Preparation method and application of a dual-network CO2 separation membrane

Abstract

The application relates to a preparation method and application of a double-network type CO2 separation membrane, and belongs to the field of gas separation membranes. The application provides an innovative research idea and preparation method, and the experimental steps are as follows: (1) molecular design and synthesis of a diamine monomer containing an alkyne group and a carboxyl group; (2) synthesis of a TB polymer containing an alkyne group and a carboxyl group; (3) double-network type CO2 separation membrane constructed by combining metal coordination and covalent bond cooperation and a gradual crosslinking strategy. The application successfully develops a novel membrane material integrating high permeability, high selectivity and excellent anti-aging performance, and breaks the traditional "trade-off" effect. The permeation coefficient of CO2 is greater than or equal to 150 Barrer, the selectivity coefficient of CO2 / N2 and CO2 / CH4 is greater than or equal to 50, and in 50-day aging data test, the CO2 permeation coefficient of the double-network type CO2 separation membrane only decreases by 2.6%, and the double-network type CO2 separation membrane has good stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-performance dual-network CO2 separation membrane for separating CO2 and a preparation method and application thereof, and belongs to the field of membrane separation. BACKGROUND

[0002] Developing efficient carbon capture and storage technology has been widely recognized as an effective strategy to reduce CO2 emissions and mitigate the negative impacts of climate change.

[0003] Although CO2 separation membrane technology shows great application potential, it still faces many challenges. As a clean and low-carbon technology, membrane separation CO2 technology has attracted widespread social attention and shown great potential in large-scale capture of CO2.

[0004] Currently, the separation and purification method of CO2 can be realized by various methods, mainly including adsorption method, cryogenic separation technology, pressure swing adsorption method (PSA method), membrane permeation separation technology, etc. The adsorption method uses the selective adsorption ability of adsorbents to CO2 for separation. Common adsorbents include activated carbon, molecular sieve, porous ceramic, and porous materials such as zeolite, alumina, etc. The advantages of the adsorption method are simple process and low energy consumption, but the regeneration and disposal of the adsorbent are problems to be considered. The cryogenic separation technology is a low-temperature distillation method that converts CO2 into a liquid or supercritical fluid, which is then separated. It requires multiple freezing separations to achieve high purity, so the investment and energy consumption are very high; the PSA method can obtain high-purity CO2, but the adsorption capacity is limited, a large amount of adsorbent is required, and the adsorption and desorption are frequent, which requires a high degree of automation. Gas membrane separation technology, with its unique technical advantages, utilizes the pressure difference between the two sides of the membrane as the mass transfer driving force and the difference in permeation rate of different gases through the membrane material to realize component separation. This technology not only has small occupation area, simple operation and green environmental protection, but also has no pollution characteristics, showing extremely broad application prospects and great potential in the field of CO2 separation.

[0005] In recent years, high polymer materials have been booming, and various materials provide a good foundation for membrane separation. Polymer membranes dominate the CO2 separation membrane market due to their excellent flexibility, film-forming property and gas separation performance. Membrane separation method mainly relies on synthetic polymer materials with customizable gas transmission properties. Although polymer membranes have been widely used in many fields, there are still many problems in realizing efficient separation of CO2 and N2 and other gases. The kinetic diameter of CO2 (3.30 Å) is similar to that of N2 (3.64 Å) and CH4 (3.80 Å), so the selectivity of traditional polymer membranes for CO2 is low, which limits their application in CO2 separation. Because CO2 is a polar gas, its special chemical properties often cause aging of the polymer membrane and may cause plasticization of the membrane, thereby affecting the stability and separation performance of the membrane material. Polyimide materials derived from aromatic dianhydride and diamine are one of the best gas separation application materials in terms of comprehensive performance. Polyimide membranes have good thermal stability, chemical stability, excellent mechanical properties and high free volume, which make them exhibit good gas selectivity and permeation capacity. However, the separation efficiency of the current polyimide membranes on the market in the separation of key gas pairs such as CO2 / N2 and CO2 / CH4 still needs to be improved, and this limitation constitutes a major challenge in the process of widely promoting and applying them in industry. SUMMARY

[0006] To solve the problems of low separation efficiency, poor selectivity and easy aging in CO2 separation membranes, the present application provides a double-network CO2 separation membrane.

[0007] In one embodiment, the double-network CO2 separation membrane is obtained by metal coordination and covalent crosslinking of a TB polymer containing an alkyne group and a carboxyl group.

[0008] The metal coordination is: dissolving the TB polymer containing an alkyne group and a carboxyl group in an organic solution of metal ions to obtain a metal coordination type CO2 separation membrane.

[0009] The covalent crosslinking is: covalent crosslinking of the metal coordination type CO2 separation membrane by heating to obtain a double-network CO2 separation membrane.

[0010] In one embodiment, the TB polymer containing an alkyne group and a carboxyl group has the following structure:

[0011]

[0012] wherein n is 20-45, and the number average molecular weight of the polymer is 20000-40000 g / mol.

[0013] The polymer containing alkyne and carboxyl is obtained by reacting a diamine monomer containing alkyne and carboxyl with formaldehyde dimethyl acetal in a trifluoroacetic acid solvent.

[0014] In one embodiment, the diamine monomer containing alkyne and carboxyl has the following structural formula:

[0015]

[0016] The present application provides an innovative polymer material, which has similar structure to polyimide, and the polymer combines the rigid structure of Troger base and the unique three-dimensional structure of triptycene. This unique molecular design contains the excellent performance of polyimide, and further improves the gas separation performance of the material by introducing the TB rigid structure and triptycene structure. The present application designs and synthesizes a diamine monomer containing alkyne and carboxyl, polymerizes the diamine monomer containing alkyne and carboxyl, and prepares a cross-linkable TB polymer. The "combination of metal coordination and covalent bond interaction" constructs a double network type CO2 separation membrane. Each unit of the polymer chain contains a triptycene structure and a rigid V-shaped bridge, forming a large free volume in the interior of the polymer membrane, which improves the CO2 permeation coefficient. On the other hand, the coordination network and the cross-linking network further adjust the pore size, improve the CO2 / N2 and CO2 / CH4 selectivity; the construction of the double network structure and the introduction of bulky groups synergistically prepare CO2 separation membranes with novel structure and excellent performance. Finally, the fully aromatic reticular polymer formed by covalent cross-linking can inhibit the spontaneous creep and relaxation of the polymer chain over time, achieve the purpose of anti-aging, and will undergo pore expansion to improve the gas permeability, and the coordination network formed will improve the gas permeability and selectivity, successfully breaking the traditional inherent trade-off effect between gas permeability and selectivity, i.e. "trade-off" effect.

