Preparation and application of amino-functionalized ionic liquid regulated ZIFP84 mixed matrix membrane

Abstract

The invention discloses preparation and application of an amino-functionalized ionic liquid regulated ZIFP84 mixed matrix membrane. The preparation comprises the following steps: S1, preparing 6FDA-DAM polyimide; s2, preparing nano particles of ZIF-7-8 and ZIF-7-8-IL (Interleukin-7-Interleukin-8); and S3, preparing the ZIF / P84 mixed matrix membrane regulated and controlled by the amino-functionalized ionic liquid. The interface compatibility is enhanced by introducing amino-functionalized ionic liquid into a ZIF / P84 mixed matrix membrane, and IL is connected with a surface metal Zn node instead of being randomly dispersed or limited in an MOF cavity. A series of ZIF-7-8-IL / P84 membranes with different loading capacities of ZIF and IL are prepared, which indicates that the IL and metal Zn on the surface of the ZIF-7-8 have a coordination effect, interface compatibility is improved, generation of interface gaps is reduced, dispersion of the ZIF-7-8 in the membrane is promoted to be more uniform, and then the mechanical property and the helium separation performance of the ZIF-7-8 / P84 mixed matrix membrane are improved.

Description

Technical Field

[0001] The invention relates to the technical field of gas separation materials, and in particular to the preparation and application of a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid. Background Art

[0002] As a colorless, odorless, monatomic rare gas, helium plays an irreplaceable and important role in the fields of national defense, biomedicine, nuclear facilities, electrical industry, semiconductor manufacturing and cryogenic industry due to its excellent physical and chemical properties. It is an important resource related to national security and the development of high-tech industries. Helium is mainly distributed in the mantle, rocks, air and natural gas, but currently commercial helium is mainly extracted from natural gas, which is the only way to utilize helium resources. In recent years, with the development of membrane separation technology, the direct use of membrane separation process technology to enrich and recover the raw gas and the low-grade helium in the LNG tail gas is the future development direction of helium extraction technology. Among the many mixed matrix membrane fillers reported, the zeolite imidazole acid framework (ZIF) has the characteristics of high specific surface area and porosity, adjustable pore structure, low density, etc., which provides great potential for making high-performance membranes.

[0003] Although mixed matrix membranes have many advantages, the interface incompatibility of polymer-filler and / or excessive interface interaction leading to non-selective voids that reduce gas selectivity or interface densification that reduces gas permeability remain huge challenges for the successful preparation of mixed matrix membranes. Reference [Chem. Sci., 2018, 9(17): 4027-4043] uses ionic liquids (ILs) with characteristics such as low volatility, good chemical stability and thermal stability as lubricants or MOF hole occupiers, adsorbed on the MOF / polymer interface, so that MOF has better adhesion with the polymer matrix. The randomly dispersed ILs improve the interface compatibility and helium permeability, effectively improving the gas separation performance of the mixed matrix membrane. Patent [202211716991.4] produces a fluorine-containing cross-linkable polyimide-based carbon molecular sieve membrane by high-temperature calcination and carbonization, and further regulates the pore structure of the carbon molecular sieve membrane to fine-tune the separation performance of the membrane, thereby improving the service life of the high-carbon molecular sieve membrane in an industrial operating environment, with a helium flux of 265 Barrer and a helium / methane selectivity of 36. This method has low helium flux and selectivity, and its preparation is slightly complicated. Patent [202310031470.3] prepares an ultra-thin copolymer polyimide membrane for He separation by dip-coating technology, achieving a dense surface cortex and a double-layer structure with a sponge-like support inside. Compared with polymer membranes with finger-like pore structures inside, it has better support performance, higher selectivity for He / N2 and He / CH4 binary mixtures, and a helium / methane selectivity of up to 465, but a helium flux of 52 Barrer. The helium flux of this method is low. Most reported MOF nanoparticles have weak interfacial interactions with polymer matrices, and the degree of improvement in interfacial compatibility is limited. Therefore, ILs that can improve interfacial interactions are urgently needed when constructing good interfacial structures and high-performance mixed matrix membranes for helium extraction from natural gas. Summary of the invention

[0004] The purpose of the present invention is to solve the shortcomings of the prior art and to propose a preparation and application of a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid.

[0005] In order to achieve the above object, the present invention adopts the following technical scheme: a method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid, comprising the following steps:

[0006] S1: Preparation of 6FDA-DAM polyimide;

[0007] S2: Preparation of ZIF-7-8 and ZIF-7-8-IL nanoparticles;

[0008] S3: Preparation of ZIF / P84 mixed matrix membrane regulated by amino-functionalized ionic liquid.

