A method for preparing a uiO-66-nh2-based mixed matrix membrane

Abstract

The application provides a preparation method of a UiO-66-NH2-based mixed matrix membrane, which comprises the following steps: 3,3',4,4'-diphenyltetracarboxylic dianhydride is prepared by adding 4-chloro-N-methyl phthalimide, a catalyst A, a reducing agent and an additive into an aprotic solvent; then UiO-66-NH2 is added into the reaction system to obtain anhydride-capped UiO-66-NH2 (BPDA); UiO-66-NH2 (BPDA), BPDA and ODA are added into DMAC, a dehydrating agent and a catalyst B are added to obtain BPDA-ODA type polyimide containing UiO-66-NH2; and the BPDA-ODA type polyimide containing UiO-66-NH2 and DMAC are configured into a casting solution to obtain a mixed matrix membrane UiO-66-NH2 / BPDA-ODA-N. Compared with the traditional direct doping method for preparing the mixed matrix membrane, the preparation method greatly improves the doping amount of UiO-66-NH2, which makes the permeation flux of CO2 further improved while the selectivity of retaining CO2 is reserved, and the CO2 separation performance is more excellent.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, and in particular relates to a method for preparing a UiO-66-NH2-based mixed matrix membrane. Background Technology

[0002] Currently, the world's main energy supply still relies on carbon-based fuels, primarily coal, oil, and natural gas. The main gas produced by the combustion of fossil fuels is CO2, a major greenhouse gas. Excessive CO2 traps solar radiation in the atmosphere, leading to global warming—a phenomenon known as the greenhouse effect. Therefore, the separation and capture of carbon dioxide has become a crucial research topic.

[0003] The main CO2 separation technologies include absorption, adsorption, cryogenic distillation, and membrane separation. Among these, membrane separation is becoming the dominant technology due to its advantages such as low energy consumption, small footprint, and environmental friendliness. Among various membrane materials, hybrid matrix membranes can combine the advantages of both packing material and base membrane, resulting in significantly improved CO2 permeate flux and selectivity compared to pure membranes.

[0004] Currently, polyimide-based membranes exhibit excellent overall performance, but their CO2 permeation flux is relatively low. Introducing UiO-66-NH2 as a filler for doping can largely solve this problem. However, although UiO-66-NH2, as a MOF material, has good interfacial compatibility with the polyimide base membrane, according to relevant literature, the optimal doping concentration is generally only 10wt%-20wt%. Exceeding this value leads to significant non-selective voids, affecting CO2 separation performance. A novel method was used to prepare a hybrid matrix membrane, achieving an optimal doping concentration of 60%. Compared to pure membranes, this resulted in a CO2 permeation flux increase of over 160% and a CO2 / CH4 selectivity increase of over 30%. Summary of the Invention

[0005] In view of this, the present invention aims to synthesize 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, react it with UiO-66-NH2 to obtain its capped UiO-66-NH2 (BPDA), and then react it with BPDA and ODA together via interfacial growth to prepare a novel mixed matrix membrane. Compared with the traditional direct doping method for preparing mixed matrix membranes, this method greatly increases the doping amount of UiO-66-NH2, which allows for the retention of CO2 selectivity while further improving CO2 permeation flux, resulting in superior CO2 separation performance.

[0006] To achieve the above objectives, the technical solution of the present invention is implemented as follows:

[0007] A method for preparing a UiO-66-NH2-based hybrid matrix membrane includes the following steps:

[0008] (1) Preparation of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride:

[0009] Under a protective atmosphere, 4-chloro-N-methylphthalimide, catalyst A, reducing agent, and additives are added to an aprotic solvent and reacted at 40-60°C for 10-18 hours. The solvent is recovered, recrystallized, and dried to obtain bisaminobenzeneimide. The obtained bisaminobenzeneimide is hydrolyzed to form a salt using a salt-forming solvent. The insoluble matter is removed, the acid is adjusted, and the salt is dried to obtain biphenyltetracarboxylic acid. Biphenyltetracarboxylic acid is added to a benzene-based solvent and then reacted with acetic anhydride to obtain 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, abbreviated as BPDA.

[0010] (2) Dissolve the BPDA synthesized in step (1) in solvent A, then add UiO-66-NH2 to the reaction system, stir evenly, add acetic anhydride, and react at 25-50℃. After the reaction is completed, filter, wash and dry to obtain anhydride-terminated UiO-66-NH2 (BPDA).

