A method for the preparation of a gas separation membrane by magnetic field-induced photo-initiated curing

Abstract

The application belongs to the technical field of gas separation membrane preparation, and particularly relates to a method for preparing a gas separation membrane by magnetic field induction and light-induced solidification, which comprises the following steps: first, preparing polydopamine (PDA) coated magnetic nanoparticles, then mixing the magnetic nanoparticles with a prepolymer and a photoinitiator to prepare a prepolymer solution; by sequentially applying a vertical static magnetic field, an alternating magnetic field and a vertical gradient magnetic field, the magnetic nanoparticles are induced to form a gradient orientation arrangement along the film thickness direction, then ultraviolet light rapid solidification is performed under the condition of maintaining the gradient magnetic field, and finally, a finished product film is obtained after vacuum heat treatment. The gas separation membrane prepared by the method has a vertical gradient channel along the thickness direction, uniform pore size distribution and low mass transfer resistance, and simultaneously has high gas permeation flux and high separation selectivity, breaks through the upper limit of Robeson, and has excellent anti-pollution performance, and has a wide application prospect in the field of gas separation such as natural gas purification and carbon capture.

Description

Technical Field

[0001] This invention belongs to the field of gas separation membrane preparation technology, and particularly relates to a method for preparing gas separation membranes by magnetic field-induced photo-initiated curing. Background Technology

[0002] Gas membrane separation technology is a new type of separation technology that has developed rapidly in the 1980s. Compared with traditional gas separation technologies such as distillation, adsorption, and absorption, it has advantages such as low energy consumption, no secondary pollution, simple operation, small footprint, and no phase change process. It has been widely used in industrial fields such as natural gas purification, synthetic ammonia tail gas recovery, air oxygen and nitrogen separation, and industrial waste gas carbon capture, and has become one of the key technologies in modern industrial separation processes.

[0003] However, existing commercial gas separation membranes are generally limited by the Robeson limit, meaning there is an inverse relationship between gas permeation flux and separation selectivity: increasing permeation flux often leads to a decrease in selectivity, while increasing selectivity is usually accompanied by a significant decrease in flux, making it difficult to achieve both high flux and high selectivity simultaneously. Furthermore, industrial gases typically contain impurities such as dust and tar, which easily adsorb onto the membrane surface and clog the pores, causing membrane fouling. This leads to rapid degradation of membrane performance and a shortened lifespan, further limiting the large-scale application of gas membrane separation technology.

[0004] Magnetic field-induced orientation (MFOC) membrane fabrication is a recently emerging method for membrane structure control. It involves using an external magnetic field to drive the directional arrangement of magnetic packing material within the membrane substrate, thereby constructing ordered mass transfer channels. However, most existing MFOC techniques only utilize a single static magnetic field to achieve simple packing material orientation, making it difficult to construct gradient pore structures along the membrane thickness direction and simultaneously achieving both flux and selectivity. Furthermore, they often combine with traditional membrane formation methods such as thermally induced phase separation and non-solvent-induced phase separation, resulting in long formation cycles and poor pore structure controllability. Therefore, developing a method for preparing gas separation membranes that can simultaneously achieve high permeate flux, high separation selectivity, and excellent antifouling performance is a pressing technical problem in this field. Summary of the Invention

[0005] This invention addresses the technical problems of existing gas separation membranes, which cannot simultaneously achieve high permeation flux and high selectivity, and have poor antifouling performance. It proposes a method for preparing gas separation membranes by magnetic field induction and photo-initiated curing. The method constructs a vertical gradient pore structure through three-stage magnetic field induction, and combines it with rapid curing and shaping by ultraviolet light to prepare a gas separation membrane that combines high flux, high selectivity and excellent antifouling performance, thus overcoming the limitation of the Robeson limit.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is a method for preparing a gas separation membrane by magnetic field-induced photo-initiated curing, comprising the following steps:

