阅读说明：本技术 一种金属-有机骨架复合材料il@zif-67的制备方法 (Preparation method of metal-organic framework composite material IL @ ZIF-67 ) 是由 仲崇立 赵新 孙玉绣 乔志华 郭翔宇 牛瑞 于 2021-08-19 设计创作，主要内容包括：本发明公开了一种金属-有机骨架复合材料IL@ZIF-67的制备方法。即采用机械化学法,将氢氧化钴、2-甲基咪唑均匀混合并研磨30min,研磨过程中滴加一定量的离子液体(IL)的甲醇溶液,得到淡紫色的氢氧化钴、2-甲基咪唑和离子液体的混合物,将混合物在密闭条件下进行60℃加热1h,然后用甲醇洗涤离心三次、60℃真空干燥得到离子液体封装在金属-有机骨架空腔中的复合材料IL@ZIF-67。该制备方法具有制备时间短,产率高,可大规模制备的特点。IL@ZIF-67在气体分离领域尤其在烯烃/烷烃等分离领域具有良好的应用前景。(The invention discloses a preparation method of a metal-organic framework composite material IL @ ZIF-67. Uniformly mixing cobalt hydroxide and 2-methylimidazole by adopting a mechanochemical method, grinding for 30min, dropwise adding a certain amount of methanol solution of Ionic Liquid (IL) in the grinding process to obtain a mixture of light purple cobalt hydroxide, 2-methylimidazole and the ionic liquid, heating the mixture for 1h at 60 ℃ under a closed condition, washing and centrifuging the mixture for three times by using methanol, and drying the mixture in vacuum at 60 ℃ to obtain the composite material IL @ ZIF-67 with the ionic liquid encapsulated in a metal-organic framework cavity. The preparation method has the characteristics of short preparation time, high yield and large-scale preparation. The IL @ ZIF-67 has good application prospect in the field of gas separation, particularly in the field of olefin/alkane separation and the like.)

1. A preparation method of a metal-organic framework composite material IL @ ZIF-67 is characterized by comprising the following steps: the method specifically comprises the following steps:

(1) preparing a methanol solution of ionic liquid with the concentration of 1 mol/L;

(2) uniformly mixing cobalt hydroxide and 2-methylimidazole, grinding for 30min, and dripping a methanol solution of ionic liquid with a certain volume in the step (1) in the grinding process to obtain a mixture of the light purple cobalt hydroxide, the 2-methylimidazole and the ionic liquid;

(3) putting the mixture of the light purple cobalt hydroxide, the 2-methylimidazole and the ionic liquid obtained in the step (2) into a constant-temperature oven at the temperature of 60 ℃ for heating for 1h to obtain a crude product of a purple metal-organic framework composite material IL @ ZIF-67;

(4) washing and centrifuging the crude product of the metal-organic framework composite material IL @ ZIF-67 obtained in the step (3) for three times by using methanol;

(5) and then drying the composite material in a vacuum oven at 60 ℃ for 10h to finally obtain the metal-organic framework composite material IL @ ZIF-67.

2. The preparation method of the metal-organic framework composite material IL @ ZIF-67 as claimed in claim 1, wherein: in the step (1), the ionic liquid is one of 1-ethyl-3-methylimidazole tetrafluoroborate, 1-ethyl-3-methylimidazole hexafluorophosphate and 1-ethyl-3-methylimidazole bistrifluoromethylsulfonyl imide.

3. The preparation method of the metal-organic framework composite material IL @ ZIF-67 as claimed in claim 1, wherein: the dosage of the cobalt hydroxide and the 2-methylimidazole in the step (2) is as follows according to the molar ratio of the cobalt hydroxide: 2-methylimidazole is 1: 4; the volume of the methanol solution of the ionic liquid is 0mL-2.5 mL.

4. The preparation method of the metal-organic framework composite material IL @ ZIF-67 as claimed in claim 2, wherein:

the ionic liquid is 1-ethyl-3-methylimidazole tetrafluoroborate, and the dosage of the ionic liquid is 0mL, 1.0mL, 1.5mL, 2.0mL and 2.5mL respectively;

the ionic liquid is 1-ethyl-3-methylimidazole hexafluorophosphate, and the dosage of the ionic liquid is 0mL, 1.5mL and 2.5mL respectively;

the ionic liquid is 1-ethyl-3-methylimidazole bistrifluoromethanesulfonylimide salt, and the dosage of the ionic liquid is 0mL, 1.5mL and 2.5mL respectively.

