Hydrophobic ionic liquid grafted metal organic framework material, preparation method thereof and application of hydrophobic ionic liquid grafted metal organic framework material in selective adsorption of toluene steam

Abstract

The invention discloses a hydrophobic ionic liquid grafted metal organic framework material, a preparation method thereof and application of the hydrophobic ionic liquid grafted metal organic framework material in selective adsorption of toluene vapor. Hydrophobic ionic liquid is used as a modification component and is grafted to the surface of an amino-functionalized metal organic framework through an amine-aldehyde condensation reaction; the hydrophobic ionic liquid grafted metal organic framework material prepared by the method has a three-dimensional pore channel structure, a large specific surface area and rich ionic liquid sites, not only has higher hydrophobicity, but also can obviously improve the toluene vapor adsorption separation capacity, and can be used for preparing the organic framework material. Therefore, high-efficiency, high-capacity and selective reversible adsorption of toluene steam under a high-humidity condition is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of synthesizing hydrophobic ionic liquid modified defective metal-organic frameworks, and particularly relates to a hydrophobic ionic liquid grafted metal-organic framework material, a preparation method thereof, and an application in selectively adsorbing toluene vapor. Background Art

[0002] Volatile organic compounds (VOCs) are one of the three main factors causing air pollution and have attracted wide attention in the scientific community in recent years. Among various VOCs, phenyl VOCs (such as benzene, toluene, etc.) are one of the common pollutants and are widely used in fields such as medicine, chemical industry, printing, and fiber industry. At the end of 2023, emission reduction targets for VOCs were issued, so the treatment of VOCs is urgent. In addition, aromatic VOCs such as toluene often accompany a large amount of steam during emission, so it is very important to develop a new type of hydrophobic adsorbent to efficiently adsorb compounds such as toluene under humid conditions.

[0003] Currently, ionic liquids are liquid salts with negligible vapor pressure at room temperature. These compounds have excellent properties such as non-volatility, non-flammability, low melting point, high ionic conductivity, thermal stability, electrochemical stability, and recyclability. In addition, their structures are adjustable because choosing a specific cation and / or anion enables us to achieve the properties required for specific applications. Ionic liquids, as a new type of absorbent, have attracted attention due to their extremely low volatility, no secondary pollution, good solubility, high thermal stability, and designability. However, due to their high viscosity and low mass transfer properties, the current application of ionic liquids is hindered.

[0004] Metal-organic frameworks (MOFs) are a class of porous materials composed of metal ions and organic ligands, with high specific surface area, adjustable pore size, and flexible morphology, making them viable candidates for adsorbing VOCs. However, in a humid environment (50% RH), their adsorption capacity for VOCs is greatly reduced. This can be attributed to the hydrophilicity of acidic metal sites and oxygen groups in MOFs, which enhances the competitive adsorption of water to VOCs, thus severely limiting the practical application of MOFs in reducing VOC pollution under humid conditions.

[0005] Based on the design idea of ionic liquid modified MOFs, they not only have the advantages of ionic liquids but also overcome the above-mentioned hydrophilic deficiencies of MOFs. Therefore, for toluene adsorption under humid conditions, it is very meaningful to develop ionic liquid-based modified MOF adsorbents through structural regulation to improve the selective adsorption capacity of toluene. Summary of the Invention

[0006] In view of the problems existing in the prior art, the object of the present invention is to provide a hydrophobic ionic liquid grafted metal-organic framework material, a preparation method thereof, and an application in selectively adsorbing toluene vapor. The hydrophobic ionic liquid grafted metal-organic framework material obtained by the present invention has a three-dimensional pore structure. By utilizing the high specific surface area, high total pore volume, and exposed ionic liquid sites, the adsorption capacity for selectively adsorbing toluene vapor under high humidity conditions is significantly improved, thereby realizing the efficient, high-capacity, and reversible selective adsorption of toluene vapor.

[0007] To achieve the above object, the technical solution of the present invention is as follows:

[0008] The present invention provides a preparation method of a hydrophobic ionic liquid grafted metal-organic framework material, comprising the following steps:

[0009] 1) Preparation of hydrophobic ionic liquid: First, an ionic organic salt composed of an aldehyde-functionalized cation and a halogen anion is prepared by reacting an aldehyde precursor with a haloalkane. Then, the ionic organic salt is reacted with a lithium salt of a fluorine-containing compound under stirring conditions with water as a solvent. After the reaction, the obtained organic phase liquid is dried under vacuum, and the collected product after drying is the required hydrophobic ionic liquid.

