CN113413777A

CN113413777A - VZIF-67/ZIF-67-polyimide mixed matrix membrane, preparation method and application thereof

Info

Publication number: CN113413777A
Application number: CN202110872707.1A
Authority: CN
Inventors: 李健生; 陈珂; 齐俊文; 王超海; 孙秀云
Original assignee: Nanjing University of Science and Technology
Current assignee: Nanjing University of Science and Technology
Priority date: 2021-07-30
Filing date: 2021-07-30
Publication date: 2021-09-21
Anticipated expiration: 2041-07-30
Also published as: CN113413777B

Abstract

The invention discloses a VZIF-67/ZIF-67-polyimide mixed matrix membrane, a preparation method and application thereof, wherein a matrix membrane material is polyimide 6FDA-Durene, a filler is VZIF-67 or ZIF-67, the mass fraction of the filler in the mixed matrix membrane is 10-30%, and the balance is polyimide 6FDA-Durene, the VZIF-67 is uniformly dispersed in a matrix membrane solution by adopting an ultrasonic dispersion mode, and the VZIF-67/polyimide mixed matrix membrane is prepared by adopting a solution casting method. The mixed matrix membrane pair separates CO₂/CH₄The mixed gas has remarkable separation Performance (PCO)₂>1210Barrer，αCO₂/CH₄>32.5) in comparison with pure polyimide filmsHas higher CO₂The gas permeability and the separation selectivity of (2) can be applied to the purification of natural gas.

Description

VZIF-67/ZIF-67-polyimide mixed matrix membrane, preparation method and application thereof

Technical Field

The invention relates to the technical field of gas separation membranes, in particular to a VZIF-67/ZIF-67-polyimide mixed matrix membrane, a preparation method and application thereof.

Background

With the increasing consumption of fossil fuel resources, CO₂The increasing content in the atmosphere causes the greenhouse effect and the environmental problems caused by the greenhouse effect to be more and more serious, and CO₂The separation and capture of (b) is a great concern to people in all fields. Compared with the traditional liquid solvent absorption method, low-temperature rectification method, molecular sieve adsorption method and the like, the membrane separation method has the characteristics of no phase change, low energy consumption, simple equipment, convenient operation and the like. An ideal gas separation membrane material must have high permeability, high selectivity, and good chemical and thermal stability. However, it is difficult for the conventional polymer membrane to satisfy both high gas permeability and separation selectivity, i.e., to break through the upper limit of the Robeson curve. Although dense inorganic membranes can achieve both high permeation flux and high selectivity, inorganic materials are brittle, prone to defects, and expensive, thus limiting their wide industrial application. In order to overcome the limitations of the above membrane materials, mixed matrix membranes derived from the addition of inorganic fillers to polymers have become a focus of research. Inorganic fillers currently reported include zeolites, carbon nanotubes, graphene, MXene, Covalent Organic Framework (COF) materials, and Metal Organic Framework (MOF) materials. As a promising inorganic filler, MOFs have also been incorporated into polymer matrices to make Mixed Matrix Membranes (MMMs). By utilizing the molecular sieve effect of the MOF, the obtained mixed matrix membrane can break the Trade-off effect of the traditional polymer membrane. Compared with traditional inorganic fillers such as zeolite, the mixed matrix membrane based on the MOF has excellent separation performance. However, a major problem with synthetic MOF mixed matrix membranes is the poor interfacial compatibility between the MOFs and the polymers, which leads to irregular interfacial morphology and defects in the mixed matrix membrane.

Polyimide is widely applied to the preparation of gas separation membranes because of its stable chemical structure, excellent mechanical properties and high free volume distribution, so that it can have higher permeation flux and maintain higher selectivity when separating gas mixtures. However, the separation performance of polyimide membranes is required to be further improved to meet the increasingly severe demands. And the disadvantage of easy plasticization thereof causes the separation performance to be reduced, thereby hindering wider application of the polyimide film. Polyimide used for gas separation is mainly aromatic polyimide synthesized by dianhydride and diamine, and the rigidity of molecular chains and strong interaction between molecules lead the molecular chains to be tightly packed, thus leading the permeability and the separation performance of the membrane not to simultaneously meet the separation requirement, and preventing the wide application of the membrane in industry.

The zeolitic imidazole framework material is one branch of the MOF. However, research on ZIF materials has just started, the crystallization mechanism of the materials is not very complete, and the preparation of the materials only stays in the experimental stage, and thus, the mass production is almost impossible.

