PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane, preparation method thereof and CO2 separation application

Abstract

This invention relates to the field of gas separation membranes, specifically to a PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane, its preparation method, and its application in CO2 separation. The hybrid matrix membrane uses UiO-66 (PFA-IL@UiO) supported by a fluorinated ionic liquid as a porous packing material and a novel fluoropolymer PIM-1-DFBP as the polymer matrix. Due to the introduction of dual fluorine sites, this hybrid matrix membrane exhibits excellent CO2 permeability and significant CO2 / N2 selectivity in gas separation. This is attributed to the affinity microenvironment synergistically constructed by the fluorinated packing material and the fluoropolymer, which effectively promotes the dissolution and diffusion of CO2 while inhibiting the permeation of H2O and N2, enabling the separation of low-concentration CO2 in high-humidity environments.

Description

Technical Field

[0001] This invention relates to the field of gas separation membranes, specifically to a PFA-IL@UiO-PIM-1-DFBP mixed matrix membrane, its preparation method, and its application in CO2 separation. Background Technology

[0002] The combustion of fossil fuels accelerates carbon dioxide (CO2) emissions, and capturing CO2 from ambient air faces two major challenges: First, the concentration of CO2 in the air is extremely low (about 400 ppm), requiring efficient separation of CO2 from high-concentration nitrogen (about 78%); second, ambient humidity is generally high, and water molecules will seriously interfere with the separation performance of membrane materials, resulting in a significant decrease in CO2 permeability and selectivity.

[0003] Traditional polymer membrane materials generally suffer from poor CO2 / N2 selectivity, low permeate flux, and susceptibility to water vapor swelling or plasticization under low concentration and high humidity conditions, making them unsuitable for practical applications. Among numerous membrane materials, hybrid matrix membranes based on metal-organic frameworks (UiO-66) play a crucial role in membrane separation. Although UiO-66 possesses a tunable pore structure and abundant functional groups, its performance degrades easily in high humidity environments due to competitive adsorption of water molecules or structural hydration. Furthermore, its interfacial compatibility with polymer matrices is limited, leading to filler aggregation, which further affects the overall separation efficiency and long-term stability of the membrane.

[0004] Based on the current bottlenecks in separation performance and humidity control faced by membrane-based direct air capture technology, this invention, through years of exploration in the field of CO2 separation membranes, and combining the separation characteristics of CO2 separation and UiO-66-based hybrid matrix membranes, provides a method for preparing and applying a hybrid matrix membrane material suitable for the separation of low-concentration CO2 in high-humidity environments. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane, its preparation method, and its application in CO2 separation.

[0006] This invention is achieved through the following technical solution:

[0007] A method for preparing a PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane includes the following steps:

[0008] (1) Synthesis of PIM-1-DFBP polymer: 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, decafluorobiphenyl and potassium carbonate were mixed and N,N-dimethylformamide solvent was added to fully dissolve the reactant monomers. The mixture was heated and stirred in an oil bath while a protective gas was introduced. When the reaction was finished, the mixture was filtered and washed to obtain a yellow powder. The powder was placed in hydrochloric acid aqueous solution for stirring and washing, and then filtered and dried after overnight.

[0009] (2) Synthesis of UiO-66: Terephthalic acid, zirconium tetrachloride, formic acid and N,N-dimethylformamide were added to the reaction vessel in a certain proportion, and the reaction vessel was transferred to an oven for heating, followed by centrifugal drying.

[0010] (3) Synthesis of PFA-IL: 1-ethyl-3-methylimidazolium bromide and sodium perfluoropropane were dissolved in acetone, reacted at room temperature, centrifuged, and the supernatant was collected. The solvent was removed by rotary evaporation under reduced pressure. The product was washed with dichloromethane and dried to obtain the ionic liquid PFA-IL.

[0011] (4) Synthesis of PFA-IL@UiO filler: PFA-IL and UiO-66 were mixed and dissolved in acetone. The mixture was stirred continuously at room temperature until the solvent was completely evaporated. The mixture was washed with methanol and dried to obtain a white powder.

[0012] (5) Preparation of membrane material: PIM-1-DFBP polymer and PFA-IL@UiO filler are added to solvent and stirred for 1-2 days depending on the dispersion of filler. Then, it is dropped into a polytetrafluoroethylene mold, dried and shaped, peeled off, and placed in an oven to activate and dry to remove residual solvent.

