CN111187422A

CN111187422A - Preparation method of ZIF-21 crystal

Info

Publication number: CN111187422A
Application number: CN202010043834.6A
Authority: CN
Inventors: 朱荣妹; 段慧宇; 庞欢
Original assignee: Yangzhou University
Current assignee: Yangzhou University
Priority date: 2020-01-15
Filing date: 2020-01-15
Publication date: 2020-05-22

Abstract

The invention discloses a preparation method of a ZIF-21 crystal, which comprises the following steps: adding purine in N, N-dimethylformamide to Co (NO)₃)₂∙6H₂O in N, N-dimethylformamide; adding a dimethylamine solution into the mixed solution, magnetically stirring, ultrasonically treating, and centrifugally washing to obtain the ZIF-21 crystal with high crystallinity, uniform size and dodecahedral structure. The invention adopts the ultrasonic synthesis method, so that the crystallinity is high and the particle size is uniform; and the method has the advantages of simple process, low reaction temperature and short time, and is suitable for batch production.

Description

Preparation method of ZIF-21 crystal

Technical Field

The invention relates to a preparation method of a micro-nano material, in particular to a preparation method of a ZIF-21 crystal, and belongs to the field of nano material preparation.

Background

The Metal Organic Framework (MOF) is a three-dimensional porous structure, generally uses Metal ions as connection points, and Organic ligands support coordination polymers forming spatial 3D extension, and is another important novel porous material besides zeolite and carbon nanotubes, and widely applied to catalysis, energy storage and separation. MOF materials have many unique advantages, for example MOFs and their derived nanostructures provide controlled porosity and large surface area, facilitate electrolyte access to electrodes, and ensure large electrolyte/electrode contact area; the electron and ion diffusion lengths can be significantly shortened, which is beneficial for improving the rate performance of MOF-derived nanostructured electrodes. In addition, MOF and derivatives thereofLow cost, easy synthesis and large-scale production and application potential. Zeolite imidazolate framework material (ZIF) is taken as an MOF material, and organic imidazole and transition metal ions are utilized for cross-linking and coordination, so that the MOF material has better stability than a common MOF material, is more favorable for keeping the original structure during heat treatment, and has wide application in the fields of energy, catalysis and the like. For example, chen et al used an in situ limited pyrolysis process to convert ZIF-8 into a nitrogen rich meso-microporous carbon skeleton for efficient oxygen reduction. As a metal-free electrocatalyst, the electrocatalytic activity of the optimized nitrogen-rich meso-microporous carbon skeleton in 0.1M KOH solution has better stability and methanol resistance compared with the commercially available 30 wt% Pt/C catalyst (Advanced Functional Materials, 26(45), 8334-8344). The particle size, purity and crystallinity of the ZIF material have great influence on the performance of the material, the ZIF material is no exception, and the high crystallinity and uniform size are favorable for improving the performance. For example, Zn-MOF with different degrees of crystallinity and particle sizes (20-800 nm) is synthesized by a method of accelerating or delaying nucleation adopted by season et al by introducing different secondary ligands, and the Zn-MOF with high degree of crystallinity and proper size is found to have the detection limit as low as 0.1ppm and the performance is better than that of Zn-MOF (MOF) (with the performance being better than that of other sizes)CrystEngComm, 21(42), 6414-6422). As a ZIF material, the synthesis and activation of ZIF-21 have been studied by Coronas et al as early as 2011, and the ZIF-21 has a huge application prospect in many fields. (RSC Advances, 1(5), 917-922). However, the existing methods such as the solvothermal method and the stirring method have the problems of long reaction time, high heating temperature, non-uniform particle size of synthesized particles, low crystallinity and the like, so that the search for an efficient and controllable synthesis method is of great significance.

Disclosure of Invention

The invention aims to provide a preparation method of a ZIF-21 crystal.

The technical scheme for realizing the aim of the invention is as follows: a preparation method of ZIF-21 crystal comprises the following steps:

(1) adding purine in N, N-Dimethylformamide (DMF) to Co (NO)₃)₂∙6H₂Of OIn N, N-dimethylformamide solution;

(2) adding a dimethylamine solution into the mixed solution obtained in the step (1), magnetically stirring, ultrasonically treating, and centrifugally washing.

Preferably, the purine is reacted with Co (NO)₃)₂∙6H₂The mass ratio of O is 3:1-3:1.5, preferably 3: 1.3.

Preferably, the concentration of the purine N, N-dimethylformamide solution is 50-70 mg/ml, preferably 60 mg/ml; co (NO)₃)₂∙6H₂The concentration of the O N, N-dimethylformamide solution is 22-30 mg/ml, preferably 26 mg/ml.

Preferably, a purine in N, N-dimethylformamide is added to Co (NO) at a rate of 3-4 drops/s₃)₂∙6H₂O in N, N-dimethylformamide.

Preferably, dimethylamine is reacted with Co (NO)₃)₂∙6H₂The mass ratio of O is 0.5-1:1, preferably 0.86: 1.

Preferably, the dimethylamine solution is a methanol solution of dimethylamine having a concentration of 2 mol L^-1。

Preferably, the magnetic stirring time is 30 min; the ultrasonic temperature is 40-50 ℃, and the ultrasonic time is 5-7 h.

Compared with the prior art, the invention has the following beneficial effects: the invention efficiently and controllably synthesizes the ZIF-21 crystal with high crystallinity and uniform particle size by an ultrasonic synthesis method. Thanks to the ultrasonic synthesis method, the ZIF-21 crystal has high crystallinity and uniform particle size; and the method has the advantages of simple process, low reaction temperature and short time, and is suitable for batch production.

