Preparation method and application of a membrane material suitable for low-concentration CO2 separation

Abstract

The application discloses a preparation method and application of a membrane material suitable for low-concentration CO2 separation. The mixed matrix membrane prepared by the method is a MOF material with fluorine element sites as filler under the condition that the filler skeleton is not changed, and PIM-1 and PIM-2 are used as polymer matrix. The application overcomes the deficiency in the field of low-concentration CO2 membrane separation in a humid environment, combines the filler rich in fluorine element sites and the polymer matrix, explores the polymer synthesis mode, temperature and time, and successfully synthesizes the mixed matrix membrane suitable for low-concentration CO2 separation in a humid environment by exploring the way of adding fluorine element sites under the condition that the metal organic skeleton is not changed. The MOF-based mixed matrix membrane with multiple fluorine element sites has good CO2 permeability and super-high CO2 / N2 selectivity in the field of membrane separation, and the polymer matrix, the MOF filler and the CO2 molecules have strong affinity.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of gas separation membranes, in particular to a preparation method and application of a membrane material suitable for low-concentration CO2 separation. BACKGROUND

[0002] With the continuous development of human society and industrialization, CO2 emission has been the main factor of global warming. The low CO2 composition of 300~400ppm in the air increases the difficulty of CO2 separation, so the efficient separation, recovery and capture of low-concentration CO2 are particularly important. At present, the main method to reduce CO2 emission is through CO2 capture, carbon storage and amine washing. However, these technologies are usually used to capture CO2 in flue gas, which has high energy consumption and certain environmental pollution. Gas separation membrane has the characteristics of green environmental protection, easy preparation and small occupation area. At the same time, in many reported academic journals, there are few reports on low-concentration CO2 membrane separation, and the low-concentration CO2 affects the separation of the membrane and has the problems of not easy to separate and not high selectivity and high flux. Therefore, it is crucial to develop a membrane material suitable for low-concentration CO2 separation.

[0003] Among many membrane materials, mixed matrix membranes (MMM) based on metal organic frameworks (MOF) play a crucial role in the field of membrane separation, and the separation of low-concentration CO2 cannot be separated from MOF-based mixed matrix membranes. In the composition of MOF-based mixed matrix membranes, there are two parts of polymer matrix and MOF filler. Constructing groups with strong affinity to CO2 into MOF-based mixed matrix membranes is of great significance to the separation of low-concentration CO2.

[0004] In view of the global climate warming, environmental deterioration and other climate problems, through years of exploration in the field of CO2 separation membranes, combined with the separation characteristics of CO2 separation and MOF-based mixed matrix membranes, the present application provides a membrane material suitable for low-concentration CO2 separation in a humid environment, a preparation method and application. SUMMARY

[0005] The present application mixes two self-polymer microporous polymers (PIM-1 and PIM-2) with strong affinity to CO2 and high flux as the blending polymer matrix of the mixed matrix membrane, and at the same time, a suitable filler for the polymer matrix is synthesized. The filler is mixed into the blending polymer matrix to form a membrane material suitable for low-concentration CO2 separation. The affinity of the polymer to CO2 is changed by adjusting the amount of polymer monomer, catalyst and solvent. The particle size, pore size and affinity to CO2 of the filler are changed by adjusting the ratio between the metal salt and the organic ligand in the synthesis of the filler and the content of the adjusting agent. Thus, the CO2 flux and CO2 selectivity in membrane separation are changed.

[0006] The technical problem to be solved by the present application is to synthesize and prepare a membrane suitable for low-concentration CO2 (CO2:N2 ratio in the range of 1:99~15:85) separation. First, the problem of low selectivity of the polymer matrix itself under low-concentration CO2 is solved; by introducing F, the hydrophobicity of the membrane channel is forced, and the problems of instability of the membrane in a humid environment and insufficient CO2 adsorption sites are solved. The synthesis method, amount, time and operation of the polymer are explored. Second, the synthesis of the filler and its application in the blended polymer matrix are solved, and the synthesis method, amount, time and reaction method of the filler are explored. The application of the filler and the preparation method of the mixed matrix membrane are explored.

