阅读说明：本技术 一种聚离子液体功能化MOFs材料的制备及其在合成异胡薄荷醇中的应用 (Preparation of polyion liquid functionalized MOFs material and application of polyion liquid functionalized MOFs material in synthesis of isopulegol ) 是由 李玲 卢佳尧 邱挺 叶长燊 陈杰 葛雪惠 于 2020-12-04 设计创作，主要内容包括：本发明涉及一种聚离子液体功能化MOFs材料(UiO-66)的制备及其在合成异胡薄荷醇中的应用,属于复合材料技术领域。本发明利用含羧酸基团的咪唑为聚离子液体单体,采用热溶剂法将其与UiO-66结合后聚合再离子交换,成功合成了聚咪唑离子液体功能化MOFs材料(UiO-PIL)。该材料在香茅醛合成异胡薄荷醇反应中,在绿色温和的条件下,表现出优异的催化性能,与UiO-66相比催化性能大幅度提升。(The invention relates to a preparation method of polyion liquid functionalized MOFs materials (UiO-66) and application thereof in synthesis of isopulegol, belonging to the technical field of composite materials. The invention utilizes imidazole containing carboxylic acid group as polyion liquid monomer, adopts a hot solvent method to combine the imidazole with UiO-66, then polymerizes and exchanges ions, and successfully synthesizes the polyion ionic liquid functionalized MOFs material (UiO-PIL). The material shows excellent catalytic performance under green and mild conditions in the reaction of synthesizing isopulegol from citronellal, and the catalytic performance is greatly improved compared with UiO-66.)

1. A preparation method of polyion liquid functionalized MOFs materials is characterized by comprising the following specific steps:

(1) dissolving carboxyl imidazole, zirconium chloride and carboxylic acid ligand in DMF according to a certain proportion, adding glacial acetic acid, performing ultrasonic treatment for 30 min, crystallizing for a certain time at 110-130 ℃, washing and drying to obtain a precursor of the polyion liquid functionalized MOFs material;

(2) polymerizing the precursor and epoxy chloropropane for a certain time at a certain temperature, and then carrying out ion exchange, washing and drying to obtain the polyion liquid functionalized MOFs material.

2. The method of claim 1, wherein: the carboxyl imidazole in the step (1) is one of imidazole-2-formic acid, imidazole-4, 5-dicarboxylic acid, benzimidazole-4-carboxylic acid and 1-methyl-4-imidazole formic acid.

3. The method of claim 1, wherein: the molar ratio of the zirconium chloride to the carboxylic acid ligand in the step (1) is 1.0: 0.5-2.0, wherein the molar ratio of the carboxyl imidazole to the carboxylic acid ligand is 0.5-5.0: 1.0.

4. the method of claim 1, wherein: the reaction time in the step (1) is 24-48 h.

5. The method of claim 1, wherein: the carboxylic acid ligand in the step (1) is one of terephthalic acid, 4' -biphenyldicarboxylic acid and trimesic acid.

6. The method of claim 1, wherein: the polymerization time in the step (2) is 24-96 hours.

7. The method of claim 1, wherein: the polymerization temperature in the step (2) is 45-85 ℃.

8. The method of claim 1, wherein: the ion for ion exchange in the step (2) is Cu^{2 +}、Al³⁺、Fe³⁺、Zr⁴⁺、Sn⁴⁺One kind of (1).

9. The method of claim 1, wherein: and (3) the ion exchange time in the step (2) is 12-24 h.

10. The application of the polyion liquid functionalized MOFs material prepared by the preparation method according to claim 1 in the reaction of synthesizing isopulegol from citronellal.

Technical Field

The invention belongs to the technical field of composite material synthesis, and particularly relates to a preparation method of a polyion liquid functionalized MOFs material and application of the polyion liquid functionalized MOFs material in a reaction of synthesizing isopulegol from citronellal.

Background

Menthol is an important aromatic chemical, can be applied to industries such as food, medicine, daily necessities and the like, and the demand of menthol is increasing in recent years. Menthol on the market at present mainly comes from natural purification and separation, and the yield of the natural purified menthol is unstable due to the limitations of climate, geography and the like. Compared with the prior art, the artificial synthesized menthol has higher economy and better stability, can meet the market demand better and has great advantages. The isopulegol is an important intermediate for artificially synthesizing the menthol, so that the preparation of the isopulegol by cyclizing the citronellal is a key step for synthesizing the menthol, and the selection of the catalyst is a key factor for influencing the result of the isomerization reaction. Such as diatomaceous earth and SiO₂Sulfuric acid, acetic anhydride, zinc bromide, acidic oxides, rhodium complexes and the like can be used for cyclizing catalysis of citronellal, and the catalysts have the problems of low selectivity of isopulegol, large using amount of the catalyst, slow reaction rate, difficult recovery, harsh reaction conditions and the like. Therefore, a catalyst with high catalytic performance and capable of being recycled needs to be synthesized, and isopulegol is synthesized under green and mild conditions.

