A gallic acid-based MOF composite film and a preparation method and application thereof

Abstract

The application discloses a gallic acid-based MOF composite membrane and a preparation method and application thereof, and belongs to the technical field of membrane separation. The preparation method of the gallic acid-based MOF composite membrane comprises vertically growing non-dense continuous columnar metal-gallic acid materials on a porous substrate, and then growing MOFs materials in the middle of the columnar metal-gallic acid materials through an interfacial synthesis method, so that a membrane with high olefin / alkane separation performance is obtained. The preparation process is simple, the material is easy to obtain, and the production can be easily enlarged. The prepared separation membrane has good separation effect and stability, and has a potential application prospect.

Description

Technical Field

[0001] The present invention belongs to the technical field of membrane separation, and in particular relates to a gallic acid-based MOF composite membrane and a preparation method and application thereof. Background Art

[0002] The separation of olefins and alkanes is one of the most important separation systems in petrochemical production. Due to the extremely similar physical and chemical properties of these two substances, traditional separation methods often have problems such as high equipment investment costs and high operating energy consumption. Membrane separation technology has the advantages of no phase change, low energy consumption, and no secondary pollution. It has been widely used in related fields such as gas separation and liquid separation. Membrane materials are the core of membrane separation technology. Therefore, the development of membrane materials directly affects the development of membrane separation technology. The membrane materials currently used are mainly polymers, but most polymer membranes have a "trade-off" effect between selectivity and permeation flux, and are prone to swelling during the olefin / alkane separation process, resulting in serious degradation of separation performance. Therefore, there is an urgent need to develop new membrane materials to solve the above problems.

[0003] Metal-organic frameworks (MOFs) are a new type of crystalline material constructed from metal ions / metal clusters and organic ligands. They have the advantages of high porosity, rich variety, and precisely tunable pore structure, making them ideal materials for membrane separation. Gallic acid-based MOF materials have been shown to have good sieving properties for alkenes / alkanes (especially ethylene / ethane and propylene / propane). However, the preparation of gallic acid-based MOF membranes is usually done by solvothermal synthesis. Because this method prioritizes homogeneous nucleation and slows heterogeneous nucleation, it is difficult to form a dense separation membrane during the preparation process. Summary of the Invention

[0004] In response to the above problems, the purpose of the present invention is to provide a gallic acid-based MOF composite membrane and its preparation method and application. The present invention adopts the method of pre-growing a non-dense and continuous columnar gallic acid-based metal organic framework material vertically on a porous substrate, and then grows a MOFs material with a low reaction energy barrier in the middle of the columnar gallic acid-based MOFs material through an interfacial synthesis method. This composite structure membrane can effectively give play to the advantages of the two MOF materials, thereby obtaining a membrane with high olefin / alkane separation performance. The preparation process of the present invention is simple and low in cost, the materials are easily available, and the preparation can be scaled up. The prepared membrane has good low-carbon hydrocarbon separation effect and stability, and has potential application prospects.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A method for preparing a gallic acid-based MOF composite membrane comprises the following steps:

[0007] (1) The porous substrate is modified with dopamine to provide sufficient nucleation sites for the growth of the gallic acid-based film;

[0008] (2) placing the porous substrate obtained in step (1) into a gallic acid-based MOF synthesis solution and performing a microwave synthesis reaction to obtain a vertically grown discontinuous metal-gallate membrane;

[0009] (3) immersing the vertically grown discontinuous metal-gallate film obtained in step (2) in a metal salt solution;

[0010] (4) The membrane in step (3) is taken out and directly placed in a ligand solution for interfacial growth to obtain a gallic acid-based MOF composite membrane.

[0011] Based on the above technical solution, further, the dopamine modification described in step (1) is specifically to immerse the porous substrate in a dopamine hydrochloride solution of 0.05-0.2 mol / L tris(hydroxymethyl)aminomethane, 0.1-0.8 mol / L dopamine hydrochloride, 0.01-0.1 mol / L CuSO4 and 0.0001-0.01 mol / L H2O2 for 10-60 min, and then dry it.

[0012] Based on the above technical solution, further, the material of the porous substrate described in step (1) is inorganic oxide, polymer, metal, preferably one or a combination of two or more of polytetrafluoroethylene, polyacrylic acid, stainless steel mesh, aluminum oxide, zirconium oxide, titanium oxide, and silicon oxide.

[0013] Based on the above technical solution, further, the structure of the porous substrate described in step (1) is one of flat plate, sheet, tubular, and capillary.

[0014] Based on the above technical solution, further, the gallic acid-based MOF synthesis solution in step (2) is an aqueous solution in which metal salt and gallic acid are dissolved.

