In addition, the thorium-based MOF material modified by ionic liquid has good recyclability. After five cycles of catalytic reaction, the catalytic activity of the material has not decreased significantly, and it has good application prospects in catalyzing CO2 as a photocatalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The three-dimensional porous framework of the Th-MOF material prepared in Example 1;

[0032] Figure 2 The X-ray powder diffraction (PXRD) spectrum obtained by simulating the single crystal data of the Th-MOF material prepared in Example 1 and the overlay of the PXRD spectra actually measured for the Th-MOF material and Th-MOF-[MIM(CH2)4Br]Br;

[0033] Figure 3 FT-IR images of Th-MOF and Th-MOF-[MIM(CH2)4Br]Br prepared in Example 1;

[0034] Figure 4 This is a diagram of the photocatalytic recycling of Th-MOF-[MIM(CH2)4Br]Br prepared in Example 1. DETAILED DESCRIPTION

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] The present invention will be further described below with reference to the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it. However, the embodiments are not intended to limit the present invention.

[0037] The test equipment and parameters involved in the following embodiments are as follows:

[0038] X-ray single crystal diffraction characterization and structural analysis: Select a single crystal of appropriate size under a microscope and use the German Bruker APEX-IICCD single crystal diffractometer to analyze the structure of the crystal. X-ray diffraction data were collected at 170 K. All crystallographic data were corrected for Lp factors and empirical absorption using the SADABS program. The initial structure was solved by direct methods, and all non-hydrogen atoms in the backbone were anisotropically refined using full-matrix least-squares methods. The coordinates of all hydrogen atoms on parent carbons were obtained by theoretical hydrogenation, and the coordinates of hydrogen atoms on H2O were obtained by the difference Fourier method, followed by isotropic correction. Simulated X-ray powder diffraction patterns of the single crystal data were obtained using Mercury software.

[0039] X-ray powder diffraction characterization test: X-ray powder diffraction data were collected on a Rigaku D / MAX-2500 powder diffractometer with a voltage of 40 kV and a current of 100 mA, using graphite monochromatized copper target X-rays (Cu-Kα, ), continuous scanning is completed in the range of 3° to 50°.

[0040] Fourier transform infrared spectroscopy characterization test: Fourier transform infrared spectroscopy data collection was completed on a ThermoScientific Smart OMNI-Transmission infrared spectrometer using spectrally pure potassium bromide pellets in the range of 450 to 4000 cm -1 Continuous scanning within the range is completed.

[0041] The nitrogen adsorption and desorption test was performed using a Micromeritics ASAP2460 physical adsorption instrument to measure the N2 adsorption and desorption isotherm at 77K.

[0042] Example 1

[0043] This embodiment relates to the preparation of a metal organic framework material Th-MOF and a thorium-based MOF material Th-MOF-[MIM(CH2)4Br]Br modified with an ionic liquid [MIM(CH2)4Br]Br, wherein the structure of the ionic liquid [MIM(CH2)4Br]Br is as follows:

[0044]

[0045] The specific operations are as follows:

[0046] Preparation of Th-MOF: Th(NO3)4 and tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene ligand were dissolved in DMF solution, 200 μL HCl was added to a 7 mL glass sample bottle, the reaction temperature was 80°C, and the reaction time was 72 h to obtain Th-MOF material.

[0047] Preparation of Th-MOF-[MIM(CH2)4Br]Br: The above-mentioned Th-MOF material and [MIM(CH2)4Br]Br were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0, heated at 65°C for 24 hours, and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and vacuum dried at 100°C for 12 hours to obtain the ionic liquid-modified thorium-based MOF material Th-MOF-[MIM(CH2)4Br]Br.

[0048] For the Th-MOF material prepared in this example, single crystals of appropriate size were selected for X-ray single crystal diffraction characterization; some parameters for crystallographic diffraction point data collection and structure refinement of the Th-MOF material are shown in Table 1:

[0049] Table 1 Th-MOF single crystal parameters

[0050]

[0051]

[0052] The crystal structure analysis results of Th-MOF prepared in this example are as follows: In the Th-MOF crystal structure, thorium ions form a binuclear unit with carboxyl O and coordinated H2O in an octa-coordinated manner, containing 2 Th 4+ ion, 2 tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene tetravalent anion ligands, and 4 coordinated water molecules.