Metal organic framework Materials (MOFs) are a new class of functionalized crystalline composites. The method has the advantages of high porosity, large specific surface area and the like, and the self network topological structure can be regulated and controlled by selecting different metal ions and organic ligands. The various advantages of the MOFs materials have attracted more and more attention in the field of catalysis.

The polyion liquid (PIL) is an ionic liquid polymer which is generated by polymerizing an ionic liquid monomer and has an anionic group and a cationic group on a repeating unit, and has the excellent performances of the ionic liquid and the polymer. The functionalized polyionic liquid is developed from the functionalized ionic liquid, and overcomes the fluidity of the ionic liquid. The research focuses on the controllable property of the structure, and designs and synthesizes stable and functional materials with special performance. In recent years, the method has been widely applied to the fields of polymer chemistry, electrochemistry, material science, energy science and the like.

The Frederik project is combined to synthesize a series of modified UiO-66 materials for catalyzing citronellal to synthesize isopulegol, wherein the unmodified UiO-66 materials take toluene as a solvent and react for 24 hours at 100 ℃, and the yield of the isopulegol only reaches 23%. The UiO-66 material modified by amino, nitro, methyl and other groups takes toluene as a solvent, and the highest yield is only 81 percent after 24 hours of reaction at 100 ℃. According to the invention, by utilizing the ion exchange property of the polyion liquid and adopting a hot solvent method, firstly, the polyion liquid monomer is coordinated with the metal in the UO-66, then the polymerization is carried out, and then the ion exchange is carried out, so that the synthesized polyion liquid functionalized MOFs material is applied to the synthesis of isopulegol from citronellal, ethanol is used as a solvent, the reaction is carried out at room temperature for 1-2 h, the yield can reach more than 90%, and the catalytic performance is excellent.

Disclosure of Invention

The invention aims to provide a method for synthesizing a polyion liquid functionalized MOFs material capable of catalyzing citronellal to synthesize isopulegol in a green and mild environment.

In order to achieve the purpose, the invention adopts the following technical scheme:

a preparation method of polyion liquid functionalized MOFs materials comprises the following steps: the polyion liquid functionalized MOFs material (UiO-PIL) is synthesized by using carboxyl-containing imidazole as a polyion liquid monomer, utilizing the characteristic that the polyion liquid can be subjected to ion exchange and simultaneously the carboxyl group of the polyion liquid can be coordinated and combined with the MOFs metal cluster, and adopting a hot solvent method to embed the polyion liquid monomer into the MOFs material and then carrying out polymerization and ion exchange. The specific synthesis steps are as follows:

(1) dissolving carboxyl imidazole, zirconium chloride and carboxylic acid ligand in DMF according to a certain proportion, adding glacial acetic acid, performing ultrasonic treatment for 30 min, crystallizing for a certain time at 110-130 ℃, washing, and drying to obtain a precursor of the polyion liquid functionalized MOFs material;

(2) and polymerizing the precursor and epoxy chloropropane at a certain temperature for a certain time, then carrying out ion exchange, washing and drying to obtain the polyion liquid functionalized MOFs material.

The carboxyl imidazole in the step (1) is one of imidazole-2-formic acid, imidazole-4, 5-dicarboxylic acid, benzimidazole-4-carboxylic acid and 1-methyl-4-imidazole carboxylic acid.

The molar ratio of zirconium chloride to carboxylic acid ligand in step (1) above is 1.0: 0.5 to 2.0 of a carboxyl imidazole and

the molar ratio of the used carboxylic acid ligand is 0.5-5.0: 1.0.

the reaction time in the step (1) is 24-48 h.

The carboxylic acid ligand in the step (1) is one of terephthalic acid, 4' -biphenyldicarboxylic acid and trimesic acid.

The polymerization temperature in the step (2) is 45-85 ℃.

The polymerization time in the step (2) is 24-96 hours.

The ion to be ion-exchanged in the step (2) is Cu²⁺、Al³⁺、Fe³⁺、Zr⁴⁺、Sn⁴⁺One kind of (1).

The ion exchange time in the step (2) is 12-24 h.

The synthesized material is applied to the reaction of synthesizing isopulegol from citronellal, and the method comprises the following steps: adding the polyion liquid functionalized MOFs material into a solvent, stirring at room temperature, and reacting with citronellal for 1-2 h.

The invention has the beneficial effects that:

the invention provides a method for synthesizing polyion liquid functionalized MOFs materials. The polyion liquid functionalized MOFs material prepared by the invention can reach a yield of more than 90% by stirring for 1-2 hours at room temperature in the reaction of synthesizing isopulegol from citronellal, and has excellent catalytic performance.

