A CO2 separation composite membrane with nucleophilic-coordination bifunction and a preparation method and application thereof

Abstract

The application belongs to the technical field of gas separation membrane materials, and provides a CO2 separation composite membrane with nucleophilic-coordination bifunctionality, a preparation method and application thereof; the composite membrane comprises a porous support layer, a functional buffer layer and a selection layer arranged in sequence, reaction-type metal organic framework nanoparticles are concentrated and localized in an interface region between the functional buffer layer and the selection layer, and are covalently connected with the functional buffer layer and the selection layer respectively, forming an interface bridging structure; the composite membrane simultaneously has nucleophilic CO2 transmission function and metal coordination type CO2 transmission function, effectively avoiding particle agglomeration and non-selective interface gap problems, and showing excellent long-term operation stability under high humidity and pressure fluctuation conditions, and can be used for CO2 separation, enrichment or removal in a CO2-containing mixed gas.

Description

Technical Field

[0001] This application relates to the field of gas separation membrane material technology, and more specifically, to a CO2 separation composite membrane with nucleophilic-coordination dual function, its preparation method, and its application. Background Technology

[0002] Membrane separation technology boasts advantages such as low energy consumption, compact processes, continuous operation, and ease of modular integration, making it a crucial technological route for flue gas decarbonization, natural gas purification, and industrial separation of carbon dioxide (CO2)-containing gases. To enhance the selective CO2 transport capacity of membranes, functional sites capable of reversible interactions with CO2 are typically introduced into the selective layer. Nucleophilic nitrogen-containing sites, such as those containing amino groups, can promote CO2 transport through reversible nucleophilic reactions; materials with open metal sites or coordinated unsaturated metal sites can enhance CO2 adsorption and transport through reversible coordination interactions. Theoretically, integrating both types of sites within the same membrane could potentially further improve CO2 separation performance.

[0003] In existing technologies, bifunctional enhanced transport membranes are typically prepared using a direct blending method, where metal-organic framework (MOF) nanoparticles are mixed with a film-forming carrier or polymer solution to form a membrane. However, in this method, the MOFs are usually randomly dispersed or physically embedded within the selective layer, lacking effective control over their spatial distribution. This leads to particle aggregation and the formation of non-selective interfacial voids between the particles and the polymer. More importantly, in the physically blended state, there is a lack of stable chemical bonding between the MOFs and the underlying buffer layer, relying mainly on polymer embedding or weak interactions to maintain their position. Under conditions of high humidity, high CO2 partial pressure, pressure fluctuations, or long-term operation, the swelling and relaxation of polymer segments can cause particle migration and expansion of interfacial voids, resulting in decreased membrane separation performance and even structural failure. Therefore, simply increasing the MOF content cannot fundamentally solve the problems of uncontrollable particle spatial arrangement and insufficient interfacial stability.

[0004] To address the shortcomings of existing technologies, this invention proposes to predefine the spatial position of the metal-organic framework before the formation of the selective layer, so that it is concentrated and fixed between the functional buffer layer and the selective layer. The reactive functional groups on its surface are used to form stable chemical connections with the upper and lower membrane layers respectively, so that the metal-organic framework is transformed from a randomly dispersed functional filler into an interfacial bridging node connecting the upper and lower membrane layers. This reduces particle aggregation, non-selective interfacial voids and interfacial relaxation during operation while retaining the metal coordination CO2 promoting transport function, thereby improving the structural integrity and long-term separation stability of the composite membrane. Summary of the Invention

[0005] This invention provides a CO2 separation composite membrane with nucleophilic-coordination dual function, its preparation method, and its application. The composite membrane comprises a porous support layer, a functional buffer layer, and a selective layer arranged sequentially. The selective layer is formed by interfacial polymerization of a nucleophilic film-forming support and a polyfunctional acyl chloride monomer. Reactive metal-organic framework nanoparticles are concentrated and localized in the interfacial region between the functional buffer layer and the selective layer. The reactive functional groups on their surfaces form covalent chemical connections with the functional buffer layer and the selective layer, respectively, constituting an interfacial bridging structure between the functional buffer layer, the reactive metal-organic framework, and the selective layer.

[0006] This composite membrane possesses both the nucleophilic CO2 transport function provided by nitrogen-containing sites in a nucleophilic film-forming carrier and the reversible coordination transport function of CO2 provided by metal sites in a reactive metal-organic framework. The two types of functional sites form a relay transport path in series in space, which can give full play to the synergistic effect.