[0053] X-ray powder diffraction spectrum simulated from single crystal data and PXRD spectrum actually measured for Th-MOF Figure 1 To ( Figure 2 ), proving that the bulk synthesized Th-MOF materials are phase-pure.

[0054] The PXRD overlay of Th-MOF-[MIM(CH2)4Br]Br modified with Th-MOF and [MIM(CH2)4Br]Br ionic liquid is shown in the figure. Figure 2 As shown in the figure, it can be seen that ionic liquid modification does not affect the crystal structure of Th-MOF material.

[0055] Figure 3 The FT-IR image of Th-MOF-[MIM(CH2)4Br]Br material modified with Th-MOF material and [MIM(CH2)4Br]Br ionic liquid is shown in the figure. -1 The characteristic peaks at the wavenumbers around 2900-3100 cm correspond to the stretching vibration peaks of the C=O bond in Th-MOF. -1 The wave number around is the C-H bond stretching vibration peak; 1500cm -1 The wave number is the stretching vibration of C=N on the imidazole ring. The infrared results show that the ionic liquid is successfully composited on the thorium-based MOF.

[0056] Example 2

[0057] This embodiment relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)4Cl]Cl modified by an ionic liquid [MIM(CH2)4Cl]Cl, wherein the structure of the ionic liquid [MIM(CH2)4Cl]Cl is as follows:

[0058]

[0059] The specific operations are as follows:

[0060] Preparation of Th-MOF-[MIM(CH2)4Cl]Cl: The Th-MOF material prepared in Example 1 and [MIM(CH2)4Cl]Cl were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuo at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)4Cl]Cl.

[0061] Example 3

[0062] This embodiment relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)4I]I modified with an ionic liquid [MIM(CH2)4I]I, wherein the structure of the ionic liquid [MIM(CH2)4I]I is as follows:

[0063]

[0064] The specific operations are as follows:

[0065] Preparation of Th-MOF-[MIM(CH2)4I]I: The Th-MOF material prepared in Example 1 and [MIM(CH2)4I]I were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuo at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)4I]I.

[0066] Example 4

[0067] This embodiment relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)2Br]Br modified with an ionic liquid [MIM(CH2)2Br]Br, wherein the structure of the ionic liquid [MIM(CH2)2Br]Br is as follows:

[0068]

[0069] The specific operations are as follows:

[0070] Preparation of Th-MOF-[MIM(CH2)2Br]Br: The Th-MOF material prepared in Example 1 and [MIM(CH2)2Br]Br were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuum at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)2Br]Br.

[0071] Example 5

[0072] This embodiment relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)3Br]Br modified with an ionic liquid [MIM(CH2)3Br]Br, wherein the structure of the ionic liquid [MIM(CH2)3Br]Br is as follows:

[0073]

[0074] The specific operations are as follows:

[0075] Preparation of Th-MOF-[MIM(CH2)3Br]Br: The Th-MOF material prepared in Example 1 and [MIM(CH2)3Br]Br were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuum at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)3Br]Br.

[0076] Example 6

[0077] This embodiment relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)5Br]Br modified with an ionic liquid [MIM(CH2)5Br]Br, wherein the structure of the ionic liquid [MIM(CH2)5Br]Br is as follows:

[0078]

[0079] The specific operations are as follows:

[0080] Preparation of Th-MOF-[MIM(CH2)5Br]Br: The Th-MOF material prepared in Example 1 and [MIM(CH2)5Br]Br were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuum at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)5Br]Br.

[0081] Example 7

[0082] This embodiment relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)6Br]Br modified with an ionic liquid [MIM(CH2)6Br]Br, wherein the structure of the ionic liquid [MIM(CH2)6Br]Br is as follows:

[0083]

[0084] The specific operations are as follows:

[0085] Preparation of Th-MOF-[MIM(CH2)6Br]Br: The Th-MOF material prepared in Example 1 and [MIM(CH2)6Br]Br were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuum at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)6Br]Br.