[0015] Based on the above technical solution, further, the metal salt described in step (2) is selected from Mg 2+ 、Co 2+ 、Ni 2+ 、In 2+ 、Fe 2+ 、Zn 2+ 、Mn 2+ 、Cu 2+ One or more metal salts.

[0016] Based on the above technical solution, further, the reaction temperature in step (2) is 0-250°C, preferably 50-150°C; the reaction time is 0.1-720h, preferably 1-24h; the gallic acid concentration is 0.01mmol / L-10mol / L, preferably 1mmol / L-300mmol / L; and the metal salt concentration is 0.01mmol / L-10mol / L, preferably 1mmol / L-300mmol / L.

[0017] Based on the above technical solution, further, the metal salt in step (3) is selected from Zn 2+ Mg 2+ 、Co 2+ 、Ni 2+ 、Cu 2+ The concentration of one or more metal salts in the solution is 0.01 mmol / L to 70 mol / L, preferably 0.5 mmol / L to 10 mmol / L.

[0018] Based on the above technical solution, further, the soaking time in step (3) is 0.001 to 20 hours.

[0019] Based on the above technical solution, further, the ligand in step (4) is selected from one or a combination of two or more of 2-methylimidazole, imidazole, benzimidazole, aminobenzimidazole ligand, terephthalic acid, and aminoterephthalic acid.

[0020] Based on the above technical solution, further, in step (4), the concentration of the ligand solution is 0.01 mol / L to 10 mol / L, preferably 0.1 mol / L to 5 mol / L.

[0021] Based on the above technical solution, further, in step (4), the reaction temperature is 0 to 250° C., preferably 50 to 120° C.; and the reaction time is 0.01 to 720 h, preferably 1 to 12 h.

[0022] Based on the above technical solution, further, the solvent of the solution in step (3) and step (4) is one or a mixed solution of two or more of water, methanol, ethanol, acetone, dichloromethane, chloroform, n-hexane, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

[0023] Another aspect of the present invention provides a gallic acid-based MOF composite membrane prepared by the above-mentioned preparation method.

[0024] The present invention also provides applications of the gallic acid-based MOF composite membrane in fields such as gas separation and liquid separation, preferably in light hydrocarbon purification.

[0025] Based on the above technical solution, further, specifically olefin / alkane separation.

[0026] Based on the above technical solution, further, the olefins / alkanes include C3H6 / C3H8 and C2H4 / C2H6. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0028] Figure 1 This is a scanning electron microscope image of the surface of the gallic acid-based MOF composite membrane. DETAILED DESCRIPTION

[0029] The gallic acid-based MOF composite membrane and its separation performance of the present invention are further described in detail below with reference to the following examples. However, the present invention is not limited to the following examples.

[0030] Example 1

[0031] A method for preparing a separation membrane comprises the following steps:

[0032] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO4, and 0.001 mol of H2O2 and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a φ18 mm commercial flat Al2O3 microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0033] (2) Prepare a mixed solution of 0.3 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine and sonicate until completely dissolved;

[0034] (3) placing the treated flat Al2O3 microfiltration membrane in the precursor solution prepared in step (2), transferring the system to a hydrothermal reactor, and placing it in a 100°C oven for reaction for 4 hours to allow vertical Co(OH)2 nanosheets to grow in situ on the substrate surface. After the reaction, rinse with ethanol three times and dry in a vacuum at 50°C for 12 hours.

[0035] (4) The substrate with vertical Co(OH)2 nanosheets in (3) was placed in a 0.5 mol / L gallic acid aqueous solution, subjected to microwave synthesis, and reacted at 100°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate film.

[0036] (5) The vertically grown discontinuous Co-gallate film in (4) was immersed in a 1 mmol / L CoCl2·6H2O aqueous solution for 12 h;

[0037] (6) The discontinuous Co-gallate membrane soaked in CoCl2·6H2O in (5) was taken out and placed in 2-methylimidazole (0.1 mol / L) / sodium formate (0.5 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 100°C for 2 h. After the reaction, the membrane was taken out and rinsed three times with ethanol and dried in vacuum at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0038] The obtained separation membrane was subjected to a gas separation performance test in a Wicke-Kallenbach membrane module. The test gas was a mixture of C3H6 / C3H8 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.2 MPa, and argon was used as the purge gas.

[0039] The separation performance of gallic acid-based MOF composite membrane for C3H6 / C3H8 is as follows: C3H6 permeance is 207.8GPU, and C3H6 / C3H8 separation ratio is 105.7.