[0007] In the preparation process, a functional buffer layer with a first functional group is first formed on the surface of a porous support layer. Then, reactive metal-organic framework nanoparticles with a second functional group on the surface are covalently fixed to the surface of the functional buffer layer through a ring-opening reaction. After removing the unfixed nanoparticles, the nanoparticles are sequentially contacted with an aqueous solution of a nucleophilic film-forming carrier and an organic phase solution containing polyfunctional acyl chloride monomers to form a selective layer through interfacial polymerization. This allows the metal-organic framework to be covalently linked to the selective layer. Finally, the nanoparticles are cured to obtain the final product.

[0008] Compared with existing physically blended bifunctional membranes, this invention transforms the metal-organic framework from randomly dispersed functional fillers into interfacial bridging nodes connecting the upper and lower membrane layers, effectively avoiding particle agglomeration and non-selective interfacial voids. This significantly improves the long-term operational stability and separation performance retention of the composite membrane under conditions of high humidity, high CO2 partial pressure, and pressure fluctuations. It can be widely used for the separation, enrichment, or removal of CO2 from flue gas, natural gas, biogas, syngas, and industrial CO2-containing tail gas.

[0009] In a first aspect, the present invention provides a method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function, comprising the following steps: S1: A polydimethylsiloxane layer is formed on the surface of a porous support layer, and the surface of the polydimethylsiloxane layer is functionalized to introduce a first functional group that can chemically react with a reactive metal-organic framework to obtain a functional buffer layer. S2: Contact reactive metal-organic framework nanoparticles with the functional buffer layer. The reactive metal-organic framework nanoparticles have a second functional group on their surface. The second functional group undergoes a ring-opening reaction with the first functional group to covalently fix the reactive metal-organic framework to the surface of the functional buffer layer. Remove the unfixed reactive metal-organic framework nanoparticles to obtain a support film with a reactive metal-organic framework fixed on its surface. S3: The support membrane obtained in S2 is sequentially contacted with an aqueous solution of a nucleophilic film-forming carrier and an organic solution containing polyfunctional acyl chloride monomers to form a selective layer through interfacial polymerization. The reactive metal-organic framework is then covalently linked to the selective layer to obtain a composite membrane precursor. S4: The composite membrane precursor is cured to obtain the bifunctional CO2 separation composite membrane.

[0010] Preferably, the first functional group is an epoxy group and the second functional group is an amino group; the functionalization treatment in S1 includes: after activating the surface of the polydimethylsiloxane layer, surface functionalization is performed using an epoxy-containing silane coupling agent to introduce epoxy groups onto the surface of the polydimethylsiloxane layer.

[0011] Preferably, the porous support layer is selected from one of polyethersulfone, polysulfone, polyacrylonitrile, polyvinylidene fluoride, or polyimide.

[0012] Preferably, the activation treatment is oxygen plasma treatment and / or ultraviolet ozone treatment; the epoxy-containing silane coupling agent is 3-glycidoxypropyltrimethoxysilane.

[0013] Preferably, the reactive metal-organic framework is selected from one or more of amino-functionalized MIL-101(Cr), amino-functionalized Ni-MOF-74, amino-functionalized Zn-MOF-74, and amino-functionalized HKUST-1, mixed in any proportion; the nucleophilic film-forming support is selected from one or more of aminoethylpiperazine, 2,5-diaminobenzenesulfonic acid, diethylenetriamine, and triethylenetetramine, mixed in any proportion.

[0014] Preferably, the reactive metal-organic framework nanoparticles in S2 are in contact with the functional buffer layer in the form of a dispersion, wherein the mass concentration of the dispersion is 0.01 wt.% to 2 wt.%.

[0015] Preferably, the mass concentration of the nucleophilic film-forming support aqueous solution in S3 is 0.1 wt.% to 15 wt.%; the polyfunctional acyl chloride monomer is pyromellitic trimethylol chloride, and the mass concentration of the polyfunctional acyl chloride monomer organic solution is 0.01 wt.% to 2.0 wt.%.

[0016] Preferably, in S3, the contact time between the aqueous phase solution of the nucleophilic film-forming carrier and the membrane surface is 0.5 min to 30 min, and the contact time between the organic phase solution containing polyfunctional acyl chloride monomer and the membrane surface is 5 s to 10 min; in S4, the curing temperature is 40℃ to 80℃, and the time is 1 min to 30 min.