Drawings

FIG. 1 is an XRD pattern for UiO and UiO-PIL;

FIG. 2 is an infrared spectrum of UiO and UiO-PIL;

FIG. 3 is a scanning electron micrograph of UiO and UiO-PIL, wherein (a) UiO and (b) UiO-PIL;

FIG. 4 is a graph of pore size distribution for UiO and UiO-PIL.

Detailed description of the invention

The invention is further illustrated by the following specific examples. The scope of the invention is not limited to the following examples.

Example 1

(1) Preparation of UiO materials

0.6mmol of imidazole-4, 5-dicarboxylic acid, 1.2mmol of terephthalic acid and 1.2mmol of zirconium chloride are uniformly dispersed in 42mL of DMF, then 3mL of glacial acetic acid is added and ultrasonic treatment is carried out, and then the mixture is poured into a 100 mL of polytetrafluoroethylene-lined hydrothermal synthesis kettle and crystallized for 24 hours at the temperature of 130 ℃. Cooling to room temperature, performing centrifugal separation, washing twice with DMF and five times with methanol respectively, and drying to obtain solid powder which is the UiO material.

(2) Preparation of UiO-prepIL material

0.12 mmol of UiO material is dispersed in ethanol, 0.06mmol of epichlorohydrin is added, and polymerization is carried out for 72h at 80 ℃. After the temperature is reduced to room temperature, centrifugal separation is carried out, the mixture is washed by ethanol for five times, and solid powder obtained after drying is UiO-prepIL.

(3) Preparation of UiO-PIL material

0.06mmol of UiO-prepIL was dispersed in ethanol, 0.06mmol of zirconium chloride was added and the exchange was carried out at 40 ℃ for 12 h. And after the reaction is finished, performing centrifugal separation, respectively washing the reaction product for three times by using ethanol and ethyl acetate, and drying to obtain solid powder, namely the UiO-PIL material.

FIG. 1 is an XRD pattern of the composite material prepared in this example, wherein UiO-PIL (10), UiO-PIL (20) and UiO-PIL (30) correspond to UiO-PIL materials having the ligands terephthalic acid and imidazole 4, 5-imidazoledicarboxylic acid in the ratios of 2:1, 1:1 and 1:5, respectively. As can be seen in an XRD (X-ray diffraction) pattern of the UiO-PIL material, the crystal form of the material is not greatly influenced by the functionalization of the polyion liquid. Diffraction peaks appear in the UiO-PIL material at 7.36 degrees, 8.48 degrees, 12.04 degrees, 14.15 degrees, 17.08 degrees, 22.25 degrees, 25.68 degrees and 33.12 degrees, and the diffraction peaks also correspond to the UiO-66, which indicates that the MOFs material belongs to the UiO-66.

FIG. 2 is an infrared spectrum of the composite material prepared in this example. As can be seen from FIG. 2, UiO-PIL is 1560cm in comparison to UiO^-1Has a characteristic absorption peak of C = N at 1440 cm^-1Is at occurrence of-CH₂Characteristic absorption peak of 1250 cm^-1The characteristic absorption peak of C-N appears, which indicates that the preparation of UiO-PIL is successful.

FIG. 3 is a scanning electron microscope image of the composite material prepared in this example. As can be seen from FIG. 3, both UiO and UiO-PIL have a sheet structure and have a larger difference from the octahedral crystal structure of UiO-66, which is presumed that the appearance of the UiO-66 material is changed because the addition of the carboxyl imidazole generates a competitive action with the carboxylic acid ligand.

FIG. 4 is a graph showing the pore size distribution of the composite material produced in this example. It can be seen from fig. 4 that the UiO material contains both micropores and mesopores. While the introduction of polyionic liquids only blocks part of the microporous fraction, but does not significantly affect the mesoporous fraction with the main catalytic properties.

The application comprises the following steps: 0.05g of the synthesized material was dispersed in 3ml of an ethanol solution, and 0.5g of citronellal was added thereto to react at 25 ℃ for 2 hours. The isopulegol yield was determined to be 91.23% under the above reaction conditions.

Example 2

The application comprises the following steps: 0.05g of the synthetic material of example 1 was dispersed in 3ml of an ethanol solution, and 0.5g of citronellal was added thereto to react at 30 ℃ for 2 hours. The yield of isopulegol was determined to be 92.67% under the above reaction conditions.

Example 3

(1) Preparation of UiO materials

0.6mmol of imidazole-4, 5-dicarboxylic acid, 1.2mmol of terephthalic acid and 1.2mmol of zirconium chloride are uniformly dispersed in 42mL of DMF, then 3mL of glacial acetic acid is added and ultrasonic treatment is carried out, and then the mixture is poured into a 100 mL of polytetrafluoroethylene-lined hydrothermal synthesis kettle and crystallized for 24 hours at the temperature of 130 ℃. Cooling to room temperature, performing centrifugal separation, washing twice with DMF and five times with methanol respectively, and drying to obtain solid powder which is the UiO material.