[0017] The double network type CO2 separation membrane of the present application has high selectivity in the application system of separating CO2 / N2 and CO2 / CH4, and also has good permeability for CO2. The purity of the separated CO2 is high. In the 50-day aging data test, the CO2 permeation coefficient of the uncross-linked CO2 separation membrane decreased from 105.8 Barrer to 60.4 Barrer, with a decrease of 42.9%; while the CO2 permeation coefficient of the double network type CO2 separation membrane decreased from 158.6 Barrer to 154.4 Barrer, with a decrease of 2.6%, which has good stability.

[0018] The second object of the present application is to provide a preparation method of a CO2 separation membrane:

[0019] Step 1, metal coordination: dissolve the TB polymer containing alkyne and carboxyl group in the organic solution containing metal ions to obtain a casting solution, uniformly coat the casting solution on the base film to coordinate, dry at 60°C to obtain a metal coordination type CO2 separation membrane;

[0020] Step 2, covalent crosslinking: place the metal coordination type CO2 separation membrane in a tube furnace, under nitrogen atmosphere, at a temperature rising rate of 5°C / min, target temperature 140-200°C, covalent crosslinking, at a temperature falling rate of 10°C / min to room temperature, to obtain a double network type CO2 separation membrane.

[0021] In an embodiment, step 1 is specifically: dissolve anhydrous ferric chloride in an organic solvent to prepare a uniformly dispersed metal ion solution; dissolve the TB polymer containing alkyne and carboxyl group in the above metal ion solution, stir at room temperature for 6-12h to obtain a casting solution with uniformly dispersed metal ions, the selection layer is deposited on a polytetrafluoroethylene base film with a pore size of 0.1-1μm by coating, dried in an oven to obtain a metal crosslinking type CO2 separation membrane with a selection layer thickness of 10-20μm.

[0022] In an embodiment, step 2 is specifically: cut the metal crosslinking type CO2 separation membrane into a rectangle with a size of 6cm×4cm, place it in a tube furnace, use a ceramic sheet to clamp the membrane to prevent deformation during heating, under nitrogen atmosphere, at a temperature rising rate of 5°C / min, target 140-200°C for 30min, then at a temperature falling rate of 10°C / min to room temperature to obtain a double network type CO2 separation membrane.

[0023] In an embodiment, the preparation method of the TB polymer containing alkyne and carboxyl group is:

[0024] The TB polymer containing alkyne and carboxyl group is generated by reacting the diamine monomer containing alkyne and carboxyl group with formaldehyde dimethyl acetal in a molar ratio of 1:1-6 with trifluoroacetic acid as the solvent, and the reaction is carried out for 24-72h.

[0025] In an embodiment, the preparation steps of the diamine monomer containing alkyne and carboxyl group are:

[0026] Step 1-1, under nitrogen atmosphere and ice water bath, SnCl4 as catalyst, 14-formyl triptycene is prepared by substitution reaction of triptycene and 1,1-dichloro dimethyl ether in a molar ratio of 1:1.2-1.5 with CH2Cl2 as solvent;

[0027] Step 1-2, 14-carboxyl triptycene is prepared by redox reaction of 14-formyl triptycene and KMnO4 in a molar ratio of 1:2.0-4.0 with pyridine and deionized water as mixed solvent;

[0028] Step 1-3, 2,6-dinitro-14-carboxyltriphenylenyl was prepared by nitration reaction of 14-carboxyltriphenylenyl and 70% nitric acid in acetic anhydride as solvent with a molar ratio of 1:5.0-10.0 under the condition of ice water bath;

[0029] Step 1-4, 2,6-dinitro-14-carboxyltriphenylenyl was prepared by redox reaction of 2,6-dinitro-14-carboxyltriphenylenyl and hydrazine hydrate with a molar ratio of 1:2.0-4.0;

[0030] Step 1-5, the alkyne and carboxyl group-containing diamine monomer was prepared by substitution reaction of 2,6-dinitro-14-carboxyltriphenylenyl and 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride with a molar ratio of 2.1-2.5:1.

[0031] In one embodiment, the preparation method of the alkyne and carboxyl group-containing diamine monomer comprises the following specific steps:

[0032] Step 2-1, triphenylene and SnCl4 were added in CH2Cl2, and after being fully dissolved under nitrogen atmosphere, 1,1-dichlorodiethyl ether was added, and stirred at 0-5°C for 2-10h, and then quenched with ice water; diluted hydrochloric acid was added for acidification, and extracted with CH2Cl2; the organic phase was dried over anhydrous Na2SO4, filtered, concentrated, recrystallized from dichloromethane and petroleum ether, and dried to obtain 14-formyltriphenylene;

[0033] Step 2-2, pyridine and deionized water were mixed uniformly, 14-formyltriphenylene was added and fully dissolved, and a 2.0-4.0mol / L KMnO4 solution was slowly added dropwise; the temperature was raised to 50-90°C, and reflux reaction was carried out for 3-10h; cooled to room temperature, and remove the insoluble impurities; hydrochloric acid was added to the obtained clear solution to produce white precipitate; the precipitate was collected, washed, and recrystallized from methanol and deionized water as solvents, and dried after separation and purification to obtain 14-carboxyltriphenylene;

[0034] Step 2-3, 14-carboxyltriphenylene was added in acetic anhydride, and after being fully dissolved, 70% concentrated nitric acid was added dropwise in an ice water bath within 30min, and reacted for 6-12h; deionized water was added, and stirred vigorously for 2-6h; the precipitate was collected by filtration, washed, and dried to obtain 2,6-dinitro-14-carboxyltriphenylenyl;

[0035] Step 2-4, 2,6-dinitro-14-carboxyltriphenylenyl was dissolved in methanol, Pd / C catalyst was added, and after being fully stirred, hydrazine hydrate was added dropwise to the reaction system, and reacted at 80-90°C for 4-10h; cooled to room temperature, filtered, and dried in vacuum to remove the solvent to obtain 2,6-diamino-14-carboxyltriphenylenyl.

