A long-range conjugated organic / inorganic gas separation membrane and its preparation method

Abstract

This invention provides a long-range conjugated organic / inorganic gas separation membrane and its preparation method. The method includes the following steps: S1, placing carbon nanotubes, a reaction solvent, and a halogen in a microwave reactor to prepare halogen-functionalized carbon nanotubes; S2, uniformly dispersing long-range conjugated bromine functional building blocks, alkyne functional building blocks, a catalyst, and the bromine-functionalized carbon nanotubes obtained in S1 in the reaction solvent, and preparing a rigid framework composite material through a cross-coupling reaction; S3, preparing a long-range conjugated organic / inorganic gas separation membrane by natural sedimentation and vacuum drying of the composite material obtained in S2. The gas separation membrane prepared by this invention not only possesses a series of advantages such as a long-range conjugated structure, a wide specific surface area, uniform pore size, and ideal adsorption capacity, but also exhibits excellent mechanical flexibility and environmental tolerance. The preparation process is simple and the conditions are mild, making it a high-performance gas separation material with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of in-situ polymerization gas separation membrane technology, specifically to a long-range conjugated organic / inorganic gas separation membrane and its preparation method. Background Technology

[0002] Our understanding of air pollution should not be limited to the environmental and health problems it causes, but should also focus on the impact and feedback of air pollution on climate change, as well as the synergistic benefits of air pollution control and greenhouse gas emission reduction. Numerous studies have shown that there is a synergistic effect between air pollution control and greenhouse gas emission reduction: (1) Air pollutants and greenhouse gases share the same origin. Specifically, the combustion of fossil fuels during production and daily activities releases large amounts of particulate matter (PM) and carbon dioxide (CO2) into the atmosphere. (2) Many air pollution control measures are also effective measures to reduce greenhouse gas emissions, such as the updating and optimization of the energy structure, the adjustment of the industrial structure, and energy conservation and consumption reduction. Therefore, air pollutant control measures and greenhouse gas emission reduction measures are intertwined, interact, and complement each other. Their close relationship guides the design and development of co-capture materials.

[0003] Carbon dioxide, as an important carbon-containing compound, plays a crucial role in optimizing resource utilization through adsorption and separation technology, while also providing important support for the development of fossil fuels. However, the high oxidation state, thermodynamic stability, kinetic inertia, and significantly different molecular diameters of PM and CO2 pose significant challenges to their synergistic deep treatment. Membrane separation technology is the most efficient and direct method for removing PM and separating mixtures of multiple gases. It facilitates rapid capture and separation of gases with low energy consumption, while achieving integration and automation within a relatively compact separation unit. However, the composition, proportions, and environmental conditions of waste gases at the end of industrial pipelines can vary considerably. Therefore, existing membrane processes often struggle to cope with the complex and variable challenges posed by factors such as waste gas temperature and humidity.

[0004] Organic / inorganic hybrid membranes are considered a promising technology for the synergistic capture of PM and CO2 because they effectively combine the processing advantages of inorganic templates with the design flexibility of porous organic polymer fillers. In the design of gas separation membranes, research focuses on optimizing membrane structure and fabrication processes. This is achieved by doping highly selective fillers into flexible substrates to form composite structures, thereby optimizing the physical and chemical properties of the membrane while improving gas separation performance. In the field of gas separation, conjugated microporous polymers (CMPs) offer significant advantages and enormous application potential as fillers for hybrid membranes. CMPs possess unique pore structures and high specific surface areas, providing ample gas channels and facilitating accelerated separation processes. Due to their tunable chemical composition and functional sites, CMPs can selectively adsorb specific gases, thereby enhancing the membrane's binding specificity and affinity. Through organic integration with flexible substrates, CMPs enhance mechanical strength and durability while improving membrane separation performance, making them ideal for efficient and sustainable gas separation.

[0005] However, the practical application of organic-inorganic hybrid membranes is hindered by challenges such as interfacial compatibility between fillers and substrates, uniform filler dispersion, and concerns about membrane stability and processability. With the continuous development and interdisciplinary integration of materials science, interfacial polymerization technology combines the synergistic effects of interfacial chemistry and polymerization chemistry. It can be combined with various materials (such as elemental doping and metal coordination) to form composite systems, thereby optimizing the performance and application range of composite materials. Compared with traditional polymerization systems, interfacial polymerization technology incorporating interfacial effects can not only control the grafting density, grafting configuration, and grafting efficiency of polymers on the matrix, but also significantly improve the mechanical stability and processing flexibility of separation membranes. Active sites on the substrate surface can enhance the adsorption energy of reactant molecules, allowing them to be activated simultaneously by two or more different active sites. This greatly reduces the compatibility problems of heterogeneous interfaces at the micro- and nano-scale, facilitating directional and uniform growth at the interface, making it highly attractive for the manufacture of high-value functional materials. Summary of the Invention

[0006] Objective of the Invention: To meet the demand for mixed-component gas separation materials, this invention employs microwave-assisted preparation of halogen-functionalized carbon nanotubes, which are then mixed with long-range conjugated bromine and alkyne functional building blocks and subjected to a cross-coupling reaction under a metal catalyst to prepare an organic / inorganic composite material (the conventional expression for organic polymer growth in inorganic materials is: organic / inorganic) with a planar conjugated framework and uniform pore structure. A defect-free organic / inorganic gas separation membrane is then prepared through natural sedimentation and vacuum drying. This gas separation membrane not only possesses a series of advantages such as a long-range conjugated structure, a wide specific surface area, uniform pore size, and ideal adsorption capacity, but also exhibits excellent mechanical flexibility and environmental tolerance. The preparation process is simple and the conditions are mild, making it a high-performance gas separation material with broad application prospects.