[0007] S1. Preparation of PDA@magnetic nanoparticles: Magnetic nanoparticles were dispersed in an ethanol / water mixed solution and sonicated for at least 15 min to obtain a uniform magnetic nanoparticle dispersion. Tris buffer was added to adjust the pH of the solution to weakly alkaline, and dopamine hydrochloride was added. The mixture was stirred continuously for at least 12 h to allow dopamine to self-polymerize in situ on the nanoparticle surface to form a polydopamine (PDA) coating layer. After the reaction was completed, the PDA-coated magnetic nanoparticles were collected by magnetic separation, washed at least 3 times each with deionized water and ethanol, and dried in a vacuum oven at 40 °C to obtain PDA@magnetic nanoparticles.

[0008] S2. Preparation of prepolymer solution: Add the PDA@magnetic nanoparticles to the prepolymer according to the ratio, and ultrasonically disperse for at least 15 min to ensure uniform dispersion of the particles; add photoinitiator, and stir in the dark until the photoinitiator is completely dissolved; then vacuum degas for at least 30 min under dark conditions to remove bubbles and dissolved oxygen in the system, and obtain a uniform and stable prepolymer solution.

[0009] S3. Magnetic field-induced orientation: The prepolymer liquid is uniformly injected into a high-transmittance mold with a set gap. An electromagnet or neodymium iron boron magnet array with an adjustable magnetic field is used as the magnetic field generating device, and the magnetic field is applied in the following sequence:

[0010] ① Apply a vertical static magnetic field and maintain it for a set time to allow the magnetic nanoparticles to initially align along the direction of the magnetic field;

[0011] ② Switch to an alternating magnetic field and maintain it for a set time. The oscillation of the alternating magnetic field breaks up the particle agglomerates, optimizing particle dispersion and uniformity of arrangement.

[0012] ③ Switch to a vertical gradient magnetic field and maintain it for a set time to drive magnetic nanoparticles to migrate and arrange along the film thickness direction, forming a gradient-distributed pore framework.

[0013] S4. Ultraviolet curing: While maintaining the vertical gradient magnetic field unchanged, the prepolymer liquid in the mold is irradiated with an ultraviolet light source of a set wavelength to induce rapid cross-linking and curing of the prepolymer; after curing, the magnetic field strength is slowly reduced until it is completely eliminated to obtain a gas separation membrane precursor that has been initially cross-linked and cured.

[0014] S5. Post-processing: The pre-crosslinked and cured gas separation membrane precursor is placed in a vacuum oven for heat treatment to further improve the degree of crosslinking and mechanical strength of the membrane. After naturally cooling to room temperature, the finished gas separation membrane is obtained.

[0015] Preferably, in step S1, the magnetic nanoparticles are selected from at least one of Fe3O4 nanoparticles, γ-Fe2O3 nanoparticles, α-Fe2O3 / TiO2 composite nanoparticles, Co-based nanoparticles, Ni nanoparticles, NdFeB nanoparticles, CoFe2O4 nanoparticles, NiFe2O4 nanoparticles, MnFe2O4 nanoparticles, and ZnFe2O4 nanoparticles.

[0016] Preferably, in step S1, the solid content of the magnetic nanoparticle dispersion is 0.1~10wt%; the volume ratio of ethanol to water is 1:99~99:1, preferably 1:1~1:2; the pH value of the solution is 8~10, preferably 8~9; and the mass ratio of polydopamine to magnetic nanoparticles is 1:99~99:1, preferably 1:1~1:10.

[0017] Preferably, in step S2, the prepolymer is selected from at least one of polyethylene glycol diacrylate (PEGDA), thiol-olefin system, acrylic polyurethane, polyethylene oxide composite system, and copolyimide.

[0018] Preferably, in step S2, the photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenylpropanone (1173), 1-hydroxycyclohexylphenyl ketone (184), 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone (2959), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), ethyl(2,4,6-trimethylbenzoyl)phenylphosphine ester (TPO-L), and benzophenone (BP).

