A method for preparing an in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation

Abstract

A method for preparing an in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation belongs to the field of membrane technology. This method involves constructing a polydopamine (PDA) transition layer on a polysulfone (PSF) substrate and introducing polyvinylpyrrolidone (PVP) to assist in regulating the in-situ growth of ZIF-8, forming an organic-inorganic synergistically enhanced composite separation membrane. The resulting composite membrane consists of a porous support layer, a polydopamine modified layer, and a ZIF-8 functional layer. The PDA modified layer enhances the interfacial activity of the membrane surface, the ZIF-8 functional layer provides selective channels for gas molecule transport, and PVP plays a role in regulating crystal growth and improving membrane uniformity during membrane formation. This structure facilitates the formation of a relatively continuous and dense separation layer, improving the gas separation performance of the composite membrane. The composite membrane can be used for H2 / CO2 separation.

Description

Technical Field

[0001] This invention belongs to the field of membrane separation and gas separation materials technology, specifically relating to a method for preparing an in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation. Background Technology

[0002] Hydrogen, as an important clean energy carrier, has broad application prospects in fuel cells, chemical synthesis, metallurgy, and other fields. With the rapid development of hydrogen energy utilization, higher demands are being placed on the production and purification of high-purity hydrogen. Industrial processes such as methanol reforming and natural gas reforming often generate mixed gas streams containing hydrogen and carbon dioxide. How to efficiently and cost-effectively separate and enrich hydrogen from these mixtures has become an important technical task. Traditional separation methods mainly include cryogenic separation, power-assisted separation (PSA), solvent absorption, and membrane separation. Membrane separation technology, with its advantages of low energy consumption, compact structure, and ease of modular scaling, is considered one of the important routes for selectively enriching hydrogen in syngas and reformed gases. Among numerous membrane materials, metal-organic frameworks (MOFs) are considered highly promising functional materials for gas separation due to their tunable pore size, high specific surface area, and regular pore structure. ZIF-8, in particular, has attracted widespread attention for H2 / CO2 separation due to its good chemical and thermal stability, as well as its suitable microporous structure. However, in the actual membrane construction process, the simple ZIF-8 crystal layer often suffers from problems such as intercrystalline defects, insufficient interfacial bonding and poor membrane continuity, thereby weakening its ideal molecular sieving effect. In the existing technology, the preparation of ZIF-8 composite membranes often faces the following challenges: (1) poor compatibility between ZIF-8 crystals and polymer substrates, which easily leads to non-selective defect channels; (2) crystal growth is difficult to control, which easily leads to agglomeration or incomplete coverage; (3) insufficient membrane structure stability under high temperature or high pressure operating conditions. Therefore, how to achieve uniform nucleation and continuous growth of ZIF-8 on the polymer substrate surface is the key to improving its separation performance. Dopamine can undergo self-polymerization under weakly alkaline conditions to form a polydopamine (PDA) functional layer with strong adhesion and rich in hydroxyl and amine groups on the substrate surface. This layer can not only improve the wettability and interfacial activity of the substrate membrane surface, but also provide effective sites for the adsorption of metal ions and subsequent crystal growth. Therefore, it is widely used in the interface regulation of composite membranes. On the other hand, polyvinylpyrrolidone (PVP) molecules contain polar groups such as carbonyl groups, which can react with Zn²⁺. + The interaction between the particles and ZIF-8 can, to some extent, regulate the dispersion state of metal ions and the nucleation and growth behavior of ZIF-8, thereby potentially improving membrane integrity and reducing defect channels. Based on this understanding, developing a method that combines PDA interface modification, PVP-assisted regulation, and in-situ growth of ZIF-8 to achieve controlled particle growth at the interface and in-situ formation of a continuous membrane is key to improving the gas separation performance of composite membranes. Summary of the Invention

[0003] This invention provides a method for preparing an in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation. By combining surface modification and growth regulation, a ZIF-8 separation layer is constructed on the surface of the supporting membrane to improve the interfacial bonding state, membrane continuity and separation stability of the composite membrane.