[0009] As a further description of the above technical solution:

[0010] The preparation process in step S1 is as follows: 6FDA and DAM are dried under vacuum at 80-160°C for 12-36h before use; first, the pretreated DAM is dissolved in NMP under a flowing N2 atmosphere; then, an equimolar amount of the pretreated 6FDA is added to the DAM solution, and stirred at 0-4°C for 48-72h, and the intermediate product is polyoxime acid; finally, o-dichlorobenzene is added as a dehydrating agent, and stirred at 150-180°C for 24-48h; the obtained polyimide precipitate is washed with methanol and dried in a vacuum drying oven at 180-210°C for 24-48h.

[0011] As a further description of the above technical solution:

[0012] The preparation process of the ZIF-7-8 nanoparticles is as follows: dissolving a solid mixture of 2-methylimidazole (mIm) and benzimidazole (bIm) in 10-20 mL of ultra-dry DMF; after complete dissolution, pouring 5-10 mL of a DMF solution of zinc acetate dihydrate into the mixture, and stirring at room temperature for 3-6 hours; centrifuging at a speed of 8000-12000 r / min for 20-60 minutes to obtain a white powder, washing it with methanol for 3-6 times, and detecting the methanol supernatant after centrifugation by ultraviolet-visible detection to confirm that bIm has been completely removed; finally, re-dispersing the nanoparticles in methanol for 36-72 hours for solvent exchange, and vacuum drying at 120-150° C. overnight to obtain ZIF-7-8 nanoparticles.

[0013] As a further description of the above technical solution:

[0014] The preparation process of the ZIF-7-8-IL nanoparticles is as follows: ultrasonically disperse a predetermined amount of ZIF-7-8 powder in DMF for 1-4 hours, add [C3NH2Mim][Cl] with a mass content of 1%, 5%, and 10%, respectively, stir at room temperature for 12-36 hours, and then evacuate at 100° C. overnight to remove DMF to obtain ZIF-7-8-IL composite nanoparticles.

[0015] As a further description of the above technical solution:

[0016] The preparation process in step S3 is as follows: ultrasonically disperse ZIF-7-8-IL nanoparticles with different weight contents in DMF for 1-4 hours and stir at room temperature for 12-24 hours; dissolve a specific mass of polyimide polymer in DMF, filter it using a syringe with a 0.45 μm polytetrafluoroethylene filter head, pour it into the ZIF-7-8-IL / DMF mixture, stir it overnight, and then cast it on a 10*10 cm clean and flat glass plate, and place it in a vacuum drying oven at 80-100°C overnight.

[0017] Application of mixed matrix membranes: The mixed matrix membranes obtained by the preparation method of mixed matrix membranes regulated by amino-functionalized ionic liquids are applied in helium separation

[0018] The present invention has the following beneficial effects:

[0019] 1. Compared with the prior art, the present invention enhances the interfacial compatibility by introducing amino-functionalized ionic liquid into ZIF / P84 mixed matrix membrane, in which IL is connected to the surface metal Zn node, rather than randomly dispersed or confined in the MOF cavity. A series of ZIF-7-8-IL / P84 membranes with different loading amounts of ZIF and IL were prepared, indicating that IL has a coordination effect with the metal Zn on the surface of ZIF-7-8, which improves the interfacial compatibility, reduces the generation of interfacial voids, and promotes a more uniform dispersion of ZIF-7-8 in the membrane, thereby improving the mechanical properties of ZIF-7-8 / P84 mixed matrix membrane and the separation performance of helium.

[0020] 2. Compared with the prior art, the present invention prepares an amino-functionalized ionic liquid-regulated ZIF / P84 mixed matrix membrane, improves the interface compatibility, reduces the generation of interface voids, and at the same time promotes a more uniform dispersion of ZIF-7-8 in the membrane, thereby improving the separation performance of the ZIF-7-8 / P84 sample mixed matrix membrane for He / CH4 and the mechanical properties of the membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a bar graph of pure gas He permeability and He / CH4 selectivity of ZIF-7-8 / P84 and ZIF-8 / P84MMMs at different ZIF mass loadings of the present invention;

[0022] Figure 2 It is a line graph of the mixed gas permeability coefficient and selectivity of the mixed matrix membranes of 25% ZIF-7-8 / P84 and 25% ZIF-7-8-IL(1%) / P84 at 35°C of the present invention. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1