[0013] Furthermore, in (1), the molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, and decafluorobiphenyl is 10:8:2; the molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane and potassium carbonate is 1:2.5.

[0014] Furthermore, in (1), the reaction temperature for synthesizing the polymer is 90~100℃ and the reaction time is 24~72 hours.

[0015] Furthermore, in (3), the molar ratio of 1-ethyl-3-methylimidazolium bromide and sodium perfluoropropane is 1:1.

[0016] Furthermore, in (4), the mass ratio of PFA-IL to UiO-66 is 1:10.

[0017] Furthermore, in (5), the mass ratio of PIM-1-DFBP polymer to PFA-IL@UiO is 1:(5-19), and the mass fraction of PFA-IL@UiO is 5-25wt%, preferably 20wt%.

[0018] The present invention also provides a PFA-IL@UiO-PIM-1-DFBP mixed matrix membrane prepared by the above preparation method.

[0019] The present invention also provides the application of the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane in CO2 separation.

[0020] Furthermore, the separation environment humidity is 25~100%RH, and the CO2 volume fraction is 0.04~15%.

[0021] The present invention has the following beneficial technical effects:

[0022] (1) A novel polymer synthesis method with fluorine-containing sites and strong affinity for CO2 was explored, and it was mixed with a high CO2 flux polymer, giving the blended polymer matrix of the membrane material the potential for separating low-concentration CO2. (2) A PFA-IL@UiO filler with fluorine-containing sites was synthesized and prepared and applied to the blended polymer matrix, making the overall membrane material suitable for separating low-concentration CO2 in high-humidity environments. (3) In gas separation tests, the membrane material exhibited strong separation performance under different humidity and different CO2:N2 ratios, proving that the membrane material has strong versatility. Attached Figure Description

[0023] Figure 1 : 1H NMR spectrum of PIM-1-DFBP polymer;

[0024] Figure 2 Fourier transform infrared spectrum of PIM-1-DFBP polymer;

[0025] Figure 3 Powder X-ray diffraction pattern of PFA-IL@UiO;

[0026] Figure 4 Fourier transform infrared spectrum of PFA-IL@UiO;

[0027] Figure 5 Nitrogen adsorption isotherm of PFA-IL@UiO;

[0028] Figure 6 Pore ​​structure diagram of PFA-IL@UiO;

[0029] Figure 7 Scanning electron microscope image of PFA-IL@UiO;

[0030] Figure 8 Comparison of photographs of x wt% PFA-IL@UiO mixed matrix membrane and pure PIM-1-DFBP membrane (x wt% is the mass fraction of PFA-IL, and the value of x ranges from 5 to 25);

[0031] Figure 9 Scanning electron microscope image of a 20wt% PFA-IL@UiO hybrid matrix membrane;

[0032] Figure 10 Schematic diagram of a low-concentration CO2 gas separation test device under high humidity conditions;

[0033] Figure 11 Schematic diagram of membrane separation;

[0034] Figure 12 : CO2 / N2 selectivity variation curves of mixed matrix membranes with different filler contents;

[0035] Figure 13 CO2 / N2 selectivity variation curves of 20wt% PFA-IL@UiO membrane under different humidity conditions. Detailed Implementation

[0036] Example 1: Synthesis of PIM-1-DFBP

[0037] 5,5',6,6'-Tetrahydroxy-3,3,3',3'-Tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, decafluorobiphenyl, and potassium carbonate were added to N,N-dimethylformamide solvent and dissolved completely. The molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, and decafluorobiphenyl was 10:8:2; the molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane to potassium carbonate was 1:2.5.

[0038] (2) Use a magnetic stirring heating table to heat the oil bath and introduce protective gas nitrogen or argon. Control the reaction temperature between 90 and 100°C and the reaction time is 24-72 hours. When the reaction is finished, wash with methanol or ethanol solution and place the obtained powder in a hydrochloric acid aqueous solution with a concentration of less than 5% and stir for 12-24 hours. Filter to obtain polymer powder.

[0039] The obtained PIM-1-DFBP powder was characterized as follows:

[0040] (1) Molecular weight and dispersity of PIM-1-DFBP polymer

[0041] The molecular weight and dispersity of PIM-1-DFBP polymer were tested using gel permeation chromatography, as shown in Table 1, indicating that PIM-1-DFBP has a high molecular weight.