[0036] Step 2-5, under nitrogen atmosphere, dissolve 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride in N-methyl pyrrolidone, add 2,6-diamino-14-carboxyl triptycene, stir at room temperature for 12~24h, add toluene as water carrying agent, after refluxing at 130℃ for 1~3h, increase temperature to 190℃ and react for 6~12h, cool to room temperature, add 500mL deionized water and stir vigorously, precipitate solid, wash and dry to obtain diamin monomer containing ethynyl and carboxyl groups.

[0037] In one embodiment, the method for preparing diamin monomer containing ethynyl and carboxyl groups comprises the following specific steps:

[0038] Step 3-1, add 0.01mol triptycene and 1.75mL SnCl4 in 30mL CH2Cl2, under nitrogen atmosphere, fully dissolve, then add 1.084mL 1,1-dichloro dimethyl ether, stir at 0~5℃ for 2~10h, quench with ice water; add dilute hydrochloric acid to acidify, extract with CH2Cl2; dry the organic phase with anhydrous Na2SO4, filter, then concentrate to obtain crude product; recrystallize with dichloromethane and petroleum ether, dry in 40℃ vacuum drying oven for 12~24h to obtain 14-formyl triptycene;

[0039] Step 3-2, mix 40mL pyridine with 10mL deionized water uniformly, then add 0.3g 14-formyl triptycene to ensure fully dissolved and mixed; slowly drop 50mL KMnO4 solution with concentration of 2.0~4.0mol / L into the reaction system; increase the temperature of the reaction system to 50~90℃ and reflux at this temperature range for 3~10h; after the reaction is completed, cool the system to room temperature, then centrifuge to remove insoluble impurities; add hydrochloric acid to the obtained clear solution to produce white precipitate; collect the precipitate by suction filtration and wash with deionized water to remove residual impurities; recrystallize the precipitate with methanol and deionized water as solvents, separate and purify, then dry in 40℃ vacuum drying oven for 12~24h to obtain 14-carboxyl triptycene;

[0040] Step 3-3, add 0.3g 14-carboxyl triptycene in 15mL acetic anhydride, fully dissolve, then cool in ice water bath, drop 0.4~0.6mL 70% concentrated nitric acid within 30min, react for 6~12h, add 25mL deionized water, stir vigorously for 2~6h, collect the precipitate by filtration, wash with water, dry in 50℃ vacuum drying oven for 12~24h;

[0041] Step 3-4, 0.3 g of 2,6-dinitro-14-carboxyltriphenylen is dissolved in 30 mL of methanol, 0.1 g of Pd / C catalyst is added, after stirring thoroughly, 0.1 mL of hydrazine hydrate is added dropwise into the reaction system, and the reaction is carried out at 80-90℃ for 4-10 h; then the reaction mixture is cooled to room temperature and filtered through a Celite pad; the solvent is removed in vacuum, and dried in vacuum at 50℃ for 12 h to obtain 2,6-diamino-14-carboxyltriphenylen;

[0042] Step 3-5, 0.12 g of 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride is dissolved in 30 mL of N-methylpyrrolidone under nitrogen atmosphere, 0.3 g of 2,6-diamino-14-carboxyltriphenylen is added, stirred at room temperature for 12-24 h, 10 mL of toluene is added as water carrying agent, refluxed at 130℃ for 1-3 h, then heated to 190℃ and reacted for 6-12 h, cooled to room temperature, added into 500 mL of deionized water and stirred vigorously, the solid is precipitated, washed and dried to obtain the diaminemonomer containing ethynyl and carboxyl groups.

[0043] In an embodiment, the solid content of the casting solution in step 1 is 0.5-5 wt.%.

[0044] The organic solvent includes at least one of N-methylpyrrolidone, tetrahydrofuran, N-ethylpyrrolidone or N,N-dimethylformamide.

[0045] The base film is tetrafluoroethylene, and the pore size of the base film is 0.1-1 μm.

[0046] The coordination time is 2-48 h, and the metal ion includes Cr 3+ , Cu 2+ or Fe 3+ ; and the covalent crosslinking reaction time in step 2 is 10-120 min.

[0047] A third object of the present application is to provide the use of the above-mentioned separation membrane or the separation membrane prepared according to the above-mentioned method in the separation of CO2 and N2 or the separation of CO2 and CH4.

[0048] The CO2 / N2, CO2 / CH4 single gas and mixed gas are separated by using the double network type CO2 separation membrane in the present application through negative pressure method.

[0049] Advantages

[0050] 1. All the reaction steps of the present application exhibit significant simplicity, which not only is easy to operate, but also can realize the high yield of product generation. Meanwhile, compared with the traditional method, the cost of the present application is effectively controlled, which exhibits good economy.

[0051] 2. The double-network CO2 separation membrane prepared by the method has high separation selectivity and high gas permeability, and the permeation coefficient of CO2 is greater than or equal to 150 Barrer, and the selectivity coefficient of CO2 / N2 and CO2 / CH4 is greater than or equal to 50.