[0011] (3) The UiO-66-NH2 (BPDA) synthesized in step (2), the BPDA and ODA synthesized in step (1) are added to DMAC and reacted at 0-25℃ for 6-12h. A dehydrating agent and catalyst B are added and the reaction continues for a period of time. Then, it is poured into a poor solvent and a large amount of solid is precipitated. After filtration and drying, BPDA-ODA type polyimide containing UiO-66-NH2 is obtained.

[0012] (4) Prepare a casting solution with a solid content of 5wt%-10wt% by BPDA-ODA type polyimide containing UiO-66-NH2 and DMAC in step (3), pour it into an ultra-flat culture dish, and slowly evaporate the solvent at 40-70℃ to obtain a pre-formed film. After high temperature treatment, obtain a mixed matrix film UiO-66-NH2 / BPDA-ODA-N; the mixed matrix film UiO-66-NH2 / BPDA-ODA-N, where N represents the doping amount of UiO-66-NH2, and N is 30-70, that is, the doping amount of UiO-66-NH2 is 30wt%-70wt%.

[0013] Furthermore, in step (1), the molar ratio of catalyst A, reducing agent, additive, and aminochlorophthalimide is (0.01-0.03): (0.2-0.4): (0.0002-0.001): 1.

[0014] Furthermore, in step (1), catalyst A is one or more of nickel chloride, nickel sulfate, nickel bromide, and nickel acetate.

[0015] Furthermore, in step (1), the reducing agent is one or both of zinc powder and magnesium powder; the additive is triphenylphosphine.

[0016] Furthermore, in step (1), the aprotic solvent is one or more of dimethylformamide (DMF), dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and dimethyltetrahydrofuran (2-THF).

[0017] Furthermore, the solvent used for recrystallization in step (1) is one or more of toluene, xylene, isopropanol, isobutanol, and n-hexane.

[0018] Furthermore, in step (1), the benzene reagent is one or more of benzene, toluene, o-xylene, o-dichlorobenzene, and m-xylene.

[0019] Furthermore, in step (1), the salt-forming solvent is a 15wt%-40wt% sodium hydroxide aqueous solution.

[0020] Furthermore, nitrogen is selected as the protective gas in step (1).

[0021] Furthermore, in step (2), the mass ratio of solvent A, UiO-66-NH2, and BPDA is (15-30): (3-6):1.

[0022] Furthermore, in step (2), solvent A is one or more of tetrahydrofuran, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

[0023] Furthermore, in step (3), the mass ratio of UiO-66-NH2 (BPDA) to the total mass of UiO-66-NH2 (BPDA), BPDA, and ODA is (0.3-0.7):1; the molar ratio of BPDA to ODA is 0.98-1.01:1; and the total mass of UiO-66-NH2 (BPDA), BPDA, and ODA accounts for 3wt%-7wt% of the total mass of the solution formed by UiO-66-NH2 (BPDA), BPDA, ODA, and DMAC.

[0024] Furthermore, the dehydrating agent in step (3) is acetic anhydride.

[0025] Furthermore, in step (3), catalyst B is pyridine.

[0026] Furthermore, in step (3), the unsuitable solvents are deionized water, methanol, ethanol, and isopropanol.

[0027] Furthermore, in step (3), the unsuitable solvent is ethanol.

[0028] Furthermore, in step (4), the high-temperature treatment temperature of the pre-formed film is 180-220℃.

[0029] Compared with existing technologies, the preparation method of the UiO-66-NH2-based mixed matrix membrane of the present invention has the following advantages:

[0030] This invention synthesizes a common dianhydride monomer, 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), and uses UiO-66-NH2 as a filler to synthesize a novel mixed matrix membrane, UiO-66-NH2 / BPDA-ODA-N, via an interfacial growth method. Compared with pure membranes and mixed matrix membranes prepared by conventional methods, this invention shows a higher CO2 permeation flux. The preparation method is simple, environmentally friendly, pollution-free, and has good reproducibility, providing a certain reference for large-scale production. Attached Figure Description

[0031] Figure 1 This is the synthetic route for the synthesis of -3,3',4,4'-biphenyltetracarboxylic acid dianhydride in Example 1;

[0032] Figure 2 The HPLC chromatogram of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride synthesized in Example 1 of this invention;

[0033] Figure 3 This is a schematic diagram of the preparation of the hybrid matrix membrane in Examples 2-4 of the present invention;

[0034] Figure 4 The CO2 separation performance of novel mixed matrix membranes with different UiO-66-NH2 contents is shown in the figure.

