CN110041533A - A kind of method that ionic liquid ligand displacement method prepares functional metal organic framework material - Google Patents

Abstract

The invention provides a method for preparing a functionalized metal organic framework material by an ionic liquid ligand replacement method, which belongs to the technical field of functional materials. The invention prepares and modulates the metal-organic framework material containing specific functional groups by utilizing the substitution effect of the carboxyl group functionalized ionic liquid on the carboxyl group ligand of the organic framework material. In addition to retaining the framework structure of the original metal-organic framework material, the composite material can also achieve the purpose of directional functionalization of the target metal-organic framework material by adjusting the anion species of the carboxyl-functionalized ionic liquid. The functionalized metal organic framework material prepared by the invention can be used as a catalyst for esterification and transesterification reactions such as oleic acid esterification and vegetable oil transesterification to prepare biodiesel, and has good activity and stability.

Description

An ionic liquid ligand replacement method for the preparation of functionalized metal-organic frameworks method

technical field

The invention relates to the technical field of functional material synthesis, in particular to a method for preparing a functional metal-organic framework material by performing ligand replacement with an ionic liquid containing a carboxyl group for a metal-organic framework material containing carboxyl ligands and its application.

Background technique

Ionic liquids refer to molten salts composed entirely of anions and cations, which are generally liquid at room temperature, so they are also called room temperature ionic liquids. Since room temperature ionic liquids contain equal numbers of cations and anions, they are electrically neutral as a whole. The cations of ionic liquids are organic cations, which are relatively large in volume, while the anions are inorganic anions, which are relatively small in volume. This volume difference and symmetry mismatch lead to a decrease in the electrostatic potential between the anions and cations, resulting in a low melting point. properties, so it is liquid at room temperature. Common cation types are mainly quaternary ammonium salts, quaternary phosphorus salts, alkyl substituted imidazoles and pyridines, etc., while the main types of anions are AlCl ₄ ^-1 , BF ₄ ^-1 , PF ₆ ^-1 , HSO ₄ ^-1 , CF ₃ SO ₃ ^-1 and the like. The most important thing is that these anions and cations in ionic liquids can be designed and modulated to prepare ionic liquids with different functionalities, which are considered to be one of the most valuable materials in the 21st century. However, as a catalyst, ionic liquids often form a homogeneous system or a liquid-liquid two-phase system with the reaction system, which brings many difficulties to the recovery, separation and reuse of the catalyst. This makes the study of ionic liquid immobilization become a research hotspot nowadays. At present, the commonly used carriers for immobilized ionic liquids are: silica gel (Gadenne B. Chemical Communications, 2004, 1768-1769.), molecular sieves (Udayakumar S. Applied Catalysis A: General, 2009, 368 (1-2), 97- 104.), activated carbon (Virtanen P. Catalysis Today, 2009, 147(S), S144-S148) and organic polymer materials (DongWook Kim. Angewandte Chemie International Edition, 2004, 43, 483-485.), etc., but these Materials generally have problems such as high price, poor hydrothermal stability, small specific surface area, and serious loss of active components.

Metal-organic framework material is a framework material composed of metal or metal cluster and organic ligands containing carboxyl groups and other organic ligands through coordination bonds. It has a regular grid structure and ultra-high porosity. , specific surface area, regular pore structure, adjustable structural properties, low crystalline density and various types, so it is considered as an ideal porous material. Combining ionic liquids with metal-organic frameworks to prepare new functional materials is considered to be a research direction with good application prospects. However, the existing methods for functionalizing metal-organic frameworks with ionic liquids still have certain limitations and shortcomings. For example, the commonly used methods of immobilizing ionic liquids on metal-organic frameworks by impregnation method and capillary method rely solely on physical adsorption, so the prepared functional composite materials have poor stability, and the active sites are easily lost during use. The problem. The present invention provides a method for preparing functionalized metal-organic framework materials by an ionic liquid ligand replacement method: the carboxyl-functionalized ionic liquid is used as a class of ligands, and the original ligands in the metal-organic framework materials are replaced by a ligand replacement method to realize functionalization. The coordination combination of ionic liquid and metal-organic framework material, the prepared ionic liquid-supported metal-organic framework material has the characteristics of large specific surface area, high catalytic activity and good stability.

