CN113943488B - A composite material based on polytetrafluoroethylene wrapped MOFs material and its preparation method - Google Patents

Abstract

The invention discloses a composite material based on polytetrafluoroethylene-coated MOFs material and a preparation method thereof. The composite material is formed by wrapping MOFs material by polytetrafluoroethylene. The preparation method of the composite material comprises the following steps: and dripping the polytetrafluoroethylene emulsion into the MOFs material suspension in an ultrasonic state, then placing the MOFs material suspension in liquid nitrogen for freezing, removing moisture after thawing, and drying to obtain the composite material based on the MOFs material wrapped by the polytetrafluoroethylene. The method also comprises the step of placing the composite material in an inert atmosphere to carry out annealing treatment so as to remove moisture and nonionic surfactants in the composite material. According to the invention, the PTFE/ZIF-8-370 composite material is obtained by combining the high polymer material polytetrafluoroethylene and ZIF-8 for the first time, and has excellent performances of water stability, high pressure resistance, less loss under catalytic reaction and the like, so that a new building block is provided for an unstable metal organic frame, and a new idea is provided for the design of a metal organic frame material.

Description

A composite material based on polytetrafluoroethylene wrapped MOFs material and its preparation method

technical field

The invention relates to the technical field of polymer-protected metal-organic frameworks, in particular to a composite material based on polytetrafluoroethylene-wrapped MOFs materials and a preparation method thereof.

Background technique

Metal-organic frameworks (MOFs) are widely used in gas storage and separation, biosensors, catalysis, and biomedical release due to their large specific surface area and high porosity. The zeolite imidazolate framework material ZIF-8 exhibits a special pore structure and high hydrothermal and chemical stability, so ZIF-8 has become a research hotspot in many fields. People have extended the application of ZIF-8 to aqueous solution (removal of heavy metal ions in water, photocatalytic degradation of dyes).

Nevertheless, it has been reported in the literature that ZIF-8 microcrystals are unstable in water and new substances are also generated. Therefore, protecting ZIF-8 from being decomposed in aqueous solution application or other reactions is a difficult problem to be solved in this field.

The polymer polytetrafluoroethylene (PTFE) has excellent mechanical toughness, chemical stability, corrosion resistance, high temperature resistance, high lubrication and non-stickiness, electrical insulation and good aging resistance, and it is also a super-hydrophobic material.

Different from traditional metal-organic framework materials, the combination of metal-organic framework materials and polymers can not only retain their own characteristics but also have the characteristics of polymer materials. The composite material of polytetrafluoroethylene and ZIF-8 can improve the water stability, high pressure resistance, hydrophobicity and other characteristics of ZIF-8, so that it has a wide application prospect in more fields.

Contents of the invention

The purpose of the present invention is to address the problems in the prior art, to provide a composite material based on polytetrafluoroethylene wrapped MOFs material and its preparation method, the composite material can make ZIF-8 not be destroyed in aqueous solution application or other reactions break down.

In order to achieve the above object, the present invention adopts the following technical solutions.

A composite material based on polytetrafluoroethylene wrapping MOFs material, the composite material is made of polytetrafluoroethylene wrapping MOFs material.

Preferably, the polytetrafluoroethylene accounts for 20wt%-70wt% of the composite material, and the MOFs material accounts for 30wt%-80wt% of the composite material.

Preferably, the polytetrafluoroethylene accounts for 20wt%-50wt% of the composite material, and the MOFs material accounts for 50wt%-80wt% of the composite material.

Preferably, the MOFs material is ZIF-8.

A kind of preparation method based on the composite material of polytetrafluoroethylene wrapping MOFs material described above, comprises the following steps:

Drop the polytetrafluoroethylene emulsion into the MOFs material suspension in the ultrasonic state, continue to sonicate, then freeze in liquid nitrogen, remove the water after thawing, and then dry to obtain a composite material based on polytetrafluoroethylene-wrapped MOFs material .

Preferably, the composite material based on polytetrafluoroethylene-wrapped MOFs material is placed in an inert atmosphere for annealing treatment to remove moisture and non-ionic surfactants in the composite material.