[0035] Figure 5 The CO2 separation performance diagrams for BPDA-ODA, UiO-66-NH2 / BPDA-ODA(15), and UiO-66-NH2 / BPDA-ODA-60 are shown. Detailed Implementation

[0036] Unless otherwise defined, the technical terms used in the following embodiments have the same meanings as commonly understood by those skilled in the art. Unless otherwise specified, the experimental reagents used in the following embodiments are conventional biochemical reagents; and the experimental methods described are conventional methods.

[0037] The present invention will now be described in detail with reference to the embodiments and accompanying drawings.

[0038] Example 1

[0039] (a) Synthesis of 3,3',4,4'-Biphenyldiimide

[0040] Under nitrogen protection, 26.57 g of 4-chloro-N-methylphthalimide, 2.95 g of zinc powder, 352 mg of anhydrous NiCl2, 20 mg of triphenylphosphine, and 80 mL of DMAc were added to a 500 mL three-necked flask. The mixture was reacted at 45 °C for 18 h. 60 mL of DMAc was recovered, and 60 mL of toluene was added to the system. The mixture was heated to 100 °C until completely dissolved. The insoluble matter was filtered off, and the filtrate was cooled to room temperature. A large amount of precipitate was formed. The precipitate was filtered and dried under vacuum at 90 °C for 12 h to obtain 41.65 g of 3,3',4,4'-biphenyldiimide with a purity of 98.34% and a molar yield of 95.72%.

[0041] (II) Synthesis of 3,3',4,4'-biphenyltetracarboxylic acid

[0042] 20 g of the above-mentioned 3,3',4,4'-biphenyl diimide was added to 30 mL of 25 wt% sodium hydroxide aqueous solution, heated to reflux, and reacted for 20 h. After cooling to room temperature, the pH was adjusted to 1 with concentrated hydrochloric acid, and a large amount of white solid precipitated out. The solid was washed three times with 200 mL of deionized water, and dried under vacuum at 100 °C for 12 h to obtain 20.32 g of 3,3',4,4'-biphenyl tetracarboxylic acid with a purity of 99.12% and a molar yield of 98.56%.

[0043] (III) Synthesis of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride

[0044] The above-mentioned 20g of 3,3',4,4'-biphenyltetracarboxylic acid was added to 100mL of toluene and 20mL of acetic anhydride, and reacted at 80℃ for 8h. After cooling to room temperature, the mixture was filtered to obtain a white solid, which was dried under vacuum at 90℃ for 12h to obtain 17.64g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride with a purity of 99.92% and a molar yield of 98.97%.

[0045] Example 2

[0046] (a) Synthesis of 3,3',4,4'-Biphenyldiimide

[0047] Under nitrogen protection, 25.97 g of 4-chloro-N-methylphthalimide, 1.11 g of magnesium powder, 371 mg of anhydrous NiCl2, 35 mg of triphenylphosphine, and 90 mL of 2-THF were added to a 500 mL three-necked flask. The mixture was reacted at 55 °C for 22 h. 70 mL of 2-THF was recovered, and 80 mL of a mixed solvent (v(isopropanol):v(n-hexane) = 1:1.5) was added to the system. The mixture was heated to 80 °C until completely dissolved. The insoluble matter was filtered off, and the filtrate was cooled to room temperature. A large amount of precipitate was formed. The precipitate was filtered and dried under vacuum at 90 °C for 12 h to obtain 39.91 g of 3,3',4,4'-biphenyldiimide with a purity of 97.88% and a molar yield of 93.84%.

[0048] (II) Synthesis of 3,3',4,4'-biphenyltetracarboxylic acid

[0049] 20 g of the above-mentioned 3,3',4,4'-biphenyl diimide was added to 40 mL of 20 wt% sodium hydroxide aqueous solution, heated to reflux, and reacted for 24 h. After cooling to room temperature, the pH was adjusted to 1 with concentrated hydrochloric acid, and a large amount of white solid precipitated out. The solid was washed three times with 200 mL of deionized water, and dried under vacuum at 100 °C for 12 h to obtain 38.46 g of 3,3',4,4'-biphenyl tetracarboxylic acid with a purity of 98.75% and a molar yield of 96.37%.

[0050] (III) Synthesis of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride

[0051] 20 g of the above-mentioned 3,3',4,4'-biphenyltetracarboxylic acid was added to 120 mL of o-xylene and 20 mL of acetic anhydride, and reacted at 90 °C for 8 h. After cooling to room temperature, the mixture was filtered to obtain a white solid, which was dried under vacuum at 90 °C for 12 h to obtain 17.38 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride with a purity of 99.78% and a molar yield of 97.61%.