[0007] The technical scheme adopted by the present application is a preparation method of a membrane material suitable for low-concentration CO2 separation, and the method steps are as follows:

[0008] Step S1, synthesis of PIM-2 polymer: the reactants are prepared by weighing 5, 5', 6, 6'-tetrahydroxy-3, 3, 3', 3'-tetramethyl-1, 1'-spirobiphenyl, decafluorobiphenyl and potassium carbonate in proportion and adding them into a round-bottom flask; then N,N-dimethylformamide solvent is added to fully dissolve the reactants; and the reactants are placed in an oil bath stirrer for heating and stirring and protected by a protective gas; when the reaction is completed, the reactants are filtered and washed to obtain a grayish white powder; then the grayish white powder is stirred and washed in hydrochloric acid aqueous solution; after overnight, it is filtered and dried to obtain a polymer powder;

[0009] Step S2, synthesis of MOF filler: 2,5-dicarboxyfluorobenzene, zirconium chloride, formic acid and N,N-dimethylformamide are added to the reaction kettle in a certain proportion, and the reaction kettle is transferred to an oven for heating; then centrifugal drying treatment is performed to obtain the MOF filler;

[0010] Step S3, preparation of membrane material: a certain amount of polymer powder and MOF filler are added to a solvent, the polymer powder is PIM-1 prepared in a certain proportion and PIM-2 polymer prepared in step S1, and the stirring time is 1~2 days based on the dispersion of the MOF filler to form a casting solution; the casting solution is subjected to ultrasonic treatment, and the casting solution is dropped into a mold made of polytetrafluoroethylene material to obtain a shaped membrane material;

[0011] Step S4, activation of the membrane material: the shaped membrane material is placed in an oven at a certain temperature to activate and dry to remove residual solvents, and a membrane material suitable for low-concentration CO2 separation is prepared.

[0012] Further, in step S1, 5, 5', 6, 6'-tetrahydroxy-3, 3, 3', 3'-tetramethyl-1, 1'-spirobisoindane and potassium carbonate are added to 10 mL of N, N-dimethylformamide solvent, and then pre-reacted for 0.5-1 hour; tenfluorobiphenyl is added dropwise at a flow rate of 0.5-1 mmol / mL; the reaction temperature for synthesizing the polymer is 90-100 degrees Celsius, and the reaction time is 60-72 hours, which is adjusted according to the color change of the synthesized polymer. The ratio of 5, 5', 6, 6'-tetrahydroxy-3, 3, 3', 3'-tetramethyl-1, 1'-spirobisoindane, potassium carbonate and tenfluorobiphenyl is 1:1:1. By controlling the reaction temperature and time, the molecular weight of the polymer is controlled, so as to achieve the effect of separating low-concentration carbon dioxide. The material is not applied to the separation of low-concentration carbon dioxide in the industry.

[0013] Further, in step S1, the protective gas is nitrogen or argon; at the end of the reaction, the obtained powder is washed with a methanol or ethanol solution and placed in a 5% or less concentrated hydrochloric acid aqueous solution, stirred for 12-24 hours, and then filtered to obtain a polymer powder.

[0014] Further, in step S1, the raw material ratio of 5, 5', 6, 6'-tetrahydroxy-3, 3, 3', 3'-tetramethyl-1, 1'-spirobisoindane, tenfluorobiphenyl and potassium carbonate is 1:1:1, and the amount of N, N-dimethylformamide solvent added is 10 mL, which can be increased or decreased according to the dissolution degree of the raw materials.

[0015] Further, in step S1, the tenfluorobiphenyl is replaced by tetrafluoroterephthalonitrile to synthesize a PIM-1 polymer powder; when synthesizing PIM-1, the reaction temperature is adjusted to 65 degrees Celsius and the reaction time is 72 hours.

[0016] Further, in step S2, 2, 5-dicarboxyfluorobenzene, zirconium chloride and formic acid in a ratio of 1:1:100 are added to 30 mL of N, N-dimethylformamide solvent, the reaction temperature is 120 degrees Celsius, and the reaction time is 72 hours, and then the white powder is obtained by solvent exchange washing.