SUMMARY OF THE INVENTION

In order to overcome the shortcomings and deficiencies of the prior art, the main purpose of the present invention is to provide a metal-organic framework material containing a carboxyl group ligand through ligand replacement with an ionic liquid containing a carboxyl group to prepare a functionalized metal-organic framework material. method and its application.

In order to achieve the above purpose of the invention, the technical scheme adopted in the present invention is to use the metal organic framework material containing carboxyl ligands as the parent body, and the carboxyl functionalized ionic liquid as the quasi-ligand, and perform ligand replacement in a hydrothermal synthesis kettle. The specific synthesis steps are:

(1) Disperse the metal-organic framework material containing carboxyl ligands and carboxyl-functionalized ionic liquid in a polar solvent containing 0.6 wt% organic base in proportion, and then transfer the resulting mixed solution to a hydrothermal synthesis kettle, and The reaction is carried out at high temperature, and the obtained powder is washed with N`N dimethylformamide and ethanol to obtain a metal-organic framework material modified by carboxyl-functionalized ionic liquid;

(2) The metal-organic framework material modified by the carboxyl-functionalized ionic liquid obtained in step (1) is placed in an ethanol solution containing 0.05 mol.L ^-1 sulfuric acid or an acetonitrile solution containing 0.2 wt % ferric chloride for further modification. Ethanol or acetonitrile washing can obtain functionalized metal organic framework materials containing specific groups.

The metal organic framework material containing carboxyl ligands includes one of UiO-66, MIL-101 or HKUST-1.

Described carboxyl functionalized ionic liquid includes 1-methyl-3 carboxyethyl imidazolium chloride, 1-methyl-3 carboxypropyl imidazolium chloride, 1-methyl-3 carboxybutyl imidazolium chloride, 1- Methyl-3 carboxyethyl imidazolium bromide, 1-methyl-3 carboxypropyl imidazolium bromide, 1-methyl-3 carboxybutyl imidazolium bromide, 1-methyl-3 carboxyethyl imidazole hydrogen sulfate , one of 1-methyl-3 carboxypropyl imidazole hydrogen sulfate and 1-methyl-3 carboxybutyl imidazole hydrogen sulfate.

The added mass ratio of the metal-organic framework material and the carboxyl-functionalized ionic liquid described in step (1) is 1:1-10.

The organic base described in step (1) includes one of diethylamine, triethylamine, dimethylamine or methylamine.

The polar solvent described in step (1) includes one of water, DMF or ethanol.

In step (1), the content of the metal-organic framework material and the carboxyl-functionalized ionic liquid in the polar solvent is 2.0-3.0 wt %.

The high-temperature reaction temperature in step (1) is 80-140° C., and the reaction time is 24-56 h.

Further, the catalyst prepared by the above method is used in the esterification reaction.

The beneficial effects of the present invention are:

The invention prepares and modulates the metal-organic framework material containing specific functional groups by utilizing the carboxy-functionalized ionic liquid to replace the carboxyl group ligand of the metal-organic framework material. In addition to retaining the framework structure of the original metal-organic framework material, the composite material can also achieve the purpose of directional functionalization of the metal-organic framework material by adjusting the anion species of the carboxyl-functionalized ionic liquid. In addition, in addition to good physical stability and chemical stability, the composite material prepared by this method also has the advantages of easy modification of specific functional groups, controllable adjustment of acid strength, easy recovery and separation of materials, environmental friendliness, and broad prospects for industrial application, etc. Features. The functionalized metal-organic framework material prepared by the invention has achieved good results in the synthesis reaction of oleic acid esterification and vegetable oil transesterification to prepare biodiesel as a catalyst.