(2) Preparation of UiO-prepIL material

0.12 mmol of UiO material is dispersed in ethanol, 0.06mmol of epichlorohydrin is added, and polymerization is carried out for 72h at 80 ℃. After the temperature is reduced to room temperature, centrifugal separation is carried out, the mixture is washed by ethanol for five times, and solid powder obtained after drying is UiO-prepIL.

(3) Preparation of UiO-PIL material

0.06mmol of UiO-prepIL was dispersed in ethanol, 0.06mmol of ferric chloride was added, and the mixture was exchanged at 40 ℃ for 12 hours. And after the reaction is finished, carrying out centrifugal separation, respectively washing the reaction product for three times by using ethanol and ethyl acetate, and drying the reaction product to obtain solid powder, namely the UiO-PIL (10) material.

The application comprises the following steps: 0.05g of the synthesized material was dispersed in 3ml of an ethanol solution, and 0.5g of citronellal was added thereto to react at 25 ℃ for 2 hours. The isopulegol yield was determined to be 86.43% under the above reaction conditions.

Example 4

(1) Preparation of UiO materials

0.9mmol of imidazole-4, 5-dicarboxylic acid, 0.9mmol of terephthalic acid and 1.2mmol of zirconium chloride are uniformly dispersed in 42mL of DMF, then 3mL of glacial acetic acid is added and ultrasonic treatment is carried out, and then the mixture is poured into a 100 mL of polytetrafluoroethylene-lined hydrothermal synthesis kettle and crystallized for 24 hours at the temperature of 130 ℃. Cooling to room temperature, performing centrifugal separation, washing twice with DMF and five times with methanol respectively, and drying to obtain solid powder which is the UiO material.

(2) Preparation of UiO-prepIL material

0.12 mmol of UiO material is dispersed in ethanol, 0.06mmol of epichlorohydrin is added, and polymerization is carried out for 72h at 80 ℃. After the temperature is reduced to room temperature, centrifugal separation is carried out, the mixture is washed by ethanol for five times, and solid powder obtained after drying is UiO-prepIL.

(3) Preparation of UiO-PIL material

0.06mmol of UiO-prepIL was dispersed in ethanol, 0.06mmol of zirconium chloride was added and the exchange was carried out at 40 ℃ for 12 h. And after the reaction is finished, carrying out centrifugal separation, respectively washing the reaction product for three times by using ethanol and ethyl acetate, and drying the reaction product to obtain solid powder, namely the UiO-PIL (30) material.

The application comprises the following steps: 0.05g of the synthesized material was dispersed in 3ml of an ethanol solution, and 0.5g of citronellal was added thereto to react at 25 ℃ for 2 hours. The isopulegol yield was determined to be 88.26% under the above reaction conditions.

Example 5

(1) Preparation of UiO materials

1.2mmol of imidazole-4, 5-dicarboxylic acid, 0.6mmol of terephthalic acid and 1.2mmol of zirconium chloride are uniformly dispersed in 42mL of DMF, then 3mL of glacial acetic acid is added and ultrasonic treatment is carried out, and then the mixture is poured into a 100 mL of polytetrafluoroethylene-lined hydrothermal synthesis kettle and crystallized for 24 hours at the temperature of 130 ℃. Cooling to room temperature, performing centrifugal separation, washing twice with DMF and five times with methanol respectively, and drying to obtain solid powder which is the UiO material.

(2) Preparation of UiO-prepIL material

0.12 mmol of UiO material is dispersed in ethanol, 0.06mmol of epichlorohydrin is added, and polymerization is carried out for 72h at 80 ℃. After the temperature is reduced to room temperature, centrifugal separation is carried out, the mixture is washed by ethanol for five times, and solid powder obtained after drying is UiO-prepIL.

(3) Preparation of UiO-PIL material

0.06mmol of UiO-prepIL was dispersed in ethanol, 0.06mmol of ferric chloride was added, and the mixture was exchanged at 40 ℃ for 12 hours. And after the reaction is finished, carrying out centrifugal separation, respectively washing the reaction product for three times by using ethanol and ethyl acetate, and drying the reaction product to obtain solid powder, namely the UiO-PIL (50) material.

The application comprises the following steps: 0.05g of the synthesized material was dispersed in 3ml of an ethanol solution, and 0.5g of citronellal was added thereto to react at 25 ℃ for 2 hours. The isopulegol yield was determined to be 84.90% under the above reaction conditions.

The above description is only a preferred embodiment of the present invention, and all equivalent changes and modifications made in accordance with the claims of the present invention should be covered by the present invention.