[0025] This embodiment provides a method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid, and the steps are as follows:

[0026] Preparation of 6FDA-DAM polyimide (P84)

[0027] 6FDA and DAM were dried at 80℃ under vacuum for 12h before use. First, the pretreated DAM was dissolved in NMP under flowing N2 atmosphere; then, an equimolar amount of pretreated 6FDA was added to the DAM solution (controlling the monomer concentration of 20wt%), and stirred at 0℃ for 48h. The intermediate product was polyoxime acid; finally, o-dichlorobenzene was added as a dehydrating agent and stirred at 150℃ for 24h. The obtained polyimide precipitate was washed with methanol and dried at 180℃ in a vacuum drying oven for 24h.

[0028] Preparation of ZIF-7-8 and ZIF-7-8-IL nanoparticles

[0029] Preparation of ZIF-711-8 nanoparticles: Dissolve a solid mixture of 5mmol of mIm and 11mmol of bIm in 10mL of ultra-dry DMF; after complete dissolution, pour 5mL of 2mmol of zinc acetate dihydrate in DMF solution into the above mixture and stir at room temperature for 3h; centrifuge at a speed of 8000rmin-1 for 20min to obtain a white powder, wash it with methanol 3 times, and detect the methanol supernatant after centrifugation by UV-vis to confirm that bIm has been completely removed; finally, redisperse the nanoparticles in 100mL of methanol for 36h for solvent exchange, and vacuum dry it at 120℃ overnight to obtain ZIF-7-8 nanoparticles.

[0030] Preparation of ZIF-7-8-IL nanoparticles: A predetermined amount of ZIF-7-8 powder was ultrasonically dispersed in DMF for 1 h, 1% by mass of [C3NH2Mim][Cl] was added, and after stirring at room temperature for 12 h, the mixture was vacuumed at 100 °C overnight to remove DMF to obtain ZIF-7-8-IL composite nanoparticles.

[0031] Preparation of ZIF / P84 mixed matrix membrane regulated by amino-functionalized ionic liquid

[0032] The ZIF-7-8-IL nanoparticles with different weight contents were ultrasonically dispersed in DMF for 1 hour and stirred at room temperature for 12 hours. A specific mass of P84 polymer was dissolved in DMF 3wt%, filtered using a syringe with a 0.45μm polytetrafluoroethylene filter tip, poured into the ZIF-7-8-IL / DMF mixture and stirred overnight, and then cast on a 10*10cm clean and flat glass plate and placed in a vacuum drying oven at 100°C (relative vacuum = -0.9bar) ​​overnight. As the solvent gradually evaporated, a P84 film and a mixed matrix membrane were formed, which were removed from the glass plate with deionized water.

[0033] Example 2

[0034] This embodiment provides a method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid, and the steps are as follows:

[0035] Preparation of 6FDA-DAM polyimide (P84)

[0036] 6FDA and DAM were dried under vacuum at 100°C for 12h before use. First, the pretreated DAM was dissolved in NMP under flowing N2 atmosphere; then, an equimolar amount of pretreated 6FDA was added to the DAM solution (controlling the monomer concentration of 20wt%), and stirred at 0°C for 60h. The intermediate product was polyoxime acid; finally, o-dichlorobenzene was added as a dehydrating agent and stirred at 160°C for 32h. The obtained polyimide precipitate was washed with methanol and dried in a vacuum drying oven at 190°C for 24h.

[0037] Preparation of ZIF-7-8 and ZIF-7-8-IL nanoparticles

[0038] Preparation of ZIF-722-8 nanoparticles: Dissolve a solid mixture of 7mmol of mIm and 22mmol of bIm in 20mL of ultra-dry DMF; after complete dissolution, pour 10mL of 3mmol of zinc acetate dihydrate in DMF solution into the above mixture and stir at room temperature for 4h; centrifuge at 9000rmin-1 for 30min to obtain a white powder, wash it with methanol 4 times, and detect the methanol supernatant after centrifugation by UV-vis to confirm that bIm has been completely removed; finally, redisperse the nanoparticles in 100mL of methanol for 48h for solvent exchange, and vacuum dry it at 130°C overnight to obtain ZIF-7-8 nanoparticles.

[0039] Preparation of ZIF-7-8-IL nanoparticles: A predetermined amount of ZIF-7-8 powder was ultrasonically dispersed in DMF for 2 h, 5% by mass of [C3NH2Mim][Cl] was added, and after stirring at room temperature for 24 h, the mixture was vacuumed at 100 °C overnight to remove DMF to obtain ZIF-7-8-IL composite nanoparticles.

