A cof-tpa-1 / zif-9 composite film and a preparation method and application thereof

Abstract

The application provides a COF-TpPa-1 / ZIF-9 composite film and a preparation method and application thereof, and the preparation method comprises the following steps: S1, COF-TpPa-1 is dissolved in deionized water, and then the obtained solution is applied to a substrate and dried, and after drying, a bottom film covered with COF-TpPa-1 powder is formed on the substrate; S2, Co gel is applied to the bottom film and dried, and after drying, a Co gel layer is formed on the bottom film; S3, the Co gel layer is converted by using benzimidazole, and after the conversion is completed, the COF-TpPa-1 / ZIF-9 composite film is obtained. According to the application, COF-TpPa-1 is doped into ZIF-9 film material by a gas phase conversion method, a full nanopore composite film is constructed, the gas permeability of the film material is greatly improved while the original selectivity of the film material is basically retained, and the generation of interface defects is avoided.

Description

Technical Field

[0001] This invention relates to a COF-TpPa-1 / ZIF-9 composite membrane, its preparation method and application, belonging to the field of membrane materials and separation technology. Background Technology

[0002] Membrane-based gas separation technology has attracted widespread attention due to its advantages such as high recovery rate, low energy consumption, and simple operation. An ideal membrane material should have a suitable and uniform pore size to ensure high selectivity, while minimizing transport resistance to maintain high permeability. Metal-organic frameworks (MOFs), as an emerging crystalline porous material, are considered ideal materials for membrane-based gas separation due to their ultra-high porosity and tunable pore environment. Since Liu et al. prepared the first continuous MOF-5 polycrystalline membrane on an alumina substrate in 2009, an increasing number of MOF membranes have been successfully synthesized and studied. To improve the selectivity of the prepared MOF membranes, researchers have explored numerous control strategies, including guest molecule modification and organic ligand regulation. Among these, organic ligand regulation strategies mainly include functional group modification and ligand length adjustment. By constructing isomorphic MOF materials through functionalized ligands, the pore environment can be directionally regulated to achieve efficient separation. Furthermore, by changing the ligand length, highly selective ultraporous MOF membranes with molecular sieve effects can be obtained.

[0003] However, these highly selective microporous membranes often exhibit relatively low permeability due to their high transport resistance. For industrial applications, low permeability means that a large membrane area is required to achieve the desired flux, ultimately leading to increased costs. Therefore, improving the permeability of MOF membranes is an urgent problem to be solved, yet research in this area has been rarely reported.

[0004] Directly increasing the pore size of MOF materials can improve the gas permeability of the membrane material, but it will reduce the selectivity of the material. Reducing the membrane thickness can also effectively improve gas permeability, and this method can retain the high selectivity of the membrane material itself, provided that the membrane material is continuous, but its preparation method is usually more complex. Accordingly, introducing other macroporous materials into MOFs to reduce the effective membrane thickness has become a feasible approach to improve the gas permeability of membrane materials. For example, Nair et al. (Angew. Chem. Int. Ed. 2019, 58, 236–239) introduced other macroporous materials into MOFs to reduce the effective membrane thickness. ZIF-8 (pore size ) was incorporated as a dispersed phase material. In the prepared ZIF-8 / MFI composite membrane, the C3H6 permeability was higher than the reported value in the literature, while the high selectivity of the composite membrane for C3H6 / C3H8 remained unchanged. However, the interfacial compatibility between the all-inorganic filler and the MOF material was not high, which may further lead to the generation of interfacial defects.

[0005] Based on the above, providing a novel COF-TpPa-1 / ZIF-9 composite membrane, its preparation method, and its application has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the aforementioned shortcomings and deficiencies, one objective of this invention is to provide a method for preparing a COF-TpPa-1 / ZIF-9 composite membrane.

[0007] Another object of the present invention is to provide a COF-TpPa-1 / ZIF-9 composite membrane prepared by the above-described method for preparing COF-TpPa-1 / ZIF-9 composite membrane.

[0008] Another object of the present invention is to provide the application of the above-described COF-TpPa-1 / ZIF-9 composite membrane in gas separation.

[0009] To achieve the above objectives, on the one hand, the present invention provides a method for preparing a COF-TpPa-1 / ZIF-9 composite membrane, wherein the preparation method includes:

[0010] S1: First, COF-TpPa-1 is dissolved in deionized water, and then the resulting solution is coated onto a porous substrate and dried. After drying, a bottom film of COF-TpPa-1 powder is covered on the substrate.

[0011] S2: Co gel is applied to the base film and then dried. After drying, the base film is covered with a Co gel layer.

[0012] S3: The Co gel layer is converted using benzimidazole, and the COF-TpPa-1 / ZIF-9 composite membrane is obtained after the conversion.