[0086] Comparative Example 1

[0087] This comparative example relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)3CH3]BF4 modified with an ionic liquid [MIM(CH2)3CH3]BF4, wherein the structure of the ionic liquid [MIM(CH2)3CH3]BF4 is as follows:

[0088]

[0089] The specific operations are as follows:

[0090] Preparation of Th-MOF-[MIM(CH2)3CH3]BF4: The Th-MOF material prepared in Example 1 and [MIM(CH2)3CH3]BF4 were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and vacuum dried at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)3CH3]BF4.

[0091] Comparative Example 2

[0092] This comparative example relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)3CH3]Cl modified by an ionic liquid [MIM(CH2)3CH3]Cl, wherein the structure of the ionic liquid [MIM(CH2)3CH3]Cl is as follows:

[0093]

[0094] The specific operations are as follows:

[0095] Preparation of Th-MOF-[MIM(CH2)3CH3]Cl: The Th-MOF material prepared in Example 1 and [MIM(CH2)3CH3]Cl were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuo at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)3CH3]Cl.

[0096] Comparative Example 3

[0097] This comparative example relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)3CH3]Br modified by an ionic liquid [MIM(CH2)3CH3]Br, wherein the structure of the ionic liquid [MIM(CH2)3CH3]Br is as follows:

[0098]

[0099] The specific operations are as follows:

[0100] Preparation of Th-MOF-[MIM(CH2)3CH3]Br: The Th-MOF material prepared in Example 1 and [MIM(CH2)3CH3]Br were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0, heated at 65°C for 24 hours, and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and vacuum dried at 100°C for 12 hours to obtain Th-MOF-[MIM(CH2)3CH3]Br.

[0101] Comparative Example 4

[0102] This comparative example relates to the preparation of a thorium-based MOF material Th-MOF-[MIM(CH2)3CH3]I modified with an ionic liquid [MIM(CH2)3CH3]I, wherein the structure of the ionic liquid [MIM(CH2)3CH3]I is as follows:

[0103]

[0104] The specific operations are as follows:

[0105] Preparation of Th-MOF-[MIM(CH2)3CH3]I: The Th-MOF material prepared in Example 1 and [MIM(CH2)3CH3]I were added to a mixed solution of 15 mL of acetonitrile and 5 mL of DMF in a mass ratio of 1.0:10.0. The mixture was heated at 65°C for 24 h and then cooled to room temperature. The mixture was washed with acetonitrile and DMF several times, respectively, and dried in vacuo at 100°C for 12 h to obtain Th-MOF-[MIM(CH2)3CH3]I.

[0106] Performance Testing

[0107] (1) Photocatalytic performance test

[0108] The thorium-based MOF material prepared in Example 1 and the ionic liquid-modified thorium-based MOF materials prepared in Examples 1-7 and Comparative Examples 1-4 were used as photocatalysts for catalytic reduction of CO2. The specific operation was as follows:

[0109] 20 mg of thorium-based MOF material (Th-MOF) or thorium-based MOF material modified with each ionic liquid, 50 mg of Na2SO3, and 20 mL of H2O were added to a 120 mL photocatalytic reactor respectively; under light-proof conditions, the gas in the reactor was replaced with CO2 three times, and the continuous introduction of CO2 should be maintained for 30-40 minutes to make the CO2 pressure in the reactor reach 0.5 MPa, and then the reactor was illuminated for 3 hours; after the reaction, the gas in the photocatalytic reactor was analyzed and detected using gas chromatography.

[0110] The yields of CO and CH4 produced by catalytic reduction of CO2 by different photocatalysts are shown in Table 2 below:

[0111] Table 2

[0112]

[0113]

[0114] As shown in Table 2, the thorium-based MOF material (Th-MOF) prepared in Example 1 has a good photocatalytic effect on CO2, and the photocatalytic effect of the thorium-based MOF material (Th-MOF) prepared in Example 1 is good. n X]Y (e.g. [MIM(CH2) containing terminal Br) 2-6 The thorium-based MOF material prepared in Example 1 was modified with [MIM(CH2)4Cl]Br, [MIM(CH2)4Cl]Cl containing a terminal Cl, and [MIM(CH2)4I]I containing a terminal I), which can effectively improve the conversion efficiency of CO2 and exhibit excellent photocatalytic performance. Among them, compared with the unmodified thorium-based MOF material, the amount of CO and CH4 generated by the photocatalytic reduction of CO2 by the thorium-based MOF material modified with [MIM(CH2)4I]I containing a terminal I increased by more than 50%. However, the photocatalytic performance of the thorium-based MOF material modified with [MIM(CH2)3CH3]BF4, [MIM(CH2)3CH3]Cl, [MIM(CH2)3CH3]Br, and [MIM(CH2)3CH3]I, which do not contain halogenated terminal groups, was significantly reduced, and the yield of the reduction product CO prepared by its catalytic reduction was only 19%-79% of the catalytic yield of the unmodified thorium-based MOF material.

