Mixed matrix membrane based on two-dimensional fullerene nanosheets as well as preparation method and application of mixed matrix membrane

Abstract

The invention discloses a mixed matrix membrane based on two-dimensional fullerene nanosheets as well as a preparation method and application thereof, and belongs to the field of gas separation membranes. According to the preparation method, a two-dimensional fullerene nanosheet 2D-C60 is used as a porous filler and is uniformly mixed with an intrinsic microporous polymer PIM-1 in an organic solvent to obtain a membrane casting solution, and the mixed matrix membrane is prepared by evaporating the solvent in a mold and is used for efficiently and selectively separating gas. The 2D-C60 nanosheet filler in the prepared mixed matrix membrane provides an ideal gas transportation and screening channel, and the gas separation performance of the mixed matrix membrane is effectively improved. The CO2 permeability coefficient and CO2 / N2 selectivity of the 2D-C60-based mixed matrix membrane are remarkably improved, and meanwhile, the 2D-C60-based mixed matrix membrane shows excellent physical aging resistance and plasticizing resistance. Meanwhile, the prepared mixed base membrane shows the application potential in the field of gas separation.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of gas separation membranes, and relates to a mixed matrix membrane based on two-dimensional fullerene nanosheets, a preparation method and application thereof. BACKGROUND

[0002] Increasing carbon dioxide (CO2) concentration in the atmosphere is a key inducement of the greenhouse effect. Among various separation technologies for CO2 capture, membrane separation technology provides an energy-efficient alternative compared to cryogenic distillation and absorption or adsorption. Polymer membranes as separation membranes have unique advantages such as high energy efficiency, easy processing, good ductility and small footprint, and maintain a leading position in the market. Generally, the permeability of traditional polymer membranes follows the adsorption-diffusion model (P i =D i ×S i , P i , D i and S i represent the permeability coefficient, diffusion coefficient and solubility coefficient of gas i, respectively). This model is essentially subject to the trade-off effect between gas permeability and selectivity, i.e. the Robinson upper limit, resulting in a dilemma between productivity and efficiency in practical applications.

[0003] Traditional membrane separation improves adsorption selectivity (such as CO2 / N2 system) by enhancing gas-membrane interface interaction, but has the bottlenecks of poor long-term stability and difficulty in regeneration. While improving the diffusion selectivity of specific gas pairs is a more practical method, which is determined by two key factors of enthalpy and entropy. In the diffusion process, inhibiting the movement of larger size gas molecules will significantly improve the entropy, thus providing higher diffusion selectivity. Two-dimensional micro-nano materials such as two-dimensional metal organic framework (MOFs), graphene, layered transition metal dichalcogenide (TMDs), MXene, g-C3N4 have certain potential in membrane separation. Generally, even if the gas with smaller kinetic diameter such as helium (He) cannot pass through the plane of defect-free two-dimensional material sheet. The precise interlayer nanochannel of two-dimensional material has been designed for gas separation, and hydrogen (H2) purification has been achieved.

[0004] Gas transport depends on the disordered defects of the above-mentioned two-dimensional material, the boundary between adjacent layers, and the length of the interlayer gas channel determined by the lateral size, which makes it difficult to quantify the efficiency of transporting gas. On the other hand, constructing ultra-small pores in the plane of the sheet can provide a channel for efficient gas transport. Ion etching, plasma (O2, Ar, etc.) etching and chemical etching are the main methods of in-plane pore formation of two-dimensional sheets, but it is difficult to accurately size the pore size between two sub-angstrom-sized gases, and the equipment cost is high, requires a harsh chemical environment and consumes a large amount of time. Therefore, for the separation of CO2 / N2 and other gas systems, simple and efficient separation technology still needs to be developed. SUMMARY

[0005] To solve the above problems, the application provides a mixed matrix membrane based on two-dimensional fullerene nanosheet, its preparation method and application, the application provides a new porous filler, i.e. two-dimensional fullerene nanosheet with porous structure, and the mixed matrix membrane based on the two-dimensional fullerene nanosheet can simply and efficiently realize selective separation of CO2 / N2.

[0006] Mixed matrix membranes (MMMs) are a kind of polymer-based membranes composed of polymers and molecular sieve fillers, and are a promising alternative material for easy separation of CO2. Among porous micro-nano fillers, two-dimensional materials are widely used in mixed matrix membranes to improve the separation performance of polymer membranes. There are two ways to improve the pore distribution by cooperating with two-dimensional materials or to endow the polymer matrix with molecular sieving channels, i.e. drilling holes on the plane and adjusting the interlayer space, which can improve the CO2 separation performance to some extent. Therefore, designing a porous filler with sufficient transport space and precise molecular sieving channel will be more likely to achieve sufficient CO2 separation.

[0007] The application provides a two-dimensional fullerene nanosheet, which has a lateral size of 0.1-5 μm and a thickness of 1-20 nm; the two-dimensional fullerene nanosheet has a periodic porous structure and an interlayer slit channel.

[0008] The application provides a preparation method of the two-dimensional fullerene nanosheet as described above, which comprises the following steps:

[0009] S1) providing interlayer metal-doped C 60 polymer crystals;

[0010] S2) removing metal atoms of the interlayer metal-doped C 60 polymer crystals, and then ultrasonically peeling in a solvent, performing solid-liquid separation to obtain a solid phase, freeze-drying the solid phase to obtain the two-dimensional fullerene nanosheet.

