CN110144048A - An Electrochemical and Rapid Synthesis of Bimetallic Zn/Co-ZIF-8 - Google Patents

Abstract

The invention discloses a method for electrochemically rapidly synthesizing bimetallic Zn/Co-ZIF-8, which can successfully reduce the synthesis time to 5 min. The specific steps of the synthesis method are as follows: take 2-methylimidazole and tetrabutylammonium bromide with a conjugated structure and a certain amount of metal cobalt salt in a beaker, then add N,N-dimethylformamide and Ethanol, stirring ultrasonically to make it dissolve evenly; use zinc flakes as the negative and positive stages, mix the uniform solution as the electrolyte, and react with electricity; centrifuge the reacted product to remove the upper liquid, and then use N,N-dimethylformamide Wash with ethanol once and twice respectively; dry at high temperature to obtain bimetallic Zn/Co‑ZIF‑8 solid powder. The present invention synthesizes bimetallic Zn/Co-ZIF-8 through an electrochemical method, which not only has simple operation and mild conditions, but also greatly shortens the reaction time and improves the synthesis yield. The synthesized material not only contains two kinds of metals, but also has a high specific surface area and a stable structure, and has a good application prospect in the preparation of supercapacitors.

Description

An Electrochemical and Rapid Synthesis of Bimetallic Zn/Co-ZIF-8

technical field

The invention belongs to the field of preparation of multi-metal-doped metal-organic frameworks, and in particular relates to a method for electrochemically rapidly synthesizing bimetallic Zn/Co-ZIF-8.

Background technique

Metal Organic Frameworks (MOFs) are a class of crystalline porous materials with a periodic network structure formed by self-assembly of inorganic metal-centered metal ions (or metal clusters) and bridging organic ligands. . It is not only different from inorganic porous materials, but also different from general organic complexes. It has both the rigidity of inorganic materials and the flexibility of organic materials. The high porosity, low density, large specific surface area, regular channel, adjustable pore size, structural diversity and tailorability of MOFs make them present great development potential and attractive development prospects in modern materials research. For example, gas adsorption and separation, gas storage, organic catalysis, optoelectronic materials, chemical sensors and other fields.

However, structural instability and other defects restrict the development and application of MOFs. Therefore, functional modification of traditional MOFs to improve the properties and stability of materials has become a research trend. At present, mixed-component MOFs (Mixed-component MOFs, MC-MOFs) have begun to attract researchers' attention. MC-MOFs can be divided into two categories: multi-ligand MOFs and multi-metal center MOFs. Compared with single-metal MOFs, multi-metal-doped MOFs maintain the same structure and pores as the corresponding single-metal MOFs, and multiple metals are roughly uniformly distributed in the lattice, with faster coordination and crystallization rates. The coordination of multiple metals in the same framework structure promotes the generation of more internal defects in the crystal, which makes the specific surface area of multi-metallic MOFs materials increase to a certain extent compared with single-metal materials. In addition, the various properties of multi-metal doped MOFs in some practical applications have surpassed some corresponding single-metal MOFs materials. For example, the bimetallic MOF (Co/Fe) synthesized by Yang et al. with trimesic acid as a ligand, when it is used as a catalyst to detect H ₂ O ₂ , the detection of H ₂ O ₂ in the range of 10-100 μM The limit is 5μM (R ² =0.997), and its effect is higher than that of the corresponding single metal MOFs material. Liu et al. synthesized MOF-74-Co/Fe nanoarrays on nickel foam under the assisted conditions of polyaniline, and prepared NF@PANI@MOF-74-Co/FeNRAs composites after high temperature treatment under nitrogen protection. When used as electrocatalysis for oxygen evolution reaction, it exhibits higher electrocatalytic activity than single metal materials. The Co-Fe-P composites obtained by Zhang et al. by phosphating Co/FeMOFs also showed good catalytic activity and stability when used as OER catalysts.

At present, the synthesis methods of bimetals can be mainly divided into two categories, one-pot method and metal center substitution method. The one-pot method is usually used to synthesize metal ions and organic ligands into a specific solvent system by solvothermal method, or ultrasonic-assisted, microwave-assisted, steam-assisted, etc., which is a typical self-assembly process. Kaur et al. controllably synthesized Co _x Zn _100-x -ZIF-8 by coordinating the addition of M(NO ₃ )·H ₂ O (M=Co, Zn) and adjusting the ratio of Co/Zn. The metal center substitution method is a method to obtain bimetallic MOFs materials by replacing the metals in the synthesized MOFs with other metals, which is generally completed under liquid phase conditions. The above two methods are time-consuming, high in energy consumption and low in yield. The present invention adopts the electrochemical method to quickly and massively synthesize bimetallic MOFs materials for the first time.

Contents of the invention

The main purpose of the present invention is to provide a method for quickly and easily synthesizing bimetallic Zn/Co-ZIF-8 materials, aiming at efficiently, low energy consumption, and controllable synthesis of metal-organic framework materials with bimetallic materials, while improving production efficiency. Rate.

