CN115463562B - Preparation method for rapidly synthesizing metal-organic framework MOF (metal-organic framework) membrane material without defects - Google Patents
Preparation method for rapidly synthesizing metal-organic framework MOF (metal-organic framework) membrane material without defects Download PDFInfo
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- B01D53/22—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols by diffusion
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Abstract
The application discloses a preparation method of a metal-organic framework MOF film material capable of being rapidly synthesized without defects, in particular to a preparation method of a copper-based MOF film material. Using Lewis acid-base theory, carboxylic acid ligand pKa can be a major indicator of metal-ligand bond strength, with carboxylic acid ligands with lower pKa being more competitive in metal node connection than carboxylic acids with higher pKa. According to the invention, the metal composite nano sheet membrane containing the higher pKa carboxylic acid ligand is prepared on the organic polymer support and used as a metal source, and ligand exchange can be realized through simple low pKa ligand solution soaking, so that the metal-organic framework membrane material with no defects is prepared. The method is simple and easy to operate, does not need high-temperature solvothermal treatment, and can be rapidly prepared at room temperature; the MOF film material prepared by the method overcomes the defects that the traditional pure MOF film has poor mechanical property, is not easy to prepare in large area, is easy to have defects after synthesis, and the like; the method belongs to a method for preparing MOF membrane materials in situ, provides reference for the reported realization of defect-free large-area construction of a plurality of MOF membrane materials, and has wide application prospect.
Description
Technical Field
The invention discloses a preparation method for rapidly synthesizing a metal-organic framework MOF film material without defects, and particularly relates to a preparation method for a copper-based metal-organic framework film material.
Background
The membrane separation process has the characteristics of no phase change, no pollution to a separation system, flexible layout, small occupied area and the like, so the development of the membrane separation technology is widely focused by people. The selection and design of membrane materials are key to the membrane separation process, and many microporous membrane materials are expected to break through the Trade-Off effect of the traditional polymer materials, namely, the permeability and selectivity of the membrane are improved at the same time, so that the efficient separation of the membrane process is realized.
The metal-organic framework (Metal Organic Framework, MOF) refers to a porous material with a periodic network structure formed by coordination self-assembly of inorganic metal ions and organic ligands. Compared with the traditional porous materials such as molecular sieve, active carbon, silica gel and the like, the MOF material has the characteristics of excellent thermal stability, chemical stability, ultra-high porosity, specific surface area, uniform and continuous pores, adjustable structure, pore size, adjustable chemical property and the like, and has wide application prospect in the fields of gas adsorption and separation, pervaporation, electrochemistry, catalysis, biomedicine and the like.
The metal-organic framework film material can realize densification crosslinking film formation on the surface of an organic or inorganic support body by controlling the formation and growth of crystals. The main components of commonly used synthetic MOF membranes are: in-situ crystallization (direct growth or solvothermal), secondary growth, deposition, etc. However, since the difference in thermal expansion coefficients between the MOF film and the substrate makes the MOF film easily cracked in the subsequent heat treatment, and even falls off from the substrate, making its application in the fields of gas separation, pervaporation, etc. severely limited, how to produce a continuous and dense MOF film on a substrate has gradually been developed as one of the subjects of intense research today.
In summary, the invention aims at the problems of easy formation of cracks, defects, poor mechanical properties and the like in the MOF film preparation process, and aims to adopt a preparation method for rapidly synthesizing a flawless metal-organic framework film material, namely, a metal composite nano-sheet film containing a ligand with higher pKa is prepared on an organic polymer support as a metal source, and ligand exchange can be realized through simple low pKa ligand solution soaking, so that a continuous and compact flawless MOF film is prepared.
Disclosure of Invention
The invention aims to solve a series of problems that the MOF film prepared by the traditional method is easy to form crack defects, poor in mechanical property, difficult to prepare in a large area and the like, and provides a method for successfully and quickly preparing a defect-free MOF film material by adopting a simple ligand exchange method.