[0019] Preferably, in step S2, the amount of the prepolymer added is 78-99 wt%, preferably 85-95 wt%, based on the total mass of the prepolymer liquid; the amount of the PDA@magnetic nanoparticles added is 1-20 wt%, preferably 5-15 wt%; and the amount of the photoinitiator added is 0.1-2 wt%, preferably 1-2 wt%.

[0020] Preferably, in step S3, the magnetic field strength of the vertical static magnetic field is 1~1000G, preferably 200~500G; the application time is 1~120s, preferably 20~50s. The magnetic field strength of the alternating magnetic field is 1~1000G, preferably 100~300G; the frequency is 1~1000Hz, preferably 1~10Hz; the application time is 1~120s, preferably 1~80s. The magnetic field strength of the vertical gradient magnetic field is 0~1000G, preferably 0~500G; the magnetic field gradient is 1~100G / mm, preferably 10~100G / mm.

[0021] Preferably, in step S4, the wavelength of the ultraviolet light source is 365 nm; the irradiation intensity is 1~1000 mW / cm², preferably 50~100 mW / cm²; and the irradiation time is 1~300 s, preferably 30~150 s.

[0022] Preferably, in step S5, the heat treatment temperature is 40~150℃, more preferably 80~120℃; and the heat treatment time is 1~24h, more preferably 2~4h.

[0023] Compared with the prior art, the advantages and positive effects of the present invention are as follows:

[0024] 1. This invention employs a three-stage magnetic field induction strategy of "static magnetic field initial orientation - alternating magnetic field dispersion and homogenization - gradient magnetic field gradient arrangement", which can precisely control the spatial distribution of magnetic nanoparticles in the membrane substrate and construct a vertical gradient pore structure along the membrane thickness direction: the feed side has a larger pore size, which can reduce gas mass transfer resistance and increase permeation flux; the permeation side has a smaller pore size, which can play a molecular sieving role and ensure high separation selectivity, thereby breaking through the traditional Robeson limit and achieving both high throughput and high selectivity.

[0025] 2. This invention uses ultraviolet light-induced curing technology, which can complete the rapid cross-linking of the prepolymer within seconds to minutes. During the curing process, the gradient magnetic field is kept constant and then slowly demagnetized. This can accurately shape the gradient pore structure induced by the magnetic field, avoid structural rebound, and achieve high controllability of the pore structure. The film formation efficiency is much higher than that of traditional thermosetting and phase inversion methods.

[0026] 3. This invention uses polydopamine (PDA) to coat the surface of magnetic nanoparticles, which can significantly improve the dispersibility and interfacial compatibility of nanoparticles in the prepolymer and reduce membrane defects. At the same time, the hydrophilicity of PDA can improve the wettability of the membrane surface, reduce the adsorption tendency of dust and other impurities, improve the antifouling performance of the membrane, and extend its service life.

[0027] 4. The preparation process of this invention is simple and the parameters are highly adjustable. The pore structure and separation performance of the membrane can be flexibly controlled by adjusting parameters such as the amount of nanoparticles added, magnetic field gradient, and UV curing intensity. It is suitable for large-scale production and has broad application prospects in gas separation fields such as natural gas decarbonization, industrial flue gas carbon capture, and organic vapor recovery. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the vertical gradient pore structure of the gas separation membrane prepared according to the present invention. Detailed Implementation

[0030] To better understand the above-mentioned objectives, features, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0031] Numerous specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways than those described herein, and therefore the invention is not limited to the specific embodiments disclosed in the following specification.

[0032] In this example, all raw materials used are commercially available conventional chemical reagents; the performance testing methods are uniformly as follows:

[0033] The permeation fluxes of CO2 and CH4 were measured using a BONA-GS-17 gas permeation tester at 25℃ and 0.1MPa, and the CO2 / CH4 separation selectivity was calculated.