[0040] Preparation of ZIF / P84 mixed matrix membrane regulated by amino-functionalized ionic liquid

[0041] The ZIF-7-8-IL nanoparticles with different weight contents were ultrasonically dispersed in DMF for 2 hours and stirred at room temperature for 16 hours. A specific mass of P84 polymer was dissolved in DMF 4wt%, filtered using a syringe with a 0.45μm polytetrafluoroethylene filter tip, poured into the ZIF-7-8-IL / DMF mixture and stirred overnight, then cast on a 10*10cm clean and flat glass plate and placed in a vacuum drying oven at 100°C (relative vacuum = -0.9bar) ​​overnight. As the solvent gradually evaporated, a P84 film and a mixed matrix membrane were formed, which were removed from the glass plate with deionized water.

[0042] Example 3

[0043] This embodiment provides a method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid, and the steps are as follows:

[0044] Preparation of 6FDA-DAM polyimide (P84)

[0045] 6FDA and DAM were dried at 120℃ under vacuum for 24h before use. First, the pretreated DAM was dissolved in NMP under flowing N2 atmosphere; then, an equimolar amount of pretreated 6FDA was added to the DAM solution (controlling the monomer concentration of 20wt%), and stirred at 4℃ for 72h. The intermediate product was polyoxime acid; finally, o-dichlorobenzene was added as a dehydrating agent and stirred at 170℃ for 48h. The obtained polyimide precipitate was washed with methanol and dried at 200℃ in a vacuum drying oven for 48h.

[0046] Preparation of ZIF-7-8 and ZIF-7-8-IL nanoparticles

[0047] Preparation of ZIF-735-8 nanoparticles: Dissolve a solid mixture of 10 mmol of mIm and 35 mmol of bIm in 20 mL of ultra-dry DMF; after complete dissolution, pour 10 mL of 5 mmol of zinc acetate dihydrate in DMF into the above mixture and stir at room temperature for 6 hours; centrifuge at 12000 rmin-1 for 60 minutes to obtain a white powder, wash it with methanol 6 times, and detect the methanol supernatant after centrifugation by UV-vis to confirm that bIm has been completely removed; finally, redisperse the nanoparticles in 100 mL of methanol for 72 hours for solvent exchange, and vacuum dry it at 150°C overnight to obtain ZIF-7-8 nanoparticles.

[0048] Preparation of ZIF-7-8-IL nanoparticles: A predetermined amount of ZIF-7-8 powder was ultrasonically dispersed in DMF for 4 h, 10% by mass of [C3NH2Mim][Cl] was added, and after stirring at room temperature for 36 h, the mixture was vacuumed at 100 °C overnight to remove DMF to obtain ZIF-7-8-IL composite nanoparticles.

[0049] Preparation of two-dimensional ZIF-67 modified polyimide mixed matrix membranes regulated by ionic liquids

[0050] The ZIF-7-8-IL nanoparticles with different weight contents were ultrasonically dispersed in DMF for 3 h and stirred at room temperature for 20 h. A specific mass of P84 polymer was dissolved in DMF 5 wt %, filtered using a syringe with a 0.45 μm polytetrafluoroethylene filter tip, poured into the ZIF-7-8-IL / DMF mixture and stirred overnight, then cast on a 10*10 cm clean and flat glass plate and placed in a vacuum drying oven at 100°C (relative vacuum = -0.9 bar) overnight. As the solvent gradually evaporated, a P84 film and a mixed matrix membrane were formed, which were removed from the glass plate with deionized water.

[0051] Example 4

[0052] This embodiment provides a method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid, and the steps are as follows:

[0053] Preparation of 6FDA-DAM polyimide (P84)

[0054] 6FDA and DAM were dried under vacuum at 160°C for 12h before use. First, the pretreated DAM was dissolved in NMP under flowing N2 atmosphere; then, an equimolar amount of pretreated 6FDA was added to the DAM solution (controlling the monomer concentration of 20wt%) and stirred at 4°C for 72h. The intermediate product was polyoxime acid; finally, o-dichlorobenzene was added as a dehydrating agent and stirred at 180°C for 24h. The obtained polyimide precipitate was washed with methanol and dried in a vacuum drying oven at 210°C for 24h.