[0004] Its characteristic is that a PDA transition layer is formed on the surface of a polysulfone film by dopamine self-polymerization, and a Zn²⁺ layer is formed on the surface of the PDA transition layer. + The PVP synergistic system induces in-situ growth of ZIF-8 to form a ZIF-8 separation layer, ultimately yielding a dense and continuous ZIF-8 composite membrane.

[0005] Specifically, the particle size of the ZIF-8 crystal is determined by the PVP concentration and Zn²⁺. + Concentration is synergistically regulated to ensure uniform dispersion in the membrane and the formation of continuous transport channels; the thickness of the PDA transition layer is in the nanometer range, the ZIF-8 crystals are distributed in the nanometer range with a particle size range of 20-40 nm, and the thickness of the selective layer is about 40-50 nm.

[0006] This invention provides a method for preparing the above-mentioned composite membrane, comprising the following steps: Step a: Immerse the supporting membrane in a Tris-HCl weakly alkaline buffer solution of dopamine hydrochloride (DA-HCl) to allow dopamine to undergo an oxidative self-polymerization reaction on the surface of the base membrane to form a PDA functional layer; after the reaction is completed, rinse quickly with deionized water to obtain a PDA-modified intermediate membrane. Step b: Impregnate the above intermediate membrane with a solution containing Zn²⁺. + In a mixed solution of Zn²⁺ and PVP, + It is adsorbed and dispersed on the surface and in the micropores of the PDA layer with the assistance of PVP; Step c: After drying or lightly blowing dry, immerse the membrane in a 2-methylimidazole (2-MI) solution to allow ZIF-8 to nucleate and grow in situ on the surface of the PDA layer. After washing and drying, the in-situ constructed ZIF-8 composite membrane is obtained.

[0007] Specifically, in step a, the supporting membrane is selected from polysulfone ultrafiltration membranes; Specifically, in step a, the concentration of DA-HCl is 2 mg / mL, the solvent is Tris-HCl buffer, the reaction temperature is room temperature, and the soaking time is 8 h; Specifically, in step b, Zn² + The source is selected from zinc nitrate (Zn(NO3)2·6H2O) or zinc chloride (ZnCl2), and the solvent is one or more of methanol or deionized water; Zn² +The solution concentration is 0.01–0.04 mol / L; Specifically, in step b, the molecular weight of PVP is K30, and the mass concentration of PVP in the impregnation solution is 0.1–0.5 wt%. Specifically, in step c, the solvent corresponding to the 2-methylimidazole solution is selected from methanol or deionized water, the concentration of the 2-methylimidazole solution is 0.08–0.32 mol / L, the reaction time is 8 h, the drying temperature is 60 ℃, and the drying time is 6–8 h.

[0008] Preferably, in step a, the concentration of Tris-HCl buffer is 10 mM, the concentration of dopamine hydrochloride is 2 mg / mL, the pH is 8.5, and the reaction time is 8 h. As a preferred option, Zn² in step b + The source is Zn(NO3)2·6H2O, the solvent is methanol, and Zn² + The concentration was 0.02 mol / L, the molecular weight of PVP was K30, the concentration of PVP was 0.2 wt%, and after ultrasonic dispersion, it was impregnated at room temperature for 30 min. As a preferred option, Zn² in step b + The molar ratio of 2-methylimidazole to 2-methylimidazole is 1:8; Preferably, the solvent in step c is methanol, the reaction time is 8 h, and the drying time in the oven at 60 ℃ is 8 h; Preferably, the preparation method described in steps b and c is the impregnation method, and the reaction temperature is room temperature.

[0009] The ZIF-8 composite membrane constructed in situ by the present invention is mainly used for gas separation, especially the separation of H2 / CO2.

[0010] A composite film was prepared by combining the metal-organic framework material ZIF-8 with a PDA transition layer and a PVP-assisted control layer through in-situ growth and interface regulation. During the preparation process, the PDA functional layer first self-polymerized on the surface of a polysulfone substrate, providing active sites for subsequent metal ion adsorption and crystal growth. Subsequently, Zn²⁺ was used to... + The PVP synergistic impregnation system utilizes the coordination regulation effect of PVP on metal ions to promote the uniform nucleation and continuous growth of ZIF-8 on the PDA layer surface, forming a dense composite separation layer with strong interfacial bonding. The synergistic effect of PDA's adhesion and reactivity, PVP's dispersion regulation effect, and ZIF-8's molecular sieving effect contribute to improving the membrane's structural integrity and gas separation performance.