The purpose of the present invention is achieved through the following technical solutions.

A method for rapidly synthesizing a metal-organic framework material with bimetallic Zn/Co-ZIF-8, comprising the steps of:

Step 1. Get imidazole with a conjugated structure, tetrabutylammonium bromide and a certain amount of metal cobalt salt as a template and increase conductivity in a 50mL beaker, then add N,N-dimethylformamide (DMF ) and ethanol, ultrasonically mixed to form a dispersion;

Step 2. Take two zinc sheets with a size of 5cm×0.5cm×0.1cm and polish them with sandpaper, then wash them with ethanol until the surface is smooth and free of impurities, and dry them for later use;

Step 3. Using the pretreated zinc flakes on the surface in step 2 as anode and cathode respectively, turning on the power supply, adjusting the voltage, and reacting for a certain period of time to obtain the product.

Step 4. Centrifuge the product after the reaction in step 3 to remove the upper liquid, add N,N-dimethylformamide to wash once, then add ethanol to wash twice, the centrifuge speed is 6000-10000r/min, and the centrifugation time is 5- 10min;

Step 5. Dry the product washed in step 4 at a temperature of 60-100° C. for 1-3 hours to obtain purple MOFs powder.

Preferably, the amount of N,N-dimethylformamide (DMF) added in step 1 is 10 mL; the amount of ethanol added is 40 mL; and the ultrasonic time is 6 min.

Preferably, the added amount of Co(NO ₃ ) ₂ ·6H ₂ O is 0.08 g, and the added amount of the conductive salt is 0.6 g.

Preferably, the voltage adjustment amount in step 3 is 5-9V; the reaction time is 2h.

Preferably, the centrifugation speed in step 4 is 8000r/min; the centrifugation time is 7min.

Preferably, the temperature in step 5 in step 5 is 70° C.; the drying time is 1 h.

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

(1) The method of the present invention uses the electrochemical method to synthesize bimetallic MOFs material for the first time, and the morphology of the synthesized Zn/Co-ZIF-8 material is a nano-scale crystal layer, which can increase the specific surface area of the material.

(2) Compared with the traditional synthesis method, the method of the present invention is simple and controllable, and the ratio of the two metals in the MOF can be adjusted by adjusting the amount of cobalt salt added.

(3) The present invention can quickly synthesize metal-organic framework materials with bimetallic doping at room temperature only by applying an external electric field. The operation is simple, the conditions are mild, steps such as heating and ultrasound are avoided, and energy consumption is low. energy.

Description of drawings

FIG. 1 is an X-ray diffraction (XRD) pattern of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1 using a standard spectrum.

FIG. 2 is an infrared (FT-IR) spectrum of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1.

3 is a scanning electron microscope (SEM) photo of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1 of the present invention.

Fig. 4 is the elemental analysis (EDS) of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1 of the present invention.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and examples, but the protection scope of the present invention is not limited to the range expressed in the examples.

Example 1

At room temperature, use 1500 sandpaper-polished zinc sheets as cathode and anode electrodes, dissolve 0.1g dimethylimidazole, 0.6g conductive salt and 0.08g Co(NO ₃ ) ₂ ·6H ₂ O in 10mL of DMF and 40mL of ethanol solution, Ultrasonic 6min to do solvent system. Turn on the power supply, adjust the reaction voltage to 5-9V, and the reaction time is 2 hours. The obtained product is washed once and twice with DMF and ethanol respectively, and centrifuged for 6 minutes at a speed of 8000 r/min. The resultant was placed in a drying oven at 80° C. for 1 h to prepare a bimetallic Zn/Co-ZIF-8 material, labeled as sample A1.

Example 2

Embodiment 2: This embodiment differs from Embodiment 1 in that the amount of conductive salt added is 0.4-0.6 g, and other steps and parameters are the same as Embodiment 1.

Example 3

Embodiment 3: This embodiment differs from Embodiment 1 or 2 in that the amount of metal cobalt salt added is 0.02-0.1 g, and other steps and parameters are the same as Embodiment 1 or 2.

Example 4

Specific embodiment 4: The difference between this embodiment and specific embodiments 1 to 3 is that the ratio of DMF and absolute ethanol in the solvent system is from 0:5 to 5:0, and the total volume remains unchanged at 50 mL. Other steps and The parameters are the same as in one of Embodiments 1 to 3.

The effect of the present invention is analyzed on behalf of the characterization results of the bimetallic Zn/Co-ZIF-8 material prepared under the condition of the best condition in the embodiment, that is, the voltage of 5V in Example 1.

(1) Crystal structure properties of rapidly synthesized bimetallic Zn/Co-ZIF-8

The crystal structure of Example 1 of the present invention was characterized by a D/MAX-3BX X-ray diffractometer produced by Japan Rigaku Company.