[0052] 3. The triphenylene structure is introduced in the method, which can effectively inhibit the stacking phenomenon between molecules, thereby significantly increasing the free volume in the membrane, and further improving the gas permeability. In addition, the carboxyl group is introduced in the method, so that the coordination reaction can occur at room temperature, and then a stable coordination crosslinking network is formed. Meanwhile, the alkyne group is introduced in the method, which can induce the Diels-Alder addition reaction under heating conditions, and a special network structure with full aromatic characteristics is generated. This structure not only can effectively inhibit the peristalsis of polymer chains, significantly improve the anti-aging performance of the membrane, thereby prolonging the service life of the membrane, but also realizes the hole expansion effect through the covalent crosslinking effect, further improves the permeability and selectivity of the polymer membrane. The prepared membrane also exhibits good mechanical properties, and has been preliminarily realized industrial preparation. BRIEF DESCRIPTION OF DRAWINGS

[0053] Figure 1 Figure a is a schematic diagram of a gas permeability experimental device; Figure b is a gas diffusion coefficient and gas permeability; 1-2 are pressure gauges, 3-9 are valves, 10 is a buffer tank, 11 is a pressure gauge, 12 is a computer, 13 is a pump, and 14 is a membrane cell.

[0054] Figure 2 Figure a1 is a front view of the uncrosslinked CO2 separation membrane in Comparative Example 1, Figure a2 is a back view of the uncrosslinked CO2 separation membrane in Comparative Example 1; Figure b1 is a front view of the metal coordination type CO2 separation membrane-1 in Comparative Example 2, Figure b2 is a back view of the metal coordination type CO2 separation membrane-1 in Comparative Example 2; Figure c1 is a front view of the double-network CO2 separation membrane-1 in Example 1, and Figure c2 is a back view of the double-network CO2 separation membrane-1 in Example 1. DETAILED DESCRIPTION

[0055] The scheme of the present application is further described below by combining with the implementation examples, and the examples are not limitations of the present application unless specifically indicated. The raw materials used in the examples are all purchased from the market.

[0056] The test method used in the present application is constant volume pressure change method, and the gas permeability of the membrane is measured by the gas permeability test device prepared in the laboratory. Figure 2 The test gas is CO2, N2 and CH4. The specific operation steps are as follows:

[0057] (1) According to the actual size of the sample cell, the film sample needs to be cut to form a circular piece with appropriate size. Then, the thickness of each area of the film sample is measured, and the average thickness value is calculated. In the sample loading process, the appropriate sealing ring is added to ensure the air tightness of the device, and all interfaces are tightly screwed to prevent gas leakage during the experiment or use;

[0058] (2) After the vacuum environment is established inside the system, valve 4 is opened, and all other valves are kept closed. Each experimental cycle is set to 1 hour, and 0.1 MPa of raw gas is introduced into the upstream volume of the system. When mixed gas experiments are performed, all valves except valve 8 are opened to allow argon to be swept on the transverse side to maintain a stable transmembrane pressure difference of 0.1 MPa. To ensure the reliability and consistency of the experimental results, each film sample needs to be repeated at least three times.

[0059] (3) After the test is completed, ensure that the gas in the device is discharged completely through the tail gas treatment device. Then turn off the power of the device and take out the completed sample.

[0060] 1. The gas permeability parameter calculation method of the present application:

[0061] (1)

[0062] In the formula: P is the gas permeability coefficient (Barrer [1 Barrer = 1 × 10 -10 cm 3 (STP) × cm / (cm 2 × s × cmHg) ]; Q is the cumulative amount of gas permeation from the start to t (cm 3 ); A is the area of the membrane (cm 2 ); l is the thickness of the membrane (cm); ΔP is the pressure difference between the upstream and downstream sides (MPa).

[0063] 2. The calculation formula of gas selectivity of the present application:

[0064] (2)

[0065] In the formula: α i / j represents the ideal selectivity of the membrane to gas components CO2 and CH4, N2; P i represents the permeability coefficient of CO2 (Barrer); P j represents the permeability coefficient of gas components CH4, N2 (Barrer).

[0066] Example 1 Preparation of a double network type CO2 separation membrane -1 process as follows:

[0067] 1. Preparation of diamine monomer containing alkyne and carboxyl groups:

[0068] Step 1. Add 2.54 g of triptycene and 1.75 mL of SnCl4 in 30 mL of CH2Cl2, after complete dissolution under nitrogen atmosphere, add 1.08 mL of 1,1-dichloro dimethyl ether, stir for 2 h at 0-5 °C, quench with ice water. Add dilute hydrochloric acid to acidify, extract with CH2Cl2. Dry the organic phase over anhydrous Na2SO4, filter, then concentrate to obtain the crude product. Recrystallize from CH2Cl2 and petroleum ether, dry in a vacuum oven at 40 °C for 12 h to obtain 14-formyl triptycene;

[0069] Step 2. Mix 40 mL of pyridine with 10 mL of deionized water uniformly, then add 0.3 g of 14-formyl triptycene to ensure complete dissolution and mixing. Next, slowly add 50 mL of KMnO4 solution with a concentration of 2.0 mol / L to the reaction system. Warm the reaction system to 50 °C and reflux at this temperature range for 3 h. After the reaction is complete, cool the system to room temperature, then remove the insoluble impurities by centrifugation. Add hydrochloric acid to the resulting clear solution to produce a white precipitate. Collect the precipitate by filtration and wash with deionized water to remove residual impurities. Finally, recrystallize the precipitate using methanol and deionized water as solvents, separate and purify by the separation and purification steps, and dry in a vacuum oven at 40 °C for 12 h to obtain 14-carboxyl triptycene;

[0070] Step 3. Add 0.3 g of 14-carboxyl triptycene in 15 mL of acetic anhydride, after complete dissolution, cool in an ice water bath, add 0.4 mL of 70% concentrated nitric acid dropwise within 30 min, react for 6 h, add 25 mL of deionized water, stir vigorously for 2 h, collect the precipitate by filtration, wash with water, and dry in a vacuum oven at 50 °C for 12 h;