Description of drawings

Fig. 1 is a schematic diagram of the preparation principle of the catalytic material of the present invention.

FIG. 2 is an X-ray diffraction pattern of the catalytic material prepared in Example 1. FIG.

3 is a field emission scanning electron microscope image of the catalytic material prepared in Example 1.

Specific implementation method

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

Example 1

(1) Preparation of 1-methyl-3-carboxyethylimidazolium chloride

Accurately weigh 0.01 mol of methyl bromopropionate into a 25 mL round-bottomed flask, add 0.01 mol of 1-methylimidazole (molar ratio 1:1) dropwise under magnetic stirring, and reflux at 80 °C for 48 h , a pale yellow viscous substance was obtained, cooled to room temperature, washed with ether (10 mL×3), and dried in vacuo. Under magnetic stirring, the obtained product was added dropwise with 0.01 mol HCl (40% v/v aqueous solution) Acidified, refluxed at 80 °C for 30 min, cooled to room temperature, washed with ether (10 mL×3), and dried in vacuo.

(2) Preparation of UiO-66

0.0848 g of ZrCl ₄ , 0.0603 g of terephthalic acid and 0.9045 g of benzoic acid were dissolved in 42 mL of DMF solvent, and sonicated for 30 min. Then, the reaction solution was poured into a hydrothermal synthesis kettle lined with PTFE, kept at a constant temperature of 120 °C for 24 h, cooled to room temperature naturally, centrifuged to remove the solvent, washed three times with DMF and methanol, and dried at 80 °C The powder sample UiO-66 was obtained overnight.

(3) Preparation of 1-methyl-3-carboxyethylimidazole hydrogen sulfate functionalized metal organic framework materials

Accurately weigh 1.0 g of 1-methyl-3-carboxyethylimidazolium chloride and 0.3 g of triethylamine and disperse them in 50 mL of DMF, then add 0.2 g of UiO-66 powder and ultrasonically disperse for 30 min to make the free 1- Methyl-3 carboxyethyl imidazolium chloride fully entered the cavity of UiO-66, and finally the turbid liquid was poured into a 50 mL polytetrafluoroethylene-lined hydrothermal synthesis kettle, and crystallized at 120 °C for 48 h , centrifuged, washed twice with N`N dimethylformamide (DMF) and ethanol, respectively, to obtain carboxyl ionic liquid-modified metal-organic framework composites; Put it in a 100 mL round-bottomed flask, add 50 mL of 0.05 mol.L ^-1 sulfuric acid ethanol solution, stir at 70 °C for 2 h, and wash with ethanol to obtain 1-methyl-3 carboxyethyl imidazole hydrogen sulfate. metal organic framework materials.

(4) The above catalyst is used for esterification reaction

1.5 g of the 1-methyl-3-carboxyethylimidazole hydrogen sulfate-functionalized metal-organic framework material catalyst prepared in step (3), 28.2 g of oleic acid and 32 g of methanol were added to a 100 mL round-bottomed flask, and the Under the condition of 80 ℃, the yield of methyl oleate was 92.8% after the reaction for 6 h. After the catalyst was centrifuged and dried, the yield decreased by less than 2.2% after repeated use under the same experimental conditions.

Example 2

(1) Preparation of 1-methyl-3-carboxyethylimidazolium chloride: the same as in Example 1.

(2) Preparation of MIL-101

Mix 2.0 g of chromium nitrate nonahydrate, 0.83 g of terephthalic acid and 20 mL of deionized water, and dissolve by ultrasonic for 30 min. Then, the mixed suspension was poured into a 50 mL PTFE-lined hydrothermal synthesis kettle, kept at a constant temperature of 220 °C for 18 h, cooled to room temperature, centrifuged to remove the solvent, and washed with DMF and methanol Three times, dried at 80°C overnight to obtain powder sample MIL-101.