[0042] Table 1. Molecular weight and dispersity data of PIM-1-DFBP polymer

[0043] <![CDATA[Number average molecular weight ( M n ) (g·mol -1 )]]> <![CDATA[Weight-average molecular weight ( M w ) (g·mol -1 )]]> Dispersion Index (PDI) PIM-1-DFBP 77188 175053 2.27

[0044] (2) 1H NMR spectrum of PIM-1-DFBP polymer

[0045] The successful synthesis of PIM-1-DFBP polymer was confirmed by 1H NMR spectroscopy. See details below. Figure 1 .

[0046] (3) Fourier transform infrared spectrum of PIM-1-DFBP polymer

[0047] Fourier transform infrared spectroscopy detected stretching vibration peaks of the CF bonds in the PIM-1-DFBP polymer, proving the successful introduction of the F site. (See details...) Figure 2 .

[0048] Example 2 Synthesis of filler PFA-IL@UiO

[0049] (1) Synthesis of UiO-66

[0050] Terephthalic acid, zirconium tetrachloride, formic acid, and N,N-dimethylformamide were added to a reaction vessel in a specific ratio, and the reaction vessel was then transferred to an oven for heating. The reaction temperature was 120°C, and the reaction time was 72 hours. At the end of the reaction, N,N-dimethylformamide and methanol were used for solvent exchange. The precipitate was then collected by centrifugation and dried to obtain a white filler powder.

[0051] The molar ratio of terephthalic acid, zirconium tetrachloride and formic acid in the synthesis of UiO-66 is 1:1:100, and the amount of N,N-dimethylformamide solvent added is 24 mL (which can be increased or decreased according to the degree of solubility of the monomer raw materials, compared with the molar ratio of the raw materials).

[0052] (2) Synthesis of PFA-IL

[0053] 1-Ethyl-3-methylimidazolium bromide and sodium perfluoropropane were mixed in a molar ratio of 1:1, dissolved in acetone, reacted at room temperature for 1-3 hours, centrifuged, and the supernatant was collected. The solvent was removed by rotary evaporation under reduced pressure. The resulting product was washed with dichloromethane and dried to obtain the ionic liquid PFA-IL.

[0054] (3) Synthesis of PFA-IL@UiO packing

[0055] Mix 10 mg PFA-IL and 100 mg UiO-66, dissolve in 10 mL acetone, stir continuously at room temperature until the solvent is completely evaporated, wash with methanol and dry to obtain a white powder.

[0056] Characterization of packing material PFA-IL@UiO:

[0057] Powder X-ray diffraction of PFA-IL@UiO

[0058] Comparison of the powder X-ray diffraction peaks with those of theoretical UiO-66 and synthesized UiO-66 shows that the introduction of PFA-IL into UiO-66 does not change its structure. (See details...) Figure 3 .

[0059] Fourier transform infrared spectrum of PFA-IL@UiO

[0060] Fourier transform infrared spectroscopy confirms the successful integration of PFA-IL into UiO-66. See details below. Figure 4 .

[0061] Specific surface area and porosity analysis of PFA-IL@UiO

[0062] The specific surface area of ​​PFA-IL@UiO is 1287 m². 2 ·g −1 The apertures are 6.9 Å, 7.4 Å, and 11.2 Å, see details below. Figure 5-6 .

[0063] Scanning electron microscope image of PFA-IL@UiO

[0064] Scanning electron microscopy images show that the crystal morphology of PFA-IL@UiO retains the original octahedral shape of UiO-66, further demonstrating that the introduction of PFA-IL did not alter the structure of UiO-66. (See details...) Figure 7 .

[0065] Example 3: Preparation of a mixed matrix membrane (named x wt% PFA-IL@UiO, where x wt% is the mass fraction of PFA-IL, and x ranges from 5 to 25):

[0066] (1) Preparation of membrane material: The polymer PIM-1-DFBP powder obtained in Example 1 and the PFA-IL@UiO filler obtained in Example 2 were added to chloroform solvent according to a certain mass ratio, stirred for 1-2 days, and then ultrasonically dispersed. Subsequently, it was placed in an ultrasonic instrument for ultrasonic treatment. It was dropped into a polytetrafluoroethylene mold and placed in a chloroform vapor environment overnight to evaporate. The pure PIM-1-DFBP membrane material was peeled off and placed in a 60°C oven for activation drying to remove residual solvent.