[0007] This invention provides a long-range conjugated organic / inorganic gas separation membrane and its preparation method. The method includes the following steps:

[0008] Step S1, Preparation of halogen-functionalized carbon nanotubes: Pretreatment of carbon nanotubes with a mixture of concentrated nitric acid and concentrated sulfuric acid (cleaning the surface of carbon nanotubes to remove surface impurities and increase surface activity, the carbon nanotubes are generally 15-35 mL of carbon nanotubes), dispersing the treated carbon nanotubes in a reaction solvent, slowly adding halogen and ultrasonically dispersing to obtain a mixture, transferring the mixture to a microwave reaction tube, and preparing halogen-functionalized carbon nanotubes in a microwave reactor;

[0009] Step S2, preparation of rigid framework structure composite material: Halogen-functionalized carbon nanotubes, long-range conjugated bromine functional building blocks, alkyne functional building blocks and catalyst are thoroughly mixed in the reaction solvent, and after continuous reaction at constant temperature, the rigid framework structure composite material is cleaned by solvent replacement and Soxhlet extraction.

[0010] Step S3, Preparation of long-range conjugated organic / inorganic gas separation membrane: After thorough cleaning, the composite material is subjected to natural sedimentation and vacuum drying to prepare a long-range conjugated organic / inorganic gas separation membrane with a continuous rigid skeleton and uniform pore size.

[0011] In step S1, the carbon nanotubes are at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, the volume ratio of the concentrated nitric acid and concentrated sulfuric acid mixture is 1:1 to 3:1, and the amount of carbon nanotubes used is 0.3 to 1.0 g.

[0012] In step S1, the reaction solvent is at least one of tetrachloromethane, dichloromethane, N,N-dimethyl sulfoxide, and N-methylpyrrolidone, and the amount of the reaction solvent is 15-35 mL. The halogen is at least one of chlorine, bromine, and iodine, and the amount of the halogen is 1-4 mL.

[0013] In step S1, the output power of the microwave reactor is 100-300W, the reaction temperature is 70-150℃, and the reaction time is 10-60 minutes.

[0014] In step S2, the reaction solvent is at least one of toluene, N,N-dimethylformamide, 1,2-dichloroethane, and tetrahydrofuran. The reaction solvent is mixed with triethylamine, and the volume ratio of the reaction solvent to triethylamine is 1:1 to 3:1. The catalyst is tetratetraphenylphosphine palladium and cuprous iodide, and the molar ratio of the two catalysts is 1:5 to 1:15.

[0015] In step S2, the long-range conjugated bromine functional building block is at least one of 1,6-dibromopyrene, 2,7-dibromopyrene, 1,8-dibromopyrene, and 1,3,6,8-tetrabromopyrene, and the molar ratio of reaction units of the long-range conjugated bromine functional building block to the alkyne functional building block is 1:1 to 2:1.

[0016] In step S2, the reaction temperature of the constant-temperature continuous reaction is 80-100°C, and the reaction time is 48-84 hours.

[0017] In step S2, the solvents used for solvent replacement are dichloromethane, chloroform, acetone, deionized water and methanol in sequence, and the solvents used for Soxhlet extraction are at least one of methanol, chloroform and dichloromethane.

[0018] In step S3, the vacuum drying temperature is 40–80°C, the vacuum degree is less than or equal to -0.09 MPa, and the drying time is 6–24 hours.

[0019] The present invention also provides a long-range conjugated organic-inorganic gas separation membrane, which is prepared by the method described above and can be applied to the effective adsorption and separation of CO2 / N2 under mixed conditions.

[0020] Beneficial Effects: This invention provides a long-range conjugated organic / inorganic gas separation membrane and its preparation method. Halogenated functionalized carbon nanotubes are prepared using a microwave-assisted method. These nanotubes are then mixed with functional building blocks and structural building blocks and subjected to a cross-coupling reaction under a metal catalyst to prepare a stable composite material with a continuous rigid structure and uniform pore size. The long-range conjugated organic / inorganic gas separation membrane is prepared through natural sedimentation and vacuum drying. The specific surface area of ​​this hybrid membrane is 184-301 m². 2 With a pore size of 1.67-2.33 nm, a CO2 adsorption capacity of 1.7-2.8 mmol / g, and a CO2 / N2 separation selectivity of 12-54, this material not only possesses a series of advantages such as long-range conjugated structure, broad specific surface area, uniform pore size, and ideal adsorption capacity, but also exhibits excellent mechanical flexibility and environmental tolerance. Its preparation process is simple and requires mild conditions, making it a high-performance gas separation material with broad application prospects. Attached Figure Description

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments, and the advantages of the present invention in the above and / or other aspects will become clearer.