[0013] In this invention, the amount of COF-TpPa-1, water, Co gel, and benzimidazole used in the preparation of the COF-TpPa-1 / ZIF-9 composite membrane, or the thickness of the base membrane and Co gel layer, are not specifically required. They can all be reasonably adjusted according to the actual operation needs.

[0014] As a specific embodiment of the preparation method described above in this invention, in S1, the preparation method of COF-TpPa-1 includes:

[0015] p-phenylenediamine, p-toluenesulfonic acid, and trialdehyde phloroglucinol were mixed and then subjected to dry grinding, wet grinding, washing, and drying in sequence to obtain COF-TpPa-1.

[0016] As a specific embodiment of the preparation method described above in this invention, in S1, the preparation method of COF-TpPa-1 specifically includes:

[0017] First, p-phenylenediamine, p-toluenesulfonic acid, and trialdehyde-resorcinol were mixed in a mass ratio of 1-1.5:9.5-10:1-1.5 and then ball-milled for 2-5 hours. Then, an appropriate amount of deionized water was added to the resulting reaction system, and ball milling was continued for 0.4-0.6 hours. The product was then collected by centrifugation and washed sequentially with DMF, deionized water, acetone, and deionized water. Finally, the washed product was vacuum dried at 80-100℃ for 5-8 hours to obtain COF-TpPa-1.

[0018] As a specific embodiment of the preparation method described above in this invention, in S1, the ball milling treatment for 2-5 hours, i.e., the particle size of the powder particles obtained after dry milling is 100-500 nm.

[0019] In one specific embodiment of the preparation method described above in this invention, the porous substrate comprises α-Al2O3.

[0020] As a specific embodiment of the preparation method described above in this invention, in step S2, the preparation method of the Co gel includes:

[0021] Under heating and stirring conditions, Co(Ac)₂·4H₂O was fully dispersed in ethylene glycol methyl ether. After cooling, ethanolamine was added to the resulting system, and stirring was continued to obtain a uniform Co gel. This invention does not specify the exact amounts of Co(Ac)₂·4H₂O, ethylene glycol methyl ether, and ethanolamine used in the preparation of the Co gel; the amounts can be adjusted reasonably according to actual operational needs.

[0022] As a specific embodiment of the preparation method described above in this invention, in step S2, the heating and stirring conditions are: temperature 60-75℃, stirring time 0.5-1.5h.

[0023] As a specific embodiment of the preparation method described above in this invention, in step S2, the heating and stirring conditions are: temperature 65-75℃, stirring time 0.5-1.5h.

[0024] In a specific embodiment of the preparation method described above in this invention, in step S2, the cooling is performed to 15-30°C, and then stirring is continued for 10-15 hours after cooling to 15-30°C.

[0025] In one specific embodiment of the preparation method described above in this invention, in step S2, Co gel is applied to the base film using a dip-coating method.

[0026] As a specific embodiment of the preparation method described above in this invention, in step S3, the Co gel layer is converted using benzimidazole, specifically including:

[0027] First, benzimidazole is placed at the bottom of the reactor. Then, the product obtained in S2 is placed horizontally on the support inside the reactor with the Co gel layer side facing up. The reactor is then sealed and heated to convert the Co gel layer using benzimidazole. After the conversion is completed, the membrane is washed and dried to obtain the COF-TpPa-1 / ZIF-9 composite membrane.

[0028] In one specific embodiment of the preparation method described above in this invention, in step S3, the heating temperature is 170-200℃ and the holding time is 2-20h.

[0029] In one specific embodiment of the preparation method described above in this invention, in step S3, the washing is performed using N,N-dimethylformamide.

[0030] As a specific embodiment of the preparation method described above in this invention, in step S3, the drying is vacuum drying at 60-120°C for 0.5-3 hours, preferably vacuum drying at 100-120°C for 2-3 hours.

[0031] As a specific embodiment of the preparation method described above in this invention, the preparation method specifically includes:

[0032] (1) Synthesis of Co gel:

[0033] 9.3624 g of Co(Ac)2·4H2O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 60-75 °C for 0.5-1.5 h. After cooling to 15-30 °C, 4.6 mL of ethanolamine was added to the resulting system and stirring was continued for 10-15 h to obtain the Co gel.

[0034] (2) Synthesis of COF-TpPa-1:

[0035] p-phenylenediamine, p-toluenesulfonic acid, and trialdehyde-resorcinol were mixed in a mass ratio of 1-1.5:9.5-10:1-1.5 and ball-milled for 2-5 hours. Then, an appropriate amount of deionized water was added to the resulting system, and ball milling was continued for 0.4-0.6 hours. The product was collected by centrifugation, and then washed sequentially with DMF, deionized water, acetone, and deionized water. Finally, the washed product was vacuum dried at 80-100℃ for 5-8 hours.

[0036] (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane:

[0037] 1) First, disperse the COF-TpPa-1 synthesized in step (2) in an appropriate amount of deionized water, then coat the resulting solution onto an α-Al2O3 substrate and bake it in an oven at 60-100℃ for 0.5-3h. After drying, the substrate is covered with a bottom film of COF-TpPa-1 powder.