Technical Field

The invention discloses a preparation method of a metal-organic framework composite material, and particularly relates to a preparation method of a composite material (IL @ ZIF-67) with ionic liquid encapsulated in a metal-organic framework cavity.

Background

The metal-organic framework (MOF) is a novel porous material, and a coordination polymer with a periodic network structure, which is assembled by inorganic metal ions and organic ligands, has the characteristics of high porosity, high specific surface area, adjustable pore size and the like, and has wide application prospects in the aspects of gas separation, electrochemistry, catalysis, medicine and the like.

Ionic Liquids (IL) are salts composed of asymmetric organic cations paired with inorganic or organic anions, and are typically liquids at room temperature. They have tunable physical and chemical properties, such as high electrochemical and thermal stability, non-flammability, negligible volatility and high gas solubility, and are now widely used in catalysis, extraction and gas separation.

The MOF material with high porosity and adjustable structure is combined with other functional materials to construct a composite material, so that the composite material can exert excellent characteristics exceeding those of raw materials, and the MOF composite material has a synergistic effect so as to be widely applied to the fields of gas adsorption and storage, heterogeneous catalysis, chemical sensing and the like.

The IL is packaged into a cavity (IL @ MOF) of the MOF, the efficient combination of the ionic liquid and the MOF material is realized while the pore size of the MOF is precisely regulated, the novel functionalized composite porous material is prepared, and the synergistic effect of the IL and the MOF material is favorable for fully playing the advantages of the two materials. At present, the main method for synthesizing the IL @ MOF composite material is an impregnation method, and the method consumes waste time and has low synthesis efficiency, so that a large amount of ionic liquid is lost, the waste of raw materials is caused, and the large-scale preparation is difficult to realize. IL @ ZIF-67 is an ideal material for separating olefin/alkane in MOF composite materials, and can be used as a gas separation adsorbent and a filler of a gas separation membrane.

The invention adopts a mechanochemical method to prepare the IL @ ZIF-67 composite material (IL is 1-ethyl-3-methylimidazolium tetrafluoroborate, or 1-ethyl-3-methylimidazolium hexafluorophosphate, or 1-ethyl-3-methylimidazolium bistrifluoromethylsulfonyl imide), and the mechanochemical method is expected to become a main method for preparing the IL @ MOF composite material as a synthetic method which is green, economical, efficient and easy to produce in batches.

Disclosure of Invention

The invention aims to solve the technical problems of long preparation time, low yield, difficulty in large-scale synthesis and the like of the impregnation method for synthesizing the metal-organic framework composite material IL @ ZIF-67, and provides a preparation method of the metal-organic framework composite material IL @ ZIF-67, which is rapid and can be synthesized in a large scale.

The invention adopts the following technical scheme: a preparation method of a metal-organic framework composite material IL @ ZIF-67 specifically comprises the following steps:

(1) preparing a methanol solution of ionic liquid with the concentration of 1 mol/L;

(2) uniformly mixing cobalt hydroxide and 2-methylimidazole, grinding for 30min, and dripping a methanol solution of ionic liquid with a certain volume in the step (1) in the grinding process to obtain a mixture of the light purple cobalt hydroxide, the 2-methylimidazole and the ionic liquid;

(3) putting the mixture of the light purple cobalt hydroxide, the 2-methylimidazole and the ionic liquid obtained in the step (2) into a constant-temperature oven at 60 ℃ for heating for 1h, wherein the aim is to accelerate the coordination of metal cobalt and a ligand to further generate a ZIF-67 crystal and accelerate the ionic liquid to enter holes of the ZIF-67, so as to obtain a crude product of the purple metal-organic framework composite material IL @ ZIF-67;

(4) washing and centrifuging the crude product of the metal-organic framework composite material IL @ ZIF-67 obtained in the step (3) for three times by using methanol, wherein the purpose is to wash off redundant 2-methylimidazole;

(5) and then drying the substrate in a vacuum oven at 60 ℃ for 10 hours, wherein the aim is to remove methanol, and finally obtaining the metal-organic framework composite material IL @ ZIF-67.

Further, the ionic liquid is 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF)₄) 1-Ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF)₆) 1-Ethyl-3-methylimidazolium bistrifluoromethylsulfonyl imide salt (EMIMTf)₂N) is selected;

further, the dosage of the cobalt hydroxide and the 2-methylimidazole is calculated according to the molar ratio of the cobalt hydroxide: 2-methylimidazole is 1: 4; the volume of the methanol solution of the ionic liquid is 0mL-2.5 mL;

further, the ionic liquid is 1-ethyl-3-methylimidazole tetrafluoroborate, and the dosage of the ionic liquid is 0mL, 1.0mL, 1.5mL, 2.0mL and 2.5mL respectively;

the ionic liquid is 1-ethyl-3-methylimidazole hexafluorophosphate, and the dosage of the ionic liquid is 0mL, 1.5mL and 2.5mL respectively;

further, the ionic liquid is 1-ethyl-3-methylimidazole bistrifluoromethanesulfonylimide salt, and the dosage of the ionic liquid is 0mL, 1.5mL and 2.5mL respectively.