[0017] Secondly, the present invention provides a CO2 separation composite membrane with nucleophilic-coordination dual function.

[0018] Preferably, the reactive metal-organic framework nanoparticles are localized in the interface region between the functional buffer layer and the selective layer, and are covalently connected to the first functional group on the surface of the functional buffer layer and the polyfunctional acyl chloride monomer in the selective layer through the second functional group on their surface, thereby forming an interface bridging structure connecting the functional buffer layer and the selective layer.

[0019] Thirdly, the present invention provides an application of a CO2 separation composite membrane with nucleophilic-coordination dual function in the separation of CO2-containing gas mixtures.

[0020] In summary, the present invention has at least one of the following beneficial technical effects: 1. This invention constructs an interfacial bridging structure with the reactive metal-organic framework as the core node by pre-covalently fixing a reactive metal-organic framework to the surface of a functional buffer layer and establishing a covalent connection between it and the subsequently formed selective layer. This achieves tight molecular-level coupling between the upper and lower membrane layers through bidirectional chemical bonding. The metal-organic framework transforms from a randomly dispersed functional filler in traditional physical blend membranes into a bridging node connecting the upper and lower membrane layers, eliminating particle aggregation and non-selective interfacial voids at the structural level.

[0021] 2. This invention provides CO2 nucleophilic transport function through nitrogen-containing sites in a nucleophilic film-forming support, and provides CO2 reversible coordination transport function through open metal sites in a reactive metal-organic framework localized at the interface. The two types of functional sites form a tandem relay transport path in space, realizing the synergistic effect of nucleophilic-coordination dual-function CO2-promoting transport, which is beneficial to simultaneously improve the CO2 permeation rate and separation selectivity of the membrane.

[0022] 3. This invention permanently locks the metal-organic framework at the interface between the functional buffer layer and the selective layer through bidirectional covalent bonding, effectively suppressing particle migration and interface relaxation under high humidity, high pressure, and pressure fluctuation conditions. Application examples show that, compared with physically blended bifunctional membranes, the interface-fixed membrane of this invention achieves a CO2 / N2 selectivity retention rate of 94.0% after 168 hours of operation under high humidity conditions (compared to only 71.7% for physically blended membranes), and a selectivity retention rate of 93.0% after 20 pressure cycles (compared to only 68.0% for physically blended membranes). This demonstrates significantly superior long-term operational stability and resistance to pressure fluctuations, making it more suitable for actual separation conditions of CO2-containing mixtures such as flue gas, natural gas, and syngas. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 The following is a flowchart illustrating the preparation process of the reactive metal-organic framework interface-immobilized bifunctional CO2 separation composite membrane provided in this application embodiment; Figure 2 This paper presents a comparison of the CO2 / N2 separation performance of interfacial immobilized bifunctional membranes constructed with different reactive metal-organic frameworks when using AEP as a nucleophilic membrane-forming support, as provided in the embodiments of this application. Figure 3 The illustration shows a comparison of the CO2 / N2 separation performance of interfacial immobilized bifunctional membranes constructed with different nucleophilic membrane-forming supports when using NH2-MIL-101(Cr) as a reactive metal-organic framework, as provided in the embodiments of this application. Figure 4 The accompanying diagram shows a comparison of the CO2 / N2 separation performance of bifunctional membranes with different construction methods provided in the embodiments and comparative examples of this application; Figure 5 This paper presents a comparison chart showing the performance retention rates of CO2 permeation rate and CO2 / N2 selectivity of the interface-fixed membrane and the physically blended membrane provided in this application embodiment after 168 h of continuous operation under high humidity conditions. Figure 6 The diagram shows a comparison of the performance retention rates of CO2 permeation rate and CO2 / N2 selectivity between the interface-fixed membrane and the physically blended membrane provided in the embodiments of this application during 20 pressure cycle tests. Detailed Implementation

[0025] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention. Furthermore, all other embodiments obtained by those skilled in the art without inventive effort are within the protection scope of the present invention.

[0026] Specific experimental steps or conditions are not specified in the embodiments; they can be performed according to the conventional experimental steps or conditions described in the prior art. Reagents and other instruments used, unless otherwise specified, are all commercially available conventional reagent products. Furthermore, the accompanying drawings are merely illustrative diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore, repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0027] Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of this specification.