[0067] The formula for calculating the amount of filler to be added is as follows:

[0068]

[0069] In this embodiment, five mixed matrix membranes were obtained: 5wt% PFA-IL@UiO, 10wt% PFA-IL@UiO, 15wt% PFA-IL@UiO, 20wt% PFA-IL@UiO, and 25wt% PFA-IL@UiO.

[0070] Comparative Example 1: Preparation of pure PIM-1-DFBP membrane

[0071] Add 137 mg of PIM-1-DFBP polymer powder and 3 mL of chloroform solvent to a 10 mL glass bottle, stir for 12 hours, and then sonicate. Drop the mixture onto a polytetrafluoroethylene mold and place it in a chloroform vapor environment overnight to evaporate. Peel off the pure PIM-1-DFBP membrane material and place it in a 60 °C oven for activation and drying.

[0072] Comparative Example 2: Preparation of PIM-1 membrane

[0073] (1) Synthesis of PIM-1 polymer: 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, potassium carbonate, and N,N-dimethylformamide were sequentially added to a three-necked flask and mixed thoroughly. Argon or nitrogen gas was introduced for protection, and the mixture was magnetically stirred at 65°C for 72 hours. After the reaction mixture cooled to room temperature, the crude product was filtered and washed three times with methanol. The resulting solid was then transferred to a 0.1 wt% aqueous hydrochloric acid solution and stirred overnight. Finally, the yellow powder was collected by filtration and dried in a vacuum oven at 80°C for 12 hours to obtain PIM-1 powder.

[0074] (2) Preparation of PIM-1 membrane material: 137 mg of PIM-1 polymer powder and 3 mL of chloroform solvent were added to a 10 mL glass bottle and stirred for 12 hours. Then, the mixture was ultrasonically treated. The mixture was dropped into a polytetrafluoroethylene mold and placed in a chloroform vapor environment overnight to evaporate. The pure PIM-1 membrane material was peeled off and placed in a 60 °C oven for activation and drying.

[0075] Comparative Example 3: Preparation and Characterization of 20wt% PIM-2 / PIM-1 Membranes

[0076] (1) Synthesis of PIM-2 polymer: 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, potassium carbonate, and N,N-dimethylformamide were sequentially added to a three-necked flask and mixed thoroughly. Argon or nitrogen gas was introduced for protection, and the mixture was magnetically stirred at 95°C for 1 hour. Subsequently, an N,N-dimethylformamide solution containing decafluorobiphenyl was added. Then, under an argon or nitrogen atmosphere, the mixture was stirred at 95°C for 72 hours. The resulting grayish-white solution was filtered, and the collected solid was stirred overnight in a 5wt% hydrochloric acid aqueous solution. Finally, the crude product was washed with methanol for 6 hours with stirring, filtered again, and dried in a vacuum oven at 80°C for 12 hours to obtain PIM-2 powder.

[0077] (2) Preparation of 20wt% PIM-2 / PIM-1 membrane material: 109.6 mg of PIM-1 polymer powder, 27.4 mg of PIM-2 polymer powder, and 3 mL of chloroform solvent were added to a 10 mL glass bottle and stirred for 12 hours. The mixture was then sonicated. The mixture was dropped into a polytetrafluoroethylene mold and placed in a chloroform vapor environment overnight for evaporation. The 20wt% PIM-2 / PIM-1 membrane material was peeled off and placed in a 60℃ oven for activation and drying.

[0078] Comparative Example 4: Preparation and Characterization of 20wt% TFA-IL@UiO Hybrid Matrix Membrane

[0079] (1) Synthesis of TFA-IL: 1-Ethyl-3-methylimidazolium bromide and sodium perfluoroacetate were dissolved in acetone and stirred at room temperature for 1 hour. After the reaction was completed, the supernatant was collected by centrifugation, the solvent was removed by rotary evaporation under reduced pressure, and the product was washed with dichloromethane and dried.

[0080] (2) Synthesis of TFA-IL@UiO filler: TFA-IL was dissolved in acetone, and then UiO-66 powder was added. The mixture was continuously stirred until the acetone was completely evaporated at room temperature. The crude product was repeatedly washed with methanol to remove any unbound TFA-IL from the particle surface, and the sample was dried overnight in a vacuum oven at 60°C.