Drawings

FIG. 1 is an SEM photograph of crystals of ZIF-21 obtained by hydrothermal synthesis of a comparative example.

FIG. 2 is an SEM image of crystals of ZIF-21 prepared by ultrasonic synthesis in the example.

FIG. 3 is a ZIF-21 crystal XRD pattern of the comparative example obtained by hydrothermal synthesis.

FIG. 4 is a crystal XRD pattern of ZIF-21 synthesized by example sonication.

Detailed Description

The technical solution of the present invention is described in detail below with reference to the accompanying drawings, but the scope of the present invention is not limited to the embodiments.

Comparative example: at room temperature, 0.5 mL of DMF was taken and placed in a vial, and Co (NO) was weighed₃)₂∙6H₂O13 mg, poured into a vial with 0.5 mL of DMF and placed on a magnetic stirrer and the stirring turned on until ready for use. 0.5 mL of DMF was taken out and put in another vial, 30mg of purine was weighed and poured into the vial, and after the solution was clarified, the solution of purine in DMF was taken up by a 1 mL syringe and gradually dropped into the solution of cobalt nitrate in DMF at a rate of 3 to 4 drops/s. Then another syringe was used to aspirate 0.2 mL of a solution of dimethylamine in methanol into the solution. After stirring for a further 30 min, the vial was placed in a teflon liner and placed in the reaction vessel. And (3) putting the reaction kettle into an oven, setting the temperature to be 80 ℃, and heating for 24 hours. After the completion, adding a proper amount of absolute ethyl alcohol-water (volume ratio is 1:1) for dispersion, centrifuging, and repeating the centrifugal washing process for multiple times.

The Scanning Electron Microscope (SEM) detection of the product has the following results: FIG. 1 shows that the hydrothermally synthesized ZIF-21 crystals had high impurity content and non-uniform particle size.

The product was subjected to X-ray diffraction (XRD) detection, with the following results: FIG. 3 shows that the diffraction peak is not significant, indicating that the crystallinity of the hydrothermally synthesized ZIF-21 crystal is low.

Example (b): at room temperature, 0.5 mL of DMF was taken and placed in a vial, and Co (NO) was weighed₃)₂∙6H₂O13 mg, poured into a vial containing 0.5 ml of ldmf and placed on a magnetic stirrer, and the stirring was turned on for further use. 0.5 mL of DMF was taken out and put in another vial, 30mg of purine was weighed and poured into the vial, and after the solution was clarified, the solution of purine in DMF was taken up by a 1 mL syringe and gradually dropped into the solution of cobalt nitrate in DMF at a rate of 3 to 4 drops/s. Then another syringe was used to aspirate 0.2 mL of a solution of dimethylamine in methanol into the solution. Stirring for 30 min, placing into ultrasonic cleaning apparatus, setting temperature at 45 deg.C, and continuously performing ultrasonic treatment for 6 h. After the completion, adding a proper amount of absolute ethyl alcohol-water (volume ratio is 1:1) for dispersion, centrifuging, and repeating centrifugal washing for multiple times.

The Scanning Electron Microscope (SEM) detection of the product has the following results: FIG. 2 shows that the ZIF-21 crystals are dodecahedral particles having a diameter of about 1 to 2 μm.

The product was subjected to X-ray diffraction (XRD) detection, with the following results: FIG. 4 shows almost no hetero-peak, indicating that the resulting ZIF-21 crystal is high in crystallinity and purity.

The ZIF-21 crystal prepared by the invention adopts a Scanning Electron Microscope (SEM) to analyze the size, the morphology, the microstructure and the like.

The phase, crystallinity and the like of the ZIF-21 crystal prepared by the invention are analyzed by X-ray diffraction (XRD).

The invention efficiently and controllably synthesizes the ZIF-21 crystal with high crystallinity and uniform particle size by an ultrasonic synthesis method. Thanks to the ultrasonic synthesis method, the ZIF-21 crystal has high crystallinity and uniform particle size; and the method has the advantages of simple process, low reaction temperature and short time, and is suitable for batch production.

As noted above, while the present invention has been shown and described with reference to certain preferred embodiments, it is not to be construed as limited thereto. Various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A preparation method of a ZIF-21 crystal is characterized by comprising the following steps:

(1) adding purine in N, N-dimethylformamide to Co (NO)₃)₂∙6H₂O in N, N-dimethylformamide;

2. The method of claim 1, wherein the purine is Co (NO)₃)₂∙6H₂The mass ratio of O is 3:1-3:1.5, preferably 3: 1.3.

3. The process according to claim 1, wherein the concentration of the purine in N, N-dimethylformamide is 50 to 70mg/ml, preferably 60 mg/ml; co (NO)₃)₂∙6H₂The concentration of the O N, N-dimethylformamide solution is 22-30 mg/ml, preferably 26 mg/ml.

4. The method of claim 1, wherein the purine in N, N-dimethylformamide is added to Co (NO) at a rate of 3 to 4 drops/s₃)₂∙6H₂O in N, N-dimethylformamide.

5. The method of claim 1, wherein dimethylamine is reacted with Co (NO)₃)₂∙6H₂The mass ratio of O is 0.5-1:1, preferably 0.86: 1.

6. The method of claim 1, wherein the dimethylamine solution is a solution of dimethylamine in methanol at a concentration of 2 mol L^-1。

7. The method of claim 1, wherein the magnetic stirring time is 30 min; the ultrasonic temperature is 40-50 ℃, the ultrasonic time is 5-7 h, and the mixed solution of absolute ethyl alcohol and water with the volume ratio of 1:1 is adopted for centrifugal washing.