The ionic liquid is not limited to the three types, and can also be ionic liquid of tetrafluoroborate, hexafluorophosphate and bistrifluoromethanesulfonimide.

By adopting the technical scheme, the whole preparation process adopts one-step in-situ synthesis, so compared with an impregnation method, the preparation method has the characteristics of short preparation time, high yield and large-scale synthesis. The IL @ ZIF-67 is synthesized by an impregnation method in two steps, namely, the ZIF-67 is synthesized firstly, at least 18 hours are needed, and the yield is particularly low; then IL @ ZIF-67 is synthesized, a large amount of volatile organic solvents such as acetone, trichloromethane and the like are adopted, the solvents have great harm to human bodies and the environment, and a large amount of time is also needed for subsequent washing, centrifugal drying and the like. The preparation method of the invention has short preparation time which is not more than 24 hours, and the solvent only adopts a small amount of methanol with relatively low toxicity. The yield of the IL @ ZIF-67 synthesized by the impregnation method is particularly low and less than 60%, the yield is limited, and the preparation method provided by the invention has the yield as high as 99.9%, and the yield can realize batch production. Therefore, the preparation method of the invention has the advantage of large-scale synthesis.

The invention has the advantages that: the preparation method has the characteristics of short preparation time, high yield and large-scale preparation. The IL @ ZIF-67 has good application prospect in the field of gas separation, particularly in the field of olefin/alkane separation and the like.

Drawings

Figure 1 is the XRD spectrum of example 1.

FIG. 2 is an IR spectrum of example 1.

FIG. 3 shows N in example 1₂Adsorption isotherm plot.

FIG. 4 is a SEM photograph of example 1.

Figure 5 is the XRD spectrum of example 2.

FIG. 6 is an IR spectrum of example 2.

FIG. 7 shows N in example 2₂Adsorption isotherm plot.

FIG. 8 is a SEM photograph of example 2.

Figure 9 is the XRD spectrum of example 3.

FIG. 10 is an IR spectrum of example 3.

FIG. 11 shows N in example 3₂Adsorption isotherm plot.

FIG. 12 is a SEM photograph of example 3.

Detailed Description

The technical solution of the present invention is further described below by referring to several specific embodiments and the accompanying drawings.

The invention is innovative in synthesizing IL @ ZIF-67 by a mechanochemical method, the heating temperature is controlled to be 60 ℃, the ionic liquid can be effectively accelerated to enter the holes of the ZIF-67, and the cobalt hydroxide and the 2-methylimidazole can completely react at 60 ℃, so that the yield of the IL @ ZIF-67 reaches 99.9%. This is a departure from other synthetic methods. IL @ ZIF-67 prepared by a mechanochemical method generates more metal vacant sites which are in the aspects of adsorption (gas adsorption, dye adsorption, iodine adsorption and boron adsorption), membrane separation (gas separation membrane and battery diaphragm) and catalysis (catalytic hydrogenation and photocatalytic reduction of CO₂) The aspects have shown great potential for application.

The model of the equipment used in the embodiments of the present invention and the information of the manufacturer are as follows:

a vacuum oven with the model of DHG-9053-A, Shanghai sperm macro implementation Equipment Co., Ltd; x-ray diffractometer (XRD) model D2 PHASER, manufactured by Bruker, Germany; a specific surface area and aperture analyzer, model 3H-2000PS2, manufactured by Betsard instruments science and technology (Beijing) Inc.; fourier Infrared Spectroscopy (FT-IR) model TENSOR II, produced by Bruker, Germany; scanning Electron Microscope (SEM) model Drop Shape Analyzer 100, produced by Bruker, Germany.

The raw material information used in the examples of the present invention is as follows: cobalt hydroxide, 99% specification, purchased from Schenss Biotechnology Ltd; 2-methylimidazole with the specification of 98% and purchased from the university of Aladdin Biotechnology, Inc.; methanol with the specification of analytical purity is purchased from chemical reagents of national drug group, Inc.; 1-Ethyl-3-methylimidazolium tetrafluoroborate (EMIMBF)₄) 1-ethyl-3-methylimidazolium hexafluorophosphate (EMIMPF)₆) 1-ethyl-3-methylimidazolium bistrifluoromethylsulfonyl imide salt (EMIMTf)₂N), the specifications are all 97%, and the products are all purchased from the Aladdin Biotechnology, Inc.