[0115] (2) Stability test

[0116] The Th-MOF-[MIM(CH2)4Br]Br prepared in Example 1 was subjected to the above-mentioned photocatalytic reduction of CO2, and then the catalyst was recovered (centrifugation, filtration, washing with water several times, and vacuum drying at 100°C); the above-mentioned cycle operation was repeated 5 times, and the yield change of the reduction product was shown in the figure below. Figure 4 As shown in the figure, the catalytic performance of the catalyst did not decrease significantly after repeated use. Therefore, it can be seen that the above-mentioned Th-MOF-[MIM(CH2)4Br]Br has good catalytic stability and can be reused.

[0117] The above-described embodiments are merely preferred examples for the purpose of fully illustrating the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

Claims

1. A method for preparing an ionic liquid modified thorium-based MOF material, characterized in that: The following steps are involved: (1) reacting a water-soluble thorium salt with tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene in the presence of an acidic regulator and a solvent to obtain a thorium-based MOF material; (2) The thorium-based MOF material prepared in step (1) was mixed with the ionic liquid [MIM(CH2) n X]Y reacts in the presence of a solvent to obtain an ionic liquid-modified thorium-based MOF material; The ionic liquid [MIM(CH2) n The structure of X]Y is as follows: ， Wherein, n is any integer from 2 to 6; X is Cl, Br or I; Y is Cl, Br or I.

2. The preparation method according to claim 1, characterized in that In step (1), the water-soluble thorium salt is thorium nitrate and / or thorium nitrate hydrate; The molar ratio of the water-soluble thorium salt to tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene is (2.0-2.1):(0.9-1.0).

3. The preparation method according to claim 1, characterized in that In step (1), the acidic regulator is hydrochloric acid, nitric acid, formic acid or acetic acid, and the reaction pH is adjusted to 3-5; The solvent is N,N-dimethylformamide or a mixed solvent of N,N-dimethylformamide and water.

4. The preparation method according to claim 1, characterized in that In step (1), the reaction temperature is 80-100°C and the reaction time is 48 h-72 h.

5. The preparation method according to claim 1, characterized in that In step (1), the chemical formula of the thorium-based MOF material is Th2(C 54 H 32 O8)2(H2O)4,C 54 H 32 O8 is a tetrakis[4-(4'-carboxyphenyl)phenyl]ethylene tetravalent anion ligand; the thorium-based MOF material belongs to the monoclinic system, and the space group is C 2 / m , the unit cell parameters are a = 10.9187(18) Å, b = 42.378(7) Å, c = 15.497(3) Å, α=γ=90°, β = 105.213(5)°, Z = 4.

6. The preparation method according to claim 1, characterized in that In step (2), the thorium-based MOF material and the ionic liquid [MIM(CH2) n The mass ratio of X]Y is (1-1.5):(10-15); The solvent is a mixed solvent of acetonitrile and N,N-dimethylformamide.

7. The preparation method according to claim 1, characterized in that In step (2), the reaction temperature is 60-70°C and the reaction time is 24 h-48 h; The product after the reaction is filtered, washed, and vacuum-dried to obtain the thorium-based MOF material modified by the ionic liquid.

8. The preparation method according to claim 1, characterized in that In step (2), the BET specific surface area of ​​the thorium-based MOF material modified by the ionic liquid is 120-200 m 2 ·g -1 , pore volume is 0.054-0.1022 cm³·g -1 , the pore size is 2.34-5.51 nm.

9. An ionic liquid modified thorium-based MOF material, characterized in that: The compound is prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the thorium-based MOF material modified with an ionic liquid according to claim 9 as a photocatalyst in a photocatalytic CO2 reduction reaction.

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