Technical principle of the present application
The application pertinently utilizes the carboxylic acid ligand with lower pKa to play a more competitive role in the connection of metal nodes than the carboxylic acid with higher pKa, and the higher pKa ligand can be orderly displaced and removed from the metal composite framework by only soaking in the solution of the lower pKa ligand, so that the regulation and control synthesis of the large-area defect-free MOF membrane is realized. The method is simple and easy to implement, and can prepare the MOF film in a large area without defects and maintain the original pore structure and chemical stability of the MOF.
The technical scheme of the invention is as follows:
the metal-organic framework (MOF) membrane material comprises a hydrophilically modified polysulfone membrane, a metal composite nano-sheet membrane and a metal-organic framework membrane, wherein the metal composite nano-sheet membrane is grown on the surface of the hydrophilically modified polysulfone membrane in situ, a metal source on the surface of the nano-sheet membrane containing a ligand with a higher pKa is utilized to react with the ligand with a lower pKa, and the metal-organic framework (MOF) membrane without defects is synthesized on the metal composite nano-sheet membrane in situ.
The thickness of the hydrophilic modified polysulfone membrane is 50-200nm, preferably 50-70nm, the thickness of the metal composite nano-sheet membrane is 50-800 nm, preferably 150-500nm, and the thickness of the metal-organic framework (MOF) membrane is 100-5000 nm, preferably 500-1500nm, wherein the thickness of the metal-organic framework (MOF) membrane can be adjusted according to the growth density of the metal composite nano-sheet membrane on the surface of the hydrophilic modified polysulfone membrane.
The preparation method of the defect-free metal-organic framework (MOF) membrane material specifically comprises the following steps:
(1) Sequentially coating Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane (M) PSf ）；
The polysulfone is a commercial ultrafiltration polysulfone membrane with an average pore diameter of 20-50 nm;
the structural formula of the polydimethylsiloxane is
Wherein n is 300-500;
the polyvinyl alcohol has a polymerization degree=1700 and an alcoholysis degree=87-89%;
(2) Synthesizing a metal composite nano sheet membrane on the surface of the hydrophilic modified polysulfone obtained in the step (1) by adopting a low-temperature solid-phase synthesis method to obtain a metal nano sheet membrane/hydrophilic modified polysulfone membrane (H/M) PSf ）；
The metal salt is anhydrous copper acetate;
the higher pKa ligand is 4-fluorobenzoic acid (pka=4.15), 4-chlorobenzoic acid (pka=3.98), 4-bromobenzoic acid (pka=3.96) or 4-iodobenzoic acid (pka=4.00), preferably 4-fluorobenzoic acid (pka=4.15).
(3) Immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in methanol/water solution containing ligand with lower pKa upside down, standing at normal temperature for reaction to obtain flawless metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material (MOF/H/M) PSf ）。
The lower pKa ligand is trimesic acid (pka=2.12), terephthalic acid (pka=3.51), etc., preferably trimesic acid (pka=2.12);
the volume ratio of the methanol to the aqueous solution is 99:1-1:50, preferably 50:50;
the step (1) is realized through the following operation steps:
firstly, preparing a Polydimethylsiloxane (PDMS)/n-heptane solution with the concentration of 0.1-1.0 wt%, coating the PDMS/n-heptane solution on the surface of polysulfone by using a scraper, wherein the coating thickness is 0.03 mu m-1.00 mu m, and then drying for 16-24 hours under the conditions that the temperature is 60 ℃ and the humidity is 40% RH to obtain the PDMS-coated polysulfone; secondly, preparing polyvinyl alcohol (PVA)/water solution with the concentration of 0.01 to 0.5 weight percent, soaking polysulfone coated with PDMS in the PVA/water solution, and reacting for 0.5 to 4 hoursDrying at 30deg.C and 40% RH for 4-12 hr to obtain hydrophilic modified polysulfone membrane (M) PSf ). The examples herein are illustrated only with a 50nm thickness of hydrophilically modified polysulfone and are not limited to other thicknesses of hydrophilically modified polysulfone membranes.