[0022] Figure 1 This is a scanning electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 1.

[0023] Figure 2 This is a transmission electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 1.

[0024] Figure 3 This is the Fourier transform infrared spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 1.

[0025] Figure 4 This is the powder X-ray diffraction spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 1.

[0026] Figure 5 This is a nitrogen adsorption-desorption isotherm curve of the long-range conjugated organic / inorganic gas separation membrane in Example 1.

[0027] Figure 6 This is a scanning electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 2.

[0028] Figure 7 This is a transmission electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 2.

[0029] Figure 8 This is the Fourier transform infrared spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 2.

[0030] Figure 9 This is the powder X-ray diffraction spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 2.

[0031] Figure 10 This is the nitrogen adsorption-desorption isotherm curve of the long-range conjugated organic / inorganic gas separation membrane in Example 2.

[0032] Figure 11 This is a scanning electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 3.

[0033] Figure 12 This is a transmission electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 3.

[0034] Figure 13 This is the Fourier transform infrared spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 3.

[0035] Figure 14 This is the powder X-ray diffraction spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 3.

[0036] Figure 15 This is a pore size distribution curve of the long-range conjugated organic / inorganic gas separation membrane in Example 3.

[0037] Figure 16 This is a scanning electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 4.

[0038] Figure 17 This is a transmission electron microscope image of the long-range conjugated organic / inorganic gas separation membrane in Example 4.

[0039] Figure 18 This is the Fourier transform infrared spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 4.

[0040] Figure 19 This is the powder X-ray diffraction spectrum of the long-range conjugated organic / inorganic gas separation membrane in Example 4.

[0041] Figure 20 This is a pore size distribution curve of the long-range conjugated organic / inorganic gas separation membrane in Example 4.

[0042] Figure 21 This is a flowchart of the method of the present invention. Detailed Implementation

[0043] Example 1

[0044] like Figure 21 As shown, this embodiment provides a method for preparing a long-range conjugated organic / inorganic gas separation membrane, including the following steps:

[0045] S11. Preparation of halogen-functionalized carbon nanotubes: 0.5 g of single-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 3:1) and dispersed in carbon tetrachloride. 2 mL of bromine was slowly added dropwise under ultrasonic conditions. The mixture was then transferred to a microwave reaction tube and sealed. The reaction was carried out in a microwave reactor (output power 150 W, reaction temperature 80 °C, reaction time 30 min) to prepare halogen-functionalized carbon nanotubes.

[0046] S12. Preparation of rigid framework composite material: A mixture of halogenated functionalized carbon nanotubes prepared in S11, 1,3,6,8-tetrabromopyrene, 1,3,5-triacetylenebenzene (molar ratio 1:1), and anhydrous N,N-dimethylformamide was placed in a round-bottom flask. Dry triethylamine (N,N-dimethylformamide to triethylamine volume ratio 2:1), tetratetraphenylphosphine palladium, and cuprous iodide (molar ratio 1:10) were added, and the reaction was carried out at 90°C under argon atmosphere for 72 hours. The solvent was successively replaced with dichloromethane, acetone, deionized water, and methanol, followed by Soxhlet extraction with methanol for 48 hours to prepare the rigid framework composite material.

[0047] S13. Preparation of long-range conjugated organic / inorganic gas separation membrane: The composite material prepared in S12 was used to prepare a long-range conjugated organic / inorganic gas separation membrane with a continuous rigid framework and uniform pore size through natural sedimentation and vacuum drying (drying temperature 60℃, vacuum degree -0.09MPa, drying time 12 hours), with a specific surface area of ​​301m². 2 / g, with an average pore size of 1.67nm.

[0048] Figure 1 The image shown is a scanning electron microscope image of the gas separation membrane obtained in Example 1, indicating that the material is a three-dimensional network structure in which a porous CMP adsorption active layer uniformly encapsulates carbon nanotubes.

[0049] Figure 2 The image shown is a transmission electron microscope (TEM) image of the gas separation membrane obtained in Example 1, indicating that the material has a core-shell structure with CMPs as the porous outer shell and carbon nanotubes as the supporting core, and the CMPs layer thickness is 4-8 nm.

[0050] Figure 3 The Fourier transform infrared spectrum of the gas separation membrane obtained in Example 1 shows that the material structure contains the stretching vibrations of terminal alkyne (-C≡CH) and C=C and C≡C.

[0051] Figure 4 The powder X-ray diffraction pattern of the gas separation membrane obtained in Example 1 shows that the material has a diffraction peak (18°) representing amorphous CMPs and diffraction peaks (28° and 43°) representing the (002) and (100) crystal planes of carbon nanotubes.

[0052] Figure 5 The N2 adsorption-desorption isotherm curve of the gas separation membrane obtained in Example 1 shows that the material has a large specific surface area and a hierarchical porous structure.