Example 1

Metal-organic framework composite material namely EMIMBF₄@ ZIF-67, prepared by a process comprising the steps of:

0.925g of cobalt hydroxide (10mmol) and 3.284g of 2-methylimidazole (40mmol) are placed in a mortar to be uniformly mixed and ground for 30min, and a certain volume of EMIMBF is dropwise added in the grinding process₄The mixture of light purple cobalt hydroxide, 2-methylimidazole and ionic liquid is obtained by the methanol solution, then the mixture is placed in a constant temperature oven for heating at the temperature of 60 ℃ for 1 hour, then methanol with the volume of 7-8 times of that of the mixture is used for washing and centrifuging for three times to obtain purple crystal precipitate, and finally the purple crystal precipitate is placed in a vacuum oven for drying at the temperature of 60 ℃ and under the pressure of-0.1 MPa to obtain the metal-organic framework composite material, namely EMIMBF₄@ ZIF-67, in 99.9% yield (yield ═ mass of product actually produced/mass of product theoretically produced).

Example 2

Metal-organic framework composite material EMIMPF₆@ ZIF-67, prepared by a process comprising the steps of:

0.925g of cobalt hydroxide (10mmol) and 3.284g of 2-methylimidazole (40mmol) were placed in a mortarMixing, grinding for 30min, and adding EMIMPF with a certain volume₆The mixture of light purple cobalt hydroxide, 2-methylimidazole and ionic liquid is obtained by the methanol solution, then the mixture is placed in a constant temperature oven for heating at the temperature of 60 ℃ for 1 hour, then methanol with the volume of 7-8 times of that of the mixture is used for washing and centrifuging for three times to obtain purple crystal precipitate, and finally the purple crystal precipitate is placed in a vacuum oven for drying at the temperature of 60 ℃ and under the pressure of-0.1 MPa to obtain the metal-organic framework composite material, namely EMIMPF₆@ ZIF-67, in 99.9% yield (yield ═ mass of product actually produced/mass of product theoretically produced).

Example 3

Metal-organic framework composite material EMIMTf₂N @ ZIF-67, prepared by a process comprising the steps of:

0.925g of cobalt hydroxide (10mmol) and 3.284g of 2-methylimidazole (40mmol) are placed in a mortar to be uniformly mixed and ground for 30min, and a certain volume of EMIMTf is dropwise added in the grinding process₂Obtaining a mixture of light purple cobalt hydroxide, 2-methylimidazole and ionic liquid by using a methanol solution of N, then placing the mixture in a constant-temperature oven to control the temperature to be 60 ℃ for 1 hour for heating, then washing and centrifuging the mixture for three times by using methanol with the volume being 7-8 times of that of the mixture to obtain purple crystal precipitate, finally placing the precipitate in a vacuum oven to control the temperature to be 60 ℃ and drying the precipitate under the pressure of-0.1 MPa to obtain the metal-organic framework composite material EMIMTf₂N @ ZIF-67 in 99.9% yield (yield-mass of actual product/mass of theoretical product).

The metal-organic framework composite materials obtained in the above examples 1 to 3 were subjected to X-ray diffractometry, that is, the following materials: EMIMBF₄@ZIF-67、EMIMPF₆@ZIF-67、EMIMTf₂XRD (X-ray diffraction) measurement is carried out on the N @ ZIF-67, and from figures 1, 5 and 9, ZIF-67 with different ionic liquid loading amounts is identical to the simulated spectrogram of the ZIF-67, and has characteristic peaks of the ZIF-67, which indicates that the ZIF-67 is successfully prepared.

The metal-organic framework composite material obtained in the above examples 1 to 3 was treated by a fourier infrared spectrometer: EMIMBF₄@ZIF-67、EMIMPF₆@ZIF-67、EMIMTf₂[email protected] infrared spectrometry on ZIF-67 by using ZIF-67 and EMIMBF respectively₄ZIF-67 and EMIMPF₆ZIF-67 and EMIMTf₂N as control, the obtained IR spectra are shown in FIG. 2, FIG. 6 and FIG. 10, and EMIMBF can be seen from FIG. 2₄@ ZIF-67 at 1060cm^-1Around the occurrence of EMIMBF₄Characteristic peak of (A), EMIMPF can be seen from FIG. 6₆@ ZIF-67 at 840cm^-1Nearby occurrence of EMIMPF₆Characteristic peak of (A), EMIMTf can be seen from FIG. 10₂N @ ZIF-67 at 1200cm^-1And 1060cm^-1Around the occurrence of EMIMTf₂N, thereby indicating that the metal-organic framework composite is: EMIMBF₄@ZIF-67、EMIMPF₆@ZIF-67、EMIMTf₂N @ ZIF-67 has functional groups corresponding to the ionic liquid, which indicates that the ionic liquid and the ZIF-67 are successfully compounded.