[0028] In the description of this invention, it should be understood that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0029] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0030] To enable those skilled in the art to better understand this application, the following embodiments are provided to illustrate in detail a CO2 separation composite membrane with nucleophilic-coordination dual function, its preparation method, and its application.

[0031] Example Example 1 A method for preparing an AEP / amino-functionalized HKUST-1 interfacial immobilization bifunctional CO2 separation composite membrane (preparation process as follows) Figure 1 (As shown), including the following steps: The polyethersulfone porous support membrane was washed with deionized water and dried. A buffer layer solution with a polydimethylsiloxane concentration of 2 wt.% and a crosslinking agent concentration of 0.2 wt.% was prepared by dissolving polydimethylsiloxane and a crosslinking agent in n-hexane. The buffer layer solution was uniformly coated onto the surface of the polyethersulfone support membrane and pre-cured at 40°C to obtain a support membrane with a polydimethylsiloxane buffer layer.

[0032] The surface of the obtained polydimethylsiloxane buffer layer is activated by oxygen plasma and / or ultraviolet ozone to generate active groups such as hydroxyl groups on its surface. Subsequently, the activated membrane is brought into contact with a functionalized solution containing 3-glycidoxypropyltrimethoxysilane. After reaction and cleaning, epoxy groups are introduced into the surface of the polydimethylsiloxane buffer layer to obtain a functional buffer layer.

[0033] Amino-functionalized HKUST-1 nanoparticles were added to an aqueous dispersion medium and ultrasonically dispersed for 30 min to prepare a reactive metal-organic framework dispersion with a mass concentration of 0.1 wt.%. The resulting dispersion was then contacted with a functional buffer layer, allowing the amino groups on the surface of the amino-functionalized HKUST-1 nanoparticles to undergo a ring-opening reaction with the epoxy groups on the surface of the functional buffer layer, thereby immobilizing the amino-functionalized HKUST-1 nanoparticles on the surface of the functional buffer layer. After the reaction was complete, the nanoparticles were thoroughly washed with deionized water to remove any unstable metal-organic framework nanoparticles.

[0034] The support membrane with amino-functionalized HKUST-1 fixed at the above interface was contacted with an aqueous solution of aminoethylpiperazine (AEP) with a mass concentration of 5 wt.% for 10 min. After removing the excess aqueous solution from the membrane surface, it was contacted with a hexane solution of trimesoyl chloride (TMC) with a mass concentration of 0.15 wt.% and reacted for 2 min to form a selective layer on the membrane surface.

[0035] The resulting membrane was heat-treated at 60 °C for 10 min to further solidify the selective layer, resulting in an AEP / amino-functionalized HKUST-1 interface-fixed bifunctional CO2 separation composite membrane.

[0036] Example 2 A method for preparing an AEP / amino-functionalized Ni-MOF-74 interfacial immobilized bifunctional CO2 separation composite membrane. In this embodiment, the polyethersulfone support layer, polydimethylsiloxane buffer layer, surface activation and epoxy functionalization method of the buffer layer, the concentration of aminoethylpiperazine, the concentration of trimesoyl chloride, the interfacial polymerization conditions, and the heat treatment conditions are all the same as in Example 1.

[0037] Unlike Example 1, the reactive metal-organic framework material was replaced by amino-functionalized Ni-MOF-74 instead of amino-functionalized HKUST-1. The amino-functionalized Ni-MOF-74 was prepared into an aqueous dispersion with a mass concentration of 0.1 wt.%, and after ultrasonic dispersion for 30 min, it was brought into contact with the functional buffer layer. Ni-MOF-74 was immobilized on the surface of the functional buffer layer through a ring-opening reaction between the amino and epoxy groups on its surface. After removing unimmobilized particles, AEP / TMC interfacial polymerization and heat treatment were performed to obtain an AEP / amino-functionalized Ni-MOF-74 interfacially immobilized bifunctional CO2 separation composite membrane.

[0038] Example 3 A method for preparing an AEP / amino-functionalized Zn-MOF-74 interfacial immobilized bifunctional CO2 separation composite membrane. The preparation method in this embodiment is basically the same as in Example 1, except that the reactive metal-organic framework material is replaced with amino-functionalized Zn-MOF-74.