[0017] Further, in step S2, the raw material ratio of 2,5-dicarboxyfluorobenzene, zirconium chloride, and formic acid is 1:1:100, and the amount of N,N-dimethylformamide solvent added is 30 mL, which is increased or decreased according to the degree of dissolution of the raw materials. By adding 2,5-dicarboxyfluorobenzene, a MOF filler suitable for low-concentration carbon dioxide is synthesized. In this synthesis method, a MOF filler suitable for low-concentration carbon dioxide is synthesized. Not only is the raw material simply replaced, but the reaction temperature of 120 degrees Celsius and the time of 72 hours and the proportion of formic acid added are also the result of our innovative exploration in this formula. Moreover, the adsorption amount of CO2 of the MOF filler can finally reach 45 cm 3 / g, which is about 10% higher than the CO2 adsorption amount of 40 cm 3 / g of the UiO-66 MOF filler with the same framework structure under the same conditions. This is very important for the separation of low-concentration CO2.

[0018] Further, in step S2, the reaction temperature for synthesizing the MOF filler is 120 degrees Celsius, and the reaction time is 72 hours; at the end of the reaction, solvent exchange is performed with N,N-dimethylformamide and methanol; then centrifugation is performed to obtain the precipitate and dry the white filler powder.

[0019] Further, in step S3, the mass fraction of PIM-2 in the total mass of the polymer is 10wt%. The addition of PIM-2 can effectively enhance the affinity of the membrane material for low-concentration CO2, because the addition of F element sites on the membrane material improves the low-concentration CO2 separation capacity of the membrane material.

[0020] Further, in step S3, PIM-2 is added to chloroform or tetrahydrofuran solvent and stirred for 12 hours, then PIM-1 is added, and ultrasonic treatment is performed every 1-2 hours for 30 minutes during the stirring period.

[0021] Further, in step S3, after the two polymers are uniformly mixed, a certain amount of MOF filler is added, and stirring is performed for 1-2 days, and ultrasonic treatment is performed every 1-2 hours for 30 minutes during the stirring period. The optimal amount of MOF filler is 25wt%. The membrane material has good low-concentration CO2 separation effect under this amount of MOF filler.

[0022] Further, in step S3, before casting the membrane material, the casting solution should be ultrasonically treated for 30 minutes. The ultrasonically treated casting solution is dropped into a round polytetrafluoroethylene mold, and it is placed in chloroform or tetrahydrofuran vapor, and volatilized at room temperature, and peeled off and activated.

[0023] Further, in step S3, the proportion of the mixed polymer and the filler is expressed by mass fraction; the solvent for dissolving the polymer and the filler is chloroform or tetrahydrofuran; after the casting solution is added dropwise into the mold, it should be placed in a steam environment of the solvent used and left to dry and form, and then peeled off. In this part, the present application mainly explores the proportion between PIM-1 and PIM-2, so as to form a stable, not easy to break, high mechanical strength, and good CO2 separation effect membrane material, so that the polymer matrix with 10% PIM-2 addition amount is the best. After adding PIM-2, the separation effect of the membrane material on CO2 is enhanced, which is an important indicator for the separation of low concentration CO2. In the addition of MOF filler, it is found that when the MOF filler addition amount reaches 25wt%, the membrane material has good separation performance under low concentration CO2 (compared with most membrane materials and reaches 2019 Robeson upper bounds), and under the same MOF filler content, the 25wt% UiO-66 material filler exists filler agglomeration phenomenon, which is not conducive to the high selectivity screening of the membrane material under low concentration CO2. In summary, by considering the flexibility, performance and suitable element sites of the material in the membrane material, PIM-2 containing multiple F sites, MOF filler with F sites (MOF filler synthesized by 2,5-dicarboxyfluorobenzene) and PIM-1 polymer with good CO2 separation effect are introduced, through the exploration of the conditions in the material synthesis and the optimization of the membrane preparation process, the membrane material in the present application is obtained. And overcome the disadvantage that the membrane material is not suitable for low concentration CO2 separation.

[0024] Further, in step S4, the membrane material is placed in a vacuum oven at 60 degrees Celsius for activation of the membrane material.