[0055] Preparation of ZIF-7-8 and ZIF-7-8-IL nanoparticles

[0056] Preparation of ZIF-748-8 nanoparticles: Dissolve a solid mixture of 10 mmol of mIm and 48 mmol of bIm in 20 mL of ultra-dry DMF; after complete dissolution, pour 10 mL of 5 mmol of zinc acetate dihydrate in DMF into the above mixture and stir at room temperature for 5 hours; centrifuge at a speed of 10000 rmin-1 for 40 minutes to obtain a white powder, wash it with methanol 5 times, and detect the methanol supernatant after centrifugation by UV-vis to confirm that bIm has been completely removed; finally, the nanoparticles are redispersed in 100 mL of methanol for 60 hours for solvent exchange, and vacuum dried at 140°C overnight to obtain ZIF-7-8 nanoparticles.

[0057] Preparation of ZIF-7-8-IL nanoparticles: A predetermined amount of ZIF-7-8 powder was ultrasonically dispersed in DMF for 3 h, 10% by mass of [C3NH2Mim][Cl] was added, and after stirring at room temperature for 24 h, the mixture was vacuumed at 100 °C overnight to remove DMF to obtain ZIF-7-8-IL composite nanoparticles.

[0058] Preparation of ZIF / P84 mixed matrix membrane regulated by amino-functionalized ionic liquid

[0059] The ZIF-7-8-IL nanoparticles with different weight contents were ultrasonically dispersed in DMF for 4 hours and stirred at room temperature for 24 hours. A specific mass of P84 polymer was dissolved in DMF 5wt%, filtered using a syringe with a 0.45μm polytetrafluoroethylene filter tip, poured into the ZIF-7-8-IL / DMF mixture and stirred overnight, and then cast on a 10*10cm clean and flat glass plate and placed in a vacuum drying oven at 100°C (relative vacuum = -0.9bar) ​​overnight. As the solvent gradually evaporated, a P84 film and a mixed matrix membrane were formed, which were removed from the glass plate with deionized water.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that except for the absence of bIm, the other processes are the same as the preparation of ZIF-7x-8 nanoparticles. Under the same ZIF loading, the test results of CO2 / CH4 selectivity of ZIF-7-8 / P84 mixed matrix membrane and ZIF-8 / P84 are as follows: Figure 1 shown.

[0062] The gas separation performance of the mixed matrix membranes prepared in Examples 1 to 4 and Comparative Example 1 was tested as follows:

[0063] Table 1 shows the BET specific surface area, pore volume and average pore diameter of ZIF-7-8 prepared in Examples 1 to 4 and ZIF-7-8-IL nanoparticles with different amounts of [C3NH2Mim][Cl] ionic liquid added. Figure 2 In order to investigate the separation performance of ZIF-7-8 / P84 membrane for He / CH4 without adding [C3NH2Mim][Cl] ionic liquid, the separation performance of mixed matrix membranes of 25% ZIF-7-8 / P84 and 25% ZIF-7-8-IL(1%) / P84 for He / CH4 mixed gas was evaluated.

[0064] Table 1 BET specific surface area, pore volume and average pore size of ZIF-7-8 and ZIF-7-8-IL nanoparticles

[0065]

[0066] As can be seen from Table 1, the BET surface areas of ZIF-7-8-IL (1%), ZIF-7-8-IL (5%) and ZIF-7-8-IL (10%) are 1084, 985, 885 and 419 m 2 g -1 As the IL content increases from 0 to 10%, the total pore volume decreases from 0.369 to 0.146 m 3 g -1 When the IL addition amount was 1%, the BET specific surface area and pore volume decreased by 9% and 7%, respectively; when the IL addition amount was 10%, the BET specific surface area and pore volume decreased more significantly due to the partial filling or blocking effect of the IL.

[0067] The pure gas permeability of He and CH4 of ZIF-7-8 / P84 and ZIF-7-8-IL / P84 mixed matrix membranes was tested by constant volume-variable pressure method at 35℃ and 2bar feed pressure. The window size was reduced by adjusting the six-ring window composition (ratio of bIm and mIm) in the framework structure through the mixed ligand strategy, thus enhancing the molecular sieving effect of ZIF-7-8 / P84 mixed matrix membrane on He / CH4. Figure 1 As shown in Figure 3, at the same ZIF loading, the ZIF-7-8 / P84 mixed matrix membrane exhibited higher He / CH4 selectivity than ZIF-8 / P84. Specifically, the He permeabilities of 10% ZIF-7-8 / P84 and 10% ZIF-8 / P84 mixed matrix membranes were very similar, while the former showed a 25% increase in He / CH4 selectivity.