Disclosure of Invention

The invention aims to provide a VZIF-67/ZIF-67-polyimide mixed matrix membrane containing a functional layer, a preparation method and application thereof, and aims to realize CO (carbon monoxide) by utilizing the special channel size of the VZIF-67/ZIF-67₂Thereby improving the CO of the polyimide 6FDA-Durene membrane₂Separation performance.

In order to achieve the purpose, the invention provides the following scheme:

the invention provides a VZIF-67/ZIF-67-polyimide mixed matrix membrane, wherein a matrix membrane material is polyimide 6FDA-Durene, a filler is functionalized VZIF-67 or non-functionalized ZIF-67, the mass fraction of the VZIF-67 or ZIF-67 in the mixed matrix membrane is 10-30%, and the balance is polyimide 6 FDA-Durene.

The VZIF-67 nano particle is a core-shell VZIF-67 material with a sodalite SOD structure, which is prepared by controlling the growth of a zeolite imidazole salt framework-67 (ZIF-67) and the polymerization of aminophenol and formaldehyde through dynamics.

The preparation method of the VZIF-67 nano particle comprises the following steps: 20g of 2-methylimidazole (2-MeIm) and 1mL of formaldehyde solution (mass concentration: 37%) were added to 300mL of distilled water and stirred for 15min, and the solution was designated as solution A. Then 1g of Co (NO) was weighed₃)·6H₂O and 0.1g of 4-aminophenol were dissolved in 150mL of a mixture of water and ethanol (water/ethanol volume ratio: 2/1), and the solution was designated as solution B. And mixing the solution A and the solution B, stirring for 12 hours at room temperature, centrifugally collecting the generated dark purple solid, washing twice with water and ethanol respectively, and drying in a vacuum drying oven at 60 ℃ to obtain the VZIF-67 nano particle.

The VZIF-67 material not only shows the stability (chemical stability and thermal stability) of the zeolite molecular sieve, but also has large pore volume and flexible pore diameter. Because of the extremely high specific surface area, high porosity and special pore structure of the VZIF-67 material, the VZIF-67 particles are used as a novel porous zeolite imidazole framework material, and the special pore structure of the VZIF-67 particles is used for CO₂、CH₄Has good screening effect. For realizing CO in mixed gas₂/CH₄The effective separation of the two has important practical significance. In addition, compared with the monomer ZIF-67, the surface functional layer of the VZIF-67 improves the interface compatibility of the VZIF-67 and polyimide.

Further, the polyimide 6FDA-Durene is a glassy polymer. The organic phase substrate in the VZIF-67/ZIF-67-polyimide mixed matrix membrane is 6FDA-Durene whole series.

Further, the mixed matrix film has a film thickness of 40 to 100 μm, and the film area is not limited.

The invention also provides a preparation method of the VZIF-67/ZIF-67-polyimide mixed matrix membrane, which comprises the following steps:

a) preparing a casting solution: firstly, dissolving polyimide 6FDA-Durene in a solvent to obtain 6FDA-Durene solution; then adding VZIF-67 or ZIF-67 into the 6FDA-Durene solution, and dispersing the solution into the 6FDA-Durene solution by adopting an ultrasonic and violent stirring method to obtain a casting solution;

b) defoaming the casting solution;

c) pouring the casting solution into a mold, evaporating the solvent to form a film, and drying to remove the residual solvent in the film.

Further, in the step a), the solvent is selected from one of chloroform, dichloromethane, N-dimethylformamide or N-methylpyrrolidone.

Further, in the step a), the polyimide 6FDA-Durene powder is added into the uniformly dispersed VZIF-67 solution for dissolving in two times, one tenth of the required 6FDA-Durene is added for the first time, and the residual 6FDA-Durene powder is added after the polyimide is completely dissolved.

Further, in the step b), the defoaming method adopts one of standing, negative pressure or ultrasonic defoaming.

Further, in the step c), the mixed matrix membrane is firstly dried at room temperature, then dried at 60-80 ℃ for 8-12 h, and then dried in vacuum at 130-170 ℃ for 2-4 days.

The invention also provides application of the VZIF-67/ZIF-67-polyimide mixed matrix membrane in serving as a gas separation membrane.

Further, the mixed matrix membrane is used for selectively separating CO₂/CH₄And (4) mixing the gases.