[0053] In the figure, Transmittance represents transmittance, Wavenumber represents wavenumber, Intensity represents intensity, 2Theta represents 2θ diffraction angle, Quantity Adsorbed represents adsorption amount, and Relative pressure represents relative pressure.

[0054] Example 2

[0055] This embodiment provides a method for preparing a long-range conjugated organic / inorganic gas separation membrane, including the following steps:

[0056] S21. Preparation of halogen-functionalized carbon nanotubes: 0.3 g of double-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 2:1) and dispersed in dichloromethane. 2 mL of iodine was slowly added dropwise under ultrasonic conditions. The mixture was then transferred to a microwave reaction tube and sealed. The reaction was carried out in a microwave reactor (output power 300 W, reaction temperature 150 °C, reaction time 60 min) to prepare halogen-functionalized carbon nanotubes.

[0057] S22. Preparation of rigid framework composite material: A mixture of halogenated functionalized carbon nanotubes prepared in S21, 1,6-dibromopyrene, 1,3,5-triacetylene (molar ratio 3:2), and anhydrous toluene was placed in a round-bottom flask. Dry triethylamine (toluene to triethylamine volume ratio 1:1), tetrakis(triphenylphosphine) palladium, and cuprous iodide (molar ratio 1:15) were added, and the reaction was carried out at 100°C under argon atmosphere for 48 hours. The solvent was successively replaced with chloroform, acetone, deionized water, and methanol, and further Soxhlet extraction with chloroform was performed for 48 hours to prepare the rigid framework composite material.

[0058] S23. Preparation of long-range conjugated organic / inorganic gas separation membrane: The composite material prepared in S22 was used to prepare a long-range conjugated organic / inorganic gas separation membrane with a continuous rigid framework and uniform pore size through natural sedimentation and vacuum drying (drying temperature 40℃, vacuum degree -0.08MPa, drying time 24 hours), with a specific surface area of ​​279m². 2 / g, with an average pore size of 1.88nm.

[0059] Figure 6 The image shown is a scanning electron microscope image of the gas separation membrane obtained in Example 2, indicating that the material is a three-dimensional network structure in which a porous CMP adsorption active layer uniformly encapsulates carbon nanotubes.

[0060] Figure 7 The image shown is a transmission electron microscope (TEM) image of the gas separation membrane obtained in Example 2, indicating that the material has a core-shell structure with CMPs as the porous outer shell and carbon nanotubes as the supporting core, and the CMPs layer thickness is 4-8 nm.

[0061] Figure 8 The Fourier transform infrared spectrum of the gas separation membrane obtained in Example 2 shows that the material structure contains stretching vibrations of terminal alkyne (-C≡CH) and C=C and C≡C.

[0062] Figure 9 The powder X-ray diffraction pattern of the gas separation membrane obtained in Example 2 shows that the material has a diffraction peak (18°) representing amorphous CMPs and diffraction peaks (28° and 43°) representing the (002) and (100) crystal planes of carbon nanotubes.

[0063] Figure 10 The N2 adsorption-desorption isotherm curve of the gas separation membrane obtained in Example 2 shows that the material has a large specific surface area and a hierarchical porous structure.

[0064] Example 3

[0065] This embodiment provides a method for preparing a long-range conjugated organic / inorganic gas separation membrane, including the following steps:

[0066] S31. Preparation of halogen-functionalized carbon nanotubes: 1.0 g of multi-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 3:2) and dispersed in N,N-dimethyl sulfoxide. Chlorine was slowly introduced under ultrasonic conditions, and the mixture was transferred to a microwave reaction tube and sealed. The reaction was carried out in a microwave reactor (output power 100 W, reaction temperature 70 °C, reaction time 10 min) to prepare halogen-functionalized carbon nanotubes.

[0067] S32. Preparation of rigid framework composite material: A mixture of halogenated functionalized carbon nanotubes prepared in S31, 2,7-dibromopyrene, 1,3,5-triacetylenebenzene (molar ratio 4:3), and anhydrous 1,2-dichloroethane was placed in a round-bottom flask. Dry triethylamine (1,2-dichloroethane to triethylamine volume ratio 3:2), tetrakis(triphenylphosphine)palladium, and cuprous iodide (molar ratio 1:5) were added, and the reaction was carried out at 80°C under argon atmosphere for 84 hours. The solvent was successively replaced with chloroform, dichloromethane, acetone, deionized water, and methanol, followed by Soxhlet extraction with dichloromethane for 48 hours to prepare the rigid framework composite material.

[0068] S33. Preparation of long-range conjugated organic / inorganic gas separation membrane: The composite material prepared in S32 was used to prepare a long-range conjugated organic / inorganic gas separation membrane with a continuous rigid framework and uniform pore size through natural sedimentation and vacuum drying (drying temperature 80℃, vacuum degree -0.07MPa, drying time 8 hours), with a specific surface area of ​​267m². 2 / g, with an average pore size of 1.95nm.

[0069] Figure 11 The image shown is a scanning electron microscope image of the gas separation membrane obtained in Example 3, indicating that the material is a three-dimensional network structure in which a porous CMP adsorption active layer uniformly encapsulates carbon nanotubes.

