阅读说明：本技术 一种在外部电场条件下制备zif-8材料的方法 (Method for preparing ZIF-8 material under external electric field condition ) 是由 魏嫣莹 吕露茜 李理波 赵娅俐 杨夏怡 洪细鲁 于 2020-12-23 设计创作，主要内容包括：本发明属于制备金属有机骨架技术领域,公开了一种在外部电场条件下制备ZIF-8材料的方法。具体包括：1)分别配制金属盐和有机配体的溶液；2)在一定强度的外部电场下混合金属盐和有机配体溶液,静置使其反应；3)将分散液进行离心,洗涤下层沉淀,干燥得到ZIF-8产物。本发明的方法简单,生产效率高,可扩大化生产；在外部电场的作用下,所制备的ZIF-8材料与传统的ZIF-8材料具有不同的相组成。(The invention belongs to the technical field of preparation of metal organic frameworks, and discloses a method for preparing a ZIF-8 material under the condition of an external electric field. The method specifically comprises the following steps: 1) respectively preparing solutions of metal salt and organic ligand; 2) mixing metal salt and organic ligand solution under an external electric field with certain strength, and standing for reaction; 3) and centrifuging the dispersion liquid, washing the lower-layer precipitate, and drying to obtain a ZIF-8 product. The method is simple, has high production efficiency and can realize expanded production; under the action of an external electric field, the prepared ZIF-8 material has a different phase composition from the traditional ZIF-8 material.)

1. A method for preparing a ZIF-8 material under the condition of an external electric field is characterized by comprising the following steps of:

(1) taking Zn (NO) at normal temperature₃)₂·6H₂Dissolving O in methanol, and performing ultrasonic treatment until the solution is clear to obtain solution1；

(2) Dissolving 2-methylimidazole in methanol at normal temperature, and performing ultrasonic treatment until the solution is clear to obtain a precursor solution 2;

(3) mixing the solution 1 in the step (1) and the solution 2 in the step (2) under an electric field, and standing to react to generate ZIF-8;

(4) and (4) centrifuging, washing and drying the turbid solution obtained in the step (3) to obtain ZIF-8 powder.

2. The method of claim 1, wherein step (1) comprises providing Zn (NO) in the solution 1₃)₂·6H₂The concentration of O is 0.05-0.2mol/L, and the ultrasonic time is 5-30 min.

3. The method according to claim 1, wherein the concentration of 2-methylimidazole in the solution 2 in the step (2) is 0.05-0.5mol/L, and the time of the ultrasonic treatment is 5-30 min.

4. The method according to claim 1, wherein the volume ratio of the solution 1 in the step (1) to the solution 2 in the step (2) is 0.2-5: 1.

5. the method of claim 1, wherein the electric field in step (3) has a strength of 10-1000V/mm and a standing time of 10-36 h.

6. The method as claimed in claim 1, wherein the rotation speed of the centrifugation in step (4) is 1000-8000rpm, and the centrifugation time is 10-30 min.

7. The method according to claim 1, wherein the washing in step (4) is 2 to 4 times with methanol.

8. The method according to any one of claims 1 to 7, wherein the drying temperature in step (4) is 60 to 100 ℃ and the drying time is 6 to 12 hours.

Technical Field

The invention belongs to the technical field of preparation of metal organic frameworks, and particularly relates to a method for preparing a ZIF-8 material under the condition of an external electric field.

Background

Metal Organic Frameworks (MOFs) are inorganic-organic hybrid materials consisting of metal ions or ion clusters and organic ligands coordinated. The material has been widely studied in the field of material science due to its characteristics of definite structure, adjustable aperture, high surface area and adjustable function. MOFs have a wide range of potential uses including gas storage, separation, catalysis, supercapacitors, and the like.

Zeolitic Imidazolate Frameworks (ZIFs) are a class of MOFs coordinated by metal ions and imidazolate ligands. In their structures, the M-IM-M angles at which the metal tetrahedra bridge with the imidazolate approach 145 °, consistent with the Si-O-Si angles in zeolites, and thus ZIFs generally have a topology similar to that of zeolite structures. Unlike other MOFs, ZIFs have excellent chemical and thermal stability and are considered promising materials for gas storage and gas separation.