(3) Preparation of 1-methyl-3-carboxyethylimidazolium ferric chloride functionalized metal organic framework materials

Accurately weigh 1.0 g of 1-methyl-3-carboxyethylimidazolium chloride and 0.3 g of triethylamine and disperse it in 50 mL of DMF, then add 0.2 g of MIL-101 powder and ultrasonically disperse it for 30 min to make the free 1- Methyl-3 carboxyethyl imidazolium chloride fully entered the cavity of MIL-101, and finally the turbid liquid was poured into a 50 mL polytetrafluoroethylene-lined hydrothermal synthesis kettle, and crystallized at 120 ℃ for 48 h , centrifuged, washed twice with DMF and ethanol, respectively, to obtain carboxyl ionic liquid-modified metal-organic framework composites; the obtained carboxyl ionic liquid-modified metal-organic framework composites and 0.1 g of anhydrous ferric chloride were placed in 100 mL 50 mL of acetonitrile was added to the round-bottomed flask, stirred at 83 °C for 24 h, and washed with acetonitrile to obtain a metal-organic framework material functionalized with 1-methyl-3-carboxyethylimidazolium ferric chloride.

(4) The above catalysts are used for transesterification

0.8 g of the above-mentioned 1-methyl-3-carboxyethylimidazolium ferric chloride functionalized metal-organic framework material catalyst, 8.71 g of palm oil and 9.6 g of methanol were added to the autoclave, under the conditions of 125 °C and 1 MPa. , reacted for 6 hours, the yield of biodiesel was 85.6%, and after the catalyst was centrifuged, washed and dried, the repeated use yield decreased by less than 1.0%

Example 3

(1) Preparation of 1-methyl-3-carboxypropylimidazolium chloride.

Accurately weigh 0.01 mol of methyl bromobutyrate into a 25 mL round-bottomed flask, add 0.01 mol of 1-methylimidazole dropwise (molar ratio 1:1) under magnetic stirring, and reflux at 80 °C for 48 h , a pale yellow viscous substance was obtained, cooled to room temperature, washed with diethyl ether (10 mL×3), and dried in vacuo. The obtained product was acidified by dropwise addition of 0.01 mol HCl (40% aqueous solution) under the condition of magnetic stirring, Reflux at 80 °C for 30 min, cooled to room temperature, washed with ether (10 mL×3), and dried in vacuo.

(2) Preparation of MIL-101: Same as Example 2.

(3) Preparation of 1-methyl-3-carboxypropylimidazolium ferric chloride functionalized metal organic framework materials

Accurately weigh 1.1 g of 1-methyl-3-carboxypropylimidazolium chloride and 0.3 g of triethylamine and disperse them in 50 mL of DMF, then add 0.2 g of MIL-101 powder and ultrasonically disperse for 30 min to make the free 1- Methyl-3 carboxypropyl imidazolium chloride fully entered the cavity of MIL-101, and finally the turbid liquid was poured into a 50 mL polytetrafluoroethylene-lined hydrothermal synthesis kettle, and crystallized at 120 ℃ for 48 h , centrifuged, washed twice with DMF and ethanol, respectively, to obtain carboxyl ionic liquid-modified metal-organic framework composites; the obtained carboxyl ionic liquid-modified metal-organic framework composites and 0.1 g of anhydrous ferric chloride were placed in 100 mL 50 mL of acetonitrile was added to the round-bottomed flask, stirred at 83 °C for 24 h, and washed with acetonitrile to obtain a metal-organic framework material functionalized with 1-methyl-3-carboxypropylimidazolium ferric chloride salt.

(4) The above catalysts are used for oleic acid esterification and transesterification reactions

1.5 g of the above-mentioned 1-methyl-3-carboxypropylimidazole hydrogen sulfate functionalized metal-organic framework material catalyst, 28.2 g of oleic acid and 32 g of methanol were added to a 100 mL round-bottom flask, and the reaction was carried out at 80 °C. After 6 h, the yield of methyl oleate was 93.2%.