The step (2) is realized through the following operation steps:
uniformly coating a higher pKa ligand/methanol solution with the concentration of 5-150mmol/L on the surface of the hydrophilic modified polysulfone obtained in the step (1) to a thickness of 20-200 nm, and then drying for 4-8h at 30 ℃ and 40% RH to obtain a hydrophilic modified polysulfone membrane coated with the higher pKa ligand; next, the hydrophilically modified polysulfone membrane coated with the ligand of higher pKa is soaked in a metal salt/water solution with a concentration of 0.25wt% for 0.5-H-2H, and then dried for 24H at 30 ℃ and 40% rh to obtain a metal composite nano-sheet membrane/hydrophilically modified polysulfone membrane (H/M PSf ). In the examples of the present application, 4-fluorobenzoic acid is used as the ligand with higher pKa, and other ligands with higher pKa are not limited, and the prepared metal composite nano-sheet membrane/hydrophilically modified polysulfone membrane is denoted as H 4-F /M PSf . The examples herein are illustrated with 60 mmol/L4-fluorobenzoic acid only and are not limiting of other concentrations of higher pKa ligand solutions.
The step (3) is realized through the following operation steps:
firstly preparing a methanol/water solution with the concentration of 0.1mmol/L-100mmol/L of a ligand with lower pKa, inversely immersing the metal composite nano-sheet membrane/hydrophilic modified polysulfone membrane obtained in the step (2) into the methanol/water solution of the ligand with lower pKa, standing for reaction for 4-24 hours at normal temperature, fully washing the surface of the membrane with methanol for 2 times, and then drying for 24 hours at 30 ℃ and 40% RH to obtain a metal-organic framework membrane/metal nano-sheet membrane/hydrophilic modified polysulfone membrane material (MOF/H/MPSF) without defects.
The metal-organic framework (MOF) membrane material has uniform pore size, and the type of the membrane material can be regulated and controlled according to the ligand (pKa) used in the preparation process, and has different membrane separation performances, so that the metal-organic framework (MOF) membrane material can be used in separation processes of gas separation and pervaporation.
Advantageous technical effects of the present application
The defect-free metal-organic framework (MOF) membrane material has the advantages that the lower pKa carboxylic acid ligand is more competitive in the aspect of metal node connection than the higher pKa carboxylic acid ligand, the higher pKa ligand can be orderly removed from the metal composite framework by only soaking in the solution of the lower pKa ligand, the regulation and control synthesis of the large-area defect-free MOF membrane is realized,
further, the application solves the problem that the MOF film in the related technology is easy to form cracks, defects, poor mechanical properties and the like in the preparation process, so that the separation film with good permeability and selectivity is obtained, and the MOF separation film has a universal prospect.
Furthermore, the preparation method has the advantages of low reaction temperature, simple process, easy large-area preparation and the like, and is suitable for industrial mass production.
Drawings
FIG. 1 is H in examples 1-5 4-F /M PSF SEM image (a) of the film surface and SEM image (b) of the cross section.
FIG. 2 is a SEM surface view (a) of a HKUST-1 film prepared in example 1 at a concentration of 2.5mmol/L in trimesic acid/methanol solution; SEM surface map (b) of HKUST-1 membrane prepared at 5mmol/L of trimesic acid/methanol solution.
FIG. 3 is a SEM surface view (a) and a cross-sectional view (b) of a HKUST-1 membrane of example 2 having a trimesic acid/methanol solution concentration of 10 mmol/L.
FIG. 4 is a SEM surface view (a) and a cross-sectional view (b) of a HKUST-1 membrane of example 3 having a trimesic acid/methanol solution concentration of 15 mmol/L.