The ZIF-8 material is a ZIF material which is researched and synthesized by Yaghi subject group in the United states and has excellent performance. ZIF-8 materials have been reported to be synthesized from zinc salts (zinc nitrate) and 2-methylimidazole in solvents (methanol, water, N-dimethylformamide) by solvothermal or room temperature. Due to the effective pore size of ZIF-8 Between C₃H₆ And C₃H₈ Is considered to separate C by molecular sieve₃H₆/C₃H₈And thus has attracted the attention of a wide range of researchers.

The ZIF-8 material has three different crystal phases, namely cubic phase ZIF-8_ IMonoclinic phase ZIF-8_ Cm and triclinic phase ZIF-8_ R3 m. Caro et al found that an in situ electric field (500V/mm) was applied to the outside of the ZIF-8 film, the ZIF-8 film being made of a flexible IPhase transformation into rigid Cm phase, which is advantageous for C₃H₆/C₃H₈And (4) screening. Caro and Wang et al synthesized ZIF-8 films by a fast current drive method, and generated a ZIF-8 film with Cm phase as the main phase due to the inherent distortion of ZIF-8 lattice caused by the local in-situ electric field formed by direct current. From the above studies, it can be seen that the electric field has an effect on the phase composition of ZIF-8. However, the preparation of ZIF-8 powder having different phase compositions has not been reported so far.

Disclosure of Invention

In order to overcome the defects of the prior synthesis technology, the invention aims to provide a method for preparing a ZIF-8 material under the condition of an external electric field.

The purpose of the invention is realized by the following technical scheme:

a method for preparing a ZIF-8 material under external electric field conditions, comprising the steps of:

(1) taking Zn (NO) at normal temperature₃)₂·6H₂Dissolving O in methanol, and performing ultrasonic treatment until the solution is clear to obtain a solution 1;

(2) dissolving 2-methylimidazole in methanol at normal temperature, and performing ultrasonic treatment until the solution is clear to obtain a precursor solution 2;

(3) mixing the solution 1 in the step (1) and the solution 2 in the step (2) under an electric field, and standing to react to generate ZIF-8;

(4) and (4) centrifuging, washing and drying the turbid solution obtained in the step (3) to obtain ZIF-8 powder.

Preferably, the time of the ultrasound in the step (1) is 5-30 min.

Preferably, Zn (NO) in the solution 1 in the step (1)₃)₂·6H₂The concentration of O is 0.05-0.2 mol/L.

Preferably, the concentration of the 2-methylimidazole in the solution 2 in the step (2) is 0.05-0.5mol/L, and the time of the ultrasonic treatment is 5-30 min.

Preferably, the volume ratio of the solution 1 of step (1) to the solution 2 of step (2) is 0.2-5: 1.

preferably, the strength of the electric field in the step (3) is 10-1000V/mm.

Preferably, the standing temperature in the step (3) is normal temperature, and the standing time is 10-36 h.

Preferably, the rotation speed of the centrifugation in the step (4) is 1000-8000rpm, and the centrifugation time is 10-30 min.

Preferably, the washing in step (4) is 2 to 4 times with methanol.

Preferably, the drying temperature in the step (4) is 60-100 ℃, and the drying time is 6-12 h.

Compared with the prior art, the invention has the following advantages and beneficial effects:

(1) the ZIF-8 powder is prepared in the presence of an external electric field, and the generation of a rigid phase is proved, so that the method has good universality; compared with in-situ current-driven synthesis, the operation process is simplified, and independent ZIF-8 rigid powder can be obtained;

(2) the room temperature synthesis method adopted by the invention is simple and convenient, and the applied external electric field is also easy to implement, thereby providing possibility for amplified production.

Drawings

FIG. 1 is a front micro-topography of the synthesized ZIF-8 under the electric field of example 1.

Detailed Description

The present invention is described in further detail with reference to examples, but the embodiments and the scope of the present invention are not limited thereto.