[0011] Preferably, step S1 comprises: mixing Mg metal powder with fullerene powder, and then obtaining interlayer metal Mg-doped C by chemical vapor transport through a temperature gradient 60 polymer crystals; in step S2, Mg atoms of the interlayer metal Mg-doped C 60 polymer crystals are removed by soaking in an acid solution; the acid solution is one or more of nitric acid, acetic acid, and hydrochloric acid;

[0012] In step S2, the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, and water;

[0013] In step S2, the solid-liquid separation to obtain the solid phase comprises: removing the precipitate by low-speed centrifugation, and then performing high-speed centrifugation on the supernatant to collect the precipitate.

[0014] The present application provides a two-dimensional fullerene nanosheet (2D-C 60 nanosheet) having a unique periodic porous structure and interlayer slit channel, which can be used as a porous filler of a mixed matrix membrane, thereby enabling horizontal arrangement and uniform dispersion of two-dimensional fullerenes in the membrane, providing efficient gas transport and screening channels, and being conducive to efficient CO2 / N2 selective separation.

[0015] Meanwhile, the present application provides the use of the two-dimensional fullerene nanosheet as described above as a porous filler in a separation membrane.

[0016] The present application provides a mixed matrix membrane based on two-dimensional fullerene nanosheets, comprising: a self-microporous polymer base membrane and a porous filler distributed in the self-microporous polymer base membrane, wherein the porous filler is the two-dimensional fullerene nanosheet as described above.

[0017] Preferably, the thickness of the mixed matrix membrane is 20-80 μm; and the mass fraction of the two-dimensional fullerene nanosheet is 0.1wt%-50wt%.

[0018] The present application provides a preparation method of the mixed matrix membrane as described above, comprising the following steps:

[0019] The two-dimensional fullerene nanosheet as described above and the self-polymer microporous polymer are mixed and dispersed in an organic solvent to obtain a mixed solution;

[0020] The mixed solution is placed in a mold, and the organic solvent therein is evaporated to obtain the mixed matrix membrane based on two-dimensional fullerene nanosheets.

[0021] Preferably, the two-dimensional fullerene nanosheet and the self-polymer microporous polymer are respectively dispersed in an organic solvent, and then ultrasonically mixed and filtered to obtain a mixed solution;

[0022] The evaporation of the organic solvent in the mixture is carried out at room temperature, and the drying obtains the mixed matrix membrane based on the two-dimensional fullerene nanosheet.

[0023] Preferably, the organic solvent is one or more of dichloromethane, trichloromethane, tetrahydrofuran, methanol, ethanol and isopropanol; the mass fraction of the two-dimensional fullerene nanosheet dispersed in the organic solvent is 0.1wt%-50wt%, the concentration of the self-polymerized microporous polymer dispersed in the organic solvent is 5-30mg / mL; and the ultrasonic time is 1-120min.

[0024] In addition, the application provides the use of the mixed matrix membrane as described above in gas separation.

[0025] The application provides a mixed matrix membrane based on 2D-C 60 nanosheets and a preparation method thereof. 60 The 2D-C 60 nanosheets are selected as porous fillers, and a self-microporous polymer (PIM-1) is used as a polymer-based film; different mass fractions of 2D-C 60 nanosheets and PIM-1 are mixed to prepare a mixed matrix membrane with good compatibility by a solution-casting-evaporation method. 60 The mixed matrix membrane based on 2D-C 60 nanosheets can significantly improve the separation capacity of a polymer membrane for a CO2 / N2 gas pair, and the CO2 permeation coefficient and CO2 / N2 selectivity are both significantly improved. 60 The 2D-C 60 nanosheets can inhibit the free movement of polymer chains, and have good anti-physical aging and plasticizing properties. The application provides a new idea for using two-dimensional materials with unique porous structures and interlayer channels as fillers in mixed matrix membranes for practical carbon dioxide separation. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 A preparation flowchart of 2D-C 60 nanosheets involved in the embodiments of the application is shown in the drawings.

[0027] Figure 2 Single crystal X-ray diffraction (XRD) results of fullerene polymer crystals in Embodiment 1 of the application are shown in the drawings.

[0028] Figure 3 Scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) images of 2D-C 60 nanosheets used in Embodiments 1-4 of the application are shown in the drawings.

[0029] Figure 4 Scanning electron microscope (SEM), transmission electron microscope (TEM) and atomic force microscope (AFM) images of 2D-C 60Aberration-corrected transmission electron microscopy (AC-TEM) images of the nanosheets;

[0030] Figure 5 SEM top view, bottom view and cross-sectional view images of the mixed matrix membranes ((PIM-(2D-C 60 )-x%(x=0.1、0.5、5、20) membranes) prepared in Examples 1-4 of the present application;

[0031] Figure 6 Data graphs of CO2 permeance and CO2 / N2 selectivity of the membranes prepared in Examples 1-4 ((PIM-(2D-C 60 )-x%(x=0.1、0.5、5、20) membranes) and Comparative Example 1 (PIM-1 membrane) at 35℃, 3.5 Bar;

[0032] Figure 7 Data graphs of CO2 permeance and CO2 / N2 selectivity of the membranes prepared in Examples 1-4 and Comparative Example 1 at different pressure conditions;

[0033] Figure 8 Data graphs of CO2 permeance and CO2 / N2 selectivity of the membranes prepared in Examples 1-4 and Comparative Example 1 at different temperature conditions;

[0034] Figure 9 Data graphs of CO2 permeance and CO2 / N2 selectivity of the membranes prepared in Examples 1-4 and Comparative Example 1 at long time use conditions. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work are within the protection scope of the present application.