[0025] Further, an application of a membrane material suitable for low concentration CO2 separation, a preparation method of a membrane material suitable for low concentration CO2 separation, and a membrane material suitable for low concentration CO2 separation, i.e. CO2:N2 ratio is within the range of 1:99~15:85; can be directly used for low concentration CO2 separation without any post-treatment; the use form can be folded, curled or cut according to the change of application scene.

[0026] The present application has the following advantages: (1) a polymer synthesis method with strong affinity for CO2 is explored, and the polymer is mixed with a high CO2 flux polymer, so that the blended polymer matrix of the membrane material has the potential for low concentration CO2 separation. (2) The filler suitable for low concentration CO2 separation is synthesized and prepared and applied to the blended polymer matrix, so that the whole membrane material is suitable for low concentration CO2 separation. (3) In the gas separation test, the membrane material shows strong separation performance for different CO2:N2 ratios, which proves that the improved membrane material has strong universality. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 The figure is a schematic diagram of the gas separation of the present application.

[0028] Fig. 2 The figure is a schematic diagram of the gas separation test process of the present application.

[0029] Fig. 3 The figure is a mixed polymer matrix membrane separation performance graph under the condition of CO2:N2=15:85 (note: the low concentration CO2 gas separation performance graph of the MOF filler is not given, but the membrane performance can be judged according to the examples). DETAILED DESCRIPTION

[0030] In order to make the purpose, scheme and advantages of the present application clearer and more obvious, the following specific examples and their drawings are further explained and described.

[0031] As Figs. 1-3 shown, the present application is a preparation method and application of a membrane material suitable for low concentration CO2 separation. The mixed matrix membrane prepared by the method adds MOF material with fluorine element sites as filler while keeping the filler skeleton unchanged, and PIM-1 and PIM-2 as polymer matrix. The present application overcomes the shortcomings in the field of low concentration CO2 membrane separation in a humid environment. The filler rich in fluorine element sites and the polymer matrix are combined, and the polymer synthesis method, temperature and time are explored. By exploring the way of adding fluorine element sites while keeping the metal organic skeleton unchanged, a mixed matrix membrane suitable for low concentration CO2 separation in a humid environment is successfully synthesized and prepared. The advantages and benefits of the present application are that the MOF-based mixed matrix membrane with multiple fluorine element sites shows good CO2 permeability and ultra-high CO2 / N2 selectivity in the field of membrane separation, and the strong affinity between the polymer matrix, the MOF filler and the CO2 molecule.

[0032] To demonstrate the strong low-concentration CO2 separation ability of the membrane material, we conducted low-concentration CO2 gas separation tests on the mixed matrix membranes prepared by synthesis, and the test methods are described in the following examples and results. In the examples, the CO2 flux and selectivity of the membrane material for various CO2:N2 gas ratios (mainly CO2:N2 = 1:99~15:85) were tested as shown in the accompanying drawings.

[0033] Example 1, exploration of PIM-2 synthesis

[0034] (1) Change the amount and ratio of monomers

[0035] 5, 5', 6, 6'-tetrahydroxy-3, 3, 3', 3'-tetramethyl-1, 1'-spiro-bisindane, decafluorobiphenyl and potassium carbonate were weighed according to the ratio of 1:1:1 and added to 10~20 mL of N,N-dimethylformamide solvent.

[0036] (2) Change the reaction temperature and time

[0037] Oil bath heating was performed using a magnetic stirring heating table, and the reaction temperature was controlled between 90~100 degrees Celsius. The reaction time was adjusted according to the reaction conditions.

[0038] (3) The obtained powder was tested for molecular weight.

[0039] (4) The obtained powder was characterized by X-ray diffraction, Fourier infrared spectroscopy, etc.

[0040] Example 2, preparation of blended polymers with different PIM-2 doping ratios

[0041] (1) Preparation of pure PIM-1 membrane material

[0042] 137 mg of PIM-1 polymer powder and 3 mL of chloroform solvent were added to a 10 mL glass bottle and stirred for 12 hours, then placed in an ultrasonic instrument for ultrasonic treatment. Drop it into a polytetrafluoroethylene mold and place it in a chloroform vapor environment overnight to evaporate. Peel off the pure PIM-1 membrane material and place it in a 60 degree Celsius vacuum oven for activation and drying.