[0039] Amino-functionalized Zn-MOF-74 was added to an aqueous dispersion medium and ultrasonically dispersed for 30 min to prepare a dispersion with a mass concentration of 0.1 wt.%. This dispersion was then contacted with a polydimethylsiloxane functional buffer layer with epoxy groups on its surface. Interfacial immobilization of Zn-MOF-74 was achieved through the reaction of the surface amino groups with the epoxy groups. After thorough washing to remove unfixed particles, the mixture was sequentially contacted with a 5 wt.% aqueous solution of aminoethylpiperazine and a 0.15 wt.% solution of trimesoyl chloride-n-hexane for interfacial polymerization. The mixture was then heat-treated at 60 °C for 10 min to obtain an AEP / amino-functionalized Zn-MOF-74 interfacial immobilized bifunctional CO2 separation composite membrane.

[0040] Example 4 A method for preparing an AEP / NH2-MIL-101(Cr) interfacial immobilized bifunctional CO2 separation composite membrane. A polyethersulfone porous support membrane is washed with deionized water and dried. A hexane solution containing 2 wt.% polydimethylsiloxane and 0.2 wt.% crosslinking agent is coated onto its surface, and pre-cured at 40 °C to form a polydimethylsiloxane buffer layer.

[0041] The surface of the polydimethylsiloxane buffer layer was activated by oxygen plasma and / or ultraviolet ozone, followed by surface functionalization with 3-glycidyl etheroxypropyltrimethoxysilane to introduce epoxy groups onto the buffer layer surface. NH2-MIL-101(Cr) nanoparticles were added to an aqueous dispersion medium and ultrasonically dispersed for 30 min to prepare a 0.1 wt.% NH2-MIL-101(Cr) dispersion. This dispersion was then brought into contact with the functional buffer layer, and the ring-opening reaction between the amino groups on the NH2-MIL-101(Cr) surface and the epoxy groups on the functional buffer layer surface immobilized NH2-MIL-101(Cr) onto the surface of the functional buffer layer. After the reaction, the surface was thoroughly washed with deionized water to remove unimmobilized NH2-MIL-101(Cr) particles. Subsequently, the membrane immobilized with NH2-MIL-101(Cr) was contacted with a 5 wt.% aqueous solution of aminoethylpiperazine for 10 min. After removing excess liquid from the surface, it was contacted with a 0.15 wt.% hexane solution of trimesoyl chloride and reacted for 2 min. The reactive amino groups on the surface of NH2-MIL-101(Cr) that were not involved in interfacial immobilization could further react with trimesoyl chloride, thereby enhancing the interfacial bonding between the metal-organic framework and the formed selective layer. The resulting membrane was heat-treated at 60 °C for 10 min to obtain an AEP / NH2-MIL-101(Cr) interfacial immobilization bifunctional CO2 separation composite membrane.

[0042] The CO2 / N2 separation performance of the composite membranes obtained in Examples 1-4 is as follows: Figure 2As shown, this study compares the effects of different metal-organic framework materials on the performance of AEP-based bifunctional CO2 separation composite membranes. NH2-MIL-101(Cr) used in Example 4 possesses both surface-reactive amino groups and CO2-affinity metal sites, making it a representative reactive metal-organic framework material for subsequent comparisons and stability evaluations of different nucleophilic film-forming supports.

[0043] Example 5 A method for preparing a bifunctional CO2 separation composite membrane with 2,5-diaminobenzenesulfonic acid / NH2-MIL-101(Cr) interface immobilization. In this embodiment, the steps of porous support layer, polydimethylsiloxane buffer layer, epoxy functionalization of buffer layer surface, and NH2-MIL-101(Cr) interface immobilization are the same as in Example 4.

[0044] The difference lies in the use of 2,5-diaminobenzenesulfonic acid as the nucleophilic film-forming support. The supported membrane immobilized with NH₂-MIL-101(Cr) was contacted with a 2 wt.% aqueous solution of 2,5-diaminobenzenesulfonic acid for 10 min. After removing excess aqueous phase from the surface, it was contacted with a 0.15 wt.% solution of trimesoyl chloride and reacted for 2 min, forming a selective layer on the membrane surface. Subsequently, it was heat-treated at 60 °C for 10 min to obtain a bifunctional CO₂ separation composite membrane with an immobilized 2,5-diaminobenzenesulfonic acid / NH₂-MIL-101(Cr) interface.