[0011] To address the problems of numerous intergranular defects, weak interfacial bonding, and complex preparation methods in ZIF-type films, this invention employs PDA surface self-polymerization modification combined with PVP-assisted Zn²⁺. +Anchored nucleation strategy enables ZIF-8 crystals to be uniformly distributed and continuously grown on the polysulfone substrate surface, forming a dense and continuous composite structure. The PDA functional layer enhances interfacial bonding and provides nucleation sites, PVP regulates the metal ion dispersion state and crystal growth kinetics, and the porous structure of ZIF-8 provides rapid gas diffusion channels. The synergistic effect of these three elements helps improve the membrane's structural integrity and separation performance. Compared to the control membrane with only a PDA layer, the H2 / CO2 selectivity of the composite membrane increased from 3.98 to 12.86, an improvement of approximately 3.23 times; compared to the ZIF-8-PDA membrane without PVP, its selectivity increased from 5.45 to 12.86, an improvement of approximately 2.36 times. Attached Figure Description

[0012] Figure 1 SEM images of the surface of PSf base film (a), PDA modified film (b), and ZIF-8 composite film (c).

[0013] Figure 2 Cross-sectional SEM images of the PSf base film (d), the PDA modified film (e), and the ZIF-8 composite film (f). Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0015] This invention provides a ZIF-8 composite membrane prepared by in-situ growth. The composite membrane is prepared by constructing a PDA transition functional layer on the surface of a polysulfone substrate and introducing PVP to assist in the in-situ growth of ZIF-8. During the preparation process, the adhesion and reactivity of the PDA layer, the coordination regulation effect of PVP on metal ions, and the molecular sieving effect of ZIF-8 work synergistically to form a dense composite separation layer with strong interfacial bonding, thereby improving the structural integrity and gas separation performance of the membrane.

[0016] Specifically, the ZIF-8 porous coordination framework material exhibits excellent sieving properties for small molecule gases. ZIF-8 crystals are self-assembled from zinc ions and 2-methylimidazolium ligands, with a pore size of approximately 0.34 nm. This effectively restricts the passage of large molecule gases while allowing the diffusion of small molecule gases, thereby improving the hydrogen permeation rate and H2 / CO2 selectivity. In-situ growth of ZIF-8 crystals on the surface of the PDA layer can simultaneously improve the membrane's permeability and selectivity, solving the problem of traditional polymer membranes' difficulty in achieving a balance between flux and selectivity.

[0017] Specifically, the PDA transition layer is formed by the oxidative self-polymerization of dopamine in a weakly alkaline Tris-HCl buffer (pH 8.5), with a thickness on the nanometer scale. It is rich in active functional groups such as hydroxyl and amine groups, which can enhance the wettability and reactivity of the substrate surface and provide Zn²⁺. + Adsorption provides coordination sites, thereby promoting uniform nucleation and continuous growth of ZIF-8.

[0018] Specifically, the PVP plays a role in interface regulation and defect repair in the preparation of composite films. The amide carbonyl group in the PVP molecule can react with Zn²⁺. + Coordination interactions occur, regulating the dispersion state of metal ions and the nucleation and growth kinetics of ZIF-8. The PVP concentration is varied according to the concentration of the impregnation solution used for in-situ ZIF-8 growth; for example, when the PVP concentration is 0.1–0.2 wt%, the H2 / CO2 selectivity is significantly improved, and although the gas permeation rate decreases somewhat, it remains at a high level, indicating that an appropriate amount of PVP helps improve Zn²⁺ nucleation and growth. + The dispersion and uniformity of PVP at the interface promote the formation of a continuous ZIF-8 crystal layer with fewer defects. However, when the PVP concentration is 0.3–0.5 wt%, the permeation rates of H2 and CO2 decrease significantly, and the selectivity also declines, indicating that excessive PVP may cause pore blockage or increase mass transfer resistance. Controlling the PVP concentration at around 0.2 wt% allows the ZIF-8 crystals to form a continuous and uniform microporous layer structure on the membrane surface, improving the microchannel structure of the separation layer and enhancing the gas separation performance and structural stability of the membrane.