[0043] (2) Preparation of PIM-2 / PIM-1 blended membrane material with different doping ratios.

[0044] The membrane preparation method is the same as in (1), only when adding polymer powder, PIM-2 polymer powder is added according to a certain ratio, as follows:

[0045] ;

[0046] (3) The obtained membrane material is characterized by X-ray diffraction, Fourier infrared spectrum, specific surface area and porosity analysis, scanning electron microscope and the like.

[0047] Example 3, preparation and characterization of mixed matrix membranes with different filler doping ratios

[0048] (1) The preparation method of the filler used in the application is described in the summary.

[0049] (2) The filler is characterized by X-ray diffraction, Fourier infrared spectrum, specific surface area and porosity analysis, scanning electron microscope and the like.

[0050] (3) The prepared filler is mixed with the blended polymer matrix to prepare a MOF-based mixed matrix membrane suitable for low-concentration CO2 separation.

[0051] A certain amount of filler is weighed and dispersed in chloroform solvent, and placed in an ultrasonic instrument to disperse into a uniform suspension. The blended polymer in example 2(2) is added. The rest of the operation is the same as the membrane preparation method in example 2(1).

[0052] The calculation formula of the amount of filler added is as follows:

[0053] ;

[0054] Example 4, low-concentration CO2 gas separation test of the prepared membrane material

[0055] In the test, we use CO2, N2 and He three kinds of gas, gas flow meter, gas mixing tank, self-made metal membrane cell, gas chromatograph and connected computer. (As Fig. 2 shown)

[0056] In the test, the CO2:N2 ratio is set to 1:99~15:85, the test temperature is 25 degrees Celsius, the test transmembrane pressure is 1 bar, the test relative humidity is 10~85%, and the He gas purge gas is usually determined by the flow rate of the mixed gas. The actual test values are as follows:

[0057]

[0058] The obtained membrane material in example 2 is subjected to low-concentration CO2 (CO2:N2=15:85) gas separation test (as Fig. 3 shown), and the specific results are shown in the following table:

[0059]

[0060] From the test results, we can see that with the increase of PIM-2 addition amount, the permeation rate of CO2 decreases, but its CO2 / N2 selectivity increases, which is beneficial to us to separate low concentration CO2 gas. And combined with the mechanical strength of the membrane material obtained in Example 2, the membrane material with 10% PIM-2 addition amount is selected as the blended polymer matrix to prepare the mixed matrix membrane.

[0061] The membrane material obtained in Example 3 is subjected to low concentration CO2 (CO2:N2=15:85) gas separation test, and the specific results are shown in the following table:

[0062]

[0063] From the test results, we can see that with the increase of filler addition amount, the permeation rate of CO2 increases greatly, which benefits from the large number of gas transmission channels in the filler, thereby facilitating the transport and transmission of low concentration CO2. At the same time, the addition of a large number of fluorine element sites is also an important factor for separating low concentration CO2. Combined with the actual data parameters, when the filler addition amount increases to 30%, the CO2 / N2 selectivity decreases greatly, which is due to the agglomeration of the filler particles in the membrane material.

[0064] The membrane material in Example 3 is subjected to 10-85% relative humidity test, and the test method and test environment are the same as those of other membrane materials, only a humidity bottle and a safety bottle are added at the mixed gas inlet. The specific results are shown in the following table:

[0065]

[0066] The membrane material in Example 3 is subjected to 1-15% CO2 concentration test, and good gas separation performance can also be obtained. The test method and test environment are the same as those of other membrane materials, and will not be described here.

[0067] In summary, the application of the application is a kind of membrane material suitable for low concentration CO2 separation, preparation method and application, which adopts multi-fluorine element site, blended polymer matrix method. In the case of slightly changing the overall mechanical strength of the membrane material and not changing the separation performance, the PIM-2 polymer matrix is synthesized and prepared, which enhances the affinity of the membrane material for low concentration CO2. At the same time, without changing the MOF filler skeleton, the introduction of fluorine atoms increases the hydrophobicity and binding force of MOF filler to CO2 molecules, thereby improving the overall separation ability of the membrane material for low concentration CO2 in a humid environment.