[0052] Example 3

[0053] 1 g of BPDA and 25 mL of DMAc were added to a 100 mL three-necked flask and stirred at room temperature until dissolved. Then, 5 g of UiO-66-NH2 was added and stirred until homogeneous. 5 mL of acetic anhydride was then added, and the mixture was reacted at 40 °C for 8 h. The resulting solid was washed three times with 50 mL of DMAc, filtered, and dried under vacuum at 110 °C for 12 h to obtain 5.1 g of anhydride-terminated UiO-66-NH2 (BPDA).

[0054] Example 4

[0055] Under nitrogen protection, 7.27 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 5 g of 4,4'-diaminodiphenyl ether, 18.41 g of UiO-66-NH2 (BPDA), and 500 mL of DMAc were added to a 1000 mL three-necked flask and stirred at room temperature for 12 h. Then, 1.79 g of pyridine and 17.83 g of acetic anhydride were added, and the reaction continued for another 8 h, at which point the system became viscous. This was then added to 1000 mL of ethanol, resulting in the precipitation of a large amount of solid. After filtration, the solid was washed again with the same volume of ethanol, filtered, and dried under vacuum at 150 °C for 24 h to obtain 28.65 g of BPDA-ODA polyimide containing UiO-66-NH2, with a UiO-66-NH2 content of 60 wt%.

[0056] Example 5

[0057] The difference from Example 4 is the addition ratio of UiO-66-NH2; the other steps are the same as in Example 3, and BPDA-ODA polyimides with UiO-66-NH2 contents of 30wt%, 40wt%, 50wt%, and 70wt% are prepared.

[0058] Example 6

[0059] 0.5 g of the polyimide prepared in Example 4 was weighed and added to 7 mL of DMAc. After stirring evenly, the mixture was poured into an ultraflat culture dish, and the solvent was slowly evaporated at 60 °C to obtain a pre-formed membrane. The pre-formed membrane was then vacuum-dried at 180 °C for 24 h to obtain the novel hybrid matrix membrane BPDA-ODA-60. Gas separation experiments were performed on it, and the CO2 permeation flux was 61.38 Barrer, while the CO2 / CH4 selectivity was 39.72.

[0060] Example 7

[0061] The difference from Example 6 is that the polyimide used for membrane formation is the same as that synthesized in Example 5. All other steps are the same as in Example 6, and novel hybrid matrix membranes BPDA-ODA-30, BPDA-ODA-40, BPDA-ODA-50, and BPDA-ODA-70 are prepared. Gas separation experiments were conducted on them, and the CO2 permeation flux was 34.52-53.12 Barrer, and the CO2 / CH4 selectivity was 28.93-34.54.

[0062] Comparative Example 1

[0063] Under nitrogen protection, 7.27 g of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 5 g of 4,4'-diaminodiphenyl ether, and 180 mL of DMAc were added to a 500 mL three-necked flask and stirred at room temperature for 12 h. Then, 1.79 g of pyridine and 17.83 g of acetic anhydride were added, and the reaction continued for another 8 h, at which point the system became viscous. The mixture was then added to 500 mL of ethanol, resulting in the precipitation of a large amount of solid. After filtration, the solid was washed again with the same volume of ethanol, filtered, and dried under vacuum at 150 °C for 24 h to obtain 11.85 g of polyimide (BPDA-ODA).

[0064] 0.5 g of the prepared polyimide was weighed and added to 7 mL of DMAc. After stirring evenly, the mixture was poured into an ultraflat culture dish, and the solvent was slowly evaporated at 60 °C to obtain a pre-formed membrane. The pre-formed membrane was then vacuum-dried at 180 °C for 24 h to obtain the pure membrane BPDA-ODA. Gas separation experiments were performed on it, and the CO2 permeation flux was 23.51 Barrer, and the CO2 / CH4 selectivity was 29.86.

