Gallate-based MOF (Metal Organic Framework) composite membrane as well as preparation method and application thereof

Abstract

The invention discloses a gallate-based MOF composite membrane as well as 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 the following steps: vertically growing a non-compact and continuous columnar metal-gallic acid material on a porous substrate, and then growing an MOFs material in the middle of the columnar metal-gallic acid material through an interface synthesis method, thereby obtaining the membrane with high olefin / alkane separation performance. The preparation process is simple, materials are easy to obtain, expanded production is facilitated, and the prepared separation membrane has a good separation effect and stability and has potential application prospects.

Description

Technical Field

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

[0002] The separation of olefins / alkanes is one of the most important separation systems in petrochemical production. Since the physical and chemical properties of these two substances are very similar, 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 attenuation of separation performance. Therefore, it is urgent to develop new membrane materials to solve the above problems.

[0003] Metal-organic framework (MOFs) materials are a new type of crystalline material constructed by metal ions / metal clusters and organic ligands. They have the advantages of high porosity, rich variety, and precise control of pore structure, making them ideal materials in the field of membrane separation. Gallic acid-based MOF materials have been shown to have good screening performance for olefins / alkanes (especially ethylene / ethane, propylene / propane). However, the preparation of gallic acid-based MOF membranes usually adopts the solvothermal synthesis method. Since this method preferentially nucleates homogeneously and has a slow heterogeneous nucleation rate, it is difficult to form a dense separation membrane during the preparation process. Summary of the invention

[0004] In view of 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 a pre-vertical growth of a non-dense and continuous columnar gallic acid-based metal organic framework material 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 by an interfacial synthesis method. The membrane of this composite structure can effectively exert 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 easy to obtain, 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 gallic acid-based film;

[0008] (2) placing the porous substrate obtained in step (1) into a gallic acid-based MOF synthesis solution, performing a microwave synthesis reaction, and obtaining 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) After taking out the membrane in step (3), directly placing it in a ligand solution for interfacial growth, a gallic acid-based MOF composite membrane can be obtained.

[0011] Based on the above technical scheme, 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 scheme, 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; 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 one or more metal salts in the solution have a concentration of 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.; 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 the application of the gallic acid-based MOF composite membrane in the fields of gas separation, liquid separation, etc., preferably in the purification of light hydrocarbons.

[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 in conjunction with the 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, wash it and dry it in an oven;

[0033] (2) preparing a mixed solution of 0.3 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine, and performing ultrasonication until the solution is 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, placing it in a 100°C oven for reaction for 4 hours, so that vertical Co(OH)2 nanosheets are grown in situ on the substrate surface, and rinsing it with ethanol three times after the reaction, and vacuum drying it at 50°C for 12 hours;

[0035] (4) placing the substrate with vertical Co(OH)2 nanosheets in (3) into a 0.5 mol / L gallic acid aqueous solution, performing microwave synthesis, reacting at 100°C for 2 h, washing with methanol three times after the reaction, and vacuum drying at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate film;

[0036] (5) Immerse the vertically grown discontinuous Co-gallate film in (4) 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 a 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 a vacuum at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0038] The obtained separation membrane was tested for gas separation performance 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 sweep gas.

[0039] The separation performance of gallic acid-based MOF composite membrane for C3H6 / C3H8 is as follows: the permeability of C3H6 is 207.8GPU, and the separation ratio of C3H6 / C3H8 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, wash it and dry it in an oven;

[0043] (2) placing the flat Al2O3 microfiltration membrane obtained in (1) into an aqueous solution containing 0.1 mol / L nickel nitrate and 0.1 mol / L gallic acid, performing microwave synthesis, reacting at 120°C for 2 h, washing with methanol three times after the reaction, and vacuum drying 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 a 2-methylimidazole (0.5 mol / L) / sodium formate (0.1 mmol / L) methanol solution for interfacial synthesis at a reaction temperature of 120°C for 2 h. After the reaction was completed, the membrane was taken out and rinsed three times with ethanol and dried in a vacuum at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0046] The obtained separation membrane was tested for gas separation performance 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 sweep gas.

[0047] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 356.5 GPU, 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, wash it and dry it in an oven;

[0051] (2) placing the flat Al2O3 microfiltration membrane obtained in (1) into an aqueous solution containing 0.1 mol / L cobalt nitrate and 0.1 mol / L gallic acid, performing microwave synthesis, reacting at 120°C for 2 h, washing with methanol three times after the reaction, and vacuum drying 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 taken out 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 the reaction, the membrane was taken out and rinsed with ethanol three times, and vacuum dried at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0054] The obtained separation membrane was tested for gas separation performance 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 sweep 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 tris(hydroxymethyl)aminomethane, 0.4 mol dopamine hydrochloride, 0.05 mol CuSO4 and 0.001 mol 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, wash it and dry it in an oven;

[0059] (2) placing the flat Al2O3 microfiltration membrane obtained in (1) into an aqueous solution containing 0.1 mol / L magnesium nitrate and 0.1 mol / L gallic acid, performing microwave synthesis, reacting at 120°C for 2 h, washing with methanol three times after the reaction, and vacuum drying 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 taken out 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 the reaction, the membrane was taken out and rinsed with ethanol three times, and vacuum dried at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0062] The obtained separation membrane was tested for gas separation performance 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 sweep gas.