Preferably, the annealing treatment is to place the composite material based on polytetrafluoroethylene-wrapped MOFs material in a tube furnace with argon flow, heat to 120° C. for 20 minutes, and then raise the temperature to 370° C. for 30 minutes.

Preferably, the polytetrafluoroethylene emulsion includes 60wt% polytetrafluoroethylene, 30wt% non-ionic surfactant and 10wt% water. The nonionic surfactant is.

Preferably, the concentration of the MOFs material suspension is 11 mg/ml.

Preferably, the ultrasonic time is 2 minutes.

Preferably, the drying temperature is 100°C.

Because PTFE has excellent mechanical toughness, chemical stability, corrosion resistance, hydrophobicity and other properties, it can effectively solve the problem of ZIF-8 being decomposed in aqueous solution, while retaining the original characteristics of ZIF-8.

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

(1) The composite material of the present invention has excellent properties such as high pressure resistance, good water stability, and less loss under catalytic reaction, which provides a new building block for unstable metal organic frameworks and provides a basis for the design of metal organic framework materials new ideas.

(2) The composite material of the present invention exhibits higher hydrophobicity than ZIF-8, and after annealing treatment, the hydrophobicity of the composite material is further improved.

Description of drawings

Fig. 1a is a scanning electron microscope image (left) and a transmission electron microscope image (right) of 80% PTFE/ZIF-8 of Example 2 of the present invention.

Fig. 1b is a scanning electron microscope image (left) and a transmission electron microscope image (right) of 80% PTFE/ZIF-8-370 of Example 3 of the present invention.

Fig. 1c is a scanning electron microscope image (left) and a transmission electron microscope image (right) of 50% PTFE/ZIF-8 of Example 2 of the present invention.

Fig. 1d is a scanning electron microscope image (left) and a transmission electron microscope image (right) of 50% PTFE/ZIF-8-370 of Example 3 of the present invention.

Fig. 2 is a graph showing the water stability test results of the ZIF-8 of Example 1 of the present invention and the PTFE/ZIF-8-370 composite material of Example 3.

Fig. 3 is a graph showing the stability test results of the ZIF-8 of Example 1, the PTFE/ZIF-8 composite material of Example 2 and the PTFE/ZIF-8-370 composite material of Example 3 of the present invention under high pressure.

Fig. 4 is a graph showing the recovery rate results of the ZIF-8 in Example 1 of the present invention, the PTFE/ZIF-8 composite material in Example 2, and the PTFE/ZIF-8-370 composite material in Example 3 as catalysts.

Fig. 5 is a water contact angle diagram of the ZIF-8 of Example 1 of the present invention, the PTFE/ZIF-8 composite material of Example 2, and the PTFE/ZIF-8-370 composite material of Example 3.

Detailed ways

The specific implementation of the present invention will be further described below in conjunction with the examples, but the embodiments of the present invention are not limited thereto.

The experimental methods in the following examples, unless otherwise specified, are conventional methods; the chemical reagents and raw materials used, unless otherwise specified, are conventional raw materials in the art and are commercially available.

Main source of reagents:

Zinc nitrate hexahydrate: CAS registration number 10196-18-6;

2-methylimidazole: CAS accession number 693-98-1;

PTFE emulsion: CAS registration number 9002-84-0;

Tetrahydrofuran (CAS accession number: 109-99-9), benzaldehyde (CAS accession number: 100-52-7), malononitrile (CAS accession number: 109-77-3), acetonitrile (CAS accession number 75-05 -8), ethanol (CAS accession number 64-17-5);

The preparation of embodiment 1, ZIF-8

(1) Weigh 1.17g of zinc nitrate hexahydrate in a 20ml small glass bottle, add 8ml of deionized water, put 20.27g of 2-methylimidazole in a 250mL Erlenmeyer flask, add 80ml of deionized water;

(2) Ultrasonic the glass bottle and Erlenmeyer flask of step (1) until the solid dissolves;

(3) Take the solution in the glass bottle of step (2), slowly drop it into the solution of 2-methylimidazole, and then stir for 5min;

(4) The turbid liquid obtained in step (3) was centrifuged to obtain a white solid product, which was washed three times with ethanol, and dried in a vacuum oven at 100°C for 12 hours to obtain ZIF-8 powder.