[0034] Antifouling performance test: Under the conditions of 25℃ and 7MPa, a CO2 / CH4 mixed gas (volume ratio 50:50) containing dust was continuously introduced for 24h, and the CO2 permeation flux and CO2 / CH4 selectivity were measured again. The antifouling ability of the membrane was evaluated by the performance change rate.

[0035] Example 1: The method for preparing a gas separation membrane by magnetic field-induced photo-initiated curing in this example includes the following steps:

[0036] S1. Preparation of PDA@Fe3O4 nanoparticles: Fe3O4 nanoparticles were dispersed in a mixed solution of ethanol / water at a volume ratio of 1:1 and sonicated for 15 min to obtain a Fe3O4 nanoparticle dispersion with a solid content of 10 wt%. Tris buffer was added to adjust the pH of the solution to 8.5, and dopamine hydrochloride was added to control the mass ratio of polydopamine to Fe3O4 nanoparticles to 1:10. The mixture was stirred continuously for 12 h. After the reaction was completed, the product was collected by magnetic separation, washed three times each with deionized water and ethanol, and dried in a vacuum oven at 40 °C to obtain PDA@Fe3O4 nanoparticles.

[0037] S2. Preparation of prepolymer: 94wt% PEGDA prepolymer and 5wt% PDA@Fe3O4 nanoparticles were mixed by mass percentage and ultrasonically dispersed for 15min; 1wt% photoinitiator 1173 (2-hydroxy-2-methyl-1-phenylpropanone) was added and stirred in the dark until completely dissolved; then vacuum degassing was carried out in the dark for 30min to obtain a homogeneous prepolymer.

[0038] S3. Magnetic field-induced orientation: Inject the prepolymer liquid into a high-transmittance mold with a set gap, and apply a magnetic field using an electromagnet: First, apply a vertical static magnetic field with an intensity of 300G for 30s; then switch to an alternating magnetic field with a frequency of 10Hz and an intensity of 200G for 60s; finally, switch to a vertical gradient magnetic field with an intensity range of 0~500G and a gradient of 10G / mm, and maintain it until curing is complete.

[0039] S4. UV Curing: Maintaining a constant vertical gradient magnetic field, irradiate with a UV light source of 365nm wavelength and 50mW / cm² intensity for 150s; after curing, slowly reduce the magnetic field intensity to zero to obtain a pre-crosslinked membrane precursor. S5. Post-treatment: Place the membrane precursor in a vacuum oven and heat-treat at 120℃ for 2h. After natural cooling to room temperature, obtain the finished gas separation membrane.

[0040] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1815 GPU, and the CO2 / CH4 selectivity is 121. After continuously introducing a mixture of dusty gas for 24 hours, the CO2 permeation flux is 1796 GPU, the CO2 / CH4 selectivity is 124, and the flux decay rate is about 1.05%, indicating excellent antifouling performance.

[0041] Example 2 is basically the same as Example 1, except that in step S2, the amount of PEGDA added is 89wt%, the amount of PDA@Fe3O4 nanoparticles added is 10wt%, and the amount of photoinitiator 1173 added is 1wt%.

[0042] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1578 GPU, and the CO2 / CH4 selectivity is 143. After continuously introducing a mixture of dusty gas for 24 hours, the CO2 permeation flux is 1500 GPU, the CO2 / CH4 selectivity is 150, and the flux decay rate is about 4.94%.

[0043] Example 3 is basically the same as Example 1, except that in step S2, the amount of PEGDA added is 84wt%, the amount of PDA@Fe3O4 nanoparticles added is 15wt%, and the amount of photoinitiator 1173 added is 1wt%.

[0044] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1296 GPU, and the CO2 / CH4 selectivity is 187. After continuously introducing a mixture of dusty gas for 24 hours, the CO2 permeation flux is 1179 GPU, the CO2 / CH4 selectivity is 179, and the flux decay rate is about 9.03%.

[0045] Example 4 is basically the same as Example 1, except that in step S3, the gradient of the vertical gradient magnetic field is 50G / mm.