[0038] 2) The Co gel obtained in step (1) is then applied to the base film using the dip-coating method, and then dried at 100-120℃ for 0.5-3h. After drying, the base film is covered with a Co gel layer.

[0039] 3) Place benzimidazole at the bottom of the reactor, then place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer side facing up. Seal the reactor and place it in an oven at 170-200℃ for 2-20 hours to convert the Co gel layer using benzimidazole. Wash the membrane material obtained after conversion with DMF to remove the ligands deposited on the surface of the membrane material. After washing, vacuum dry at 60-120℃ for 0.5-3 hours to obtain the COF-TpPa-1 / ZIF-9 composite membrane.

[0040] On the other hand, the present invention also provides a COF-TpPa-1 / ZIF-9 composite membrane, wherein the COF-TpPa-1 / ZIF-9 composite membrane is prepared by the above-described method for preparing COF-TpPa-1 / ZIF-9 composite membrane, and is a binary all-nanoporous composite membrane, wherein COF-TpPa-1 is doped into the ZIF-9 membrane.

[0041] In another aspect, the present invention also provides the application of the above-described COF-TpPa-1 / ZIF-9 composite membrane in gas separation.

[0042] As a specific embodiment of the application described above in this invention, the gas separation includes the separation of H2 and CO2.

[0043] As a specific embodiment of the above-described application of the present invention, in the separation process of H2 and CO2, the Wicke-Kallenbach permeation technology is used to conduct a single-component gas permeation test, wherein argon is used as the purge gas, the argon flow rate is 40 mL / min, the feed gas transmembrane partial pressure difference is 1.6 bar, and the test temperature is 25 °C.

[0044] Compared with the prior art, the beneficial technical effects achieved by the present invention include:

[0045] This invention utilizes a gas-phase conversion method to dope a large-pore organic nanocrystalline porous material (covalent organic framework material, COF), specifically COF-TpPa-1, into a ZIF-9 membrane material, effectively compositing the two to construct a fully nanoporous composite membrane. This method improves gas permeability while retaining the gas separation ratio, significantly enhancing gas permeability while essentially preserving the original selectivity of the membrane material. Furthermore, as a pure organic material, COF exhibits good interfacial compatibility with the MOF matrix, i.e., the ZIF-9 membrane, avoiding the generation of interfacial defects. Compared to a pure ZIF-9 membrane, the COF-TpPa-1 / ZIF-9 composite membrane prepared by this invention shows a significantly increased gas flux, indicating that doping with the large-pore crystalline material COF-TpPa-1 can effectively improve the gas flux of the resulting composite membrane. Additionally, the preparation method of the COF-TpPa-1 / ZIF-9 composite membrane provided by this invention effectively reduces the use of organic reagents, and the materials used in the gas-phase conversion process can be recycled, reducing manufacturing costs and pollution. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 The FTIR spectra of COF-TpPa-1 powder prepared in Examples 1-5 of this invention are shown in Test Example 1 of this invention.

[0048] Figure 2 The XRD patterns of the COF-TpPa-1 / ZIF-9 composite membrane provided in Example 1 and the ZIF-9 membrane provided in Comparative Example 1 are shown in Test Example 2 of the present invention.

[0049] Figure 3a This is a SEM image (50 μm) of the COF-TpPa-1 / ZIF-9 composite membrane provided in Example 1 of Test Example 3 of the present invention.

[0050] Figure 3b This is a SEM image (25 μm) of the COF-TpPa-1 / ZIF-9 composite membrane provided in Example 1 of Test Example 3 of the present invention. Detailed Implementation

[0051] It should be noted that the term "comprising" and any variations thereof in the specification, claims, and accompanying drawings of this invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or devices.

[0052] The "range" disclosed in this invention is given in the form of a lower limit and an upper limit. It can be one or more lower limits and one or more upper limits, respectively. A given range is defined by selecting a lower limit and an upper limit. The selected lower and upper limits define the boundaries of the particular range. All ranges defined in this way are composable, meaning that any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for specific parameters, it is also expected that ranges of 60-110 and 80-120 are also expected. Furthermore, if the listed minimum range values ​​are 1 and 2, and the listed maximum range values ​​are 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5.

[0053] In this invention, unless otherwise specified, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this invention, and "0-5" is simply a shortened representation of these numerical combinations.

[0054] In this invention, unless otherwise specified, all embodiments and preferred embodiments mentioned in this invention can be combined with each other to form new technical solutions.

[0055] In this invention, unless otherwise specified, all technical features and preferred features mentioned in this invention can be combined with each other to form new technical solutions.