[0036] The present application provides a two-dimensional fullerene nanosheet, which has a lateral size of 0.1-5 μm and a thickness of 1-20 nm. The two-dimensional fullerene nanosheet has a periodic porous structure and interlayer slit channels.

[0037] Correspondingly, the present application provides a preparation method of the two-dimensional fullerene nanosheet as described above, which comprises the following steps:

[0038] S1) providing an interlayer metal-doped C 60 polymer crystal;

[0039] S2) intercalating the interlayer metal-doped C 60Metal atoms of the polymer crystal are removed, and then the polymer crystal is ultrasonically exfoliated in a solvent to obtain a solid phase, the solid phase is freeze-dried to obtain two-dimensional fullerene nanosheets.

[0040] The application provides two-dimensional fullerene nanosheets (2D-C 60 ) with a porous structure.

[0041] Referring to Figure 1 , Figure 1 The 2D-C 60 nanosheets involved in the embodiments of the application. 60 The preparation process of the 2D-C 60 nanosheets comprises the following steps: step one, preparing C 60 polymer crystals (corresponding to S1) doped with interlayer metal components); and step two, preparing porous 2D-C 60 nanosheets (corresponding to S2).

[0042] In the step one, first, the Mg metal powder and the fullerene powder are uniformly mixed, and can be placed at the bottom of a quartz tube, and after vacuum sealing, heat treatment is performed. Figure 1 As shown in (a shows a process diagram for preparing fullerene polymer crystals by a chemical vapor transport method); after 24 hours of treatment, cooling to room temperature, Mg2C 60 crystal products with metallic luster can be collected in the low-temperature zone, that is, C 60 polymer crystals doped with interlayer metal Mg.

[0043] The fullerene powder in the embodiments of the application is C 60 , and is composed of carbon atoms and has a highly symmetrical cage-shaped molecular structure; pure fullerene has no separation effect. Chemical vapor transport reaction (CVT) is to use a transport agent as a medium to realize component transport under a certain temperature gradient, to form a gas phase at the high-temperature end for diffusion, and to condense and grow into a crystal at the low-temperature end. 60 In specific embodiments of the application, the optimal molar ratio of the raw material Mg:C 60 is 4:1, and similar structures can also be obtained at other molar ratios, such as 4:1-15:1. The optimal treatment time is 20-24 hours; the optimal temperature is 600-500 degrees Celsius, and the temperature of the high-temperature zone and the low-temperature zone can be increased or decreased by about 20 degrees Celsius; and the atmosphere is vacuum. The obtained Mg2C 60 has CThe polymeric network layer and the alternately stacked Mg atomic layer, the crystal product adopts a single crystal XRD to directly determine the specific structure. In addition, in addition to the metal magnesium Mg, alkali metals such as lithium Li, sodium Na, and potassium K can also be used.

[0044] In step two, the acid solution is used to soak the interlayer metal Mg doped crystal Mg2C 60 , the Mg atoms between the layers are removed, and then ultrasonic stripping is performed in a solvent; after 8 hours, low-speed centrifugation is performed to remove the precipitate; high-speed centrifugation is performed on the obtained supernatant, the supernatant is removed, the precipitate is washed with ethanol and water (usually deionized water), and finally the precipitate is freeze-dried to collect the few-layer 2D-C 60 nanosheet. Figure 1 b, after the Mg atoms between the layers are removed by acid selective etching, the porous 2D-C 60 nanosheet is obtained by directly performing liquid-phase ultrasonic stripping in a solvent such as NMP.

[0045] The acid solution is one or more of nitric acid, acetic acid, and hydrochloric acid, and can be soaked for 24 hours. The solvent is one or more of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), methanol, ethanol, and water, preferably one or more of N-methyl pyrrolidone (NMP), N,N-dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), and has a better stripping effect. The present application does not have special requirements for the concentration of the acid solution and the etching time, and the treatment time is preferably 24 hours; the ultrasonic stripping time can be in the range of 4-12 hours, preferably 7-10 hours, and further preferably 8 hours, and the effect is best.

[0046] In step two, the low-speed centrifugation speed can be 100-3000 rpm; and the high-speed centrifugation speed can be 3000-15000 rpm. Preferably, the low-speed centrifugation speed is 500-2000 rpm; and the high-speed centrifugation speed is 5000-12000 rpm. Different centrifugation speeds are mainly used to remove products with poor stripping effect, and the present application mainly needs to obtain few-layer nanosheets at high speed.

[0047] The 2D-C 60 nanosheet prepared in the present application has a lateral size of 0.1-5 μm and a thickness of 1-20 nm; preferably, the 2D-C 60 nanosheet has a lateral size of 0.5-2 μm and a thickness of 2-10 nm. In some embodiments, the 2D-C 60 nanosheet has a regular square shape and flat edges, and the thinnest thickness is 2.2 nm corresponding to a double-layer structure, and has a large aspect ratio.