[0010] 2) Preparation of amino-functionalized metal-organic framework: Copper nitrate is dissolved in water to obtain solution one, and trimesic acid and aromatic acid are dissolved in ethanol in a certain proportion to obtain solution two. After the two solutions are stirred evenly, they are transferred to a reaction kettle and placed in an oven for reaction. After the reaction, the product is washed with water, washed with ethanol, and dried to obtain the amino-functionalized metal-organic framework material to be prepared.

[0011] 3) Preparation of ionic liquid grafted metal-organic framework: The hydrophobic ionic liquid obtained in step 1) is dissolved in methanol, and then the amino-functionalized metal-organic framework material obtained in step 2) is added, and the reaction is stirred at a certain temperature. After the reaction, the product after centrifugation, washing, and drying is the ionic liquid grafted metal-organic framework material to be prepared.

[0012] Furthermore, in step 1), the aldehyde precursor is one of 1-methyl-2-aldehyde imidazole, 1-methyl-5-aldehyde imidazole, 2-aldehyde pyridine, and aldehyde phenyl phosphine; the haloalkane is one of bromoethane, bromodecane, chlorobutane, and iodomethane; the lithium salt of the fluorine-containing compound is one of lithium bis(trifluoromethanesulfonyl)imide, lithium phenyltrifluoroacetylacetonate, lithium hexafluoroacetylacetonate, lithium thiophenetrifluoroacetylacetonate, lithium furan trifluoroacetylacetonate, and lithium hexafluorophosphate.

[0013] Further, in step 1), the molar ratio of the aldehyde group precursor to the haloalkane in the reaction is 1:1, the reaction temperature is 50 - 100 °C, and the reaction time is 4 - 24 h; the molar ratio of the obtained ionic organic salt to the lithium salt of the fluorine-containing compound is 1:1, the reaction temperature is 25 - 60 °C, and the reaction time is 3 - 24 h.

[0014] Further, in step 2), the mass-to-volume ratio of copper nitrate to water is 0.05 - 0.3:1; the mass-to-volume ratio of benzene-1,3,5-tricarboxylic acid to ethanol is 0.2 - 0.4:1; the unit of the mass is g, and the unit of the volume is mL; the aromatic acid is benzoic acid containing an amino group or isophthalic acid.

[0015] Further, in step 2), the mass ratio of copper nitrate, benzene-1,3,5-tricarboxylic acid and aromatic acid is 1.5 - 2:1:0.01 - 0.1; the reaction temperature is 100 - 120 °C; the reaction time is 12 - 24 h.

[0016] Further, in step 3), the mass ratio of the ionic liquid, the metal-organic framework material and methanol is 0.1 - 0.3:1 - 2:40 - 60, the unit of the mass is g, and the unit of the volume is mL; the reaction temperature is -5 - 25 °C; the reaction time is 4 - 24 h.

[0017] The present invention provides a hydrophobic ionic liquid grafted metal-organic framework material prepared by using the above method.

[0018] Further, the typical structural formula of the hydrophobic ionic liquid grafted metal-organic framework material is shown in the following formula Ⅰ:

[0019] The present invention also provides an application of the hydrophobic ionic liquid grafted metal-organic framework material, and the application is to use the obtained hydrophobic ionic liquid grafted metal-organic framework material for selectively adsorbing toluene vapor.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] In the present invention, NH2-CuBTC is used as the component to be modified, and an aldehyde group-functionalized ionic liquid is grafted onto the surface of NH2-CuBTC through an amine-aldehyde condensation reaction to obtain a class of hydrophobic ionic liquid grafted metal-organic framework materials IL-CuBTC. The hydrophobic ionic liquid grafted metal-organic framework material prepared by the present invention has a three-dimensional pore structure and a large specific surface area (up to 313 m 2 g -1) and contains abundant ionic liquid sites. It not only has high hydrophobicity (the water contact angle is 80.5°), but also can significantly increase the toluene vapor capture amount under high humidity conditions, thereby realizing the efficient, high-capacity, and selective reversible adsorption of toluene vapor under high humidity conditions. The preparation process of the present invention is simple, and the prepared hydrophobic ionic liquid grafted metal-organic framework material has advantages such as a large specific surface area and high toluene vapor selective adsorption, and has broad market prospects. Brief Description of the Drawings