[0071] Step 4. Dissolve 0.3 g of 2,6-dinitro-14-carboxyl triptycene in 30 mL of methanol, add 0.1 g of Pd / C catalyst, after thorough stirring, add 0.1 mL of hydrazine hydrate dropwise to the reaction system, react at 80-90 °C for 4 h. Then cool the reaction mixture to room temperature and filter through a Celite pad. Remove the solvent in vacuum and dry in a vacuum oven at 50 °C for 12 h to obtain 2,6-diamino-14-carboxyl triptycene;

[0072] Step 5, under nitrogen atmosphere, 0.12 g of 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride was dissolved in 30 mL of N-methylpyrrolidone, then 0.3 g of 2,6-diamino-14-carboxyltriphenylen was added, stirred at room temperature for 12 h, 10 mL of toluene was added as water carrying agent, refluxed at 130 °C for 1 h, then heated to 190 °C for 6 h, cooled to room temperature, added to 500 mL of deionized water and stirred vigorously, the solid was precipitated, washed and dried to obtain the diamin monomer containing ethynyl and carboxyl groups.

[0073] The structure of the diamin monomer containing ethynyl and carboxyl groups is as follows:

[0074]

[0075] 2. Synthesis of TB polymer:

[0076] Take 0.3 g of diamin monomer containing ethynyl and carboxyl groups and place it in an ice water bath, add 0.3 mL of formaldehyde dimethyl acetal to the system, add 2.4 mL of trifluoroacetic acid at a rate of 1 drop per second, react for 1 h, remove the ice water bath, react at room temperature for 24 h, then terminate the reaction with 2.5% ammonia solution, wash and dry to obtain the TB polymer containing ethynyl and carboxyl groups;

[0077] The structure of the TB polymer containing ethynyl and carboxyl groups is as follows:

[0078]

[0079] Wherein, n is 23, and the number average molecular weight of the polymer is 22894 g / mol.

[0080] 3. Preparation of double network type CO2 separation membrane by "combination of metal coordination and covalent bond interaction, step-by-step crosslinking strategy":

[0081] Step 1, prepare a metal ion solution with a uniform dispersion concentration of 1.5 x 10 -8 mol / L by dissolving FeCl3 in NMP at room temperature. Dissolve the TB polymer in the above metal ion solution and stir at room temperature for 6 h to obtain a casting solution with uniform dispersion of metal ions. Deposit the casting solution on a polytetrafluoroethylene-based membrane with a pore size of 0.1-1 μm by coating, dry in an oven at 60 °C for 48-72 h to obtain a metal crosslinked CO2 separation membrane with a selected layer thickness of 10 μm;

[0082] Step 2, cut the metal crosslinked CO2 separation membrane into a rectangle with a size of 6 cm x 4 cm and place it in a tube furnace. Use a ceramic sheet to clamp the membrane to prevent deformation during heating. Heat at a rate of 5 °C / min to a target temperature of 160 °C and hold for 30 min under a nitrogen atmosphere. Then cool to room temperature at a rate of 10 °C / min to obtain a double network type CO2 separation membrane.

[0083] Example 2 Preparation of a dual-network CO2 separation membrane - 2 Flow scheme as follows:

[0084] 1. Preparation of di-amine monomer containing alkyne and carboxyl groups:

[0085] Step 1. Add 2.54 g of triptycene and 1.75 mL of SnCl4 in 30 mL of CH2Cl2, after complete dissolution under nitrogen atmosphere, add 1.08 mL of 1,1-dichloro dimethyl ether, stir at 0-5 °C for 2 h, quench with ice water. Acidify with dilute HCl, extract with CH2Cl2. Dry the organic phase over anhydrous Na2SO4, filter, then concentrate to get the crude product. Recrystallize from CH2Cl2 and petroleum ether, dry in a vacuum oven at 40 °C for 12 h to get 14-formyl triptycene;

[0086] Step 2. Mix 40 mL of pyridine with 10 mL of deionized water, then add 0.3 g of 14-formyl triptycene, make sure it is well dissolved and mixed. Next, slowly add 50 mL of KMnO4 solution with a concentration of 2.0 mol / L into the reaction system. Warm the reaction system to 50 °C, and reflux at this temperature range for 3 h. After the reaction is completed, cool the system to room temperature, then centrifuge to remove insoluble impurities. Add hydrochloric acid to the resulting clear solution to produce a white precipitate. Collect the precipitate by suction filtration, and wash with deionized water to remove residual impurities. Finally, recrystallize the precipitate using methanol and deionized water as solvents, separate and purify, then dry in a vacuum oven at 40 °C for 12 h to get 14-carboxyl triptycene;

[0087] Step 3. Add 0.3 g of 14-carboxyl triptycene in 15 mL of acetic anhydride, after complete dissolution, cool in an ice water bath, add 0.4 mL of 70% concentrated nitric acid dropwise within 30 min, react for 4 h, add 25 mL of deionized water, stir vigorously for 2 h, filter to collect the precipitate, wash with water, and dry in a vacuum oven at 50 °C for 12 h;

[0088] Step 4. Dissolve 0.3 g of 2,6-dinitro-14-carboxyl triptycene in 30 mL of methanol, add 0.1 g of Pd / C catalyst, after thorough stirring, add 0.1 mL of hydrazine hydrate dropwise into the reaction system, react at 90 °C for 5 h. Then cool the reaction mixture to room temperature, filter through a Celite pad. Remove the solvent in vacuum, dry in a vacuum oven at 50 °C for 12 h to get 2,6-diamino-14-carboxyl triptycene;

[0089] Step 5, under nitrogen atmosphere, 0.12 g of 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride was dissolved in 30 mL of N-methylpyrrolidone, 0.3 g of 2,6-diamino-14-carboxyltriphenylen was added, stirred at room temperature for 12 h, 10 mL of toluene was added as water carrying agent, refluxed at 130℃ for 3 h, then heated to 160℃ for 8 h, cooled to room temperature, added to 500 mL of deionized water and stirred vigorously, the solid was separated, washed and dried to obtain the diamin monomer containing ethynyl and carboxyl groups.