[0081] (3) Preparation of 20wt% TFA-IL@UiO membrane material: First, the filler TFA-IL@UiO is uniformly dispersed in chloroform or tetrahydrofuran solution and ultrasonically treated. A certain proportion of PIM-1-DFBP polymer is added to the dispersed filler and uniformly dispersed in the casting solution. The suspension is stirred for 1-2 days. The casting solution is dropped into a polytetrafluoroethylene mold and placed in a chloroform or tetrahydrofuran vapor environment to dry overnight. The formed membrane material is placed in an oven at 60 or 80℃ for drying and activation.

[0082] Comparative Example 5: Preparation and Characterization of 20wt% HFBA-IL@UiO Hybrid Matrix Membrane

[0083] (1) Synthesis of HFBA-IL: 1-Ethyl-3-methylimidazolium bromide and sodium heptafluorobutyrate were dissolved in acetone and stirred at room temperature for 1 hour. After the reaction was completed, the supernatant was collected by centrifugation, the solvent was removed by rotary evaporation under reduced pressure, and the product was washed with dichloromethane and dried.

[0084] (2) Synthesis of HFBA-IL@UiO filler: HFBA-IL was dissolved in acetone, and then UiO-66 powder was added. The mixture was continuously stirred until the acetone was completely evaporated at room temperature. The crude product was repeatedly washed with methanol to remove any unbound HFBA-IL from the particle surface, and the sample was dried overnight in a vacuum oven at 60°C.

[0085] (3) Preparation of 20wt% HFBA-IL@UiO membrane material: First, the filler HFBA-IL@UiO is uniformly dispersed in chloroform or tetrahydrofuran solution and ultrasonically treated. A certain proportion of PIM-1-DFBP polymer is added to the dispersed filler and uniformly dispersed in the casting solution. The suspension is stirred for 1-2 days. The casting solution is dropped into a polytetrafluoroethylene mold and placed in a chloroform or tetrahydrofuran vapor environment to dry overnight. The formed membrane material is placed in an oven at 60 or 80℃ for drying and activation.

[0086] The photographs of the x wt% PFA-IL@UiO mixed matrix membrane obtained in Example 3 and the pure PIM-1-DFBP membrane obtained in Comparative Example 1 are shown below. Figure 8 As shown, when the amount of PFA-IL@UiO filler added is within 0~20wt%, the membrane surface is uniform and without defects, while when the amount of PFA-IL@UiO filler added reaches 25wt%, particle agglomeration occurs inside the membrane.

[0087] Scanning electron microscopy of 20wt% PFA-IL@UiO hybrid matrix membrane Figure 9 As shown, the octahedral PFA-IL@UiO filler can be clearly observed, indicating the successful introduction and uniform distribution of PFA-IL@UiO.

[0088] Low-concentration CO2 gas separation test under high humidity conditions:

[0089] In the test, a CO2:N2 mixture (1:99~15:85, v:v), compressed air (CO2 concentration of 400ppm), helium, a gas mass flow meter, a self-made metal membrane cell, a gas chromatograph, and a connected computer were used. A schematic diagram of the gas separation test is shown below. Figure 10As shown. A schematic diagram of membrane separation is shown below. Figure 11 As shown.

[0090] The membrane materials prepared in Comparative Examples 1-4 were tested for mixed gas separation under high humidity (65%RH) conditions (CO2:N2=15:85, v:v). The specific results are shown in Table 2.

[0091] Table 2. CO2 / N2 separation performance of membrane materials in Comparative Examples 1-4 under high humidity (65% RH) conditions.

[0092] Membrane material <![CDATA[CO2 Permeability (Barrer)]]> <![CDATA[N2 Permeability (Barrer)]]> <![CDATA[CO2 / N2 selectivity]]> PIM-1 3841.23 183.25 20.96 20wt% PIM-2 / PIM-1 3622.78 130.89 27.69 PIM-1-DFBP 4022.79 162.39 24.78

[0093] The test results show that PIM-1-DFBP exhibits the best overall separation performance. This is attributed to the chain twisting effect enhanced by PIM-1-DFBP, resulting in a polymer network with a larger free volume and greater porosity compared to the other two polymers.

[0094] The membrane material obtained in Example 3 was subjected to gas separation tests in a high humidity environment (65%RH) with low CO2 concentration (400ppm). The specific results are shown in Table 3 and... Figure 12 As shown:

[0095] Table 3. Low-concentration CO2 separation performance of mixed matrix membranes with different filler addition amounts at 65% RH.