The invention discloses the following technical effects:

(1) the polyimide 6FDA-Durene containing imide groups selected by the invention has the hydrogen bond interaction with amino groups and hydroxyl groups on the surface of VZIF-67, so that not only can interface defects (such as cavities) be eliminated, but also the compatibility is increased, and the unique pore channel of the VZIF-67 can block the atmospheric molecule CH₄Thereby enabling CO to be diffused₂Selective separation of molecules to further increase CO₂/CH₄Separation performance of mixed gas.

(2) Compared with pure polymer membranes and ZIF-67/polyimide mixed matrix membranes, the VZIF-67/ZIF-67-polyimide mixed matrix membrane prepared by the invention has the advantages that the gas permeability and the separation selectivity are simultaneously improved, and the VZIF-67/ZIF-67-polyimide mixed matrix membrane has a remarkable industrial application prospect;

(3) the VZIF-67/polyimide mixed matrix membrane is prepared by uniformly dispersing the VZIF-67 in a matrix membrane solution in an ultrasonic dispersion mode and adopting a solution casting method. The mixed matrix membrane pair separates CO₂/CH₄The mixed gas has remarkable separation Performance (PCO)₂>1210Barrer，αCO₂/CH₄>32.5)，Higher CO compared to pure polyimide membranes₂The gas permeability and the separation selectivity of (2) can be applied to the purification of natural gas.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.

FIG. 1 is a schematic view of a gas separation test apparatus for a mixed matrix membrane according to the present invention; wherein: 1-a pressure reducing valve; 2-a filter; 3-a gas mass flow meter; 4-screwing the valve; 5-baking oven; 6-a backpressure controller; 7-a permeation pool; 8-three-way valve; 9-a vacuum pump; 10-bubble flow meter; 11-chromatography;

FIG. 2 shows CO in the mixed matrix membrane prepared in example 1 of the present invention₂/CH₄And CO₂A graph of the relationship between permeability coefficients of (a); wherein: ■ 6 FDA-Durene; 10% of tangle-solidup root ZIF-67/6 FDA;

20％ZIF-67/6FDA；◆30％ZIF-67/6FDA；●10％VZIF-67/6FDA；

20％VZIF-67/6FDA；★30％VZIF-67/6FDA；

FIG. 3 is a scanning electron micrograph of (a) comparative example 1, (b) example 1, (c) example 2 and (d) comparative example 2;

FIG. 4 is a scanning electron micrograph of the inner surface (c) and the outer surface of the cross section (b) of the mixed matrix film (a) prepared in example 1;

FIG. 5 is a graph showing the experimental effect of gas flux cycling at high temperature of the mixed matrix membrane prepared in example 1;

FIG. 6 is a graph showing the effect of the separation selective cycle test at high temperature of the mixed matrix membrane prepared in example 1.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Further, for numerical ranges in this disclosure, it is understood that each intervening value, between the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The description and examples are intended to be illustrative only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including, but not limited to.

The preparation method of the VZIF-67 nano particle comprises the following steps: 20g of 2-MeIm and 1mL of formaldehyde solution (mass concentration: 37%) are added to 300mL of distilled water and stirred for 15min,denoted as solution A. Then 1g of Co (NO) was weighed₃)·6H₂O and 0.1g of 4-aminophenol were dissolved in 150mL of a mixture of water and ethanol (water/ethanol: 2/1), and the solution was designated as solution B. And mixing the solution A and the solution B, stirring for 12 hours at room temperature, centrifugally collecting the generated dark purple solid, washing twice with water and ethanol respectively, and drying in a vacuum drying oven at 60 ℃ to obtain the VZIF-67 nano particle.

The permeability coefficient and selectivity test procedures for examples 1-2 and comparative examples 1-2 are as follows: performing permeability test on VZIF-67 (ZIF-67)/polyimide mixed matrix membrane at 35 deg.C and 2bar (gas separation test device shown in figure 1), and mixing gas component CO₂/CH₄: 50/50 volume percent. The permeability of the porous material is obtained by a constant pressure-variable volume method. For the test of the mixed gas, the upstream mixed gas enters the upper part of the permeation cell 7 through the pressure reducing valve 1, the filter 2 and the screw valve 4, and the pressure is adjusted through the backpressure controller 6. The gas permeates to the lower part through a mixed matrix membrane in the permeation cell, the permeation gas is blown into a gas chromatograph by using helium as a blowing gas to detect the concentration of each component, and the gas flux is detected by using a soap bubble flow meter 10. The other gases in the lines and membranes were completely evacuated with a vacuum pump prior to testing.