[0070] Figure 12 The image shown is a transmission electron microscope (TEM) image of the gas separation membrane obtained in Example 3, indicating that the material has a core-shell structure with CMPs as the porous outer shell and carbon nanotubes as the supporting core, and the CMPs layer thickness is 4-8 nm.

[0071] Figure 13 The Fourier transform infrared spectrum of the gas separation membrane obtained in Example 3 shows that the material structure contains the stretching vibrations of terminal alkyne (-C≡CH) and C=C and C≡C.

[0072] Figure 14 The powder X-ray diffraction pattern of the gas separation membrane obtained in Example 3 shows that the material has a diffraction peak (18°) representing amorphous CMPs and diffraction peaks (28° and 43°) representing the (002) and (100) crystal planes of carbon nanotubes.

[0073] Figure 15The figure shows the pore size distribution curve of the gas separation membrane obtained in Example 3, indicating that the material has a large specific surface area and a hierarchical porous structure. In the figure, Pore Volume represents the pore volume, and Pore Width represents the pore size.

[0074] Example 4

[0075] This embodiment provides a method for preparing a long-range conjugated organic / inorganic gas separation membrane, including the following steps:

[0076] S41. Preparation of halogen-functionalized carbon nanotubes: 1.0 g of single-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 1:1) and dispersed in N-methylpyrrolidone. Bromine was slowly introduced under ultrasonic conditions, and the mixture was transferred to a microwave reaction tube and sealed. The reaction was carried out in a microwave reactor (output power 200 W, reaction temperature 140 °C, reaction time 20 min) to prepare halogen-functionalized carbon nanotubes.

[0077] S42. Preparation of rigid framework composite material: A mixture of halogenated functionalized carbon nanotubes prepared in S41, 1,8-dibromopyrene, 1,3,5-triacetylenebenzene (molar ratio: 2), and anhydrous tetrahydrofuran was placed in a round-bottom flask. Dry triethylamine (tetrahydrofuran to triethylamine volume ratio: 2:1), tetraphenylphosphine palladium, and cuprous iodide (molar ratio: 1:12) were added, and the reaction was carried out at 85°C under argon atmosphere for 60 hours. The solvent was successively replaced with chloroform, dichloromethane, acetone, deionized water, and methanol, followed by Soxhlet extraction with acetone for 48 hours to prepare the rigid framework composite material.

[0078] S43. Preparation of long-range conjugated organic / inorganic gas separation membrane: The composite material prepared in S42 was used to prepare a long-range conjugated organic / inorganic gas separation membrane with a continuous rigid framework and uniform pore size through natural sedimentation and vacuum drying (drying temperature 70℃, vacuum degree -0.06MPa, drying time 18 hours), with a specific surface area of ​​263m². 2 / g, with an average pore size of 1.99nm.

[0079] Figure 16 The image shown is a scanning electron microscope image of the gas separation membrane obtained in Example 4, indicating that the material is a three-dimensional network structure in which a porous CMP adsorption active layer uniformly encapsulates carbon nanotubes.

[0080] Figure 17 The image shown is a transmission electron microscope (TEM) image of the gas separation membrane obtained in Example 4, indicating that the material has a core-shell structure with CMPs as the porous outer shell and carbon nanotubes as the supporting core, and the CMPs layer thickness is 4-8 nm.

[0081] Figure 18The Fourier transform infrared spectrum of the gas separation membrane obtained in Example 4 shows that the material structure contains stretching vibrations of terminal alkyne (-C≡CH) and C=C and C≡C.

[0082] Figure 19 The powder X-ray diffraction pattern of the gas separation membrane obtained in Example 4 shows that the material has a diffraction peak (18°) representing amorphous CMPs and diffraction peaks (28° and 43°) representing the (002) and (100) crystal planes of carbon nanotubes.

[0083] Figure 20 The pore size distribution curve of the gas separation membrane obtained in Example 4 shows that the material has a large specific surface area and a hierarchical porous structure.

[0084] Comparative Example 1 (using bromine-structured blocks and long-range alkyne functional blocks)

[0085] The organic / inorganic gas separation membrane was prepared using the method described in Example 1. The difference is that this example uses a coupling reaction between an alkyne functional building block with a bromine building block to prepare a long-range conjugated composite material. Specifically, 0.5 g of single-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 3:1) and dispersed in carbon tetrachloride. 2 mL of bromine was slowly added dropwise under ultrasonic conditions, and the mixture was transferred to a microwave reaction tube and sealed. Halogenated functionalized carbon nanotubes were prepared by reacting in a microwave reactor (output power 150 W, reaction temperature 80 °C, reaction time 30 min). A mixture of halogenated functionalized carbon nanotubes, 1,3,5-tribromobenzene, 1,3,6,8-tetraethynylpyrene (molar ratio 1:1), and anhydrous N,N-dimethylformamide was placed in a round-bottom flask. Dry triethylamine (N,N-dimethylformamide to triethylamine volume ratio 2:1), tetraphenylphosphine palladium, and cuprous iodide (molar ratio 1:10) were added and reacted at 90℃ under argon for 72 hours. The solvent was successively replaced with dichloromethane, acetone, deionized water, and methanol, followed by Soxhlet extraction with methanol for 48 hours to prepare a rigid framework composite material. A partially rigid framework and uniform pore size short-range conjugated organic / inorganic gas separation membrane with a specific surface area of ​​291 m² was prepared by natural sedimentation and vacuum drying (drying temperature 60℃, vacuum degree -0.09 MPa, drying time 12 hours). 2 / g, with an average pore size of 1.73nm.