[0090] 2. Synthesis of TB polymer:

[0091] Take 0.3 g of diamin monomer containing ethynyl and carboxyl groups into an ice water bath, add 0.3 mL of formaldehyde dimethyl acetal to the system, add 2.4 mL of trifluoroacetic acid at a rate of 1 drop per second, react for 1 h, remove the ice water bath, react at room temperature for 36 h, then terminate the reaction with 2.5% ammonia solution, wash and dry to obtain TB polymer containing ethynyl and carboxyl groups;

[0092] The structure of TB polymer containing ethynyl and carboxyl groups is as follows:

[0093]

[0094] Wherein, n is 32, and the number average molecular weight of the polymer is 31254 g / mol.

[0095] 3. Preparation of double network type CO2 separation membrane by "combination of metal coordination and covalent bond interaction, step-by-step crosslinking strategy":

[0096] Step 1, under room temperature conditions, CrCl3 was dissolved in NMP to prepare a metal ion solution with a uniform dispersion concentration of 1.5×10 -8 mol / L. The TB polymer was dissolved in the above metal ion solution and stirred at room temperature for 12 h to obtain a casting solution with uniform dispersion of metal ions. The casting solution was deposited on a polytetrafluoroethylene-based membrane with a pore size of 0.1-1 μm by coating, and dried in an oven for 72 h to obtain a metal coordination type CO2 separation membrane with a selected layer thickness of about 10 μm.

[0097] Step 2, the metal crosslinking type CO2 separation membrane was cut into a rectangle with a size of 6 cm×4 cm and placed in a tube furnace. Ceramic sheets were used to clamp the membrane to prevent deformation during heating. The temperature was raised at a rate of 5℃ / min to a target temperature of 160℃ and held for 30 min, then cooled to room temperature at a rate of 10℃ / min to obtain a double network type CO2 separation membrane.

[0098] Example 3 Preparation of a double network type CO2 separation membrane-3 flow as follows:

[0099] 1. Preparation of diamin monomer containing ethynyl and carboxyl groups:

[0100] Step 1, add 2.54 g of triptycene and 1.75 mL of SnCl4 in 30 mL of CH2Cl2, after fully dissolved under nitrogen atmosphere, add 1.08 mL of 1,1-dichloro dimethyl ether, stir for 3 h at 0-5 °C, quench with ice water. Add dilute hydrochloric acid to acidify, extract with CH2Cl2. Dry the organic phase with anhydrous Na2SO4, filter, then concentrate to get the crude product. Recrystallize with CH2Cl2 and petroleum ether, dry in 40 °C vacuum oven for 24 h to get 14-formyl triptycene;

[0101] Step 2, mix 40 mL of pyridine with 10 mL of deionized water uniformly, then add 0.3 g of 14-formyl triptycene to ensure fully dissolved and mixed. Then, slowly add 50 mL of KMnO4 solution with a concentration of 2.0-4.0 mol / L to the reaction system. Warm the reaction system to 70 °C, and reflux at this temperature range for 6 h. After the reaction is completed, cool the system to room temperature, then remove the insoluble impurities by centrifugation. Add hydrochloric acid to the resulting clear solution to produce a white precipitate. Collect the precipitate by suction filtration and wash with deionized water to remove residual impurities. Finally, recrystallize the precipitate using methanol and deionized water as solvents, separate and purify, and dry in a 40 °C vacuum oven for 24 h to obtain 14-carboxyl triptycene after separation and purification;

[0102] Step 3, add 0.3 g of 14-carboxyl triptycene in 15 mL of acetic anhydride, fully dissolved, cool in an ice water bath, add 0.6 mL of 70% concentrated nitric acid dropwise within 30 min, react for 10 h, add 25 mL of deionized water, stir vigorously for 5 h, filter the precipitate, wash with water, and dry in a 50 °C vacuum oven for 24 h;

[0103] Step 4, dissolve 0.3 g of 2,6-dinitro-14-carboxyl triptycene in 30 mL of methanol, add 0.1 g of Pd / C catalyst, fully stir, then add 0.1 mL of hydrazine hydrate dropwise to the reaction system, react at 80 °C for 7 h. Then cool the reaction mixture to room temperature, filter through a Celite pad. Remove the solvent in vacuum, dry in a 50 °C vacuum oven for 12 h to obtain 2,6-diamino-14-carboxyl triptycene;

[0104] Step 5, under nitrogen atmosphere, 0.12 g of 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride was dissolved in 30 mL of N-methylpyrrolidone, then 0.3 g of 2,6-diamino-14-carboxyltriphenylen was added, stirred at room temperature for 16 h, 10 mL of toluene was added as water carrying agent, refluxed at 130 °C for 2 h, then heated to 190 °C for 10 h, cooled to room temperature, added to 500 mL of deionized water and stirred vigorously, the solid was separated, washed and dried to obtain the diamin monomer containing ethynyl and carboxyl groups;

[0105] 2. Synthesis of TB polymer:

[0106] Take 0.3 g of diamin monomer containing ethynyl and carboxyl groups into an ice water bath, add 0.3 mL of formaldehyde dimethyl acetal to the system, add 2.4 mL of trifluoroacetic acid at a rate of 1 drop per second, remove the ice water bath after 1 h of reaction, terminate the reaction with 2.5% ammonia solution after 48 h of reaction at room temperature, wash and dry to obtain TB polymer containing ethynyl and carboxyl groups;

[0107] The structure of the TB polymer containing ethynyl and carboxyl groups is as follows:

[0108]

[0109] Wherein, n is 39, and the number average molecular weight of the polymer is 38521 g / mol.