[0063] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 305.4 GPU, 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 tris(hydroxymethyl)aminomethane, 0.4 mol dopamine hydrochloride, 0.05 mol CuSO4 and 0.001 mol 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, wash it and dry it in an oven;

[0067] (2) placing the flat Al2O3 microfiltration membrane obtained in (1) into an aqueous solution containing 0.1 mol / L cobalt nitrate and 0.1 mol / L gallic acid, performing microwave synthesis, reacting at 120°C for 2 h, washing with methanol three times after the reaction, and vacuum drying 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 taken out and placed in a 2,5-dihydroxyterephthalic acid (0.1 mol / L) methanol solution for interfacial synthesis at a reaction temperature of 100°C for a reaction time of 5 h. After the reaction, the membrane was taken out 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 tested for gas separation performance 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 sweep gas.

[0071] The measured separation performance of the membrane for C3H6 / C3H8 is as follows: the C3H6 permeance is 318.6 GPU, 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, wash it and dry it in an oven;

[0075] (2) preparing a mixed solution of 0.3 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine, and performing ultrasonication until the solution is completely dissolved;

[0076] (3) placing the treated flat Al2O3 microfiltration membrane in the precursor solution prepared in step (2), transferring the system to a hydrothermal reactor, placing it in a 120°C oven for reaction for 4 hours, so that vertical Co(OH)2 nanosheets are grown in situ on the substrate surface, and rinsing it with ethanol three times after the reaction, and vacuum drying it at 50°C for 12 hours;

[0077] (4) placing the substrate with vertical Co(OH)2 nanosheets in (3) into a 0.5 mol / L gallic acid aqueous solution, performing microwave synthesis, reacting at 110°C for 2 h, washing with methanol three times after the reaction, and vacuum drying 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 taken out 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 the reaction, the membrane was taken out and rinsed with ethanol three times, and vacuum dried at 50°C for 12 h to obtain a gallic acid-based MOF composite membrane.

[0080] The obtained separation membrane was tested for gas separation performance 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 401.8 GPU, and 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, wash it and dry it in an oven;

[0085] (2) preparing a mixed solution of 0.2 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine, and performing ultrasonication until the solution is 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, placing it in a 120°C oven for reaction for 4 hours, so that vertical Co(OH)2 nanosheets are grown in situ on the substrate surface, and rinsing it with ethanol three times after the reaction, and vacuum drying it at 50°C for 12 hours;

[0087] (4) placing the substrate with vertical Co(OH)2 nanosheets in (3) into a 1 mol / L gallic acid aqueous solution, performing microwave synthesis, reacting at 120°C for 2 h, washing with methanol three times after the reaction, and vacuum drying 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 taken out 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 the reaction, the membrane was taken out and rinsed with ethanol three times, and then vacuum dried 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, wash it and dry it in an oven;

[0095] (2) preparing a mixed solution of 0.2 mol / L Co(NO3)2·6(H2O) and 0.01 mol / L hexamethylenetetramine, and performing ultrasonication until the solution is completely dissolved;

[0096] (3) placing the treated flat Al2O3 microfiltration membrane in the precursor solution prepared in step (2), transferring the system to a hydrothermal reactor, placing it in a 120°C oven for reaction for 4 hours, so that vertical Co(OH)2 nanosheets are grown in situ on the substrate surface, and rinsing it with ethanol three times after the reaction, and vacuum drying it at 50°C for 12 hours;

[0097] (4) placing the substrate with vertical Co(OH)2 nanosheets in (3) in an aqueous solution containing 0.1 mol / L gallic acid, performing microwave synthesis, reacting at 120°C for 2 h, washing with methanol three times after the reaction, and vacuum drying at 50°C for 12 h to obtain a vertically grown discontinuous Co-gallate film;

[0098] (5) Immerse the vertically grown discontinuous Co-gallate film in (4) 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 taken out 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 the reaction, the membrane was taken out and rinsed with ethanol three times, and vacuum dried 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 597.5 GPU, and 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 gallic acid-based film; (2) placing the porous substrate obtained in step (1) into a gallic acid-based MOF synthesis solution, performing a microwave synthesis reaction, and obtaining 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 a ligand solution for interfacial growth, a gallic acid-based MOF composite membrane can be obtained.

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, or capillary.

3. The preparation method according to claim 1, characterized in that: 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.

4. The preparation method according to claim 3, characterized in that: The reaction temperature in step (2) is 0-250° C., preferably 50-150° C.; the reaction time is 0.1-720 h, preferably 1-24 h; the gallic acid concentration is 0.01 mmol / L-10 mol / L, preferably 1 mmol / L-300 mmol / L; and the metal salt concentration is 0.01 mmol / L-10 mol / L, preferably 1 mmol / L-300 mmol / L.

5. The preparation method according to claim 1, characterized in that: The metal salt in step (3) is selected from Zn 2+ Mg 2+ 、Co 2 + 、Ni 2+ , Cu 2+ The one or more metal salts in the solution have a concentration of 0.01 mmol / L to 70 mol / L, preferably 0.5 mmol / L to 10 mmol / L; the immersion time is 0.001 to 20 h.

6. The preparation method according to claim 1, characterized in that: 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; the concentration of the ligand solution is 0.01 mol / L to 10 mol / L, preferably 0.1 mol / L to 5 mol / L.

7. The preparation method according to claim 1, characterized in that: In step (4), the reaction temperature is 0 to 250° C., preferably 50 to 120° C.; the reaction time is 0.1 to 720 h, preferably 1 to 12 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 obtained by the preparation method according to any one of claims 1 to 8.

10. Application of the gallic acid-based MOF composite membrane according to claim 9 in the fields of gas separation, liquid separation, etc., preferably in the purification of light hydrocarbons.

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