[0045] Example 6 A method for preparing a diethylenetriamine / NH2-MIL-101(Cr) interfacial immobilization bifunctional CO2 separation composite membrane. The functional buffer layer and the NH2-MIL-101(Cr) interfacial immobilization method in this embodiment are the same as in Example 4.

[0046] A support membrane immobilized with NH2-MIL-101(Cr) was contacted with a 2 wt.% diethylenetriamine aqueous solution for 10 min. After removing excess aqueous phase from the surface, it was contacted with a 0.15 wt.% trimesoyl chloride n-hexane solution and reacted for 2 min. Subsequently, it was heat-treated at 60 °C for 10 min to obtain a diethylenetriamine / NH2-MIL-101(Cr) interfacial immobilized bifunctional CO2 separation composite membrane.

[0047] Example 7 A method for preparing a triethylenetetramine / NH2-MIL-101(Cr) interface-immobilized bifunctional CO2 separation composite membrane. In this embodiment, the polyethersulfone porous support layer, the functional buffer layer, and the NH2-MIL-101(Cr) interface immobilization method are all the same as in Example 4.

[0048] A membrane immobilized with NH2-MIL-101(Cr) was contacted with a 2 wt.% triethylenetetramine aqueous solution for 10 min. After removing excess aqueous phase from the membrane surface, it was contacted with a 0.15 wt.% trimesoyl chloride n-hexane solution and reacted for 2 min to form a selective layer on the membrane surface. Subsequently, it was heat-treated at 60 °C for 10 min to obtain a bifunctional CO2 separation composite membrane with a triethylenetetramine / NH2-MIL-101(Cr) interface.

[0049] The CO2 / N2 separation performance of the composite membranes obtained in Examples 4-7 is as follows: Figure 3 As shown, the compatibility of four nucleophilic film-forming carriers—AEP, 2,5-diaminobenzenesulfonic acid, diethylenetriamine, and triethylenetetramine—with the NH2-MIL-101(Cr) interfacial immobilization system and their effects on CO2 separation performance were compared.

[0050] Comparative Example Comparative Example 1 A nucleophilic AEP-type reference composite membrane. The polyethersulfone support layer, polydimethylsiloxane buffer layer, aminoethylpiperazine concentration, trimesoyl chloride concentration, interfacial polymerization time, and heat treatment conditions in this comparative example are the same as those in Example 4, except that NH2-MIL-101(Cr) is not introduced.

[0051] A supported membrane with a polydimethylsiloxane buffer layer was contacted with a 5 wt.% aqueous solution of aminoethylpiperazine for 10 min. After removing excess liquid from the surface, it was contacted with a 0.15 wt.% solution of trimesoyl chloride and reacted for 2 min, followed by heat treatment at 60 °C for 10 min to obtain an AEP nucleophilic reference composite membrane. The resulting membrane contained only nucleophilic CO2 transport sites and did not contain metal-coordinated CO2 transport sites provided by the metal-organic framework.

[0052] Comparative Example 2 A bifunctional composite membrane of AEP / NH2-MIL-101(Cr) physically blended. This comparative example uses the same polyethersulfone support layer, polydimethylsiloxane buffer layer, aminoethylpiperazine, NH2-MIL-101(Cr), and trimesoyl chloride as in Example 4, but without epoxy functionalizing the polydimethylsiloxane buffer layer or pre-interface fixing of NH2-MIL-101(Cr).

[0053] NH2-MIL-101(Cr) was ultrasonically dispersed in deionized water for 30 min, followed by the addition of aminoethylpiperazine to achieve a NH2-MIL-101(Cr) concentration of 0.1 wt.% and an aminoethylpiperazine concentration of 5 wt.% in the mixed aqueous phase. Ultrasonication was continued for 10 min to obtain a homogeneous bifunctional mixed aqueous phase. A polydimethylsiloxane buffer layer support membrane was contacted with the above mixed aqueous phase for 10 min. After removing excess aqueous phase from the membrane surface, it was contacted with a 0.15 wt.% trimesoyl chloride-n-hexane solution and reacted for 2 min. Subsequently, it was heat-treated at 60 °C for 10 min to obtain an AEP / NH2-MIL-101(Cr) physically blended bifunctional composite membrane.