[0086] Comparative Example 2 (using short-range conjugated bromine functional building blocks)

[0087] The organic / inorganic gas separation membrane was prepared using the method described in Example 2. The difference is that this example uses a coupling reaction between a bromine functional building block with a short-range conjugated structure and an alkyne building block to prepare a short-range conjugated composite material. Specifically, 0.3 g of double-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 2:1) and dispersed in dichloromethane. 2 mL of iodine was slowly added dropwise under ultrasonic conditions, and the mixture was transferred to a microwave reaction tube and sealed. Halogenated functionalized carbon nanotubes were prepared by reacting in a microwave reactor (output power 300 W, reaction temperature 150 °C, reaction time 60 min). A mixture of halogenated functionalized carbon nanotubes, 2,6-dibromonaphthalene, 1,3,5-triacetylenebenzene (molar ratio 3:2), and anhydrous toluene was placed in a round-bottom flask. Dry triethylamine (toluene to triethylamine volume ratio 1:1), tetrakis(triphenylphosphine)palladium, and cuprous iodide (molar ratio 1:15) were added, and the mixture was reacted at 100 °C under argon for 48 hours. A rigid framework composite material was prepared by sequentially replacing the solvent with chloroform, acetone, deionized water, and methanol, followed by Soxhlet extraction with chloroform for 48 hours. A long-range conjugated organic / inorganic gas separation membrane with a continuous rigid framework and uniform pore size was then prepared by natural sedimentation and vacuum drying (drying temperature 40℃, vacuum degree -0.08MPa, drying time 24 hours), with a specific surface area of ​​242 m². 2 / g, with an average pore size of 2.07nm.

[0088] Comparative Example 3 (using non-conjugated bromine functional building blocks)

[0089] The organic / inorganic gas separation membrane was prepared using the method described in Example 3. The difference is that this example uses a coupling reaction between a non-conjugated bromine functional building block and an alkyne building block to prepare a short-range conjugated composite material. Specifically, 1.0 g of multi-walled carbon nanotubes were pretreated in a mixture of concentrated nitric acid and concentrated sulfuric acid (volume ratio 3:2) and dispersed in N,N-dimethyl sulfoxide. Chlorine was slowly introduced under ultrasonic conditions, and the mixture was transferred to a microwave reaction tube and sealed. Halogenated functionalized carbon nanotubes were prepared by reacting in a microwave reactor (output power 100 W, reaction temperature 70 °C, reaction time 10 min). A mixture of halogenated functionalized carbon nanotubes, 4,4'-dibromobiphenyl, 1,3,5-triethynylbenzene (molar ratio 4:3), and anhydrous 1,2-dichloroethane was placed in a round-bottom flask. Dry triethylamine (1,2-dichloroethane to triethylamine volume ratio 3:2), tetraphenylphosphine palladium, and cuprous iodide (molar ratio 1:5) were added and reacted at 80℃ under argon for 84 hours. The solvent was then successively replaced with trichloromethane, dichloromethane, acetone, deionized water, and methanol, followed by Soxhlet extraction with dichloromethane for 48 hours to prepare a rigid framework composite material. A continuous rigid framework and uniform pore size long-range conjugated organic / inorganic gas separation membrane with a specific surface area of ​​184 m² was prepared by natural sedimentation and vacuum drying (drying temperature 80℃, vacuum degree -0.07 MPa, drying time 8 hours). 2 / g, with an average pore size of 2.33nm.

[0090] Structural characterization and performance testing:

[0091] Scanning electron microscopy observation: The microstructure of the conjugated microporous polymer-carbon nanotube composite filter membrane was observed using a field emission scanning electron microscope (model JSM-7900F, NEC). Figure 1 , Figure 6 , Figure 11 , Figure 16 ).

[0092] Transmission electron microscopy observation: The microstructure of the conjugated microporous polymer-carbon nanotube composite filter membrane was observed using a field emission transmission electron microscope (TECNI G2 TF20, FEI, Netherlands). Figure 2 , Figure 7 , Figure 12 , Figure 17 ).

[0093] Functional group structure testing: The functional groups of the conjugated microporous polymer-carbon nanotube composite filter membrane were recorded using an infrared spectrometer (model VERTEX 70, Bruker, USA). Figure 3 , Figure 8 , Figure 13 , Figure 18 ).

[0094] Crystal structure testing: The crystal structure of the conjugated microporous polymer-carbon nanotube composite filter membrane was recorded using an X-ray spectrometer (model D / Max-2400, Rigaku Corporation, Japan). Figure 4 , Figure 9 , Figure 14 , Figure 19 ).