[0040] Example 2

[0041] A method for preparing a separation membrane comprises the following steps:

[0042] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO4, and 0.001 mol of H2O2 and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a φ18 mm commercial flat Al2O3 microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0043] (2) The flat Al2O3 microfiltration membrane obtained in (1) was placed in an aqueous solution containing 0.1 mol / L nickel nitrate and 0.1 mol / L gallic acid, subjected to microwave synthesis, and reacted at 120°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Ni-gallate membrane;

[0044] (3) The vertically grown discontinuous Ni-gallate film in (2) was immersed in a 1 mmol / L ZnCl2·6H2O aqueous solution for 12 h.

[0045] (4) The discontinuous Ni-gallate membrane soaked in ZnCl2·6H2O in (3) was taken out and placed in 2-methylimidazole (0.5 mol / L) / sodium formate (0.1 mmol / L) methanol solution for interfacial synthesis. The reaction temperature was 120 °C and the reaction time was 2 h. After the reaction, the membrane was taken out and rinsed three times with ethanol and dried in vacuum at 50 °C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0046] The obtained separation membrane was subjected to a gas separation performance test in a Wicke-Kallenbach membrane module. The test gas was a mixture of C3H6 / C3H8 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the purge gas.

[0047] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 356.5GPU, and the C3H6 / C3H8 separation ratio is 155.9.

[0048] Example 3

[0049] A method for preparing a separation membrane comprises the following steps:

[0050] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO4, and 0.001 mol of H2O2 and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a φ18 mm commercial flat Al2O3 microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0051] (2) The flat Al2O3 microfiltration membrane obtained in (1) was placed in an aqueous solution containing 0.1 mol / L cobalt nitrate and 0.1 mol / L gallic acid, subjected to microwave synthesis, and reacted at 120°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate membrane;

[0052] (3) The vertically grown discontinuous Co-gallate film in (2) was immersed in a 1 mmol / L ZnCl2·6H2O aqueous solution for 12 h;

[0053] (4) The discontinuous Co-gallate membrane soaked in ZnCl2·6H2O in (3) was removed and placed in a benzimidazole (0.1 mol / L) / sodium formate (0.5 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 100°C for 2 h. After completion, the membrane was removed and rinsed three times with ethanol and dried under vacuum at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0054] The obtained separation membrane was subjected to a gas separation performance test in a Wicke-Kallenbach membrane module. The test gas was a mixture of C3H6 / C3H8 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the purge gas.

[0055] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 218.5 GPU, and the C3H6 / C3H8 separation ratio is 134.4.

[0056] Example 4

[0057] A method for preparing a separation membrane comprises the following steps:

[0058] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO₄, and 0.001 mol of H₂O₂ and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a φ18 mm commercial flat Al₂O₃ microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0059] (2) The flat Al2O3 microfiltration membrane obtained in (1) was placed in an aqueous solution containing 0.1 mol / L magnesium nitrate and 0.1 mol / L gallic acid, subjected to microwave synthesis, and reacted at 120°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Mg-gallate membrane;

[0060] (3) The vertically grown discontinuous Mg-gallate film in (2) was immersed in a 1 mmol / L ZnCl2·6H2O aqueous solution for 12 h;

[0061] (4) The discontinuous Mg-gallate membrane soaked in ZnCl2·6H2O in (3) was removed and placed in a benzimidazole (0.1 mol / L) / sodium formate (0.5 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 100°C for 2 h. After completion, the membrane was removed and rinsed three times with ethanol and dried in a vacuum oven at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0062] The obtained separation membrane was subjected to a gas separation performance test in a Wicke-Kallenbach membrane module. The test gas was a mixture of C3H6 / C3H8 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the purge gas.

[0063] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 305.4GPU, and the C3H6 / C3H8 separation ratio is 114.5.

[0064] Example 5

[0065] A method for preparing a separation membrane comprises the following steps:

[0066] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO₄, and 0.001 mol of H₂O₂ and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a φ18 mm commercial flat Al₂O₃ microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0067] (2) The flat Al2O3 microfiltration membrane obtained in (1) was placed in an aqueous solution containing 0.1 mol / L cobalt nitrate and 0.1 mol / L gallic acid, subjected to microwave synthesis, and reacted at 120°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate membrane;

[0068] (3) The vertically grown discontinuous Co-gallate film in (2) was immersed in a 1 mmol / L MgCl2·6H2O aqueous solution for 12 h;

[0069] (4) The discontinuous Co-gallate membrane soaked in MgCl2·6H2O in (5) was removed and placed in a 0.1 mol / L 2,5-dihydroxyterephthalic acid (2,5-DIHT) methanol solution for interfacial synthesis at a reaction temperature of 100°C for 5 h. After completion, the membrane was removed and rinsed three times with ethanol and dried under vacuum at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0070] The obtained separation membrane was subjected to a gas separation performance test in a Wicke-Kallenbach membrane module. The test gas was a mixture of C3H6 / C3H8 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the purge gas.