The preparation of embodiment 2, PTFE/ZIF-8 composite material

1. Preparation of 80% PTFE/ZIF-8 composite material

(1) The ZIF-8 prepared in Example 1 is dispersed in deionized water, and ultrasonically obtained 5ml concentration is a suspension of 11mg/ml, and the mass ratio of PTFE and ZIF-8 is 2:8, that is, polytetrafluoroethylene PTFE in the ethylene emulsion accounts for 20% of the PTFE/ZIF-8 composite material, and the obtained polytetrafluoroethylene emulsion is slowly dropped into the ZIF-8 suspension in the ultrasonic state, and the ultrasonic (power is 100%) is continued for 2 minutes. A mixture of polytetrafluoroethylene and ZIF-8 was obtained.

(2) Completely freeze the mixture obtained in step (1) in liquid nitrogen, take it out and place it at room temperature for thawing, and remove the water after thawing.

(3) Put the moisture-removed mixture in step (2) in a vacuum drying oven at 100° C. for 6 hours, and the resulting white, cotton candy-like, fluffy product is the 80% PTFE/ZIF-8 composite material.

2. Preparation of 50% PTFE/ZIF-8 composite material

(1) The ZIF-8 prepared in Example 1 is dispersed in deionized water, and ultrasonically obtained 5ml concentration is a suspension of 11mg/ml, and the mass ratio of PTFE and ZIF-8 is 5:5, that is, polytetrafluoroethylene PTFE in the ethylene emulsion accounts for 50% of the PTFE/ZIF-8 composite material, and the obtained polytetrafluoroethylene emulsion is slowly dropped into the ZIF-8 suspension under the ultrasonic state, and the ultrasonic (power is 100%) is continued for 2 minutes. A mixture of polytetrafluoroethylene and ZIF-8 was obtained.

(2) Completely freeze the mixture obtained in step (1) in liquid nitrogen, take it out and place it at room temperature for thawing, and remove the water after thawing.

(3) Put the moisture-removed mixture in step (2) in a vacuum drying oven at 100° C. for 6 hours, and the resulting white, cotton candy-like, fluffy product is a 50% PTFE/ZIF-8 composite material.

The preparation of embodiment 3, PTFE/ZIF-8-370 composite material

The PTFE/ZIF-8 composite material obtained above was placed in a tube furnace for annealing with an argon flow.

(1) Put the sample into a tube furnace and heat it to 120°C for 20 minutes.

(2) After step (1), raise the temperature to 370° C. and keep it for 30 minutes.

(3) The brown solid obtained at last is the PTFE/ZIF-8-370 composite material.

Table 1

From the SEM image (left) of Figure 1a, it can be seen that when the mass fraction ratio of PTFE:ZIF-8 is 2:8, and the synthesized 80% PTFE/ZIF-8 is not annealed, the PTFE wrapping ZIF-8 is not uniform and cannot Wrap into a ball.

From the SEM image (left) of Figure 1c, it can be seen that when the mass fraction ratio of PTFE:ZIF-8 is 5:5, and the synthesized 50% PTFE/ZIF-8 is not annealed, PTFE can evenly wrap ZIF-8 to form spherical.

Embodiment 4, PTFE/ZIF-8 and PTFE/ZIF-8-370 composite performance test

The PTFE/ZIF-8 and PTFE/ZIF-8-370 composite material prepared in embodiment 2 and embodiment 3 are carried out stability test, and test condition is as follows:

1. Water stability test: 3ml of deionized water, stirring speed of 750rpm.

Fig. 2 is the stability test diagram of ZIF-8 and PTFE/ZIF-8-370 composite material in water in embodiment 1 and embodiment 3. It can be seen from Figure 2 that after 24 hours of stirring, the ZIF-8 frame has collapsed, but the PTFE/ZIF-8-370 basically retains the original diffraction peaks, and the frame remains stable. It shows that under the same conditions, compared with ZIF-8 microcrystals, PTFE/ZIF-8-70 composites are more stable when stirred in water for 24 hours. It can be proved that the polytetrafluoroethylene coating is able to protect ZIF-8.