[0048] The few-layer two-dimensional fullerene nanosheet has a periodic porous structure with precise size and an interlayer slit channel, and in some embodiments, the pore size of the hole surrounded in the layer is 5.96 angstroms, and the interlayer slit channel is 3.35 angstroms; it can be used as a porous filler of a mixed matrix membrane, thereby enabling horizontal arrangement and uniform dispersion of two-dimensional fullerene in the membrane, providing an ideal gas transport and screening channel, which is beneficial to improve the gas separation performance of the mixed matrix membrane, such as realizing high-efficiency CO2 / N2 selective separation. In addition, it is convenient to apply control.

[0049] The application provides application of the two-dimensional fullerene nanosheet as described above as a porous filler in a separation membrane; specifically, the application provides a mixed matrix membrane based on two-dimensional fullerene nanosheets, which can be referred to as 2D-C 60 The mixed matrix membrane based on two-dimensional fullerene nanosheets comprises a self-porous polymer base film and a porous filler distributed in the self-porous polymer base film, and the porous filler is the two-dimensional fullerene nanosheet described above.

[0050] The application provides a preparation method of the mixed matrix membrane as described above, which comprises the following steps:

[0051] The two-dimensional fullerene nanosheet described above is mixed and dispersed with a self-polymerized microporous polymer in an organic solvent to obtain a mixed solution;

[0052] The mixed solution is placed in a mold, and the organic solvent in the mixed solution is evaporated to obtain a mixed matrix membrane based on two-dimensional fullerene nanosheets.

[0053] The method of the application uses the two-dimensional fullerene (2D-C 60 ) nanosheet as a porous filler, which is uniformly dispersed and mixed with a self-porous polymer (PIM-1) in an organic solvent, and a mixed matrix membrane is prepared by a solution-casting-evaporation method, which is used for efficient separation of gases.

[0054] In the embodiments of the application, the 2D-C 60 nanosheet and the self-porous polymer PIM-1 can be uniformly dispersed in an organic solvent respectively to obtain a nanosheet dispersion and a PIM-1 solution.

[0055] The PIM-1 adopted in the embodiment of the present application belongs to a kind of self-porous polymer, and is relatively common in the field of gas separation.Self-porous polymer (polymers of intrinsic micro-porosity, PIM for short) is a kind of microporous polymer composed of twisted and rigid monomers. PIM-1 is a ladder-shaped PIM based on spiro-bisindane, and generally has a microporous structure of 0.4-0.8 nm. PIM-1 is a fluorescent yellow polymer obtained by a double aromatic nucleophilic substitution reaction of two commercial monomers 5,5',6,6'-tetrahydroxy-3,3',4,4'-tetramethyl-1,1'-spiro-bisindane (TTSBI) and tetrafluoro-p-phenylenedinitrile (TFTPN), and is generally soluble in polar solvents.

[0056] As preferred, the organic solvent is one or more of dichloromethane, trichloromethane, tetrahydrofuran, methanol, ethanol and isopropanol; the organic solvent is further dichloromethane or trichloromethane, and more preferably dichloromethane.

[0057] In the embodiment of the present application, 2D-C 60 The nanosheet dispersion solution and the PIM-1 solution are uniformly mixed by ultrasonic treatment, and a mixed solution is obtained by filtration. The mixed solution can be poured into a glass culture dish mold, and the organic solvent is allowed to evaporate naturally at room temperature. After the film material in the glass culture dish mold is peeled off, the film material is dried in a vacuum environment to ensure that the residual organic solvent is completely removed, thereby obtaining the mixed matrix film, which is denoted as PIM-(2D-C 60 )-x% film, wherein x% is the mass fraction of the 2D-C 60 nanosheet.

[0058] The mass fraction of the 2D-C 60 nanosheet dispersion solution can be 0.1wt%-50wt%, preferably 0.1wt%-20wt%, for example 0.1wt%, 0.5wt%, 1wt%, 5wt%, 6wt%, 10wt%, 15wt%, 18wt%, 20wt%, which can correspond to the loading amount of the few-layer two-dimensional fullerene nanosheet. The concentration of the PIM-1 solution is preferably 5-30mg / mL, and more preferably 10-20mg / mL. The ultrasonic treatment time can be 1-120min, preferably 10-100min, so that a uniform mixed solution (casting solution) can be obtained.

[0059] The mixed matrix membrane is prepared by evaporating solvent in a mold in the embodiment of the present application, and is used for efficient and selective separation of gas. The organic solvent is evaporated naturally at room temperature, and the room temperature is generally 15-25℃. The residual organic solvent is completely removed by vacuum drying, and the vacuum drying temperature is preferably 60-100℃. The drying time is 3-24h.

[0060] In some embodiments of the present application, the 2D-C 60 The thickness of the mixed matrix membrane containing 2D-C 60 nanosheet fillers provides ideal gas transport and screening channels, effectively improving the gas separation performance of the mixed matrix membrane for CO2 / N2. The 2D-C 60 The CO2 permeation coefficient and CO2 / N2 selectivity of the mixed matrix membrane are significantly improved, and excellent physical aging resistance and plasticization resistance are exhibited. The mixed matrix membrane prepared in the embodiment of the present application exhibits application potential in the field of gas separation, i.e., the present application provides the use of the mixed matrix membrane as described above in gas separation.