[0046] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1620 GPU, and the CO2 / CH4 selectivity is 139. After continuously introducing a mixture of dusty gas for 24 hours, the CO2 permeation flux is 1599 GPU, the CO2 / CH4 selectivity is 141, and the flux decay rate is about 1.30%.

[0047] Example 5 is basically the same as Example 1, except that in step S3, the gradient of the vertical gradient magnetic field is 100G / mm.

[0048] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1342 GPU, and the CO2 / CH4 selectivity is 178. After continuously introducing a mixture of dusty gas for 24 hours, the CO2 permeation flux is 1339 GPU, the CO2 / CH4 selectivity is 176, and the flux decay rate is about 0.22%, indicating excellent antifouling performance.

[0049] Example 6 is basically the same as Example 1, except that in step S4, the ultraviolet irradiation intensity is 80mW / cm².

[0050] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1523 GPU, and the CO2 / CH4 selectivity is 131. After continuously introducing a mixture of dust and gas for 24 hours, the CO2 permeation flux is 1487 GPU, the CO2 / CH4 selectivity is 130, and the flux decay rate is about 2.36%.

[0051] Example 7 is basically the same as Example 1, except that in step S4, the ultraviolet irradiation intensity is 100mW / cm².

[0052] Performance test results: The CO2 permeation flux of the membrane in this embodiment is 1211 GPU, and the CO2 / CH4 selectivity is 156. After continuously introducing a mixture of dusty gas for 24 hours, the CO2 permeation flux is 1199 GPU, the CO2 / CH4 selectivity is 160, and the flux decay rate is about 0.99%.

[0053] The overall performance data of each embodiment is summarized in Table 1:

[0054]

[0055] Table 1: Separation performance of fresh membrane and dust contamination after 24 hours in each embodiment

[0056] Performance pattern analysis:

[0057] 1. Effect of nanoparticle addition amount (Examples 1-3): As the amount of PDA@magnetic nanoparticles added increases, the interparticle spacing decreases, the pore size of the constructed channels shrinks, and thus the gas separation selectivity gradually improves, but the mass transfer resistance increases and the permeation flux decreases accordingly. Different separation requirements can be matched by adjusting the amount of particles added.

[0058] 2. Effect of magnetic field gradient (Examples 1, 4, 5): As the gradient of the vertical gradient magnetic field increases, the distribution gradient of nanoparticles along the membrane thickness direction becomes more significant, and the shrinkage of the permeate-side pores becomes more obvious. Therefore, the separation selectivity is improved and the permeate flux is reduced. At the same time, the gradient pore structure is more regular, the membrane surface is smoother, and the antifouling performance is further improved.

[0059] 3. Effect of UV curing strength (Examples 1, 6, 7): As the UV irradiation intensity increases, the crosslinking degree of the PEGDA prepolymer increases, the membrane matrix density increases, thus the permeation flux decreases and the separation selectivity increases.

[0060] 4. Anti-fouling performance: After 24 hours of introducing a mixture of dust-containing gas, the flux decay rate of all embodiments was less than 10%, and the decay rate of some embodiments was less than 1%, indicating that the membrane prepared by the present invention has excellent anti-fouling performance. Thanks to the hydrophilic modification of the PDA coating layer and the structural advantages of the gradient pores, it is not easy to cause pore blockage and surface contamination.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments for application in other fields. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing, characterized in that, Includes the following steps: S1. Preparation of PDA@magnetic nanoparticles: Magnetic nanoparticles were dispersed in an ethanol / water mixed solution and ultrasonically dispersed to obtain a magnetic nanoparticle dispersion. Tris buffer was added to adjust the pH of the solution to weakly alkaline. Dopamine hydrochloride was then added and the reaction was stirred to allow dopamine to polymerize in situ to form a polydopamine coating layer. After the reaction was completed, the product was collected by magnetic separation and obtained PDA@magnetic nanoparticles after washing and drying. S2. Preparation of prepolymer: PDA@magnetic nanoparticles are added to the prepolymer, ultrasonically dispersed evenly, photoinitiator is added, and stirred in the dark until completely dissolved. Then, vacuum degassing is carried out in the dark to obtain a homogeneous prepolymer. S3. Magnetic field-induced orientation: The prepolymer liquid is injected into a high-transmittance mold with a set gap, and a vertical static magnetic field, an alternating magnetic field, and a vertical gradient magnetic field are applied to the mold in sequence to complete the orientation, homogenization and gradient arrangement of magnetic nanoparticles. S4. Ultraviolet curing: Maintain the vertical gradient magnetic field and use an ultraviolet light source to irradiate and crosslink the prepolymer liquid in the mold. After curing, slowly eliminate the magnetic field to obtain a pre-crosslinked gas separation membrane precursor. S5. Post-processing: The gas separation membrane precursor is placed in a vacuum oven for heat treatment and then naturally cooled to room temperature to obtain the finished gas separation membrane.