2. Stability test under high pressure: 10mg sample, under 10Mpa, keep for 2min

Fig. 3 is the stability test diagram of ZIF-8 and its composite material kept under 10Mpa pressure for 2min in embodiment 1, 2, 3. It can be seen from Figure 3 that under the pressure of 10Mpa, the frame of ZIF-8 has completely collapsed, but the PTFE/ZIF-8 and PTFE/ZIF-8-370 composite materials still maintain the original diffraction peaks, and the frame remains stable. It shows that the PTFE/ZIF-8 and PTFE/ZIF-8-370 composite materials prepared by the present invention have high pressure resistance.

3. Catalyst recovery rate test: 20 mg of ZIF-8 and its composite materials PTFE/ZIF-8 and PTFE/ZIF-8-370 were used as catalysts to conduct catalytic tests on benzaldehyde and malononitrile at room temperature.

Fig. 4 is the figure of recovery after catalysis of ZIF-8 and its composite material in embodiment 2. It can be found from Figure 4 that ZIF-8 and its composite materials PTFE/ZIF-8 and PTFE/ZIF-8-370 are used as catalysts. After the catalytic reaction, the catalyst is washed with ethanol and dried at 60 ° C. The recovery rate of ZIF-8 is not high. To 50%, the recovery rate of 80% PTFE/ZIF-8 is about 65%, the recovery rate of 50% PTFE/ZIF-8 is 75%, and the recovery rate of 80% PTFE/ZIF-8-370 is 92.75%, 50% PTFE/ The recovery rate of ZIF-8-370 reached 96.5%. It shows that the recovery rate of ZIF-8 is the lowest during the catalytic stirring process, and the recovery rate of the composite material PTFE/ZIF-8-370 after annealing is higher.

Embodiment 5, ZIF-8 and its composite material hydrophobicity test

Hydrophobic test of ZIF-8 and its composite materials: ZIF-8 and its composite materials were placed on a glass plate and flattened, and tested on a contact angle meter.

Table 2

Figure 5 is a water contact angle diagram of ZIF-8 and its composite material in Examples 1, 2, and 3. It can be seen that ZIF-8 does not exhibit hydrophobicity. The water contact angle of PTFE/ZIF-8 is 140-150°, and the water contact angle of PTFE/ZIF-8-370 is 150-160°, showing super high hydrophobicity.

Claims (8)

1. A composite material based on polytetrafluoroethylene wrapping MOFs material, characterized in that, said composite material is formed by polytetrafluoroethylene wrapping MOFs material; The MOFs material is ZIF-8; The polytetrafluoroethylene accounts for 20wt%-70wt% of the composite material, and the MOFs material accounts for 30wt%-80wt% of the composite material. 2. a kind of composite material based on polytetrafluoroethylene wrapping MOFs material according to claim 1, is characterized in that, described polytetrafluoroethylene accounts for 20wt%-50 wt% of composite material, and described MOFs material accounts for composite 50wt%-80wt% of the material. 3. the method for preparing a kind of composite material based on polytetrafluoroethylene wrapping MOFs material described in any one of claim 1-2, is characterized in that, comprises the following steps: Drop the polytetrafluoroethylene emulsion into the MOFs material suspension in the ultrasonic state, continue to sonicate, then freeze in liquid nitrogen, remove the water after thawing, and then dry to obtain a composite material based on polytetrafluoroethylene-wrapped MOFs material . 4. method according to claim 3, is characterized in that, the composite material based on polytetrafluoroethylene wrapping MOFs material is placed under inert atmosphere and carries out annealing treatment to remove moisture and nonionic surface activity in composite material agent. 5. The method according to claim 4, wherein the annealing process is to place the composite material based on polytetrafluoroethylene wrapped MOFs material in a tube furnace of argon flow, heated to 120° C. for 20 min, and then Raise the temperature to 370°C and keep for 30min. 6. The method according to claim 3, wherein the polytetrafluoroethylene emulsion comprises 60wt% polytetrafluoroethylene, 30wt% nonionic surfactant and 10wt% water. 7. The method according to claim 3, wherein the concentration of the MOFs material suspension is 11 mg/ml. 8. The method according to claim 3, wherein the ultrasonic time is 2 minutes.

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