[0095] Specific surface area test: Nitrogen adsorption isotherms were measured at 77 K using a gas adsorption analyzer (ASAP 2060, Micromeritics, USA). Figure 5 , Figure 10 , Figure 15 , Figure 20 ).

[0096] Carbon dioxide adsorption performance testing: CO2 adsorption was performed using a gas adsorption analyzer (ASAP 2020, Micromeritics, USA). High-purity CO2 gas (99.999%) was used for adsorption measurements, while free space measurements were performed using helium gas (99.999%). Isothermal adsorption was conducted at 273 K (ice-water bath) and 298 K (water bath).

[0097] Carbon dioxide / nitrogen separation selectivity calculation: Based on the adsorption isotherms of single-component CO2 and N2 at 273K and 298K, the separation selectivity was calculated using the ideal solution adsorption theory model.

[0098] Experimental results: such as Figure 1 , Figure 6 , Figure 11 and Figure 16 As shown, conjugated microporous polymers and halogen-functionalized carbon nanotubes are grown in situ via interfacial polymerization to form a core-shell composite material. This allows the porous adsorption active layer of CMPs to possess a continuous rigid framework. In Example 1, the carbon nanotube surface is uniformly coated with conjugated microporous polymers, and the absence of obvious carbon nanotube aggregation and free conjugated microporous polymers indicates the controllable synthesis of the composite material. Using a porous adsorption active layer as the outer shell and three-dimensional carbon nanotubes as the core, the material maintains good gas flow and mass transfer efficiency while fully exposing the pore properties and adsorption sites.

[0099] like Figure 2 , Figure 7 , Figure 12 and Figure 17As shown, organic / inorganic gas separation membranes are prepared by mixing conjugated microporous polymers and halogen-functionalized carbon nanotubes. This allows for template growth with carbon nanotubes as the core and conjugated microporous polymers as the filler. The lattice fringes representing the (002) and (100) crystal planes of the carbon nanotubes and the conjugated microporous polymer representing the amorphous structure can be clearly observed. The thickness of the conjugated microporous polymer shell is approximately 4-8 nm, indicating that the conjugated microporous polymer achieves in-situ interfacial polymerization with carbon nanotubes as templates. The growth process does not affect the specific surface area and pore properties of the gas separation membrane.

[0100] like Figure 3 , Figure 8 , Figure 13 and Figure 18 As shown, the signals corresponding to C≡CH and C-Br bonds disappear, indicating that the Sonogashira coupling reaction has occurred completely. At 3082 and 804 cm⁻¹, the signals disappeared. -1 The signal observed at approximately 2200 cm corresponds to the stretching and bending vibration modes of the CH bonds within the benzene ring; -1 The observed signal can be attributed to the stretching vibration of the -C≡C- bond, and the manifestation of the characteristic functional groups indicates the successful in-situ polymerization of the conjugated microporous polymer on the carbon nanofiber surface.

[0101] like Figure 4 , Figure 9 , Figure 14 and Figure 19 As shown, the diffraction pattern shows two peaks at 28° and 43°, corresponding to the (002) and (100) crystal planes of the carbon nanotubes, respectively. The diffraction pattern shows a broad peak centered at 18°, indicating that the gas separation membrane is formed in an amorphous structure under kinetic control.

[0102] like Figure 5 , Figure 10 , Figure 15 and Figure 20 As shown, the adsorption-desorption isotherms exhibit similar trends, namely, a medium-pressure region where nitrogen adsorption gradually increases and a high-pressure region where nitrogen adsorption is rapid. Combined with the pore size distribution curve, this indicates that the gas separation membrane has a hierarchical porous structure.

[0103] Table 1 compares the specific surface area, pore size, CO2 adsorption capacity, and CO2 / N2 separation selectivity of the long-range conjugated organic / inorganic gas separation membranes obtained in the examples and comparative examples. Examples 1-4 and Comparative Examples 1 and 2 have higher specific surface areas (184 m²). 2 / g-301m 2The small pore size (1.67 nm-2.33 nm) and the carbon nanotube template used in the polymerization process do not affect the porous structure of the conjugated microporous polymer, thus achieving full exposure and expression of the porous structure; the specific surface area of ​​Comparative Example 3 is only 184 m² / g. 2 / g, with an average pore size of 2.33nm, which is due to the disordered formation of pores caused by the flipping of non-conjugate functional building blocks.

[0104] Table 1

[0105]

[0106]

[0107] The CO2 adsorption capacity and CO2 / N2 separation selectivity of long-range conjugated organic / inorganic gas separation membranes are highly correlated with specific surface area and average pore size. Examples 1-4 and Comparative Example 1, which possess ideal specific surface areas, all exhibit CO2 adsorption capacity performance exceeding 2.4 mmol / g, and separation selectivity for the two-component CO2 / N2 mixture is greater than 31, truly achieving a balance between adsorption capacity and separation selectivity. Among them, Example 1, with the highest specific surface area and smallest pore size, performs best in adsorption capacity and separation selectivity tests, achieving a CO2 adsorption capacity of 2.8 mmol / g and a separation selectivity of 54, far exceeding that of Comparative Examples 2-3 (with lower specific surface area and larger pore size, CO2 adsorption capacity ≤ 2.0 mmol / g, separation selectivity ≤ 26).