Calculation of permeability coefficient and selectivity of gas in composite membrane:

wherein A and B represent different gases, respectively. P_iThe permeability coefficient of gas i in the membrane is given in Barrer (1Barrer ═ 1 × 10)^-10cm³(STP)cm/(cm²sec cmHg)); l is the thickness of the film, cm; n is a radical of_iIs the gas permeation flux, cm³Sec; a is the effective membrane area, cm²；Δp_iIs the pressure difference across the membrane, cmHg.

Example 1

a) Accurately weighing 0.033g of dried VZIF-67 nano particles, adding the VZIF-67 nano particles into 4mL of chloroform solution, ultrasonically dispersing for 20min, and then stirring for 4h to uniformly disperse the VZIF-67 nano particles in the chloroform solution to form uniform VZIF-67 chloroform solution;

b) accurately weighing 0.3g of dried 6FDA-Durene powder, adding 0.03g of the weighed 6FDA-Durene powder into the VZIF-67 chloroform solution in the step a), stirring for 2 hours until the powder is completely dissolved, completely adding the rest 6FDA-Durene powder into a solvent, stirring for 12 hours until the powder is completely dissolved, obtaining a casting solution uniformly dissolved, and then carrying out ultrasonic defoaming;

c) pouring the defoamed membrane casting solution into a polytetrafluoroethylene culture dish with the diameter of 6cm, horizontally placing, covering the polytetrafluoroethylene culture dish with a glass funnel, volatilizing a solvent to form a membrane under indoor conditions, then putting the formed membrane and the membrane into a vacuum drying oven with the temperature of 70 ℃ for drying for 24 hours, and then heating to 150 ℃ for drying for 3 days to obtain a mixed matrix membrane with the VZIF-67 particle content of 10 wt.% and the thickness of 40-100 mu m.

Comparative example 1

a) Accurately weighing 0.3g of dried 6FDA-Durene powder, adding the powder into a clean brown reagent bottle, then accurately weighing 4mL of chloroform solution into the brown reagent bottle by using a pipette gun, magnetically stirring for 12h until 6FDA-Durene is completely dissolved to form a uniform transparent solution, and then carrying out ultrasonic defoaming;

b) pouring the solution after ultrasonic deaeration into a polytetrafluoroethylene culture dish with the diameter of 6cm, horizontally placing, covering the polytetrafluoroethylene culture dish with a glass funnel, volatilizing the solvent to form a film at room temperature, then putting the formed film and the film into a vacuum drying oven with the temperature of 70 ℃ for drying for 24h, and then heating to 150 ℃ for drying for 3 days to obtain the pure 6FDA-Durene film with the thickness of 40-100 mu m.

The mixed matrix membrane prepared in example 1 was subjected to a gas separation performance test at 35 ℃ under 0.2MPa to obtain CO₂、CH₄Has a permeability coefficient of 1210.7Barrer, 37.2 Barrer. CO thereof₂To CH₄The selectivity of (A) is: alpha CO₂/CH₄32.5. The pure 6FDA-Durene membrane prepared in comparative example 1 was also subjected to a gas separation performance test at 35 ℃ and 0.2MPa to obtain CO₂、CH₄Has permeability coefficients of 805.3Barrer and 42.4 Barrer. CO thereof₂To CH₄The selectivity of (A) is: alpha CO₂/CH₄19.1. By comparing the gas separation performance of the membranes prepared in example 1 and comparative example 1, it can be found that: after VZIF-7 nano particles are added into a 6FDA-Durene film, CO can be effectively realized₂、CH₄Separation and purification.

Example 2

a) Accurately weighing 0.075g and 0.1285g of dried VZIF-67 nanoparticles, respectively adding the dried VZIF-67 nanoparticles into 2 dry and clean brown reagent bottles, respectively and accurately transferring 4mL of chloroform solution into the 2 reagent bottles by using a liquid transfer gun, ultrasonically dispersing for 15min, and then magnetically stirring for 4h until the VZIF-67 nanoparticles are uniformly dispersed in the chloroform solution to form a uniform VZIF-67 nanoparticle solution;

b) accurately weighing 2 parts of 0.3g of dried 6FDA-Durene powder, adding one tenth of the powder into the VZIF-67 nano particle solution obtained in the step a), stirring until the powder is completely dissolved, then respectively adding the rest 6FDA-Durene powder into respective corresponding reagent bottles, stirring for 12 hours until the powder is completely dissolved, and finally obtaining a casting solution with the VZIF-67 nano particle content of 20 wt.% and 30 wt.%;

c) pouring the defoamed membrane casting solution into a polytetrafluoroethylene culture dish with the diameter of 6cm, horizontally placing, covering the polytetrafluoroethylene culture dish with a glass funnel, volatilizing a solvent to form a membrane under indoor conditions, then putting the formed membrane and the membrane together into a vacuum drying oven with the temperature of 70 ℃ for drying for 24 hours, and then heating to 150 ℃ for drying for 3 days to obtain 3 mixed matrix membranes with the thickness of 40-100 microns.