[0061] In the embodiment of the present application, the prepared mixed matrix membrane is tested for gas permeation properties, especially for the selective separation performance of CO2 / N2 system as a gas separation membrane. Compared with the pure PIM-1 membrane, the 2D-C 60 nanosheet-based mixed matrix membrane has excellent CO2 separation performance. Moreover, it has good heat resistance and plasticization resistance, and can meet the needs of actual industrial applications.

[0062] In order to better understand the technical content of the present application, specific embodiments are provided below to further illustrate the present application. It should be noted that the professional terms used in the present application are only for the purpose of describing the specific embodiments, and are not intended to limit the protection scope of the present application. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present application can be purchased from the market or prepared by the existing method.

[0063] Embodiment 1

[0064] A method for preparing a mixed matrix membrane containing 2D-C 60 nanosheet (PIM-(2D-C 60 )-0.1%) comprises the following steps:

[0065] Step 1, preparation of fullerene polymer crystal. Mg metal powder and fullerene C 60The powder was uniformly mixed and placed at the bottom of a quartz tube, and then placed in a double-temperature zone tube furnace with a temperature gradient of 600°C-500°C after vacuum sealing. After 24 hours, it was cooled to room temperature, and the Mg2C 60 crystal product in the low-temperature zone was collected.

[0066] Figure 2 For the single crystal X-ray diffraction (XRD) results of the fullerene polymer crystal in Example 1 of the present application, the small balls are Mg atoms, and the large balls are C 60 atoms. The chemical composition thereof is determined by single crystal XRD to be Mg2C 60 . The chemical formula thereof is determined to be Mg2C 60 by single crystal XRD. The polymer network layer and the Mg atom layer are alternately stacked. The Mg2C 60 crystal is a two-dimensional material. In the Mg2C 60 crystal, one C 60 molecule is covalently connected to four adjacent C 60 molecules, and the Mg atom is embedded between the C 60 layers and occupies a tetrahedral interstitial site formed by the C 60 molecules. In each C 60 layer, the C 60 molecules are covalently connected to each other in two orthogonal directions through C-C single bonds or [2+2] cycloaddition bonds, thereby constructing a covalent network with anisotropy. The bridge bonds between the C 60 cages are infinitely propagated in this direction, and four C molecules surround a pore with a diameter of 4.2 Å. The C 60 molecules are in a close-packed ab-stacked form, and the adjacent C 60 molecules between the layers form regular zigzag channels between the layers; this unique periodic pore structure and interlayer slit channel help to provide fast molecular transport and sieving channels.

[0067] Step two, preparation of 2D-C 60 nanosheets. The Mg2C 60 crystals were soaked in dilute nitric acid for 24 hours to remove the Mg atoms between the layers, and then ultrasonically exfoliated in NMP for 8 hours, followed by centrifugation at 1000 rpm to remove the precipitate. The supernatant was centrifuged at 12000 rpm, the supernatant was removed, and the precipitate was washed with ethanol and deionized water, and finally freeze-dried for 24 hours. The 2D-C 60 nanosheets were collected.

[0068] Step three, preparation of two-dimensional fullerene and PIM-1 casting solution. 0.15 mg of 2D-C 60 nanosheets were dispersed in 2 mL of dichloromethane and ultrasonically treated for 1 hour; 0.15 g of PIM-1 powder (regular material, used directly) was dissolved in 8 mL of dichloromethane to obtain a PIM-1 solution, and then ultrasonically treated for 15 minutes.

[0069] Step four, mixing and evaporation of 2D-C 60 nanosheets and PIM-1 casting solution solvent. The above 2D-C 60 nanosheet dispersion solution was mixed with PIM-1 solution and ultrasonically treated for 15 minutes to obtain PIM-1 / 2D-C 60 mixed solution. Then the solution was filtered with a PTFE filter head (to remove the agglomeration of nanosheets with poor dispersion), poured into a glass petri dish mold with a diameter of 60 mm, and the solvent was naturally evaporated at room temperature.

[0070] Step five, preparation of PIM-(2D-C 60 )-0.1% film after natural drying at room temperature. After the film material in the petri dish was peeled off, it was placed in a vacuum environment at 80°C for 8 hours of drying treatment to ensure complete removal of residual solvent, and the mixed matrix film was obtained.

[0071] Example 2

[0072] A method for preparing a mixed matrix film containing 2D-C 60 nanosheets (PIM-(2D-C 60 )-0.5%) comprises the following steps:

[0073] Step one, preparation of fullerene polymer crystals. Mg metal powder was uniformly mixed with fullerene C 60 powder, placed at the bottom of a quartz tube, vacuum sealed, and placed in a double-temperature zone tube furnace with a temperature gradient of 600°C-500°C for 24 hours, and then cooled to room temperature. The Mg2C 60 crystal product with a metallic luster was collected in the low-temperature zone.

[0074] Step two, preparation of 2D-C 60 nanosheets. The Mg2C 60 crystals were soaked in dilute nitric acid for 24 hours to remove the Mg atoms between the layers, and then ultrasonically stripped in NMP for 8 hours, followed by centrifugation at 1000 rpm to remove the precipitate. The supernatant obtained was centrifuged at 12000 rpm, the supernatant was removed, the precipitate was washed with ethanol and deionized water, and finally the precipitate was freeze-dried for 24 hours. The 2D-C 60 nanosheets were collected.