[0019] Specifically, the Zn² + Concentration primarily affects the nucleation density and crystal growth kinetics of ZIF-8. When the metal ion Zn²⁺... + When the concentration is 0.01–0.02 mol / L, the H2 permeation rate and H2 / CO2 selectivity increase simultaneously, indicating that higher metal ion concentrations are beneficial for increasing nucleation density and enhancing film continuity; while when Zn²⁺… + At concentrations of 0.03–0.04 mol / L, although the H2 permeation rate continued to increase, the selectivity decreased significantly. It is speculated that under high concentration conditions, crystal growth is too rapid, easily leading to intergranular defects or non-selective channels. (The text then abruptly shifts to a seemingly unrelated topic: "Zn²⁺...") + By controlling the concentration at around 0.02 mol / L, optimal performance can be achieved while balancing permeation rate and selectivity.

[0020] Specifically, the PDA transition layer described in this embodiment of the invention is formed in situ through a room temperature self-polymerization reaction, without the need for complex equipment; the ZIF-8 crystal is grown through a room temperature impregnation reaction, and the preparation process is relatively simple.

[0021] The preparation method of this composite membrane is simple and highly controllable, and the resulting membrane exhibits good performance in hydrogen purification and CO2 capture processes. This is achieved through a sequential process of "PDA layer formation by DA self-polymerization → Zn² impregnation". + The process of "PVP for metal ion anchoring and dispersion control → 2-MI impregnation for in-situ ZIF-8 growth → heat treatment" enables confined nucleation and firm embedding of ZIF-8 crystals on the surface of PDA functional layer. The introduction of PVP improves the uniformity of crystal distribution and the density of film layer. In terms of H2 / CO2 separation, the H2 flux can reach 289.12 GPU and the H2 / CO2 selectivity can reach 12.86.

[0022] The present invention will be further described below through specific embodiments.

[0023] In the following specific embodiments, operations without specified conditions are performed under standard conditions or conditions recommended by the manufacturer. Raw materials without specified manufacturers and specifications are all commercially available products.

[0024] Example 1 The ZIF-8 composite membrane was constructed in situ, with a PSf porous support layer as the substrate and PVP molecular weight of K30. The membrane was prepared by impregnation.

[0025] Step a: Formation of the PDA transition layer Dopamine hydrochloride was dissolved in Tris-HCl buffer (10 mM, pH 8.5) to prepare a 2 mg / mL dopamine hydrochloride solution. A clean PSf substrate membrane was immersed in this solution and reacted at room temperature for 8 h, allowing dopamine to undergo oxidative self-polymerization on the substrate membrane surface to form a PDA transition layer. After the reaction, the membrane was removed and washed with deionized water to remove unreacted monomers and residual solution from the surface. It was then dried at room temperature to obtain the PDA-modified intermediate membrane, denoted as the PDA-PSf membrane.

[0026] Step b: Zn² + / PVP Anchoring and Decentralized Control Zinc nitrate hexahydrate and PVP (K30) were dissolved in methanol to prepare Zn²⁺. + A mixed impregnation solution with a concentration of 0.02 mol / L and a PVP concentration of 0.2 wt% was prepared. The PDA-PSf membrane obtained in step a was immersed in the above mixed impregnation solution for 30 min to allow Zn²⁺ to form. + With the assistance of PVP, the liquid is adsorbed and dispersed relatively evenly on the surface of the PDA layer. After impregnation, the membrane is removed, excess liquid on the surface is gently shaken off, and it is allowed to stand at room temperature for 10 minutes.

[0027] Step c: In-situ growth of ZIF-8 and formation of composite membrane 2-Methylimidazole was dissolved in methanol to prepare a 0.16 mol / L 2-methylimidazole solution. The membrane obtained in step b was immersed in the above solution and reacted for 8 h to allow the Zn²⁺ pre-adsorbed on the membrane surface to react. + A coordination reaction with 2-methylimidazole was carried out to form a ZIF-8 layer in situ on the surface of the PDA layer. After the reaction was completed, the membrane was removed and gently rinsed with methanol to remove unreacted ligands and surface residues. It was then dried in an oven at 60 °C for 8 h to obtain the in-situ constructed ZIF-8 composite membrane.