Claims

1. A method for preparing a membrane material suitable for separating low-concentration CO2, characterized in that: The steps are as follows: Step S1, Synthesis of PIM-2 polymer: 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, decafluorobiphenyl, and potassium carbonate were weighed in a specific ratio to prepare the reactants, which were then added to a round-bottom flask. N,N-dimethylformamide solvent was then added to fully dissolve the reactants. The reactants were then heated and stirred in an oil bath with a protective gas purging. At the end of the reaction, the reactants were filtered and washed to obtain a grayish-white powder. The grayish-white powder was then washed with hydrochloric acid solution and stirred. After overnight filtration and drying, polymer powder was obtained. Step S2, synthesis of MOF packing: 2,5-dicarboxyfluorobenzene, zirconium chloride, formic acid and N,N-dimethylformamide are added to a reaction vessel in a certain proportion, and the reaction vessel is transferred to an oven for heating; then centrifugation and drying are performed to obtain MOF packing; Step S3, preparation of membrane material: A certain amount of polymer powder and MOF filler are added to a solvent. The polymer powder is PIM-1 prepared in a certain proportion and PIM-2 prepared in step S1. The mixture is stirred for 1 to 2 days based on the dispersion of MOF filler to form a casting solution. The casting solution is ultrasonically treated and then dropped into a mold made of polytetrafluoroethylene to obtain the formed membrane material. Step S4, activation of membrane material: The formed membrane material is placed in an oven at a certain temperature to activate and dry it to remove residual solvent, thereby preparing a membrane material suitable for the separation of low concentration CO2.

2. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S1, 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane and potassium carbonate were added to 10 mL of N,N-dimethylformamide solvent and reacted for 0.5 to 1 hour beforehand. Decafluorobiphenyl was added dropwise at a flow rate of 0.5 to 1 mmol / mL. The reaction temperature for polymer synthesis was 90 to 100 degrees Celsius, and the reaction time was 60 to 72 hours, which was adjusted according to the color change of the synthesized polymer.

3. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S1, the protective gas is nitrogen or argon; at the end of the reaction, the powder is washed with methanol or ethanol solution and placed in a hydrochloric acid aqueous solution with a concentration of less than 5%, stirred for 12 to 24 hours, and filtered to obtain polymer powder.

4. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S2, 2,5-dicarboxyfluorobenzene, zirconium chloride, and formic acid in a ratio of 1:1:100 were added to 30 mL of N,N-dimethylformamide solvent. The reaction temperature was 120 degrees Celsius, and the reaction time was 72 hours. After washing with solvent exchange, a white powder was obtained.

5. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S3, the mass fraction of PIM-2 in the total polymer is 10 wt%.

6. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S3, PIM-2 needs to be added to chloroform or tetrahydrofuran solvent and stirred for 12 hours before adding PIM-1, and ultrasonic treatment for 30 minutes should be performed every 1 to 2 hours during the stirring cycle.

7. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S3, after the two polymers are mixed evenly, a certain amount of MOF filler is added and stirred for 1 to 2 days. During the stirring period, ultrasonic treatment is performed for 30 minutes every 1 to 2 hours. The optimal amount of MOF filler added is 25 wt%.

8. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S3, before casting the membrane material, the casting liquid should be ultrasonically treated for 30 minutes. The ultrasonically treated casting liquid should be dripped into a polytetrafluoroethylene circular mold and placed in chloroform or tetrahydrofuran vapor to evaporate at room temperature. After peeling, it should be activated.

9. The method for preparing a membrane material suitable for low-concentration CO2 separation according to claim 1, characterized in that: In step S4, the membrane material is placed in a vacuum oven at 60 degrees Celsius to activate it.

10. An application of a membrane material suitable for the separation of low-concentration CO2, comprising the method for preparing the membrane material suitable for the separation of low-concentration CO2 as described in claim 1, characterized in that: A membrane material suitable for the separation of low-concentration CO2 was prepared and used for the separation of low-concentration CO2, that is, the CO2:N2 ratio is in the range of 1:99 to 15:85; it can be used directly in the separation of low-concentration CO2 without any post-processing. Its form can be folded, rolled, or cut to suit different application scenarios.

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