[0075] Step three, preparation of 2D-C 60 nanosheets and PIM-1 casting solution. 0.75 mg of few-layer two-dimensional fullerene nanosheets were dispersed in 2 mL of dichloromethane and ultrasonically treated for 1 hour; 0.15 g of PIM-1 powder was dissolved in 8 mL of dichloromethane to obtain a PIM-1 solution, which was then ultrasonically treated for 15 minutes.

[0076] Step four, mixing and evaporation of 2D-C 60Nanosheet and PIM-1 casting solution solvent. The 2D-C 60 nanosheets were mixed with PIM-1 solution and sonicated for 15 minutes to obtain PIM-1 / 2D-C 60 mixed solution. The PIM-1 solution was then filtered with a PTFE filter head and poured into a glass petri dish mold with a diameter of 60 mm. The solvent was allowed to evaporate naturally at room temperature.

[0077] Step five, PIM-(2D-C 60 )-0.5% film was prepared after natural drying at room temperature. After the film material in the petri dish was peeled off, it was placed in a vacuum environment at 80°C for 8 hours of drying treatment to ensure that the residual solvent was completely removed.

[0078] Example 3

[0079] A method for preparing a mixed matrix film containing 2D-C 60 nanosheets (PIM-(2D-C 60 )-5%) includes the following steps:

[0080] Step one, preparation of fullerene polymer crystals. Mg metal powder and fullerene C 60 powder were uniformly mixed and placed at the bottom of a quartz tube, which was then placed in a double-temperature zone tube furnace with a temperature gradient of 600°C-500°C after being vacuum sealed. After 24 hours, the Mg2C 60 crystal product with a metallic luster was collected in the low-temperature zone.

[0081] Step two, preparation of 2D-C 60 nanosheets. The Mg2C 60 crystals were soaked in dilute nitric acid for 24 hours to remove the Mg atoms between the layers, and then ultrasonically exfoliated in NMP for 8 hours, followed by centrifugation at 1000 rpm to remove the precipitate. The supernatant obtained was centrifuged at 12000 rpm, the supernatant was removed, and the precipitate was washed with ethanol and deionized water. Finally, the precipitate was freeze-dried for 24 hours to collect the 2D-C 60 nanosheets.

[0082] Step three, preparation of two-dimensional fullerene and PIM-1 casting solution. 7.5 mg of 2D-C 60 nanosheets were dispersed in 2 mL of dichloromethane and sonicated for 1 hour; 0.15 g of PIM-1 powder was dissolved in 8 mL of dichloromethane to obtain a PIM-1 solution, which was then sonicated for 15 minutes.

[0083] Step four, mixing and evaporation of 2D-C 60 nanosheets and PIM-1 casting solution solvent. The 2D-C 60The nanosheet dispersion was mixed with the PIM-1 solution and sonicated for 15 minutes to obtain PIM-1 / 2D-C 60 The mixed solution was filtered using a PTFE filter head and the PIM-1 solution was poured into a glass petri dish mold with a diameter of 60 mm and left to evaporate naturally at room temperature.

[0084] Step five, the PIM-(2D-C 60 )-5% film was prepared after natural drying at room temperature. After the film material in the petri dish was peeled off, it was dried at 80°C in a vacuum environment for 8 hours to ensure that the residual solvent was completely removed.

[0085] Example 4

[0086] A method for preparing a mixed matrix film containing 2D-C 60 nanosheets (PIM-(2D-C 60 )-20%) comprising the following steps:

[0087] Step one, preparation of fullerene polymer crystals. Mg metal powder was uniformly mixed with fullerene C 60 powder and placed at the bottom of a quartz tube, which was then sealed in a vacuum and placed in a double-temperature zone tube furnace with a temperature gradient of 600°C-500°C for 24 hours. After cooling to room temperature, the Mg2C 60 crystal product with a metallic luster was collected in the low-temperature zone.

[0088] Step two, preparation of 2D-C 60 nanosheets. The Mg2C 60 crystals were soaked in dilute nitric acid for 24 hours to remove the Mg atoms between the layers, and then ultrasonically exfoliated in NMP for 8 hours, followed by centrifugation at 1000 rpm to remove the precipitate. The supernatant obtained was centrifuged at 12000 rpm, the supernatant was removed, and the precipitate was washed with ethanol and deionized water. Finally, the precipitate was freeze-dried for 24 hours, and the 2D-C60nanosheets were collected.

[0089] Step three, preparation of 2D-C 60 nanosheet and PIM-1 casting solution. 30 mg of 2D-C 60 nanosheets were dispersed in 2 mL of dichloromethane and ultrasonically treated for 1 hour; 0.15 g of PIM-1 powder was dissolved in 8 mL of dichloromethane to obtain a PIM-1 solution, which was then ultrasonically treated for 15 minutes.

[0090] Step four, mixing and evaporation of 2D-C 60 nanosheet and PIM-1 casting solution solvent. The above-mentioned 2D-C 60 nanosheet dispersion was mixed with the PIM-1 solution and sonicated for 15 minutes to obtain PIM-1 / 2D-C 60Mix the solutions. Then filter the PIM-1 solution through a PTFE filter and pour it into a 60mm diameter glass petri dish mold, allowing the solvent to evaporate naturally at room temperature.