The mixed matrix membrane prepared in example 2 was subjected to a gas separation performance test at 35 ℃ under 0.2MPa, and the test results are shown in Table 1. As can be seen from Table 1, as the mass fraction of VZIF-67 in the film increased from 10% to 30%, CO₂Continuously increases in permeability coefficient of (C), while CH₄Of (2) a penetrating systemBut a slight decrease in the number. This is because the addition of VZIF-67 nanoparticles can increase the diffusion channels in the membrane, resulting in CO₂The permeability coefficient of (a) increases. However, the unique channels of VZIF-67 hinder the atmospheric molecule CH₄So that CH₄The permeability coefficient of (a) is decreased. In addition, VZIF-67/6FDA-Durene mixed matrix membrane is paired with CO₂/CH₄The selectivity of the gas separation system is improved, so that the aim of simultaneously improving the permeability coefficient and the selectivity is fulfilled, and the upper limit of Robeson (shown in figure 2) is exceeded, which indicates that the mixed matrix membrane has very ideal permeability separation performance when the gas separation system is separated. The term "upper Robeson limit" as used herein is The American scholars Robeson (Robeson L.M, The upper bound viewed, Journal of Membrane Science, 2008, 320, 390-400) based on a number of reported permeability data of polymeric membranes to specific gas molecules as CO₂The permeability coefficient of (A) is the abscissa, CO₂/CH₄The selectivity of (2) is a graph formed by data processing on the ordinate.

TABLE 1

Comparative example 2

a) Preparing pure ZIF-67 nano particles, and completely removing the solvent by vacuum drying; accurately weighing 0.033g, 0.075g and 0.1285g of dry pure ZIF-67 nanoparticles respectively, adding the dry pure ZIF-67 nanoparticles into 3 dry and clean brown reagent bottles respectively, then accurately transferring 4mL of chloroform solution into the 3 reagent bottles respectively by using a liquid transfer gun, ultrasonically dispersing for 15min, and then magnetically stirring for 4h until the ZIF-67 nanoparticles are uniformly dispersed in the chloroform solution to form a uniform ZIF-67 nanoparticle solution;

b) accurately weighing 3 parts of 0.3g of dried 6FDA-Durene powder, adding one tenth of the powder into the ZIF-67 nano particle solution in the step a), stirring until the powder is completely dissolved, then completely adding the rest 6FDA-Durene powder into respective reagent bottles, stirring for 12 hours until the powder is completely dissolved, and finally obtaining casting solution with the ZIF-67 nano particle contents of 10 wt.%, 20 wt.% and 30 wt.% respectively;

c) pouring the defoamed membrane casting solution into a polytetrafluoroethylene culture dish with the diameter of 6cm, horizontally placing, covering the polytetrafluoroethylene culture dish with a glass funnel, volatilizing the solvent to form a membrane under indoor conditions, then putting the formed membrane and a mould into a vacuum drying oven with the temperature of 70 ℃ for drying for 24 hours, and then heating to 150 ℃ for drying for 3 days to obtain a mixed matrix membrane with the thickness of 40-100 mu m.

The mixed matrix membrane prepared in comparative example 2 was subjected to a gas separation performance test at 35 ℃ under 0.2MPa, and the test results are shown in Table 2. As can be seen from Table 2, as the mass fraction of ZIF-67 in the film increased from 10% to 30%, CO₂And CH₄The permeability coefficient of (A) is increasing, while CO₂/CH₄The selectivity of (a) is increased and then decreased. This indicates that 30% of the ZIF-67/6FDA-Durene mixed matrix membrane has defects, gas molecules (CO), during the membrane preparation process₂And CH₄) Can pass through the interfacial voids quickly, resulting in a decrease in film selectivity.