[0028] Figure 1 (c) is the SEM surface of the composite film prepared in Example 1 of the present invention, with regular particle morphology. Figure 2 (f) is a SEM cross-section of the composite film prepared in Example 1 of the present invention, with a selective layer thickness of approximately 44 nm.

[0029] The composite membrane prepared in this embodiment was placed in a gas separation testing device for permeation performance testing. The test conditions were: H2 / CO2 mixed gas with a volume ratio of 1:1, a test pressure of 10 kPa, and a test temperature of 25 °C. The test results showed that the prepared composite membrane had an H2 flux of 289.12 GPU and an H2 / CO2 selectivity of 12.86 under the above conditions. This result indicates that after PVP-assisted regulation, a ZIF-8 functional layer with a certain separation function can be formed on the membrane surface, enabling the obtained composite membrane to exhibit good H2 / CO2 separation performance at 25 °C.

[0030] Comparative Experiment 1 Without introducing the PDA layer and ZIF-8 layer, the test was conducted using only the PSf base membrane. The test conditions were the same as in Example 1. The hydrogen flux of the pure PSf membrane at room temperature was measured to be 20643.50 GPU, and the H2 / CO2 selectivity was 1.73, indicating that its separation mainly relies on the loose porous structure of the base membrane itself and lacks effective molecular sieving ability.

[0031] Comparative Experiment 2 A PDA-modified membrane was prepared by introducing a PDA layer only on the surface of the PSf substrate, and the testing conditions were the same as in Example 1. The H2 flux of the PDA-modified membrane was measured to be 7116.71 GPU, and the H2 / CO2 selectivity was 3.98, indicating that the introduction of the PDA layer increased the mass transfer resistance to a certain extent, while also playing a preliminary role in regulating surface defects. Comparative Experiment 3 A ZIF-8-PDA membrane was prepared by introducing a PDA layer and a ZIF-8 layer without adding PVP. The testing conditions were the same as in Example 1. The H2 flux of the ZIF-8-PDA membrane was measured to be 1495.65 GPU, and the H2 / CO2 selectivity was 5.45, indicating that the introduction of the ZIF-8 microporous structure enhanced the membrane's size sieving effect. However, compared with Example 1 (with PVP added), its selectivity was still lower, suggesting that the introduction of PVP helps improve the growth state of ZIF-8 and membrane integrity, reduces membrane surface defects, and effectively improves H2 / CO2 separation performance.

[0032] Example 2 A series of gas separation membranes were provided, which differed from Example 1 in that the PVP concentration in step b was different, set to 0.1 wt%, 0.3 wt%, and 0.5 wt%, respectively, while the other conditions were the same as in Example 1.

[0033] Gas permeation tests were conducted on the gas separation membrane provided in Example 2. The test conditions were: (1) H2 / CO2 mixed gas (volume ratio 1:1); (2) test pressure of 10 kPa; and (3) test temperature of 25 °C. The test results showed that when the PVP concentration was 0.1 wt%, the hydrogen flux of the membrane was 1918.23 GPU and the H2 / CO2 selectivity was 5.31; when the PVP concentration was 0.3 wt%, the hydrogen flux was 187.52 GPU and the H2 / CO2 selectivity was 11.60; and when the PVP concentration was 0.5 wt%, the hydrogen flux was 94.13 GPU and the H2 / CO2 selectivity was 9.26.

[0034] Example 3 A series of gas separation membranes are provided, which differ from Example 1 in that Zn is used in step b. 2+ The concentrations were set to different values, namely 0.01 mol / L, 0.02 mol / L, and 0.04 mol / L; in step c, the concentration of 2-methylimidazole was changed proportionally, namely 0.08 mol / L, 0.16 mol / L, and 0.32 mol / L, and the other conditions were the same as in Example 1.