[0110] 3. Preparation of double network type CO2 separation membrane by "combination of metal coordination and covalent bond interaction, step-by-step crosslinking strategy":

[0111] Step 1, at room temperature, CuCl2 was dissolved in NMP to prepare a metal ion solution with a uniform dispersion concentration of 1.5×10 -8 mol / L. The TB polymer was dissolved in the above metal ion solution and stirred at room temperature for 12 h to obtain a casting solution with uniform dispersion of metal ions. The casting solution was deposited on a polytetrafluoroethylene-based membrane with a pore size of 0.1-1 μm by coating, and dried in an oven at 60 °C for 72 h to obtain a metal coordination type CO2 separation membrane with a selected layer thickness of about 10 μm;

[0112] Step 2, the metal crosslinking type CO2 separation membrane was cut into a rectangle with a size of 6 cm×4 cm and placed in a tube furnace. Ceramic sheets were used to clamp the membrane to prevent deformation during heating. The temperature was raised at a rate of 5 °C / min to a target temperature of 160 °C and held for 30 min, then cooled to room temperature at a rate of 10 °C / min to obtain a double network type CO2 separation membrane.

[0113] The polymer structure of the double network type CO2 separation membrane is as follows:

[0114] wherein n is 39, the number average molecular weight of the polymer is 38521 g / mol, and the spherical shape is Cu 2+ ions.

[0115] Preparation of uncrosslinked CO2 separation membrane of Comparative Example 1

[0116] 1. Preparation of diamin monomer containing alkyne and carboxyl group:

[0117] The same as Example 1.

[0118] 2. Synthesis of TB polymer:

[0119] The same as Example 1.

[0120] 3. Preparation of uncrosslinked CO2 separation membrane:

[0121] The TB polymer was dissolved in NMP with a solid content of 5 wt.%, and insoluble substances were removed by centrifugation. The composite membrane with a selective layer thickness of about 10 μm was obtained by coating on a PTFE base film with a pore size of 1 μm by a flow casting method and drying in a vacuum oven at 60°C for 24 h.

[0122] Preparation of metal coordination type CO2 separation membrane of Comparative Example 2

[0123] 1. Preparation of diamin monomer containing alkyne and carboxyl group:

[0124] The same as Example 1.

[0125] 2. Synthesis of TB polymer:

[0126] The same as Example 1.

[0127] 3. Metal coordination type CO2 separation membrane:

[0128] FeCl3was dissolved in NMP to prepare a metal ion solution with a uniform dispersion concentration of 1.5 x 10 -8 mol / L at room temperature. The TB polymer was dissolved in the above metal ion solution, and a casting solution with a uniform dispersion of metal ions was obtained by stirring at room temperature for 6 h. The metal coordination type CO2 separation membrane with a selective layer thickness of about 10 μm was obtained by depositing the casting solution on a polytetrafluoroethylene base film with a pore size of 0.1-1 μm by a coating method and drying in an oven for 48 h.

[0129] Preparation of covalently crosslinked CO2 separation membrane of Comparative Example 3

[0130] 1. Preparation of diamin monomer containing alkyne and carboxyl group:

[0131] The same as Example 1.

[0132] 2. Synthesis of TB polymer:

[0133] The same as Example 1.

[0134] 3. Covalently crosslinked CO2 separation membrane:

[0135] The composite membrane was cut into a rectangular shape of 6 cm x 4 cm in size and placed in a tube furnace, protected by nitrogen, with a heating rate of 5°C / min, a target temperature of 160°C for 30 minutes, and then cooled to room temperature at a rate of 10°C / min to obtain a covalently crosslinked polymer membrane.

[0136] Result analysis

[0137] According to Figure 2 The optical photograph of the separation membrane shows that the uncrosslinked CO2 separation membrane has a smooth surface without obvious defects, and the color is light yellow, while the metal coordination type CO2 separation membrane has a smooth and flat surface, and the color of the membrane surface is deepened due to the presence of Fe 3+ ; after heat treatment of the metal coordination type CO2 separation membrane, a double network type CO2 separation membrane is obtained, which still has a relatively smooth and flat surface, and the color of the membrane surface is further deepened, which can be inferred that the reaction has been completed. As can be seen from Table 1, compared with Comparative Example 1, the covalently crosslinked CO2 separation membrane and the metal coordination type CO2 separation membrane have higher CO2 / N2 and CO2 / CH4 selectivity, breaking the "trade-off" effect, and improving the gas permeation coefficient while maintaining high selectivity. Compared with Comparative Examples 2 and 3, the importance of coupling covalent crosslinking and metal coordination strategies is illustrated, and the double network structure synergistically enhances the CO2 mass transfer separation and the role of physical aging resistance. As can be seen from the long-term stability test data in Table 2, in the 50-day aging data test, the CO2 permeation coefficient of the uncrosslinked CO2 membrane decreased from 105.8 Barrer to 60.4 Barrer, a decrease of 42.9%; the CO2 permeation coefficient of the covalently crosslinked CO2 separation membrane decreased from 125.6 Barrer to 118.3 Barrer, a decrease of 5.8%; the CO2 permeation coefficient of the metal coordination type CO2 separation membrane decreased from 130.8 Barrer to 104.1 Barrer, a decrease of 20.4%; and the CO2 permeation coefficient of the double network type separation membrane decreased from 158.6 Barrer to 154.4 Barrer, a decrease of 2.6%, with good stability.

[0138] Table 1: Single component gas permeation performance data

[0139]

[0140] Table 2: Aging data

[0141]

Claims

1. A dual-network CO2 separation membrane prepared by a method combining metal coordination and covalent bonding, characterized in that, The preparation method of the separation membrane is: Step 1, metal coordination: dissolve the TB polymer containing alkyne group and carboxyl group in an organic solution containing metal ions to obtain a casting solution, uniformly coat the casting solution on a base film for coordination, dry at 60°C to obtain a metal coordination type CO2 separation membrane; the metal ions include Cr 3+ , Cu 2+ or Fe 3+ ; the TB polymer containing alkyne group and carboxyl group has the following structure: Wherein n is 20~45, the number average molecular weight of the polymer is 20000~40000g / mol; Step 2, covalent crosslinking: the metal coordination type CO2 separation membrane is placed in a tube furnace, covalent crosslinking is carried out under a nitrogen atmosphere, the temperature is raised at a rate of 5℃ / min, the target temperature is 140~200℃, the temperature is lowered to room temperature at a rate of 10℃ / min, and a double network type CO2 separation membrane is obtained.