[0091] Step 5: Prepare PIM-(2D-C) by air drying at room temperature. 60 -20% membrane. After peeling the membrane material out of the culture dish, place it in a vacuum environment at 80℃ for 8 hours to dry, ensuring that the residual solvent is completely removed, and the membrane is obtained.

[0092] Comparative Example 1

[0093] Preparation of pure polymer membrane (PIM-1):

[0094] Step 1: Dissolve 0.15g of PIM-1 powder in 8mL of dichloromethane to obtain a PIM-1 solution, and then sonicate for 15 minutes.

[0095] Step 2: Filter the PIM-1 solution using a PTFE filter and pour it into a 60mm diameter glass petri dish mold. Allow the solvent to evaporate naturally at room temperature.

[0096] Step 3: Prepare the PIM-1 membrane by air drying at room temperature. After peeling the membrane material out of the culture dish, place it in a vacuum environment at 80℃ for 8 hours to dry, ensuring that the residual solvent is completely removed, thus obtaining the pure polymer membrane PIM-1.

[0097] The preparation of nanosheets in Examples 2-4 is consistent with that in Example 1. Figure 3 The 2D-C used in Embodiments 1 to 4 of this invention 60 Scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) images of nanosheets, where (a) is a SEM image, (b) is a TEM image, and (c) is an AFM image. For Mg2C 60 After acid treatment and ultrasonic peeling, 2D-C 60 The nanosheets have a regular square shape and flat edges, with a minimum thickness of 2.2 nm, corresponding to a bilayer structure. They exhibit a large aspect ratio, which is beneficial for horizontal alignment in polymer-based films.

[0098] Figure 4 The 2D-C used in Embodiments 1 to 4 of this invention 60 Aberration-corrected transmission electron microscopy (AC-TEM) images of nanosheets show 2D-C 60 Nanosheets consist of four C 60 A porous structure formed by molecules.

[0099] Figure 5 The hybrid matrix membrane ((PIM-(2D-C)) prepared in Examples 1-4 of this invention 60SEM topography images of the top surface Top, bottom surface Bottom and cross-section Cross-section of the PIM-1 and PIM-(2D-Cx) (x = 0.1, 0.5, 5, 20) membranes. (d) is a schematic of the horizontal alignment of nanosheets in the PIM-1 matrix, which facilitates fast gas transport. When the loading of few-layer 2D-C nanosheets is low (e.g. 0.1 wt% and 0.5 wt%), the top and bottom surfaces of the membranes remain smooth; when the loading is high (>5 wt%), the top surface of the membranes becomes rough with more particles, while the flakes are deposited on the bottom surface of the membranes. 2D-C 60 The horizontal alignment of nanosheets in the mixed matrix membranes provides fast gas transport channels.

[0100] Also, the 2D-C 60 The thickness of the mixed matrix membranes of nanosheets is 38-43 pm.

[0101] The gas permeation properties of the membranes prepared in Examples 1-4 ((PIM-(2D-C 60 x) (x = 0.1, 0.5, 5, 20) and Comparative Example 1 (PIM-1 membrane) were tested at different temperatures and pressures to test the gas separation performance of the gas separation membranes, and the performance is summarized in Table 1.

[0102] Table 1 Gas permeability coefficients and ideal selectivities of PIM-1 and PIM-(2D-C 60 x) (x = 0.1, 0.5, 5, and 20) membranes

[0103]

[0104]

[0105] Figure 6 The CO2 permeability coefficients and CO2 / N2 selectivity data plots of the membranes prepared in Examples 1-4 ((PIM-(2D-C 60 x) (x = 0.1, 0.5, 5, 20) and Comparative Example 1 (PIM-1 membrane) at 35°C and 3.5 Bar. After adding 0.1 wt% and 0.5 wt% 2D-C 60 nanosheets into PIM-1, the CO2 permeability coefficients of PIM-(2D-C 60 x) membranes were significantly improved from 3875.0 Barrer for the original PIM-1 membrane to 5855.5 Barrer (PIM-(2D-C 60 -0.1%), and 11458.3 Barrer (PIM-(2D-C 60 -0.5%), which indicates that the introduced 2D-C60 nanosheets with high porosity provide more gas transport channels.

[0106] Meanwhile, the CO2 / N2 selectivity of PIM-(2D-C 60 )-0.1% and PIM-(2D-C 60 )-0.5% membranes also significantly increased, reaching 42.5 and 61.5, respectively. The CO2 / N2 selectivity of PIM-1 was enhanced after doping with 2D-C 60 nanosheets, indicating that the periodic porous structure and zigzag channels in 2D-C 60 nanosheets allowed the passage of CO2 molecules with a smaller kinetic diameter while hindering the transport of larger N2 molecules. When the loading of 2D-C 60 nanosheets reached 5 wt% or higher, the CO2 permeability and CO2 / N2 selectivity of PIM-(2D-C 60 )-x% membranes decreased with increasing loading of 2D-C 60 nanosheets. Excessive loading of 2D-C 60 nanosheets resulted in longer gas transport channels and produced non-selective voids, reducing the transport efficiency of CO2. Therefore, excessive loading of 2D-C 60 nanosheets actually reduced the CO2 / N2 separation performance.