0.8 g of the above-mentioned 1-methyl-3-carboxypropylimidazolium ferric chloride functionalized metal-organic framework material catalyst, 8.71 g of palm oil and 9.6 g of methanol were added to the autoclave, and the reaction was carried out under the conditions of 125 °C and 1 MPa. , the reaction was 6 hours, and the yield of biodiesel was 86.3%.

The above descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope of the present invention.

Claims (10)

1. an ionic liquid ligand replacement method prepares the method for functionalized metal organic framework material, it is characterized in that, with the metal organic framework material containing carboxyl ligand as parent body, carboxyl functionalized ionic liquid is class ligand, in hydrothermal Ligand replacement was carried out in the synthesis kettle. 2. the method for preparing functionalized metal organic framework material by a kind of ionic liquid ligand replacement method according to claim 1, is characterized in that, concrete synthesis step is: (1) Disperse the metal-organic framework material containing carboxyl ligands and carboxyl-functionalized ionic liquid in a polar solvent containing 0.6 wt% organic base in proportion, and then transfer the resulting mixed solution to a hydrothermal synthesis kettle, and The reaction is carried out at high temperature, and the obtained powder is washed with N`N dimethylformamide and ethanol to obtain a metal-organic framework material modified by carboxyl-functionalized ionic liquid; (2) The metal-organic framework material modified by the carboxyl-functionalized ionic liquid obtained in step (1) is placed in an ethanol solution containing 0.05 mol.L ^-1 sulfuric acid or an acetonitrile solution containing 0.2 wt % ferric chloride for further modification. Ethanol or acetonitrile washing can obtain functionalized metal organic framework materials containing specific groups. 3. the method for preparing functionalized metal organic framework material by ionic liquid ligand replacement method according to any one of claim 1 or 2, it is characterized in that: described metal organic framework material containing carboxyl ligand comprises UiO-66, One of MIL-101 or HKUST-1. 4. the method for preparing functionalized metal organic framework material by ionic liquid ligand replacement method according to any one of claim 1 or 2, it is characterized in that: described carboxyl functionalized ionic liquid comprises 1-methyl-3 carboxyethyl Imidazolium chloride, 1-methyl-3 carboxypropyl imidazolium chloride, 1-methyl-3 carboxybutyl imidazolium chloride, 1-methyl-3 carboxyethyl imidazolium bromide, 1-methyl-3 Carboxypropylimidazole bromide, 1-methyl-3-carboxybutylimidazolium bromide, 1-methyl-3-carboxyethylimidazole hydrogen sulfate, 1-methyl-3-carboxypropylimidazole hydrogen sulfate, 1- A kind of methyl-3 carboxybutyl imidazole hydrogen sulfate. 5. The method for preparing functionalized metal-organic framework material by ionic liquid ligand replacement method according to claim 2, characterized in that: the added mass ratio of the metal-organic framework material described in step (1) and the carboxyl-functionalized ionic liquid 1:1~10. 6. The method for preparing functionalized metal-organic framework materials by ionic liquid ligand replacement method according to claim 2, wherein the organic base in step (1) comprises diethylamine, triethylamine, dimethylamine or one of methylamines. 7 . The method for preparing functionalized metal organic framework materials by ionic liquid ligand replacement method according to claim 2 , wherein the polar solvent in step (1) comprises one of water, DMF or ethanol. 8 . 8 . The method for preparing functionalized metal-organic framework materials by ionic liquid ligand replacement method according to claim 1 , wherein the metal-organic framework material and the carboxyl-functionalized ionic liquid in step (1) are in a polar solvent The content is 2.0-3.0wt%. 9 . The method for preparing functionalized metal organic framework materials by ionic liquid ligand replacement method according to claim 1 , wherein the high temperature reaction temperature of step (1) is 80～140° C., and the reaction time is 24～140° C. 10 . 56 h. 10. the application of the catalyst prepared by the method as claimed in claim 1 in esterification.