[0054] The composite membranes obtained in Comparative Example 1, Comparative Example 2, and Example 4 were subjected to CO2 / N2 mixed gas separation performance tests. Figure 4 As shown, the CO2 permeation rate of the nucleophilic reference membrane obtained in Comparative Example 1 is approximately 255.6 GPU, and the CO2 / N2 selectivity is approximately 38.4; the CO2 permeation rate of the physically blended bifunctional membrane obtained in Comparative Example 2 is approximately 376.8 GPU, and the CO2 / N2 selectivity is approximately 73.6; the CO2 permeation rate of the interface-fixed bifunctional membrane of the present invention obtained in Example 4 is approximately 445.2 GPU, and the CO2 / N2 selectivity is approximately 112.93.

[0055] The above results indicate that the introduction of NH2-MIL-101(Cr) can increase the number of metal-coordinated CO2 transport sites and improve CO2 transport performance. Compared with physical blending, pre-fixing the reactive metal-organic framework at the interface between the functional buffer layer and the selective layer is beneficial to improving particle distribution and interfacial bonding, reducing non-selective interfacial voids, thereby further improving CO2 permeation rate and CO2 / N2 selectivity.

[0056] Application Examples Application Example 1 To investigate the effect of reactive metal-organic framework interface immobilization on the long-term stability of the composite membrane under high humidity, continuous high humidity CO2 / N2 mixed gas separation tests were conducted on the AEP / NH2-MIL-101(Cr) physically blended bifunctional membrane obtained in Comparative Example 2 and the AEP / NH2-MIL-101(Cr) interface-immobilized bifunctional membrane obtained in Example 4.

[0057] The test lasted 168 hours, with CO2 permeation rate and CO2 / N2 selectivity recorded every 24 hours. After 168 hours of continuous operation, the CO2 permeation rate and CO2 / N2 selectivity retention rates of the physically blended bifunctional membrane were approximately 84.5% and 71.7%, respectively; the corresponding retention rates of the interface-fixed bifunctional membrane of this invention were approximately 96.5% and 94.0%, respectively (e.g., ...). Figure 5(As shown).

[0058] The results show that, compared with physically blended bifunctional membranes, the interface-fixed bifunctional membrane of the present invention has a higher long-term separation performance retention rate under high-humidity mixed gas conditions. This indicates that the stable combination between the reactive metal-organic framework and the functional buffer layer is beneficial to suppressing particle migration, particle / polymer interface relaxation, and the resulting non-selective transfer during long-term high-humidity operation.

[0059] Application Example 2 To investigate the stability of the composite membrane under periodic pressure fluctuations, pressure cycling tests were conducted on the physically blended bifunctional membrane obtained in Comparative Example 2 and the interface-fixed bifunctional membrane obtained in Example 4, respectively.

[0060] A complete pressure cycle was defined as increasing the feed pressure from 1.0 bar to 3.0 bar and then decreasing it back to 1.0 bar, and a total of 20 pressure cycles were performed. After a certain number of cycles, the CO2 permeation rate and CO2 / N2 selectivity of the composite membrane were measured under the same benchmark test conditions, and the performance retention rate was calculated with the initial performance as 100%.

[0061] After 20 pressure cycles, the CO2 permeation rate and CO2 / N2 selectivity of the physically blended bifunctional membrane remained at approximately 82.0% and 68.0% of their initial performance, respectively; the interface-fixed bifunctional membrane of this invention maintained approximately 96.0% and 93.0%, respectively (e.g., Figure 6 (As shown).

[0062] The above results indicate that during repeated pressure loading and unloading, the interface between physically blended metal-organic framework particles and polymers is prone to structural relaxation and local particle displacement, leading to an increase in non-selective transfer. This invention effectively improves the structural stability of the particle / membrane interface by stably fixing the reactive metal-organic framework between the functional buffer layer and the selective layer, enabling the composite membrane to maintain high CO2 separation performance under pressure cycling conditions.

[0063] In summary, this invention pre-covalently fixes reactive metal-organic frameworks to the surface of a functional buffer layer and establishes a covalent connection between it and the subsequently formed selective layer, thus constructing an interfacial bridging structure with reactive metal-organic frameworks as the core nodes. This achieves tight molecular-level coupling between the functional buffer layer and the selective layer, transforming the metal-organic framework from a randomly dispersed functional filler in traditional physical blended films into a bridging node connecting the upper and lower film layers.