[0056] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying tables, drawings, and embodiments. The embodiments described below are some, but not all, embodiments of this invention, and are only used to illustrate the invention, and should not be considered as limiting the scope of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0057] Example 1

[0058] This embodiment provides a COF-TpPa-1 / ZIF-9 composite membrane, which is prepared by a method including the following specific steps:

[0059] (1) Synthesis of Co gel:

[0060] 9.3624 g of Co(Ac)₂·4H₂O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 70 °C for 1 hour. After cooling to 25 °C, 4.6 mL of ethanolamine was added to the system, and stirring was continued for 12 hours to obtain the Co gel.

[0061] (2) Synthesis of COF-TpPa-1:

[0062] 0.0972 g of p-phenylenediamine, 0.951 g of p-toluenesulfonic acid, and 0.126 g of trialdehyde phloroglucinol (mass ratio of 1:9.7:1.3) were mixed and ball-milled for 3 hours, resulting in a powder particle size of 100-500 nm. Subsequently, 50 mL of deionized water was added to the resulting reaction system, and ball milling continued for 0.5 hours. The product was collected by centrifugation and washed sequentially with DMF, deionized water, acetone, and then deionized water. The washed product was then dried under vacuum at 90 °C for 7 hours to obtain COF-TpPa-1.

[0063] (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane:

[0064] 1) Disperse 30 mg of COF-TpPa-1 synthesized in step (2) in 1 mL of water, and then uniformly coat the resulting solution onto an α-Al2O3 substrate. After drying the substrate at 90°C for 2 hours, a bottom film of COF-TpPa-1 powder is formed on the substrate.

[0065] 2) The Co gel obtained in step (1) is applied to the substrate using the dip-coating method, and then dried at 120°C for 2.5 hours. After drying, the substrate is covered with a Co gel layer.

[0066] 3) Place 1g of benzimidazole at the bottom of the reactor, place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer side facing up, then seal the reactor and place it at 190℃ for 10 hours to convert the Co gel layer. Then use DMF to wash the membrane material obtained after conversion to remove the ligands deposited on the surface. Finally, vacuum dry at 100℃ for 2 hours to prepare the COF-TpPa-1 / ZIF-9 composite membrane, denoted as M1.

[0067] Example 2

[0068] This embodiment provides a COF-TpPa-1 / ZIF-9 composite membrane, which is prepared by a method including the following specific steps:

[0069] (1) Synthesis of Co gel:

[0070] 9.3624 g of Co(Ac)₂·4H₂O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 70 °C for 1 hour. After cooling to 25 °C, 4.6 mL of ethanolamine was added to the system, and stirring was continued for 12 hours to obtain the Co gel.

[0071] (2) Synthesis of COF-TpPa-1:

[0072] 0.0972 g of p-phenylenediamine, 0.951 g of p-toluenesulfonic acid, and 0.126 g of trialdehyde phloroglucinol (mass ratio of 1:9.7:1.3) were mixed and ball-milled for 3 hours, resulting in a powder particle size of 100-500 nm. Subsequently, 50 mL of deionized water was added to the resulting reaction system, and ball milling continued for 0.5 hours. The product was collected by centrifugation and washed sequentially with DMF, deionized water, acetone, and then deionized water. The washed product was then dried under vacuum at 90 °C for 7 hours to obtain COF-TpPa-1.

[0073] (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane:

[0074] 1) Disperse 30 mg of COF-TpPa-1 synthesized in step (2) in 1 mL of water, and then uniformly coat the resulting solution onto an α-Al2O3 substrate. The treated substrate is dried at 90 °C for 2 hours. After drying, a base film of COF-TpPa-1 powder is covered on the substrate.

[0075] 2) The Co gel obtained in step (1) is applied to the substrate using the dip-coating method, and then dried at 120°C for 2.5 hours. After drying, the substrate is covered with a Co gel layer.

[0076] 3) Place 1g of benzimidazole at the bottom of the reactor, and place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer facing upward. Then seal the reactor and place it in a 190℃ oven for 2 hours to convert the Co gel layer. After conversion, wash the membrane material obtained by DMF to remove the ligands deposited on the surface. Finally, vacuum dry at 100℃ for 2 hours to prepare the COF-TpPa-1 / ZIF-9 composite membrane, denoted as M2.

[0077] In this invention, p-phenylenediamine and trialdehyde phloroglucinol are bonded together via an amine-aldehyde condensation reaction to form a crystalline porous material COF-TpPa-1. Changes in the ratio of reactants will affect the integrity of the crystal structure of COF-TpPa-1, and consequently, changes in the pore environment will further affect the performance of the composite membrane material. Therefore, Example 3 below changes the ratio of raw materials used in the synthesis of COF-TpPa-1 to examine its impact on the integrity of the crystal structure of COF-TpPa-1 and the performance of the composite membrane material.