[0071] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 318.6GPU, and the C3H6 / C3H8 separation ratio is 57.7.

[0072] Example 6

[0073] A method for preparing a separation membrane comprises the following steps:

[0074] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO4, and 0.001 mol of H2O2 and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a φ18 mm commercial flat Al2O3 microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0075] (2) Prepare a mixed solution of 0.3 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine and sonicate until completely dissolved;

[0076] (3) The treated flat Al2O3 microfiltration membrane was placed in the precursor solution prepared in step (2), and the system was transferred to a hydrothermal reactor and placed in a 120°C oven for reaction for 4 hours to allow vertical Co(OH)2 nanosheets to grow in situ on the substrate surface. After the reaction, the membrane was rinsed three times with ethanol and dried in a vacuum oven at 50°C for 12 hours.

[0077] (4) The substrate with vertical Co(OH)2 nanosheets in (3) was placed in a 0.5 mol / L gallic acid aqueous solution, subjected to microwave synthesis, and reacted at 110°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate film.

[0078] (5) Immerse the vertically grown discontinuous Co-gallate film in (4) in a 3 mmol / L CoCl2·6H2O aqueous solution for 12 h;

[0079] (6) The discontinuous Co-gallate membrane soaked in CoCl2·6H2O in (5) was removed and placed in a 2-methylimidazole (0.2 mol / L) / sodium formate (0.5 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 110°C for 2 h. After completion, the membrane was removed and rinsed three times with ethanol and dried in a vacuum oven at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0080] The obtained separation membrane was subjected to a gas separation performance test in a Wicke-Kallenbach membrane module. The test gas was a mixture of C2H4 / C2H6 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the sweep gas.

[0081] The measured separation performance of the membrane for C2H4 / C2H6 is as follows: C2H4 permeance is 401.8GPU, and the C2H4 / C2H6 separation ratio is 10.4.

[0082] Example 7

[0083] A method for preparing a separation membrane comprises the following steps:

[0084] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO₄, and 0.001 mol of H₂O₂ and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a 10 cm long commercial capillary microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0085] (2) Prepare a mixed solution of 0.2 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine and sonicate until completely dissolved;

[0086] (3) placing the treated flat Al2O3 microfiltration membrane in the precursor solution prepared in step (2), transferring the system to a hydrothermal reactor, and placing it in a 120°C oven for reaction for 4 hours to allow vertical Co(OH)2 nanosheets to grow in situ on the substrate surface. After the reaction, rinse with ethanol three times and dry in a vacuum at 50°C for 12 hours;

[0087] (4) The substrate with vertical Co(OH)2 nanosheets in (3) was placed in a 1 mol / L gallic acid aqueous solution, subjected to microwave synthesis, and reacted at 120°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate film.

[0088] (5) Immerse the vertically grown discontinuous Co-gallate film in (4) in a 3 mmol / L CoCl2·6H2O aqueous solution for 12 h;

[0089] (6) The discontinuous Co-gallate membrane soaked in CoCl2·6H2O in (5) was removed and placed in a 2-methylimidazole (0.1 mol / L) / sodium formate (0.5 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 120°C for 2 h. After completion, the membrane was removed and rinsed three times with ethanol and dried in a vacuum oven at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0090] The obtained separation membrane was subjected to a gas separation performance test in a membrane module. The test gas was a mixture of C3H6 / C3H8 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the sweep gas.

[0091] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 357.1GPU, and the C3H6 / C3H8 separation ratio is 98.8.

[0092] Example 8

[0093] A method for preparing a separation membrane comprises the following steps:

[0094] (1) Weigh 0.1 mol of tris(hydroxymethyl)aminomethane, 0.4 mol of dopamine hydrochloride, 0.05 mol of CuSO₄, and 0.001 mol of H₂O₂ and dissolve them in 1 L of deionized water to obtain a dopamine hydrochloride solution. Immerse a 10 cm long commercial capillary microfiltration membrane in the dopamine hydrochloride solution for 30 min, rinse, and dry in an oven.

[0095] (2) Prepare a mixed solution of 0.2 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine and sonicate until completely dissolved;

[0096] (3) The treated flat Al2O3 microfiltration membrane was placed in the precursor solution prepared in step (2), and the system was transferred to a hydrothermal reactor and placed in a 120°C oven for reaction for 4 hours to allow vertical Co(OH)2 nanosheets to grow in situ on the substrate surface. After the reaction, the membrane was rinsed three times with ethanol and dried in a vacuum oven at 50°C for 12 hours.