[0068] like Figure 2 As shown in the figure, when the He partial pressure is 2 bar, both membranes show low mixed gas He permeability coefficient and slightly higher He / CH4 selectivity compared with the pure gas results due to the competitive adsorption between He and CH4. The mixed gas permeability coefficient of the 25% ZIF-7-8 / P84 mixed matrix membrane decreases with the increase of He partial pressure, which may be caused by dual-mode adsorption and microcavity saturation. The mixed gas CH4 permeability coefficient of the 25% ZIF-7-8-IL (1%) / P84 mixed matrix membrane shows an upward trend when the feed pressure is higher than 8 bar, indicating that IL induces the plasticization trend of the mixed gas. With the increase of feed pressure, the He / CH4 mixed gas selectivity of the two membranes generally shows a downward trend. At the same He partial pressure, the He / CH4 mixed gas selectivity of the 25% ZIF-7-8-IL / P84 membrane is higher than that of the 25% ZIF-7-8 / P84 membrane, which again indicates that the introduction of ionic liquid enhances the interfacial compatibility.

[0069] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid, characterized in that: The following steps are involved: S1: Preparation of 6FDA-DAM polyimide; S2: Preparation of ZIF-7-8 and ZIF-7-8-IL nanoparticles; S3: Preparation of ZIF / P84 mixed matrix membrane regulated by amino-functionalized ionic liquid.

2. The method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid according to claim 1, characterized in that: The preparation process in step S1 is as follows: 6FDA and DAM are dried under vacuum at 80-160°C for 12-36h before use; first, the pretreated DAM is dissolved in NMP under a flowing N2 atmosphere; then, an equimolar amount of the pretreated 6FDA is added to the DAM solution, and stirred at 0-4°C for 48-72h, and the intermediate product is polyoxime acid; finally, o-dichlorobenzene is added as a dehydrating agent, and stirred at 150-180°C for 24-48h; the obtained polyimide precipitate is washed with methanol and dried in a vacuum drying oven at 180-210°C for 24-48h.

3. The method for preparing a ZIFP84 mixed matrix membrane regulated by amino-functionalized ionic liquid according to claim 1, characterized in that: The preparation process of the ZIF-7-8 nanoparticles is as follows: dissolving a solid mixture of 2-methylimidazole (mIm) and benzimidazole (bIm) in 10-20 mL of ultra-dry DMF; after complete dissolution, pouring 5-10 mL of a DMF solution of zinc acetate dihydrate into the mixture, and stirring at room temperature for 3-6 hours; centrifuging at a speed of 8000-12000 r / min for 20-60 minutes to obtain a white powder, washing it with methanol for 3-6 times, and detecting the methanol supernatant after centrifugation by ultraviolet-visible detection to confirm that bIm has been completely removed; finally, re-dispersing the nanoparticles in methanol for 36-72 hours for solvent exchange, and vacuum drying at 120-150° C. overnight to obtain ZIF-7-8 nanoparticles.

4. The method for preparing a ZIFP84 mixed matrix membrane regulated by an amino-functionalized ionic liquid according to claim 1, characterized in that: The preparation process of the ZIF-7-8-IL nanoparticles is as follows: ultrasonically disperse a predetermined amount of ZIF-7-8 powder in DMF for 1-4 hours, add [C3NH2Mim][Cl] with a mass content of 1%, 5%, and 10%, respectively, stir at room temperature for 12-36 hours, and then evacuate at 100° C. overnight to remove DMF to obtain ZIF-7-8-IL composite nanoparticles.

5. The method for preparing a ZIFP84 mixed matrix membrane regulated by amino-functionalized ionic liquid according to claim 1, characterized in that: The preparation process in step S3 is as follows: ultrasonically disperse ZIF-7-8-IL nanoparticles with different weight contents in DMF for 1-4 hours and stir at room temperature for 12-24 hours; dissolve a specific mass of polyimide polymer in DMF, filter it using a syringe with a 0.45 μm polytetrafluoroethylene filter head, pour it into the ZIF-7-8-IL / DMF mixture, stir it overnight, and then cast it on a 10*10 cm clean and flat glass plate, and place it in a vacuum drying oven at 80-100°C overnight.

6. Use of a mixed matrix membrane, characterized in that: The mixed matrix membrane obtained according to the method for preparing the ZIFP84 mixed matrix membrane regulated by amino-functionalized ionic liquid according to any one of claims 1 to 5 is used in helium separation.

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