[0078] Example 3

[0079] This embodiment provides a COF-TpPa-1 / ZIF-9 composite membrane, which is prepared by a method including the following specific steps:

[0080] (1) Synthesis of Co gel:

[0081] 9.3624 g of Co(Ac)₂·4H₂O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 70 °C for 1 hour. After cooling to 25 °C, 4.6 mL of ethanolamine was added to the system, and stirring was continued for 12 hours to obtain the Co gel.

[0082] (2) Synthesis of COF-TpPa-1:

[0083] 0.0972 g of p-phenylenediamine, 0.972 g of p-toluenesulfonic acid, and 0.0972 g of trialdehyde phloroglucinol (mass ratio 1:10:1) were mixed and ball-milled for 3 hours, resulting in a powder particle size of 100-500 nm. Subsequently, 50 mL of deionized water was added to the resulting reaction system, and ball milling continued for 0.5 hours. The product was collected by centrifugation and washed sequentially with DMF, deionized water, acetone, and then deionized water. The washed product was then dried under vacuum at 90 °C for 7 hours to obtain COF-TpPa-1.

[0084] (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane:

[0085] 1) Disperse 30 mg of COF-TpPa-1 synthesized in step (2) in 1 mL of water, and then uniformly coat the resulting solution onto an α-Al2O3 substrate. After drying the substrate at 90°C for 2 hours, a bottom film of COF-TpPa-1 powder is formed on the substrate.

[0086] 2) The Co gel obtained in step (1) is applied to the substrate using the dip-coating method, and then dried at 120°C for 2.5 hours. After drying, the substrate is covered with a Co gel layer.

[0087] 3) Place 1g of benzimidazole at the bottom of the reactor, and place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer facing upward. Then seal the reactor and place it at 190℃ for 10 hours to convert the Co gel layer. After conversion, wash the membrane material obtained by DMF to remove the ligands deposited on the surface. Finally, vacuum dry at 100℃ for 2 hours to prepare the COF-TpPa-1 / ZIF-9 composite membrane, denoted as M3.

[0088] Example 4

[0089] This embodiment provides a COF-TpPa-1 / ZIF-9 composite membrane, which is prepared by a method including the following specific steps:

[0090] (1) Synthesis of Co gel:

[0091] 9.3624 g of Co(Ac)₂·4H₂O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 70 °C for 1 hour. After cooling to 25 °C, 4.6 mL of ethanolamine was added to the system, and stirring was continued for 12 hours to obtain the Co gel.

[0092] (2) Synthesis of COF-TpPa-1:

[0093] 0.0972 g of p-phenylenediamine, 0.951 g of p-toluenesulfonic acid, and 0.126 g of trialdehyde phloroglucinol (mass ratio of 1:9.7:1.3) were mixed and ball-milled for 3 hours, resulting in a powder particle size of 100-500 nm. Subsequently, 50 mL of deionized water was added to the resulting reaction system, and ball milling continued for 0.5 hours. The product was collected by centrifugation and washed sequentially with DMF, deionized water, acetone, and then deionized water. The washed product was then dried under vacuum at 90 °C for 7 hours to obtain COF-TpPa-1.

[0094] (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane:

[0095] 1) Disperse 30 mg of COF-TpPa-1 synthesized in step (2) in 1 mL of water, and then uniformly coat the resulting solution onto an α-Al2O3 substrate. After drying the substrate at 90°C for 2 hours, a bottom film of COF-TpPa-1 powder is formed on the substrate.

[0096] 2) The Co gel obtained in step (1) is applied to the substrate using the dip-coating method, and then dried at 120°C for 2.5 hours. After drying, the substrate is covered with a Co gel layer.

[0097] 3) Place 1g of benzimidazole at the bottom of the reactor, and place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer facing upward. Then seal the reactor and place it at 170℃ for 10 hours to convert the Co gel layer. After conversion, wash the membrane material obtained by DMF to remove the ligands deposited on the surface. Finally, vacuum dry at 100℃ for 2 hours to prepare the COF-TpPa-1 / ZIF-9 composite membrane, denoted as M4.

[0098] Example 5

[0099] This embodiment provides a COF-TpPa-1 / ZIF-9 composite membrane, which is prepared by a method including the following specific steps:

[0100] (1) Synthesis of Co gel:

[0101] 9.3624 g of Co(Ac)₂·4H₂O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 70 °C for 1 hour. After cooling to 25 °C, 4.6 mL of ethanolamine was added to the system, and stirring was continued for 12 hours to obtain the Co gel.

[0102] (2) Synthesis of COF-TpPa-1:

[0103] 0.0972 g of p-phenylenediamine, 0.951 g of p-toluenesulfonic acid, and 0.126 g of trialdehyde phloroglucinol (mass ratio of 1:9.7:1.3) were mixed and ball-milled for 3 hours, resulting in a powder particle size of 100-500 nm. Subsequently, 50 mL of deionized water was added to the resulting reaction system, and ball milling continued for 0.5 hours. The product was collected by centrifugation and washed sequentially with DMF, deionized water, acetone, and then deionized water. The washed product was then dried under vacuum at 90 °C for 7 hours to obtain COF-TpPa-1.