[0035] Gas permeation tests were conducted on the gas separation membrane provided in Example 3. The test conditions were: (1) H2 / CO2 mixed gas (volume ratio 1:1); (2) test pressure of 10 kPa; (3) test temperature of 25 ℃. The test results showed that Zn 2+ At a concentration of 0.01 mol / L, the membrane's hydrogen flux was 259.11 GPU, and the H2 / CO2 selectivity was 11.02; Zn 2+ At a concentration of 0.02 mol / L, the hydrogen flux was 289.12 GPUs, and the H2 / CO2 selectivity was 12.86; Zn2+ At a concentration of 0.04 mol / L, the hydrogen flux was 442.35 GPU and the H2 / CO2 selectivity was 6.74.

[0036] The experimental results above show that the organic-inorganic synergistic enhancement structure formed in Example 1 through "PDA surface modification + PVP-assisted regulation + ZIF-8 in-situ growth" improves the limitations of traditional composite membrane preparation technology. In traditional processes, ZIF particles need to be prepared separately before being mixed and coated with the polymer matrix, which easily leads to uneven particle dispersion and interfacial voids between the particles and the matrix. In this application, ZIF-8 is nucleated and grown in-situ on the surface of the PDA functional layer, and uniform dispersion is achieved through PVP regulation, forming a continuous and dense separation layer. Compared with traditional processes, this method improves the interfacial compatibility, structural integrity, and molecular sieve effect of the membrane, significantly improving gas separation performance and exhibiting higher selectivity and stability. This indicates that the ZIF-8 composite membrane constructed in-situ in this invention has application potential in gas separation, especially in the field of H2 / CO2 separation.

[0037] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation, characterized in that: A polydopamine (PDA) transitional functional layer is formed on the surface of a porous support membrane through dopamine self-polymerization, and Zn²⁺ is applied to the surface of the PDA functional layer. + The PVP synergistic system induces the growth of ZIF-8 to form a ZIF-8 separation layer, ultimately yielding a dense and continuous ZIF-8 composite membrane.

2. The method for preparing an in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation according to claim 1, characterized in that, The PDA functional layer is formed by impregnation with dopamine solution using a porous support membrane; the ZIF-8 in the composite membrane is Zn²⁺. + It is formed by in-situ growth of 2-methylimidazole on PDA-modified surfaces.

3. The method for preparing the in-situ constructed ZIF-8 composite membrane for H2 / CO2 separation according to any one of claims 1-2, comprising the following steps: Step a: Immerse the supporting membrane in a Tris-HCl weakly alkaline buffer solution of dopamine hydrochloride at room temperature to allow dopamine to undergo an oxidative self-polymerization reaction on the surface of the base membrane to form a PDA functional layer; after the reaction is complete, rinse quickly with deionized water to obtain a PDA-modified intermediate membrane. Step b: Impregnate the above intermediate membrane with a solution containing Zn²⁺. + In a mixed solution of Zn²⁺ and PVP, + It is adsorbed and dispersed on the surface and in the micropores of the PDA layer with the assistance of PVP; Step c: After drying or lightly blowing dry, immerse the membrane in a 2-methylimidazole solution to allow ZIF-8 to nucleate and grow in situ on the surface of the PDA layer. After washing and drying, a dense and continuous ZIF-8 composite membrane is obtained.

4. The method according to claim 3, characterized in that: The supporting membrane is polysulfone.

5. The method according to claim 3, characterized in that, In step a, the concentration of dopamine hydrochloride solution was 2 mg / mL, the solvent was Tris-HCl buffer (pH 8.5), the reaction temperature was room temperature, and the reaction time was 8 h.

6. The method according to claim 3, characterized in that, In step b, Zn² + The source is Zn(NO3)2·6H2O, and the solvent is methanol; the concentration of Zn2+ solution is 0.01~0.04 mol / L.

7. The method according to claim 3, characterized in that, In step b, the molecular weight of PVP is K30, and the mass concentration of PVP in the impregnation solution is 0.1–0.5 wt%.

8. The method according to claim 3, characterized in that, In step b, Zn² + The molar ratio of 2-methylimidazole in step c is 1:

8.

9. The method according to claim 3, characterized in that, In step c, the solvent for the 2-methylimidazole solution is methanol; the reaction time is 8 h.

10. The ZIF-8 composite membrane according to any one of claims 1-2, used as a permeation membrane for H2 / CO2 separation.

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