Example 1

Zinc nitrate hexahydrate (Zn (NO) is weighed at normal temperature₃)₂·6H₂O) 2.97g of the particles are dissolved in about 200mL of methanol and subjected to ultrasonic treatment for 5 minutes to obtain a transparent clear solution; weighing 1.64g of 2-methylimidazole, dissolving in about 200mL of methanol, and performing ultrasonic treatment for 5 minutes to obtain a transparent clear solution; placing the obtained solution beaker on the power clamped by a direct current deviceAdding an electric field with the electric field strength of 100V/mm in the middle of the polar plate, mixing the two solutions, and reacting for 12 hours at normal temperature; centrifuging the obtained particle dispersion under 8000rpm for 20min, transferring supernatant, and washing precipitate with methanol for 2 times under the same centrifugation condition; and (3) drying the precipitate in a vacuum oven at 60 ℃ for 6h to obtain a ZIF-8 material prepared under an electric field, wherein the ZIF-8 material is marked as a sample A1.

Example 2

Zinc nitrate hexahydrate (Zn (NO) is weighed at normal temperature₃)₂·6H₂O) 5.95g of the particles are dissolved in about 100mL of methanol and subjected to ultrasonic treatment for 5 minutes to obtain a transparent clear solution; weighing 3.28g of 2-methylimidazole, dissolving in about 100mL of methanol, and carrying out ultrasonic treatment for 5 minutes to obtain a transparent clear solution; placing the obtained solution beaker in the middle of an electrode plate clamped by a direct current device, adding an electric field with the electric field strength of 20V/mm, mixing the two solutions, and reacting for 24 hours at normal temperature; centrifuging the obtained particle dispersion under 6000rpm for 20min, transferring the supernatant, and washing the precipitate with methanol for 3 times under the same centrifugation condition; and (3) drying the precipitated product in an oven at 80 ℃ for 10h to obtain a ZIF-8 material prepared under an electric field, and marking the material as a sample A2.

Example 3

Zinc nitrate hexahydrate (Zn (NO) is weighed at normal temperature₃)₂·6H₂O) 5.95g of the particles are dissolved in about 50mL of methanol and subjected to ultrasonic treatment for 10 minutes to obtain a transparent clear solution; weighing 3.28g of 2-methylimidazole, dissolving in about 50mL of methanol, and performing ultrasonic treatment for 10 minutes to obtain a transparent clear solution; placing the obtained solution beaker in the middle of an electrode plate clamped by a direct current device, adding an electric field with the electric field strength of 500V/mm, mixing the two solutions, and reacting for 10 hours at normal temperature; centrifuging the obtained particle dispersion under 8000rpm for 30min, transferring supernatant, and washing the precipitate with methanol for 2 times under the same centrifugation condition; and (3) drying the precipitate in a 100 ℃ oven for 8h to obtain a ZIF-8 material prepared under an electric field, and marking the material as a sample A3.

The characterization results of the ZIF-8 material prepared in example 1 are representative of the results of the present invention, and the characterization results of the ZIF-8 materials prepared in other examples are substantially the same as those of example 1 and are not provided.

SEM image of ZIF-8 material synthesized under electric field

The product was characterized by scanning electron microscopy, HITACHI SU8200, Hitachi, Japan. The results are shown in FIG. 1. Compared with the traditional ZIF-8, the material still maintains the octahedral structure.

Phase composition of (di) ZIF-8 material

The crystal structure of example 1 of the present invention was characterized using an X-ray diffractometer model D8-advance, manufactured by Bruker, Germany. The X-ray diffraction data of the ZIF-8 material is calculated and simulated by adopting TOPAS 4.1 software, and the ratio of three phases of the ZIF-8 is obtained and is shown in Table 1.

Table 1 shows ZIF-8 three-phase ratio data obtained by refining an X-ray diffraction pattern of ZIF-8 synthesized in an electric field in example 1;

TABLE 1

(R_wp＝4.48,R_exp＝2.43,GOF＝1.85)

As can be seen from Table 1, the ZIF-8 prepared under the electric field mainly comprises a Cm phase, and the simulation parameters reach an error range, so that the simulation calculation result is reliable.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.