[0023] Figure 1 It is a scanning electron microscope photograph of the hydrophobic ionic liquid grafted metal-organic framework material [Im][Tf2N]-CuBTC of the present invention;

[0024] Figure 2 It is the water contact angle of the hydrophobic ionic liquid grafted metal-organic framework material [Im][Tf2N]-CuBTC of the present invention;

[0025] Figure 3 It is the nitrogen adsorption and desorption diagram of the hydrophobic ionic liquid grafted metal-organic framework material [Im][Tf2N]-CuBTC of the present invention;

[0026] Figure 4 It is the breakthrough curve of the hydrophobic ionic liquid grafted metal-organic framework material [Im][Tf2N]-CuBTC of the present invention; Figure 5 It is the typical structural formula of the hydrophobic ionic liquid grafted metal-organic framework material of the present invention. Detailed Embodiments

[0027] The present invention will be further described below with reference to the drawings and embodiments, but the scope protected by the present invention is not limited to the described scope.

[0028] Example 1

[0029] 1) Synthesis of [Im][Tf2N]-CuBTC

[0030] Mix 1-methyl-2-formylimidazole (Im) with an equimolar amount of bromoethane and react at 80 °C for 8 hours to obtain the [Im][Br] ionic organic salt. Then mix [Im][Br] with an equimolar amount of [Tf2N][Li], stir at 60 °C with water as the solvent for 3 hours, and then cool the reacted material to room temperature to form a phase-separated, transparent, and stable liquid. Vacuum dry the obtained organic phase at 60 °C for 12 hours to obtain the [Im][TF2N] ionic liquid;

[0031] Dissolve 3.26 g of copper nitrate in 60 ml of water to obtain Solution 1. Dissolve 1.58 g of trimesic acid and 0.06 g of 3,5-diaminobenzoic acid in 60 ml of ethanol to obtain Solution 2. After stirring the two solutions evenly, transfer them to a reaction kettle and place it in an oven for reaction at 120 °C for 12 h. The product is washed with water, washed with ethanol and dried to obtain the NH2-CuBTC material;

[0032] Dissolve [Im][TF2N] (0.15 g) in methanol (80 ml) to obtain a solution, and then add NH2-CuBTC (1 g). The solution is stirred and reacted at 0 °C for 6 hours, and then the product after centrifugal washing and drying is the ionic liquid grafted metal-organic framework material [Im][Tf2N]-CuBTC to be prepared.

[0033] 2) Material characterization:

[0034] From Figure 1 the SEM images analysis, it can be seen from Figure (a) that CuBTC has a good crystal structure, and from Figure (b) it can be seen that the crystallinity of [Im][Tf2N]-CuBTC decreases, mainly due to doping with different ligands, resulting in a decrease in metal bond coordination.

[0035] From Figure 2 the water contact angle, [Im][Tf2N]-CuBTC has a certain hydrophobicity.

[0036] Example 2

[0037] Nitrogen adsorption measurement: The absorption device uses the BET method. First, the hydrophobic ionic liquid grafted metal-organic framework material [Im][Tf2N]-CuBTC synthesized in Example 1 is subjected to vacuum degassing activation treatment, and then the gas adsorption temperature is controlled at 77 K and the gas pressure is 0 - 100 kPa to measure the equilibrium absorption capacity and record the data. The nitrogen adsorption results are as Figure 3 shown, and the BET specific surface area is converted to 313 m 2 g -1 .

[0038] Example 3

[0039] From Figure 4 the breakthrough curve, it can be seen that the toluene absorption capacity of CuBTC is low at 2000 ppm, 298 K, and 80% RH, only 49 mg / g, while the toluene absorption capacity of [Im][Tf2N]-CuBTC under this condition is 182 mg / g, greatly improving the toluene adsorption capacity under humid conditions.