[0108] This demonstrates that the technical solution proposed in this invention enables the long-range conjugated organic / inorganic gas separation membrane to possess a continuous rigid structure, a wide specific surface area, a narrow pore size, an ideal adsorption capacity, and good separation selectivity. These advantages are likely due to: (1) using halogen-functionalized carbon nanotubes as templates to provide abundant nucleation sites for the interfacial polymerization and growth of conjugated microporous polymers; (2) the design of a continuous rigid framework promotes the structure to be in the same plane, reducing the disordered stacking and entanglement of molecular chains and promoting the formation of a uniform and continuous pore structure; (3) carbon nanotubes form a three-dimensional network structure through random weaving and arrangement, which greatly improves the unit gas throughput of the composite filter membrane and enhances the gas flow and mass transfer efficiency of the material; (4) by polymerizing conjugated microporous polymers on the surface of carbon nanotubes, the binding energy barrier is effectively broken and the active sites are fully exposed, providing a suitable pore size and sufficient accommodation space for CO2 adsorption and separation.

[0109] This invention provides a long-range conjugated organic / inorganic gas separation membrane and its preparation method. Many methods and approaches exist for implementing this technical solution; the above description is merely a preferred embodiment of the invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A method for preparing a long-range conjugated organic / inorganic gas separation membrane, characterized in that, Includes the following steps: Step S1, Preparation of halogen-functionalized carbon nanotubes: carbon nanotubes are pretreated with a mixture of concentrated nitric acid and concentrated sulfuric acid, the pretreated carbon nanotubes are dispersed in a reaction solvent, halogen is slowly added dropwise and ultrasonically dispersed to obtain a mixture, the mixture is transferred to a microwave reaction tube, and halogen-functionalized carbon nanotubes are prepared in a microwave reactor. Step S2, preparation of rigid framework structure composite material: Halogen-functionalized carbon nanotubes, long-range conjugated bromine functional building blocks, alkyne functional building blocks and catalyst are thoroughly mixed in the reaction solvent, and after continuous reaction at constant temperature, the rigid framework structure composite material is cleaned by solvent replacement and Soxhlet extraction. Step S3, Preparation of long-range conjugated organic / inorganic gas separation membrane: After thorough cleaning, the composite material is subjected to natural sedimentation and vacuum drying to prepare a long-range conjugated organic / inorganic gas separation membrane with a continuous rigid skeleton and uniform pore size.

2. The method according to claim 1, characterized in that, In step S1, the carbon nanotubes are at least one of single-walled carbon nanotubes, double-walled carbon nanotubes, and multi-walled carbon nanotubes, the volume ratio of the concentrated nitric acid and concentrated sulfuric acid mixture is 1:1 to 3:1, and the amount of carbon nanotubes used is 0.3 to 1.0 g.

3. The method according to claim 2, characterized in that, In step S1, the reaction solvent is at least one of tetrachloromethane, dichloromethane, N,N-dimethyl sulfoxide, and N-methylpyrrolidone, and the amount of the reaction solvent is 15-35 mL. The halogen is at least one of chlorine, bromine, and iodine, and the amount of the halogen is 1-4 mL.

4. The method according to claim 3, characterized in that, In step S1, the output power of the microwave reactor is 100-300W, the reaction temperature is 70-150℃, and the reaction time is 10-60 minutes.

5. The method according to claim 4, characterized in that, In step S2, the reaction solvent is at least one of toluene, N,N-dimethylformamide, 1,2-dichloroethane, and tetrahydrofuran. The reaction solvent is mixed with triethylamine, and the volume ratio of the reaction solvent to triethylamine is 1:1 to 3:

1. The catalyst is tetratetraphenylphosphine palladium and cuprous iodide, and the molar ratio of the two catalysts is 1:5 to 1:

15.

6. The method according to claim 5, characterized in that, In step S2, the long-range conjugated bromine functional building block is at least one of 1,6-dibromopyrene, 2,7-dibromopyrene, 1,8-dibromopyrene, and 1,3,6,8-tetrabromopyrene, and the molar ratio of reaction units of the long-range conjugated bromine functional building block to the alkyne functional building block is 1:1 to 2:

1.

7. The method according to claim 6, characterized in that, In step S2, the reaction temperature of the constant-temperature continuous reaction is 80-100°C, and the reaction time is 48-84 hours.

8. The method according to claim 7, characterized in that, In step S2, the solvents used for solvent replacement are dichloromethane, chloroform, acetone, deionized water and methanol in sequence, and the solvents used for Soxhlet extraction are at least one of methanol, chloroform and dichloromethane.

9. The method according to claim 8, characterized in that, In step S3, the vacuum drying temperature is 40–80°C, the vacuum degree is less than or equal to -0.09 MPa, and the drying time is 6–24 hours.

10. A long-range conjugate organic / inorganic gas separation membrane, characterized in that, Prepared using the method described in any one of claims 1 to 9.

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