2. The method for preparing a gas separation membrane by magnetic field-induced photo-initiated curing according to claim 1, characterized in that, In step S1, the magnetic nanoparticles are selected from at least one of Fe3O4 nanoparticles, γ-Fe2O3 nanoparticles, α-Fe2O3 / TiO2 composite nanoparticles, Co-based nanoparticles, Ni nanoparticles, NdFeB nanoparticles, CoFe2O4 nanoparticles, NiFe2O4 nanoparticles, MnFe2O4 nanoparticles, and ZnFe2O4 nanoparticles.

3. The method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing according to claim 1, characterized in that, In step S1, the solid content of the magnetic nanoparticle dispersion is 0.1~10wt%, the volume ratio of ethanol to water is 1:99~99:1, the pH value of the solution is 8~10, and the mass ratio of polydopamine to magnetic nanoparticles is 1:99~99:

1.

4. The method for preparing a gas separation membrane by magnetic field-induced photo-initiated curing according to claim 1, characterized in that, In step S2, the prepolymer is selected from at least one of polyethylene glycol diacrylate (PEGDA), thiol-olefin system, acrylic polyurethane, polyethylene oxide composite system, and copolyimide.

5. The method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing according to claim 1, characterized in that, In step S2, the photoinitiator is selected from at least one of 2-hydroxy-2-methyl-1-phenylpropanone (1173), 1-hydroxycyclohexylphenyl ketone (184), 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylphenylpropanone (2959), 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), ethyl(2,4,6-trimethylbenzoyl)phenylphosphine ester (TPO-L), and benzophenone (BP).

6. The method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing according to claim 1, characterized in that, In step S2, based on the total mass of the prepolymer liquid, the amount of the prepolymer added is 78~99wt%, the amount of the PDA@magnetic nanoparticles added is 1~20wt%, and the amount of the photoinitiator added is 0.1~2wt%.

7. The method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing according to claim 1, characterized in that, In step S3: the magnetic field strength of the vertical static magnetic field is 1~1000G, the application time is 1~120s, the magnetic field strength of the alternating magnetic field is 1~1000G, the frequency is 1~1000Hz, the application time is 1~120s, and the magnetic field strength of the vertical gradient magnetic field is 0~1000G, and the magnetic field gradient is 1~100G / mm.

8. The method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing according to claim 1, characterized in that, In step S4, the wavelength of the ultraviolet light source is 365 nm, and the irradiance is 1~1000 mW / cm². 2 The irradiation time is 1~300s.

9. The method for preparing a gas separation membrane by magnetic field-induced photoinitiated curing according to claim 1, characterized in that, In step S5, the heat treatment temperature is 40~150℃ and the heat treatment time is 1~24h.

10. A gas separation membrane, characterized in that, The gas separation membrane, prepared by any one of claims 1 to 9, has vertical gradient channels inside along the membrane thickness direction, and the pore size gradually decreases along the gas permeation direction.

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