To confirm that the ionic liquid was encapsulated in the pores of ZIF-67, the metal-organic framework composite obtained in examples 1 to 3 above was subjected to specific surface area and pore size analysis using: EMIMBF₄@ZIF-67、EMIMPF₆@ZIF-67、EMIMTf₂N @ ZIF-67 for N₂Adsorption test, resulting in N₂The adsorption data are shown in the table below, from which it can be seen that BET, total pore volume, and micropore volume all decreased with increasing ionic liquid amount, indicating that the ionic liquid is encapsulated into the pores of ZIF-67. Obtained N₂The adsorption isotherms are shown in FIGS. 3, 7 and 11, and it can be seen from these graphs that as the amount of ionic liquid increases, the corresponding N is increased₂The adsorption capacity is continuously reduced, and the ionic liquid occupies part of the pore cavity of the ZIF-67.

From XRD spectrum, infrared spectrum, N₂The combination of the three adsorption isotherms shows that the ionic liquid is successfully packaged to ZIL @ ZIF-67 was successfully prepared in the well of IF-67.

In order to prove that the ionic liquid has no influence on the growth of the ZIF-67 crystal, the metal-organic framework composite materials obtained in the above examples 1 to 3 were subjected to a scanning electron microscope, namely: EMIMBF₄@ZIF-67、EMIMPF₆@ZIF-67、EMIMTf₂N @ ZIF-67 is subjected to scanning electron microscope testing, the obtained scanning electron microscope images are shown in fig. 4, fig. 8 and fig. 12, and it can be seen from the images that the particle morphology of the IL @ ZIF-67 is complete, so that the ionic liquid has no influence on the growth of the ZIF-67 crystal.

Comparative example of example 3

According to the prior art (see in particular the references Vu M T, Lin R, Diao H, et al. Effect of Ionic Liquids (ILs) on MOFs/polymer interface enhancement in mixed matrix membranes [ J)]Journal of Membrane Science,2019,587.) Synthesis of Metal-organic framework composites IL @ ZIF-67, EMIMTf₂N @ ZIF-67, which comprises the following specific steps:

firstly, ZIF-67 is synthesized: mixing 8.15g of Co (NO)₃)₂·6H₂O and 9.19g of 2-methylimidazole are respectively dissolved in 700mL of methanol, then the cobalt nitrate solution is dropwise added into the 2-methylimidazole solution, the mixture is stirred for 18 hours, the mixture is centrifugally washed for three times, and the mixture is dried for 24 hours in vacuum at 100 ℃.

Then synthesizing IL @ ZIF-67, namely EMIMTf₂N @ ZIF-67: ZIF-67 was added to a solution of IL in chloroform with constant stirring and exposed to air until the chloroform was evaporated, and then dried in a vacuum oven at 100 ℃ for 24 hours. The final yield was 3.15g of EMIMTf₂N @ ZIF-67 in 50.4% yield (yield-mass of actual product/mass of theoretical product).

By comparing the yield and the productivity of the final product obtained in the example 3 with the yield and the comparative example 3, the invention can obtain that the preparation time of the metal-organic framework composite material IL @ ZIF-67 prepared by the mechanochemical method under the condition of 1h assisted at 60 ℃ is shortened by 2/3 and the productivity is improved by nearly 98 percent compared with the preparation time of the product obtained by the impregnation method in the comparative example 3.

In conclusion, the preparation method of the composite material IL @ ZIF-67 with the ionic liquid encapsulated in the metal-organic framework cavity is prepared in one step by adopting a mechanochemical method, is simple to operate, short in synthesis time and high in yield, solves the technical problems that the prior art is complex to operate, the synthesis process consumes a large amount of time and the yield is low, and is expected to become a main method for preparing the IL @ MOF composite as a green, economical and efficient synthesis method which is easy to produce in batches.

The above embodiments are merely to explain the technical solutions of the present invention in detail, and the present invention is not limited to the above embodiments, and it should be understood by those skilled in the art that all modifications and substitutions based on the above principles and spirit of the present invention should be within the protection scope of the present invention.