TABLE 2

The scanning electron microscope images of the mixed matrix membranes prepared in examples 1-2 and comparative examples 1-2 are shown in fig. 3, the scanning electron microscope image of the inner surface (c) of the cross section (b) of the mixed matrix membrane (a) prepared in example 1 is shown in fig. 4, and the experimental effect of the separation performance cycle at high temperature of the mixed matrix membrane prepared in example 1 is shown in fig. 5 and fig. 6, which are shown in fig. 3-5. FIG. 3 shows SEM images of cross-sections of pure 6FDA-Durene and mixed matrix membranes, and in FIG. 3(c), VZIF-67 has good compatibility with polyimide 6FDA-Durene due to the presence of the functional layer, and the polymer wraps around the particles well. While in FIG. 3(d), it is apparent that the particles are very largeLess encapsulated by polymer. The pure 6FDA-Durene film had a smooth and uniform morphology (FIG. 3 (a)). As shown in fig. 3(b) and (c), when the VZIF-67 loading was 10-30 wt.%, VZIF-67 was uniformly distributed in the 6FDA-Durene matrix, and VZIF-67 was well surrounded by the 6FDA-Durene matrix on 30% VZIF-67/6FDA-Durene MMMs, with no visible voids observed, indicating good adhesion between the polymer and the VZIF-67 filler. However, when the filler is ZIF-67, ZIF-67 is rarely encapsulated by the polymer due to poor compatibility between ZIF-67 and 6FDA-Durene, and an interfacial defect is inevitably generated (FIG. 3 (d)). FIG. 4 shows that VZIF-67 is uniformly distributed on either the outer surface, inner surface or cross-section of the film and is well surrounded by polymer with no visible voids observed. The separation performance of the mixed matrix membrane by temperature was further investigated, and as can be seen from fig. 5 and 6, when the temperature was increased from 35 ℃ to 45 ℃, CO was present₂The permeability coefficient of (a) is increased a lot and the selectivity is not reduced much. While the temperature continues to rise, the permeability coefficient of all gases continues to increase, and the decrease in selectivity becomes greater. Therefore, it can be seen that the mixed matrix membrane is beneficial to gas permeability when the mixed gas is separated by properly raising the temperature, and the separation performance is relatively poor when the temperature is higher.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. The VZIF-67/ZIF-67-polyimide mixed matrix membrane is characterized in that a matrix membrane material is polyimide 6FDA-Durene, a filler is VZIF-67 or ZIF-67, the mass fraction of the VZIF-67 or ZIF-67 in the mixed matrix membrane is 10-30%, and the balance is polyimide 6 FDA-Durene.

2. The VZIF-67/ZIF-67-polyimide mixed matrix membrane according to claim 1, wherein the mixed matrix membrane has a membrane thickness of 40 to 100 μm and is not limited in membrane area.

3. A method for preparing the VZIF-67/ZIF-67-polyimide mixed matrix membrane according to any one of claims 1 to 2, comprising the steps of:

a) preparing a casting solution: firstly, dissolving polyimide 6FDA-Durene in a solvent to obtain 6FDA-Durene solution; then adding VZIF-67 or ZIF-67 into the 6FDA-Durene solution, and dispersing the solution into the 6FDA-Durene solution by adopting an ultrasonic and stirring method to obtain a casting solution;

b) defoaming the casting solution;

c) pouring the casting solution into a mold, evaporating the solvent to form a film, and drying.

4. The method for preparing the VZIF-67/ZIF-67-polyimide mixed matrix membrane according to claim 3, wherein the solvent in the step a) is one selected from chloroform, dichloromethane, N-dimethylformamide, or N-methylpyrrolidone.

5. The method for preparing VZIF-67/ZIF-67-polyimide mixed matrix membrane according to claim 3, wherein in the step a), the polyimide 6FDA-Durene powder is added to the uniformly dispersed VZIF-67 solution in two portions to be dissolved, the first portion is added in one tenth of the required amount of 6FDA-Durene, and the remaining amount of 6FDA-Durene powder is added after it is completely dissolved.

6. The method for preparing the VZIF-67/ZIF-67-polyimide mixed matrix membrane according to claim 3, wherein in the step b), the defoaming method is one of standing, negative pressure or ultrasonic defoaming.

7. The VZIF-67/ZIF-67-polyimide mixed matrix membrane preparation method according to claim 3, wherein in the step c), the mixed matrix membrane is dried at room temperature, then dried at 60-80 ℃ for 8-12 h, and then dried at 130-170 ℃ for 2-4 days in vacuum.

8. Use of the VZIF-67/ZIF-67-polyimide mixed matrix membrane according to any one of claims 1 to 2 as a gas separation membrane.

9. Use according to claim 8, wherein the mixed matrix membrane selectively separates CO₂/CH₄And (4) mixing the gases.