[0065] Comparative Example 2

[0066] 0.5 g of the polyimide (BPDA-ODA) prepared in Comparative Example 1 was weighed and dissolved in 7 mL of DMAc. 88 mg of UiO-66-NH2 was added and stirred until homogeneous. The mixture was then poured into an ultraflat culture dish, and the solvent was slowly evaporated at 60 °C to obtain a pre-formed membrane. The pre-formed membrane was vacuum dried at 180 °C for 24 h to obtain the mixed matrix membrane UiO-66-NH2 / BPDA-ODA (15). Gas separation experiments were performed on it, and the CO2 permeation flux was 39.74 Barrer, and the CO2 / CH4 selectivity was 32.67.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a UiO-66-NH2-based mixed matrix membrane, characterized in that: Includes the following steps: (1) Preparation of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride: Under a protective atmosphere, 4-chloro-N-methylphthalimide, catalyst A, reducing agent, and additives are added to an aprotic solvent and reacted at 40-60°C for 10-18 hours. The solvent is recovered, recrystallized, and dried to obtain bisaminobenzeneimide. The obtained bisaminobenzeneimide is hydrolyzed to form a salt using a salt-forming solvent. The insoluble matter is removed, the acid is adjusted, and the salt is dried to obtain biphenyltetracarboxylic acid. Biphenyltetracarboxylic acid is added to a benzene-based solvent and then reacted with acetic anhydride to obtain 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, abbreviated as BPDA. (2) Dissolve the BPDA synthesized in step (1) in solvent A, then add UiO-66-NH2 to the reaction system, stir evenly, add acetic anhydride, and react at 25-50℃. After the reaction is completed, filter, wash and dry to obtain anhydride-terminated UiO-66-NH2 (BPDA). (3) The UiO-66-NH2 (BPDA) synthesized in step (2), the BPDA and ODA synthesized in step (1) are added to DMAC and reacted at 0-25℃ for 6-12h. A dehydrating agent and catalyst B are added and the reaction continues for a period of time. Then, it is poured into a poor solvent and a large amount of solid is precipitated. After filtration and drying, BPDA-ODA type polyimide containing UiO-66-NH2 is obtained. (4) Prepare a casting solution with a solid content of 5wt%-10wt% using BPDA-ODA type polyimide containing UiO-66-NH2 and DMAC in step (3), pour it into an ultra-flat culture dish, slowly evaporate the solvent at 40-70℃ to obtain a pre-made film, and then obtain a mixed matrix film UiO-66-NH2 / BPDA-ODA-N after high temperature treatment; The mixed matrix film is UiO-66-NH2 / BPDA-ODA-N, where N represents the doping amount of UiO-66-NH2. N is 30-70, which means that the doping amount of UiO-66-NH2 is 30wt%-70wt%.

2. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1, characterized in that: In step (1), the molar ratio of catalyst A, reducing agent, additive and aminochlorophthalimide is (0.01-0.03): (0.2-0.4): (0.0002-0.001):

1.

3. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1 or 2, characterized in that: In step (1), catalyst A is one or more of nickel chloride, nickel sulfate, nickel bromide, and nickel acetate; reducing agent is one or two of zinc powder and magnesium powder; additive is triphenylphosphine; aprotic solvent is one or more of dimethylformamide, dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, tetrahydrofuran, and dimethyltetrahydrofuran; the solvent used for recrystallization is one or more of toluene, xylene, isopropanol, isobutanol, and n-hexane; and benzene-based reagent is one or more of benzene, toluene, o-xylene, o-dichlorobenzene, and m-xylene.

4. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1, characterized in that: In step (1), the salt-forming solvent is a 15wt%-40wt% sodium hydroxide aqueous solution.

5. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1, characterized in that: In step (2), the mass ratio of solvent A, UiO-66-NH2, and BPDA is (15-30): (3-6):

1.

6. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1 or 5, characterized in that: In step (2), solvent A is one or more of tetrahydrofuran, dimethylformamide, dimethylacetamide, and N-methylpyrrolidone.

7. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1, characterized in that: In step (3), the mass ratio of UiO-66-NH2 (BPDA) to the total mass of UiO-66-NH2 (BPDA), BPDA, and ODA is (0.3-0.7):1; the molar ratio of BPDA to ODA is (0.98-1.01):1; and the total mass of UiO-66-NH2 (BPDA), BPDA, and ODA accounts for 3wt%-7wt% of the total mass of the solution formed by UiO-66-NH2 (BPDA), BPDA, ODA, and DMAC.

8. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1 or 7, characterized in that: In step (3), the dehydrating agent is acetic anhydride; catalyst B is pyridine; and the unsuitable solvents are deionized water, methanol, ethanol, and isopropanol.

9. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 8, characterized in that: The unsuitable solvent in step (3) is ethanol.

10. The method for preparing the UiO-66-NH2-based mixed matrix membrane according to claim 1, characterized in that: In step (4), the high-temperature treatment temperature of the pre-made film is 180-220℃.

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