[0104] (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane:

[0105] 1) Disperse 10 mg of COF-TpPa-1 synthesized in step (2) in 1 mL of water, and then uniformly coat the resulting solution onto an α-Al2O3 substrate. After drying the substrate at 90°C for 2 hours, a bottom film of COF-TpPa-1 powder is formed on the substrate.

[0106] 2) The Co gel obtained in step (1) is applied to the substrate using the dip-coating method, and then dried at 120°C for 2.5 hours. After drying, the substrate is covered with a Co gel layer.

[0107] 3) Place 1g of benzimidazole at the bottom of the reactor, and place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer facing upward. Then seal the reactor and place it at 190℃ for 10 hours to convert the Co gel layer. After conversion, wash the membrane material obtained by DMF to remove the ligands deposited on the surface. Finally, vacuum dry at 100℃ for 2 hours to prepare the COF-TpPa-1 / ZIF-9 composite membrane, denoted as M5.

[0108] Comparative Example 1

[0109] This comparative example provides a ZIF-9 membrane, which is prepared by a method including the following specific steps:

[0110] (1) Synthesis of Co gel:

[0111] 9.3624 g of Co(Ac)₂·4H₂O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 70 °C for 1 hour. After cooling to 25 °C, 4.6 mL of ethanolamine was added to the system, and stirring was continued for 12 hours to obtain the Co gel.

[0112] (2) Preparation of ZIF-9 membrane:

[0113] 1) The Co gel obtained in step (1) was coated onto the α-Al2O3 substrate using the dip-coating method, and then dried at 120°C for 2.5 hours. After drying, the substrate was covered with a Co gel layer.

[0114] 2) Place 1g of benzimidazole at the bottom of the reactor, place the product obtained in step 1) horizontally on the support inside the reactor with the Co gel layer facing upwards, then seal the reactor and react in an oven at 190°C for 10 hours to convert the Co gel layer. Finally, use DMF to wash the membrane material obtained after conversion to remove the ligands deposited on the surface, and prepare the ZIF-9 membrane, denoted as M6.

[0115] Test Example 1

[0116] In this test example, the COF-TpPa-1 powder prepared in Examples 1-5 was subjected to Fourier transform infrared (FTIR) spectroscopy using a Bruker Vertex 70 Fourier transform infrared spectrometer. The obtained FTIR spectra are shown below. Figure 1 As shown, where Figure 1 The image also shows the FTIR spectra of p-phenylenediamine and trialdehyde phloroglucinol. For example... Figure 1As shown in the FTIR spectra of p-phenylenediamine and trialdehyde phloroglucinol, COF-TpPa-1 powder was successfully obtained by ball milling in Examples 1-5 of this invention. The COF-TpPa-1 prepared by this invention is a fully organic macroporous crystalline material constructed by the amine-aldehyde condensation reaction of p-phenylenediamine and trialdehyde phloroglucinol. The ratio of raw materials used in the preparation of COF-TpPa-1 has a significant impact on the integrity of the crystal structure of the COF material.

[0117] Test Example 2

[0118] In this test example, X-ray electron diffraction (XRD) tests were performed on the COF-TpPa-1 / ZIF-9 composite film (M1) provided in Example 1 and the ZIF-9 film provided in Comparative Example 1 using a LabX XRD-6000 X-ray diffractometer manufactured by Shimadzu Corporation, Japan. The obtained XRD patterns are shown below. Figure 2 As shown.

[0119] To compare the effects of large-pore COF-TpPa-1 incorporation on the permeability and selectivity of MOF membranes, this invention prepared COF-TpPa-1 / ZIF-9 composite membranes in the examples and ZIF-9 membranes in Comparative Example 1, and performed XRD tests on both. Figure 2 The XRD diffraction pattern of the simulated ZIF-9 (i.e., ZIF-9 standard material) shown indicates that the embodiments of the present invention successfully prepared a membrane material containing ZIF-9 by gas phase transformation.

[0120] Test Example 3

[0121] In this test example, the COF-TpPa-1 / ZIF-9 composite membrane prepared in Example 1 was characterized using a JEOL JSM-6510A analytical scanning electron microscope to characterize the morphology of the membrane sample. The obtained SEM images are shown below. Figure 3a and Figure 3b As shown, Example 1 of this invention successfully prepared a continuous COF-TpPa-1 / ZIF-9 composite membrane material without obvious defects via a gas-phase transformation method.