Claims

1. A preparation method of a hydrophobic ionic liquid-grafted metal-organic framework material, characterized in that It includes the following steps: 1) Preparation of hydrophobic ionic liquid: Firstly, an ionic organic salt composed of an aldehyde-functionalized cation and a halogen anion is prepared by reacting an aldehyde precursor with a haloalkane. Then, the ionic organic salt is reacted with a lithium salt of a fluorine-containing compound under stirring conditions with water as the solvent. After the reaction, the obtained organic phase liquid is dried under vacuum, and the collected product after drying is the required hydrophobic ionic liquid; 2) Preparation of amino-functionalized metal-organic framework: Copper nitrate is dissolved in water to obtain Solution 1, and trimesic acid and aromatic acid are dissolved in ethanol in a certain ratio to obtain Solution 2. After the two solutions are stirred evenly, they are transferred to a reaction kettle and placed in an oven for reaction. After the reaction, the product is washed with water, washed with ethanol, and dried, which is the amino-functionalized metal-organic framework material to be prepared; 3) Preparation of ionic liquid grafted metal-organic framework: The hydrophobic ionic liquid obtained in step 1) is dissolved in methanol, and then the amino-functionalized metal-organic framework material obtained in step 2) is added, and the reaction is stirred at a certain temperature. After the reaction, the product after centrifugation, washing, and drying is the ionic liquid grafted metal-organic framework material to be prepared.

2. The preparation method of a hydrophobic ionic liquid grafted metal-organic framework material according to claim 1, characterized in that In step 1), the aldehyde precursor is one of 1-methyl-2-aldehyde imidazole, 1-methyl-5-aldehyde imidazole, 2-aldehyde pyridine, and aldehyde phenylphosphine; the haloalkane is one of bromoethane, bromodecane, chlorobutane, and iodomethane; the lithium salt of the fluorine-containing compound is one of lithium bis(trifluoromethylsulfonyl)imide, lithium phenyltrifluoroacetylacetonate, lithium hexafluoroacetylacetonate, lithium thiophene trifluoroacetylacetonate, lithium furan trifluoroacetylacetonate, and lithium hexafluorophosphate.

3. The preparation method of a hydrophobic ionic liquid-grafted metal-organic framework material according to claim 1, wherein In step 1), the molar ratio of the aldehyde precursor to the haloalkane in the reaction is 1:1, the reaction temperature is 50 - 100 °C, and the reaction time is 4 - 24 h; the molar ratio of the obtained ionic organic salt to the lithium salt of the fluorine-containing compound is 1:1, the reaction temperature is 25 - 60 °C, and the reaction time is 3 - 24 h.

4. The preparation method of a hydrophobic ionic liquid-grafted metal-organic framework material according to claim 1, characterized in that In step 2), the mass ratio of copper nitrate to the volume of water is 0.05 - 0.3:1; the mass ratio of trimesic acid to the volume of ethanol is 0.2 - 0.4:1; the unit of the mass is g, and the unit of the volume is mL; the aromatic acid is benzoic acid containing an amino group or isophthalic acid.

5. The preparation method of a hydrophobic ionic liquid-grafted metal-organic framework material according to claim 4, characterized in that In step 2), the mass ratio of copper nitrate, trimesic acid, and aromatic acid is 1.5 - 2:1:0.01 - 0.1; the reaction temperature is 100 - 120 °C; the reaction time is 12 - 24 h.

6. The preparation method of a hydrophobic ionic liquid-grafted metal-organic framework material according to claim 1, characterized in that In step 3), the mass ratio of the ionic liquid, the metal-organic framework material, and the volume of methanol is 0.1 - 0.3:1 - 2:40 - 60, the unit of the mass is g, and the unit of the volume is mL; the reaction temperature is -5 - 25 °C; the reaction time is 4 - 24 h.

7. A hydrophobic ionic liquid grafted metal-organic framework material prepared by using the method according to any one of claims 1 - 6.

8. The hydrophobic ionic liquid-grafted metal-organic framework material according to claim 7, characterized in that The typical structure of the hydrophobic ionic liquid grafted metal-organic framework material.

9. Use of the hydrophobic ionic liquid-grafted metal-organic framework material as described in claim 7, characterized in that The application is to use the obtained hydrophobic ionic liquid grafted metal-organic framework material for selectively adsorbing toluene vapor.

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