2. The dual-network CO2 separation membrane prepared by the method of combining metal coordination and covalent bonding of claim 1, wherein, The preparation method of the TB polymer containing an alkyne group and a carboxyl group is: The TB polymer containing an alkyne group and a carboxyl group is prepared by reacting a diamine monomer containing an alkyne group and a carboxyl group with formaldehyde dimethyl acetal in a molar ratio of 1:1~6 in trifluoroacetic acid as a solvent, and the reaction is carried out for 24~72h. The structure of the diamine monomer containing an alkyne group and a carboxyl group is as follows: 。 3. A dual-network CO2 separation membrane prepared by the method of claim 2, wherein, The preparation steps of the diamine monomer containing an alkyne group and a carboxyl group are as follows: Step 1-1, under the conditions of nitrogen atmosphere and ice water bath, 14-formyl triptycene is prepared by substitution reaction of triptycene and 1,1-dichloro dimethyl ether in a molar ratio of 1:1.2~1.5 in CH2Cl2 as a solvent and SnCl4 as a catalyst; Step 1-2, 14-carboxyl triptycene is prepared by redox reaction of 14-formyl triptycene and KMnO4 in a molar ratio of 1:2.0~4.0 in a mixed solvent of pyridine and deionized water; Step 1-3, 2,6-dinitro-14-carboxyl triptycene is prepared by nitration reaction of 14-carboxyl triptycene and 70% nitric acid in a molar ratio of 1:5.0~10.0 in acetic anhydride as a solvent under the condition of ice water bath; Step 1-4, 2,6-dinitro-14-carboxyl triptycene and hydrazine hydrate are reacted in a molar ratio of 1:2.0~4.0 by redox reaction to obtain 2,6-diamino-14-carboxyl triptycene; Step 1-5, the diamine monomer containing an alkyne group and a carboxyl group is prepared by substitution reaction of 2,6-diamino-14-carboxyl triptycene and 4,4'-(ethynyl-1,2-diyl) di phthalic anhydride in a molar ratio of 2.1~2.5:

1.

4. The dual-network CO2 separation membrane prepared by a method combining metal coordination and covalent bonding of claim 3, wherein, The preparation method of the diamine monomer containing an alkyne group and a carboxyl group comprises the following specific steps: Step 2-1, triptycene and SnCl4 are added in CH2Cl2, after being fully dissolved under nitrogen atmosphere, 1,1-dichloro dimethyl ether is added, stirring is carried out at 0~5℃ for 2~10h, and then ice water is used for quenching; dilute hydrochloric acid is added for acidification, and CH2Cl2 is used for extraction; the organic phase is dried over anhydrous Na2SO4, filtered, concentrated, recrystallized from dichloromethane and petroleum ether, and dried to obtain 14-formyl triptycene; Step 2-2, pyridine and deionized water are mixed uniformly, 14-formyl triptycene is added, and fully dissolved; a KMnO4 solution with a concentration of 2.0~4.0mol / L is slowly added dropwise; the temperature is raised to 50~90℃, and reflux reaction is carried out for 3~10h; the temperature is cooled to room temperature, and insoluble impurities are removed; hydrochloric acid is added to the obtained clear solution to generate white precipitate; The precipitate is collected, washed, recrystallized from methanol and deionized water, dried after separation and purification, and 14-carboxyl triptycene is obtained; Step 2-3, 14-carboxyltriphenylenyl was added into acetic anhydride, and after being dissolved sufficiently, 70% concentrated nitric acid was added dropwise in an ice water bath within 30 min, and the reaction was carried out for 6-12 h. Deionized water was added, and the mixture was stirred vigorously for 2-6 h. The precipitate was collected by filtration, washed, and dried to obtain 2,6-dinitro-14-carboxyltriphenylenyl; Step 2-4, 2,6-dinitro-14-carboxyltriphenylenyl was dissolved in methanol, and Pd / C catalyst was added. After being stirred sufficiently, hydrazine hydrate was added dropwise into the reaction system, and the reaction was carried out at 80-90°C for 4-10 h. The mixture was cooled to room temperature, filtered, and the solvent was removed in vacuum, and dried to obtain 2,6-diamino-14-carboxyltriphenylenyl; Step 2-5, 4,4'-(ethynyl-1,2-diyl)diphthalic anhydride was dissolved in N-methyl pyrrolidone under nitrogen atmosphere, and 2,6-diamino-14-carboxyltriphenylenyl was added. The mixture was stirred at room temperature for 12-24 h, and toluene was added as a water-carrying agent. The mixture was refluxed at 130°C for 1-3 h, and then the temperature was raised to 190°C, and the reaction was carried out for 6-12 h. The mixture was cooled to room temperature, deionized water was added, and the mixture was stirred vigorously. The solid was precipitated, washed, purified, and dried to obtain the diaminomonomer containing an alkyne group and a carboxyl group.

5. The dual-network CO2 separation membrane prepared by the method of combining metal coordination and covalent bonding according to claim 1, characterized in that, In step 1, the solid content of the casting solution is 0.5-5 wt%; The solvent of the organic solution comprises at least one of N-methyl pyrrolidone, tetrahydrofuran, N-ethyl pyrrolidone, or N,N-dimethylformamide; The base film is polytetrafluoroethylene, and the pore size of the base film is 0.1-1 μm; The metal coordination time is 2-48 h; In step 2, the covalent crosslinking reaction time is 10-120 min.

6. The dual-network CO2 separation membrane according to any one of claims 1-5 is suitable for the separation of CO2 and N2, and the separation of CO2 and CH4.

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