[0064] This composite membrane possesses both the nucleophilic CO2 transport function provided by nitrogen-containing sites in a nucleophilic film-forming carrier and the reversible coordination transport function of CO2 provided by metal sites in a reactive metal-organic framework. These two types of functional sites form a tandem relay transport pathway in space, achieving a synergistic effect of nucleophilic-coordination bifunctional CO2-promoting transport and effectively avoiding particle aggregation and non-selective interfacial porosity problems. Compared with existing physically blended bifunctional membranes, this invention exhibits significantly superior long-term operational stability and performance retention under high humidity and pressure fluctuation conditions. It can be widely applied to the separation, enrichment, or removal of CO2 from flue gas, natural gas, biogas, syngas, and industrial CO2-containing tail gas, showing promising industrial application prospects.

[0065] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0066] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0067] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0068] The foregoing has provided a detailed description of a nucleophilic-coordination dual-function CO2 separation composite membrane, its preparation method, and its applications. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function, characterized in that, Includes the following steps: S1: A polydimethylsiloxane layer is formed on the surface of a porous support layer, and the surface of the polydimethylsiloxane layer is functionalized to introduce a first functional group that can chemically react with a reactive metal-organic framework to obtain a functional buffer layer. S2: Contact reactive metal-organic framework nanoparticles with the functional buffer layer. The reactive metal-organic framework nanoparticles have a second functional group on their surface. The second functional group undergoes a ring-opening reaction with the first functional group to covalently fix the reactive metal-organic framework to the surface of the functional buffer layer. Remove the unfixed reactive metal-organic framework nanoparticles to obtain a support film with a reactive metal-organic framework fixed on its surface. S3: The support membrane obtained in S2 is sequentially contacted with an aqueous solution of a nucleophilic film-forming carrier and an organic solution containing polyfunctional acyl chloride monomers to form a selective layer through interfacial polymerization. The reactive metal-organic framework is then covalently linked to the selective layer to obtain a composite membrane precursor. S4: The composite membrane precursor is cured to obtain the bifunctional CO2 separation composite membrane.

2. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 1, characterized in that, The first functional group is an epoxy group, and the second functional group is an amino group; The functionalization process described in S1 includes: after activating the surface of the polydimethylsiloxane layer, surface functionalization is performed using an epoxy-containing silane coupling agent to introduce epoxy groups onto the surface of the polydimethylsiloxane layer.

3. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 1, characterized in that, The porous support layer is selected from one of polyethersulfone, polysulfone, polyacrylonitrile, polyvinylidene fluoride, or polyimide.

4. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 2, characterized in that, The activation treatment is oxygen plasma treatment and / or ultraviolet ozone treatment; the epoxy-containing silane coupling agent is 3-glycidoxypropyltrimethoxysilane.

5. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 1, characterized in that, The reactive metal-organic framework is selected from one or more of amino-functionalized MIL-101(Cr), amino-functionalized Ni-MOF-74, amino-functionalized Zn-MOF-74 and amino-functionalized HKUST-1, mixed in any proportion; the nucleophilic film-forming support is selected from one or more of aminoethylpiperazine, 2,5-diaminobenzenesulfonic acid, diethylenetriamine and triethylenetetramine, mixed in any proportion.

6. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 1, characterized in that, The reactive metal-organic framework nanoparticles described in S2 are in contact with the functional buffer layer in the form of a dispersion, wherein the mass concentration of the dispersion is 0.01 wt.% to 2 wt.%.

7. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 1, characterized in that, The mass concentration of the nucleophilic film-forming carrier aqueous solution in S3 is 0.1 wt.%~15 wt.%; the polyfunctional acyl chloride monomer is pyromellitic tricarboxylate chloride, and the mass concentration of the polyfunctional acyl chloride monomer organic solution is 0.01 wt.%~2.0 wt.%.

8. The method for preparing a CO2 separation composite membrane with nucleophilic-coordination dual function according to claim 1, characterized in that, The contact time between the aqueous phase solution of the nucleophilic film-forming carrier and the membrane surface in S3 is 0.5 min to 30 min, and the contact time between the organic phase solution containing polyfunctional acyl chloride monomer and the membrane surface is 5 s to 10 min; the curing temperature in S4 is 40℃ to 80℃, and the time is 1 min to 30 min.

9. A CO2 separation composite membrane prepared by the method for preparing a nucleophilic-coordination dual-function CO2 separation composite membrane as described in any one of claims 1 to 8.

10. The application of the CO2 separation composite membrane with nucleophilic-coordination dual function as described in claim 9 in the separation of CO2-containing gas mixtures.

Images