[0122] Test Example 4

[0123] In this test example, the H2 / CO2 separation performance of the COF-TpPa-1 / ZIF-9 composite membranes provided in Examples 1-5 and the ZIF-9 membrane provided in Comparative Example 1 were tested. The H2 / CO2 separation performance was tested using a Wicke-Kallenbach Technique apparatus (see Angew. Chem. Int. Ed. 2006, 45, 7053-7056). The flow rates of H2, CO2 and carrier gas (purge gas) Ar were controlled by a mass flow controller. The argon flow rate was 40 mL / min, the feed gas transmembrane partial pressure difference was 1.6 bar, and the test temperature was 25 °C.

[0124] The feed gas permeating the membrane is purged by a carrier gas and introduced into the gas chromatograph. The content of different gases is measured to ultimately determine the separation effect. The gas chromatography (GC) analysis conditions are: Shimadzu GC2014, column temperature 50℃, TCD detector, and the mixed gas composition is H2 and CO2 in a volume ratio of 1:1.

[0125] The separation performance test results of each membrane material obtained in this test example are shown in Table 1 below.

[0126] Table 1: H2 and CO2 gas fluxes and ideal separation factor at 1.6 bar pressure

[0127]

[0128]

[0129] Note: In Table 1, flux is the volume of gas that permeates per unit membrane area per unit time.

[0130] GPU: 1×10 -6 cm 3 cm -2 s -1 cmHg -1 .

[0131] As shown in Table 1 above, the separation performance of M1-M6 shows that, compared with the ZIF-9 membrane (M6), the H2 flux and CO2 flux of the COF-TpPa-1 / ZIF-9 composite membranes (M1-M5) provided in Examples 1-5 of this invention are significantly improved. Although the ideal H2 / CO2 separation factor, i.e., the H2 / CO2 selectivity, is slightly reduced, it can still meet the requirements. It can be seen that the doping of large-size COF materials has a significant effect on the permeability of MOF membrane materials.

[0132] In summary, this invention utilizes a gas-phase transformation method to dope a large-pore crystalline organic nanoporous material (covalent organic framework material, COF), specifically COF-TpPa-1, into a ZIF-9 membrane material, effectively combining the two to construct a fully nanoporous composite membrane. This method improves the gas permeability while retaining the gas separation ratio, thus significantly enhancing gas permeability while essentially preserving the original selectivity of the membrane material. Furthermore, as a pure organic material, COF exhibits good interfacial compatibility with the MOF matrix, i.e., the ZIF-9 membrane, avoiding the generation of interfacial defects. Compared to a pure ZIF-9 membrane, the COF-TpPa-1 / ZIF-9 composite membrane prepared by this invention shows a significantly increased gas flux, indicating that doping with the large-pore crystalline material COF-TpPa-1 can effectively improve the gas flux of the resulting composite membrane. Furthermore, the preparation method of the COF-TpPa-1 / ZIF-9 composite membrane provided by this invention can effectively reduce the use of organic reagents, and the materials used in the gas phase conversion process can be recycled again, reducing manufacturing costs and pollution.

[0133] The above description is merely a specific embodiment of the present invention and should not be construed as limiting the scope of the invention. Therefore, any substitution of equivalent components or equivalent changes and modifications made within the scope of protection of this patent should still fall within the scope of this patent. Furthermore, the technical features, technical features and technical inventions, and technical inventions in this invention can be freely combined and used.

Claims

1. A method for preparing a COF-TpPa-1 / ZIF-9 composite membrane, characterized in that, include: S1: First, COF-TpPa-1 is dissolved in deionized water, and then the resulting solution is coated onto a porous substrate and dried. After drying, a bottom film of COF-TpPa-1 powder is covered on the substrate. S2: Co gel is applied to the base film and then dried. After drying, the base film is covered with a Co gel layer. S3: The Co gel layer is converted using benzimidazole, and the COF-TpPa-1 / ZIF-9 composite membrane is obtained after the conversion.

2. The preparation method according to claim 1, characterized in that, In S1, the preparation method of COF-TpPa-1 includes: p-phenylenediamine, p-toluenesulfonic acid, and trialdehyde phloroglucinol were mixed and then subjected to dry grinding, wet grinding, washing, and drying in sequence to obtain COF-TpPa-1.

3. The preparation method according to claim 2, characterized in that, In S1, the preparation method of COF-TpPa-1 specifically includes: First, mix p-phenylenediamine, p-toluenesulfonic acid, and trialdehyde phloroglucinol in a mass ratio of 1-1.5:9.5-10:1-1.5 and then ball mill for 2-5 hours. Subsequently, an appropriate amount of deionized water was added to the resulting reaction system, and ball milling was continued for 0.4-0.6 hours. After collecting the product by centrifugation, the collected product was washed sequentially with DMF, deionized water, acetone, and deionized water. Finally, the washed product was vacuum dried at 80-100℃ for 5-8 hours to obtain COF-TpPa-1.

4. The preparation method according to claim 3, characterized in that, In S1, the particle size of the powder obtained after ball milling for 2-5 hours is 100-500 nm.

5. The preparation method according to any one of claims 1-4, characterized in that, The porous substrate comprises α-Al2O3.