[0096] Filler addition amount (mass fraction) <![CDATA[CO2 Permeability (Barrer)]]> <![CDATA[N2 Permeability (Barrer)]]> <![CDATA[CO2 / N2 selectivity]]> 0 4550.29 214.12 21.25 5 5540.60 233.25 23.76 10 7341.18 252.57 29.07 15 9527.72 270.09 35.28 20 12697.08 288.23 44.06 25 14233.06 390.89 36.41

[0097] The test results show that the permeability of CO2 and N2 increases with the increase of packing material content. This is due to the large number of gas transport channels in the packing material, which facilitates the transport of low-concentration CO2. Simultaneously, the addition of numerous fluorine sites is also an important factor in the separation of low-concentration CO2. The CO2 / N2 selectivity exhibits a trend of first increasing and then decreasing, reaching its maximum value when the PFA-IL@UiO loading is 20 wt%. When the loading exceeds 20 wt%, the selectivity gradually decreases, possibly due to defects caused by packing material agglomeration.

[0098] The 20wt% PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane material obtained in Example 3 was subjected to gas separation tests under high humidity (65%RH) conditions with different concentrations of CO2 (volume fraction of 0.04~15%). The specific results are shown in Table 4.

[0099] Table 4. Separation performance of 20wt% PFA-IL@UiO membrane at different CO2 concentrations.

[0100] <![CDATA[CO2 volume fraction (%)]]> <![CDATA[CO2 Permeability (Barrer)]]> <![CDATA[N2 Permeability (Barrer)]]> <![CDATA[CO2 / N2 selectivity]]> 0.04 12697.08 288.23 44.06 1 12104.12 254.52 47.57 5 11782.45 230.43 51.14 15 10533.22 188.45 55.91

[0101] The test results show that tests conducted at different CO2 concentrations (volume fractions of 0.04%–15%) indicate that the permeability of both CO2 and N2 decreases with increasing CO2 concentration. This decrease suggests that CO2 molecules competitively occupy F sites, leading to local saturation. The membrane material, after adsorbing a higher concentration of CO2, physically hinders the diffusion path of N2, resulting in a significant decrease in N2 permeability. The net increase in CO2 / N2 selectivity is due to the fact that the decrease in N2 permeability exceeds the decrease in CO2 permeability.

[0102] The 20wt% PFA-IL@UiO-PIM-1-DFBP sample from Example 3 was tested under different humidity levels (25~100%RH). Specific results are shown in Table 5 and... Figure 13 As shown:

[0103] Table 5. Separation performance of 20wt% PFA-IL@UiO membrane under different humidity conditions.

[0104] Relative humidity (percentage) <![CDATA[CO2 Permeability (Barrer)]]> <![CDATA[N2 Permeability (Barrer)]]> <![CDATA[CO2 / N2 selectivity]]> 25 10325.85 270.51 38.17 45 11546.64 276.77 41.72 65 12697.08 288.23 44.06 85 13602.67 290.20 46.87 100 14126.96 296.22 47.69

[0105] The test results show that the PFA-IL@UiO@PIM-1-DFBP hybrid matrix membrane maintains excellent low-concentration CO2 separation performance over a wide humidity range, especially under high humidity conditions.

[0106] The membrane materials in Examples 3, 3, and 4 were subjected to gas separation tests in a high humidity environment (65%RH) with low CO2 concentration (400ppm). The specific results are shown in Table 6.

[0107] Table 6. Comparison of low-concentration CO2 separation performance of membranes modified with different ionic liquids at 65% RH.

[0108] Membrane material <![CDATA[CO2 Permeability (Barrer)]]> <![CDATA[N2 Permeability (Barrer)]]> <![CDATA[CO2 / N2 selectivity]]> 20wt% TFA-IL@UiO 10003.55 281.36 35.57 20wt% PFA-IL@UiO 12697.08 288.23 44.06 20wt% HFBA-IL@UiO 13131.68 321.97 40.79

[0109] The test results show that the 20wt% PFA-IL@UiO membrane exhibits the best overall performance, superior to the 20wt% TFA-IL@UiO membrane. This is attributed to the increased fluorine density on the ionic liquid, which promotes interaction with CO2. Although HFBA-IL has the highest fluorine content, the 20wt% HFBA-IL@UiO membrane has higher permeability but lower selectivity due to lower loading efficiency caused by steric hindrance. Therefore, the performance variation of the PFA-IL@UiO@PIM-1-DFBP mixed matrix membrane under CO2 concentration highlights the role of its dual-fluorine-site driven separation mechanism, especially in high-humidity environments with low CO2 concentrations, making it a promising candidate material for membrane-based direct air separation applications.