Fig. 1 is the X-ray diffraction figure of the ZIF-8 material that adopts traditional hydrothermal synthesis and the double metal Zn/Co-ZIF-8 material that embodiment 1 prepares. As can be seen from Figure 1, compared with the traditional single metal ZIF-8, the sample A1 prepared in Example 1 has a stronger characteristic diffraction peak of the ZIF-8 metal-organic framework, indicating that there is a higher Crystallinity of the ZIF-8 component.

(2) Functional group properties of rapidly synthesized bimetallic Zn/Co-ZIF-8

Avatar Nicolet 730 infrared spectrometer produced by Avatar Corporation of the United States was used to characterize the properties of the functional groups in Example 1 of the present invention.

Fig. 2 is the infrared spectrogram of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1. It can be seen from Figure 2 that the FTIR spectrum of sample A1 prepared in Example 1 is consistent with the results of ZII-8 reported in the literature, and the weak absorption peaks at 3138cm ^-1 and 2933cm ^-1 are all CH bonds Stretching vibration absorption peaks, which are assigned to the methyl and imidazole rings. The absorption peak at 1580cm ^-1 is the stretching vibration peak of C=N, and the strong absorption peaks at 1145cm ^-1 and 990cm ^-1 are the stretching vibration absorption peaks of CN. In addition, the vibrational absorption peak of the NH bond in the methylimidazole at 1843cm- ¹ and the absorption peak of the NH...N hydrogen bond at 2600cm ^-1 were not found in the figure, which indicated that the methylimidazole functional group has been completely deprotonated, The MOFs were successfully self-assembled with metal ions released from the anode.

(3) SEM images of rapidly synthesized bimetallic Zn/Co-ZIF-8

The morphology of Example 1 of the present invention was characterized using a S-4800 scanning electron microscope produced by Shanghai Powerchip Scientific Instruments Co., Ltd.

3 is a SEM image of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1. It can be seen from the figure that the morphology of the bimetallic Zn/Co-ZIF-8 prepared by the electrochemical method is a nano-scale crystal layer.

(4) Elemental analysis of rapidly synthesized bimetallic Zn/Co-ZIF-8

An S-4800 scanning electron microscope produced by Shanghai Powerchip Scientific Instruments Co., Ltd. was used to conduct elemental analysis on Example 1 of the present invention.

FIG. 4 is an elemental analysis spectrum of the bimetallic Zn/Co-ZIF-8 material prepared in Example 1. It can be seen from the figure that the elements of the bimetallic Zn/Co-ZIF-8 prepared by the electrochemical method include C, N, O, Zn, and Co. It is proved that Co element has been successfully supported on the synthesized MOF.

Claims (8)

1. a kind of electrochemical method quickly synthesizes the method for double metal Zn/Co-ZIF-8 material, it is characterized in that: step is as follows: Step 1. Take imidazole with a conjugated structure, tetrabutylammonium bromide as a template and increase conductivity, and a certain amount of metal cobalt salt in a 50 mL beaker, and then add N,N-dimethylformamide ( DMF) and ethanol, ultrasonically mixed to form a dispersion; Step 2. Take two rectangular zinc sheets and polish them with sandpaper, then wash them with ethanol until the surface is smooth and free of impurities, and dry them for later use; Step 3. Fix the zinc sheets that have been pretreated on the surface in step 2 to the yin and yang stages of the plastic plate as the power supply with iron clips, insert the exposed part into the solution prepared in step 1, and turn on the power supply. End the experiment after reacting for a period of time; Step 4. Centrifuge the product after the reaction in step 3 to remove the upper layer liquid, add N,N-dimethylformamide to wash once, and then add ethanol to wash twice; Step 5. Dry the product washed in step 4 at a temperature of 60-100 °C for 1-3 h to obtain white MOFs powder. 2. The synthetic method according to claim 1, characterized in that: in the step 1, the conjugated imidazole is 2-methylimidazole; the metal cobalt salt is cobalt nitrate; the N,N-di The amount of methylformamide (DMF) and ethanol added was 50 mL; the sonication time was 5-15 min. 3. The synthesis method according to claim 1, characterized in that: in the step 2, the size of the zinc sheet is 5 cm×0.5 cm×0.1 cm, and the size of the sandpaper is 60-1500 mesh. 4. The method according to claim 1, characterized in that: the voltage adjustment amount in the step 3 is 4-9 V; the reaction time is 1-3 h. 5. The synthesis method according to claim 1, characterized in that: the centrifugal speed in the step 4 is 6000-10000r/min; the centrifugation time is 5-10 min. 6. The synthetic method according to claim 1, characterized in that: in the step 5, the temperature in the step 5 is preferably 70~90°C; the drying time is 1~2 h. 7. The synthetic method according to claim 1, characterized in that: said steps 1 to 4 are carried out at normal temperature. 8. The synthesis method according to claim 1, characterized in that: the added amount of the ligand is 0.1 g, the added amount of Co(NO ₃ ) ₂ ·H ₂ O is 0.02~0.1 g, and the conductive salt The added amount is 0.6 g.