6. The preparation method according to any one of claims 1-4, characterized in that, In S2, the preparation method of the Co gel includes: Co(Ac)2·4H2O was fully dispersed in ethylene glycol methyl ether under heating and stirring conditions. After cooling, ethanolamine was added to the resulting system, and stirring was continued to obtain a uniform Co gel.

7. The preparation method according to claim 6, characterized in that, In S2, the heating and stirring conditions are: temperature 60-75℃, stirring time 0.5-1.5h.

8. The preparation method according to claim 7, characterized in that, In S2, the heating and stirring conditions are: temperature 65-75℃, stirring time 0.5-1.5h.

9. The preparation method according to claim 6, characterized in that, In S2, the cooling process involves cooling to 15-30°C, followed by continued stirring for 10-15 hours after cooling to 15-30°C.

10. The preparation method according to any one of claims 1-4, characterized in that, In S2, Co gel is applied to the base film using a lifting and dipping method.

11. The preparation method according to any one of claims 1-4, characterized in that, In S3, the Co gel layer is transformed using benzimidazole, specifically including: First, benzimidazole is placed at the bottom of the reactor. Then, the product obtained in S2 is placed horizontally on the support inside the reactor with the Co gel layer side facing up. The reactor is then sealed and heated to convert the Co gel layer using benzimidazole. After the conversion is completed, the membrane is washed and dried to obtain the COF-TpPa-1 / ZIF-9 composite membrane.

12. The preparation method according to claim 11, characterized in that, In S3, the heating temperature is 170-200℃, and the holding time is 2-20h.

13. The preparation method according to claim 11, characterized in that, In S3, the washing is performed using N,N-dimethylformamide.

14. The preparation method according to claim 11, characterized in that, In S3, the drying process involves vacuum drying at 60-120℃ for 0.5-3 hours.

15. The preparation method according to claim 14, characterized in that, In S3, the drying process involves vacuum drying at 100-120℃ for 2-3 hours.

16. The preparation method according to claim 1, characterized in that, The preparation method specifically includes: (1) Synthesis of Co gel: 9.3624 g of Co(Ac)2·4H2O was dispersed in 50 mL of ethylene glycol methyl ether and stirred at 60-75℃ for 0.5-1.5 h. After cooling to 15-30℃, 4.6 mL of ethanolamine was added to the resulting system and stirring was continued for 10-15 h to obtain the Co gel. (2) Synthesis of COF-TpPa-1: p-phenylenediamine, p-toluenesulfonic acid, and trialdehyde-resorcinol were mixed in a mass ratio of 1-1.5:9.5-10:1-1.5 and ball-milled for 2-5 hours. Then, an appropriate amount of deionized water was added to the resulting system, and ball milling was continued for 0.4-0.6 hours. The product was collected by centrifugation, and then washed sequentially with DMF, deionized water, acetone, and deionized water. Finally, the washed product was vacuum dried at 80-100℃ for 5-8 hours. (3) Preparation of COF-TpPa-1 / ZIF-9 composite membrane: 1) First, disperse the COF-TpPa-1 synthesized in step (2) in an appropriate amount of deionized water, then coat the resulting solution onto an α-Al2O3 substrate and bake it in an oven at 60-100℃ for 0.5-3h. After drying, the substrate is covered with a bottom film of COF-TpPa-1 powder. 2) Then, the Co gel obtained in step (1) is applied to the base film using the dip-coating method, and then baked at 100-120℃ for 0.5-3 h. After drying, the base film is covered with a Co gel layer. 3) Place benzimidazole at the bottom of the reactor, then place the product obtained in step 2) horizontally on the support inside the reactor with the Co gel layer side facing up. Seal the reactor and place it in an oven at 170-200℃ for 2-20 hours to convert the Co gel layer using benzimidazole. Wash the membrane material obtained after conversion with DMF to remove the ligands deposited on the surface of the membrane material. After washing, vacuum dry at 60-120℃ for 0.5-3 hours to obtain the COF-TpPa-1 / ZIF-9 composite membrane.

17. A COF-TpPa-1 / ZIF-9 composite membrane, characterized in that, The COF-TpPa-1 / ZIF-9 composite membrane is prepared by the method described in any one of claims 1-16. It is a binary fully nanoporous composite membrane in which COF-TpPa-1 is doped into the ZIF-9 membrane.

18. The application of the COF-TpPa-1 / ZIF-9 composite membrane according to claim 17 in gas separation.

19. The application according to claim 18, characterized in that, The gas separation includes the separation of H2 and CO2.

20. The application according to claim 19, characterized in that, During the separation of H2 and CO2, a single-component gas permeation test was conducted using the Wicke-Kallenbach permeation technique, with argon as the purge gas at a flow rate of 40 mL / min, a feed gas transmembrane partial pressure difference of 1.6 bar, and a test temperature of 25 °C.

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