[0107] Horizontally arranged 2D-C 60 nanosheets immobilized PIM-1 chains, introducing molecularly sieved gas transport channels, so that the 2D-C 60 nanosheet-based mixed matrix membranes could well improve the CO2 separation performance even under high pressure, high temperature, and long-term use conditions.

[0108] Figure 7 The CO2 permeability and CO2 / N2 selectivity data graphs of the membranes prepared for Examples 1-4 (PIM-(2D-C 60 )-x% (x = 0.1, 0.5, 5, 20) and Comparative Example 1 (PIM-1 membrane) under different pressure conditions. The results showed that the CO2 permeability and CO2 / N2 selectivity of the 2D-C 60 nanosheet-based mixed matrix membranes were significantly improved, and they still exhibited significantly better CO2 / N2 separation capacity than the PIM-1 membrane even under high pressure conditions.

[0109] Figure 8 The CO2 permeability and CO2 / N2 selectivity data graphs of the membranes prepared for Examples 1-4 (PIM-(2D-C 60CO2 permeance and CO2 / N2 selectivity data plots of the membranes prepared in Examples 1-4 (PIM-(2D-C 60 )-0.5% maintained good CO2 / N2 selectivity, stabilized at around 30, which is much higher than the industrial requirement of 20. This result shows that the addition of 2D-C 60 nanosheets can significantly improve the thermal resistance of PIM-(2D-C 60 )-0.5% membrane, thus better meeting the needs of actual industrial applications.

[0110] Figure 9 For the membranes prepared in Examples 1-4 (PIM-(2D-C 60 CO2 permeance and CO2 / N2 selectivity data plots of the membranes prepared in Examples 1-4 (PIM-(2D-C 60 The CO2 permeance of PIM-(2D-C 60 The nanosheets arrange horizontally in the PIM-1 matrix, limiting the movement of the PIM-1 backbone, thus improving the plasticization resistance and aging resistance of the mixed matrix membrane.

[0111] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit it; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A two-dimensional fullerene nanosheet, characterized in that, The transverse dimensions are 0.1–5 μm, and the thickness is 1–20 nm; the two-dimensional fullerene nanosheets have a periodic porous structure and interlayer slit channels.

2. A method for preparing two-dimensional fullerene nanosheets as described in claim 1, characterized in that, Includes the following steps: S1) provides C for interlayer metal doping. 60 Polymer crystals; S2) The interlayer metal doped with C 60 Metal atoms of the polymer crystal are removed, followed by ultrasonic exfoliation in a solvent. A solid phase is obtained through solid-liquid separation, and the solid phase is freeze-dried to obtain two-dimensional fullerene nanosheets.

3. The method for preparing two-dimensional fullerene nanosheets according to claim 2, characterized in that, Step S1 includes: mixing Mg metal powder with fullerene powder, and then obtaining interlayer Mg-doped C through a temperature gradient chemical vapor transport method. 60 Polymer crystal; in step S2, the interlayer metal Mg-doped C 60 The Mg atoms in the polymer crystals are removed by soaking in an acid solution; the acid solution is one or more of nitric acid, acetic acid, and hydrochloric acid. In step S2, the solvent is one or more of N-methylpyrrolidone, N,N-dimethylformamide, dimethyl sulfoxide, methanol, ethanol, and water; In step S2, the solid-liquid separation to obtain the solid phase includes: removing the precipitate by low-speed centrifugation, and then centrifuging the supernatant at high speed to collect the precipitate.

4. The application of the two-dimensional fullerene nanosheets as described in claim 1 as a porous filler in separation membranes.

5. A hybrid matrix membrane based on two-dimensional fullerene nanosheets, characterized in that, include: The self-contained microporous polymer base membrane and the porous filler distributed in the self-contained microporous polymer base membrane, wherein the porous filler is the two-dimensional fullerene nanosheets as described in claim 1.

6. The hybrid matrix membrane according to claim 5, characterized in that, The thickness of the hybrid matrix membrane is 20–80 μm; the mass fraction of the two-dimensional fullerene nanosheets is 0.1 wt%–50 wt%.

7. A method for preparing a hybrid matrix membrane as described in claim 5 or 6, characterized in that, Includes the following steps: The two-dimensional fullerene nanosheets described in claim 1 are mixed and dispersed with the self-polymerized microporous polymer in an organic solvent to obtain a mixed solution; The mixed solution was placed in a mold to evaporate the organic solvent, resulting in a mixed matrix film based on two-dimensional fullerene nanosheets.

8. The method for preparing a hybrid matrix membrane according to claim 7, characterized in that, The two-dimensional fullerene nanosheets and the self-polymerized microporous polymer were dispersed in organic solvents, then ultrasonically mixed and filtered to obtain a mixed solution. The process involves evaporating the organic solvent at room temperature, followed by drying to obtain a hybrid matrix film based on two-dimensional fullerene nanosheets.

9. The method for preparing a hybrid matrix membrane according to claim 8, characterized in that, The organic solvent is one or more of dichloromethane, trichloromethane, tetrahydrofuran, methanol, ethanol and isopropanol; the mass fraction of the two-dimensional fullerene nanosheets dispersed in the organic solvent is 0.1wt% to 50wt%, and the concentration of the self-polymerizing microporous polymer dispersed in the organic solvent is 5 to 30 mg / mL; the ultrasonic time is 1 to 120 min.

10. The application of the hybrid matrix membrane as described in claim 5 or 6 in gas separation.

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