[0110] In summary, this invention discloses a membrane material, its preparation method, and its application suitable for separating low-concentration CO2 in high-humidity environments. It utilizes a dual-fluorine site synergistic mechanism to prepare a PFA-IL@UiO@PIM-1-DFBP mixed matrix membrane. The introduction of dual-fluorine sites increases the hydrophobicity of the membrane material and its binding force to CO2 molecules, thereby improving the overall separation capability of the membrane material for low-concentration CO2 in humid environments.

Claims

1. A method for preparing a PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane, characterized in that: Includes the following steps: (1) Synthesis of PIM-1-DFBP polymer: 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, decafluorobiphenyl and potassium carbonate were mixed and N,N-dimethylformamide solvent was added to fully dissolve the reactant monomers. The mixture was heated and stirred in an oil bath while a protective gas was introduced. After the reaction was completed, the mixture was filtered and washed to obtain a yellow powder. The powder was placed in hydrochloric acid aqueous solution, stirred and washed, and filtered and dried after overnight. (2) Synthesis of UiO-66: Terephthalic acid, zirconium tetrachloride, formic acid and N,N-dimethylformamide were added to the reaction vessel, and the reaction vessel was transferred to an oven for heating, followed by centrifugal drying. (3) Synthesis of PFA-IL: 1-ethyl-3-methylimidazolium bromide and sodium perfluoropropane were dissolved in acetone, reacted at room temperature, centrifuged, and the supernatant was collected. The solvent was removed by rotary evaporation under reduced pressure. The product was washed with dichloromethane and dried to obtain the ionic liquid PFA-IL. (4) Synthesis of PFA-IL@UiO filler: PFA-IL and UiO-66 were mixed and dissolved in acetone. The mixture was stirred continuously at room temperature until the solvent was completely evaporated. The mixture was washed with methanol and dried to obtain a white powder. (5) Preparation of membrane material: PIM-1-DFBP polymer and PFA-IL@UiO filler are added to solvent and stirred for 1-2 days depending on the dispersion of filler. The mixture is then dropped into a polytetrafluoroethylene mold, dried and shaped, peeled off, and placed in an oven to activate and dry to remove residual solvent.

2. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 1, characterized in that: In (1), the molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane, tetrafluoroterephthalonitrile, and decafluorobiphenyl is 10:8:2; the molar ratio of 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane and potassium carbonate is 1:2.

5.

3. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 1, characterized in that: In (1), the reaction temperature is 90~100℃ and the reaction time is 24~72 hours.

4. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 2, characterized in that: The number-average molecular weight of the PIM-1-DFBP polymer M n 77188 g·mol -1 Weight-average molecular weight M w 175053 g·mol -1 The dispersion PDI is 2.

27.

5. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 1, characterized in that: In (3), the molar ratio of 1-ethyl-3-methylimidazolium bromide and sodium perfluoropropane is 1:

1.

6. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 1, characterized in that: In (4), the mass ratio of PFA-IL to UiO-66 is 1:

10.

7. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 6, characterized in that: The PFA-IL@UiO filler has a specific surface area of 1287 m 2 ·g -1 The pore size distribution includes 6.9 Å, 7.4 Å and 11.2 Å, and the crystal structure of the filler maintains the octahedral morphology of UiO-66.

8. The method for preparing the PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane according to claim 1, characterized in that: In (5), the mass ratio of PIM-1-DFBP polymer to PFA-IL@UiO is 1:(5-19), and the mass fraction of PFA-IL@UiO is 5-25wt%.

9. A PFA-IL@UiO-PIM-1-DFBP hybrid matrix membrane prepared by the preparation method according to any one of claims 1-6, characterized in that: The hybrid matrix membrane contains difluorinated sites, including CF bonds in the polymer chain and perfluoroalkyl functional groups in the filler.

10. The application of a PFA-IL@UiO-PIM-1-DFBP mixed matrix membrane prepared by the preparation method according to any one of claims 1-6 in the separation of CO2, characterized in that: The separation is suitable for environments with humidity of 25~100%RH and CO2 volume fraction of 0.04~15%.

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