[0097] (4) The substrate with vertical Co(OH)2 nanosheets in (3) was placed in a 0.1 mol / L gallic acid aqueous solution, subjected to microwave synthesis, and reacted at 120°C for 2 h. After the reaction, it was washed three times with methanol and dried in vacuum at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate film.

[0098] (5) The vertically grown discontinuous Co-gallate film in (4) was immersed in a 2 mmol / L CoCl2·6H2O aqueous solution for 12 h;

[0099] (6) The discontinuous Co-gallate membrane soaked in CoCl2·6H2O in (5) was removed and placed in a 2-methylimidazole (0.3 mol / L) / sodium formate (0.9 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 100°C for 2 h. After completion, the membrane was removed and rinsed three times with ethanol and dried under vacuum at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0100] The obtained separation membrane was subjected to a gas separation performance test in a membrane module. The test gas was a mixture of C2H4 / C2H6 with a volume ratio of 1:1, the temperature was 25 degrees Celsius, the transmembrane pressure difference was 0.1 MPa, and argon was used as the sweep gas.

[0101] The measured separation performance of the membrane for C2H4 / C2H6 is as follows: C2H4 permeance is 597.5GPU, and the C2H4 / C2H6 separation ratio is 7.5.

Claims

1. A method for preparing a gallic acid-based MOF composite membrane, characterized in that: The following steps are involved: (1) The porous substrate is modified with dopamine to provide sufficient nucleation sites for the growth of the gallic acid-based film; (2) placing the porous substrate obtained in step (1) into a gallic acid-based MOF synthesis solution and performing a microwave synthesis reaction to obtain a vertically grown discontinuous metal-gallate membrane; (3) immersing the vertically grown discontinuous metal-gallate film obtained in step (2) in a metal salt solution; (4) After taking out the membrane in step (3), directly placing it in the ligand solution for interfacial growth, a gallic acid-based MOF composite membrane can be obtained; The gallic acid-based MOF synthesis solution in step (2) is an aqueous solution containing a metal salt and gallic acid; the metal salt is selected from Mg 2+ 、Co 2+ 、Ni 2+ 、In 2+ 、Fe 2+ 、Zn 2+ 、Mn 2+ 、Cu 2+ One or more metal salts; The metal salt in step (3) is selected from Zn 2+ Mg 2+ 、Co 2+ 、Ni 2+ 、Cu 2+ One or more metal salts; The ligand in step (4) is selected from one or a combination of two or more of 2-methylimidazole, imidazole, benzimidazole, and aminobenzimidazole ligands.

2. The preparation method according to claim 1, characterized in that The material of the porous substrate in step (1) is inorganic oxide, polymer or metal; the structure of the porous substrate is one of flat plate, sheet, tubular and capillary.

3. The preparation method according to claim 1, characterized in that The reaction temperature in step (2) is 0-250° C.; the reaction time is 0.1-720 h; the gallic acid concentration is 0.01 mmol / L-10 mol / L; and the metal salt concentration is 0.01 mmol / L-10 mol / L.

4. The preparation method according to claim 3, characterized in that The reaction temperature in step (2) is 50-150° C.; the reaction time is 1-24 h; the gallic acid concentration is 1 mmol / L-300 mmol / L; and the metal salt concentration is 1 mmol / L-300 mmol / L.

5. The preparation method according to claim 1, characterized in that The concentration of the metal salt solution in step (3) is 0.01 mmol / L~70 mol / L, and the soaking time is 0.001~20 h.

6. The preparation method according to claim 1, characterized in that The concentration of the ligand solution in step (4) is 0.01 mol / L~10 mol / L.

7. The preparation method according to claim 1, characterized in that In step (4), the reaction temperature is 0-250° C., and the reaction time is 0.1-720 h.

8. The preparation method according to claim 1, characterized in that The solvent of the solution in step (3) and step (4) is one or a mixed solution of two or more of water, methanol, ethanol, acetone, dichloromethane, chloroform, n-hexane, N-methylpyrrolidone, N,N-dimethylformamide, and N,N-dimethylacetamide.

9. A gallic acid-based MOF composite membrane prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the gallic acid-based MOF composite membrane according to claim 9 in the field of gas separation or liquid separation.

11. The use according to claim 10, characterized in that The application of the gallic acid-based MOF composite membrane in the purification of light hydrocarbons is specifically the separation of olefins / alkanes, and the olefins / alkanes include C3H6 / C3H8 and C2H4 / C2H6.

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