FIG. 5 is a SEM surface view (a) and a cross-sectional view (b) of a HKUST-1 membrane of example 4 having a concentration of trimesic acid/methanol solution of 20 mmol/L.
FIG. 6 is a SEM surface view of a HKUST-1 membrane prepared in example 5 with a concentration of 25 mmol/L trimesic acid in methanol.
Detailed Description
The technical solution of the present invention will be further described by the following several specific examples, but the present application is not limited thereto, and modifications and implementations are included in the technical scope of the present invention without departing from the content and scope of the present invention.
Example 1:
preparation method of rapid synthesis of defect-free metal-organic framework (MOF) membrane material, wherein the material is HKUST-1/H 4-F /M PSF The synthetic preparation steps are as follows:
(1) Sequentially coating Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane (M) PSf ) The specific operation steps are as follows:
firstly, preparing a Polydimethylsiloxane (PDMS)/n-heptane solution with the concentration of 0.4wt%, coating the PDMS/n-heptane solution on the surface of polysulfone by using a scraper, and then drying for 18 hours under the conditions that the temperature is 60 ℃ and the humidity is 40% RH to obtain the polysulfone coated with PDMS; secondly, preparing a polyvinyl alcohol (PVA)/water solution with the concentration of 0.25 weight percent, soaking polysulfone coated with PDMS in the PVA/water solution, reacting for 1h, and continuously drying for 8h at 30 ℃ and 40% RH to obtain M PSf And (3) a film.
(2) Adopting a low-temperature solid-phase synthesis method, and utilizing a ligand with higher pKa and metal salt to synthesize a metal composite nano sheet membrane on the surface of the hydrophilic modified polysulfone membrane obtained in the step (1) in situ to obtain the metal nano sheet membrane/hydrophilic modified polysulfone membrane (H) 4-F /M PSf ) The metal salt is anhydrous copper acetate, the ligand is 4-fluorobenzoic acid, and the specific operation steps are as follows;
firstly, uniformly coating a methanol solution with the concentration of 60mmol/L of 4-fluorobenzoic acid on the surface of hydrophilic modified polysulfone, and then drying for 6 hours at 30 ℃ and 40% RH to obtain a hydrophilic modified polysulfone membrane coated with 4-fluorobenzoic acid ligand; next, the hydrophilically modified polysulfone membrane coated with 4-fluorobenzoic acid ligand was immersed in a metal salt/water solution having a concentration of 0.25wt% for 1 hour, and then dried at 30℃and 40% RH for 24 hours to obtain H 4-F /M PSf And (3) a film.
The H obtained above was subjected to a scanning electron microscope 4-F /M PSf The surface and cross section of the film were characterized, and the SEM image obtained was as shown in FIG. 1, and it can be seen from FIG. 1 that the film was formed at M PSf The surface of the film is successfully synthesized into the metal composite nano sheet film in situ, namely H 4-F /M PSf。
(3) Immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in methanol/water solution containing ligand with lower pKa reversely, standing at normal temperature for reaction fully to obtain flawless metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material (HKUST-1/H) 4-F /M PSf ) The specific operation steps are as follows:
firstly preparing a methanol/water solution (50:50) with the concentration of 2.5mmol/L-5mmol/L trimesic acid, inversely immersing the metal composite nano-sheet membrane/hydrophilic modified polysulfone membrane obtained in the step (2) into the methanol/water solution of trimesic acid, standing for reaction for 24 hours at normal temperature, fully washing the surface of the membrane with methanol for 2 times, and then drying for 24 hours at 30 ℃ and 40% RH to obtain HKUST-1/H 4-F /M PSf 。
The HKUST-1/H obtained above was examined by a scanning electron microscope 4-F /M PSf The surface of the film was characterized and the SEM image obtained is shown in figure 2.
FIG. 2 shows H 4-F /M PSf HKUST-1 seed particles of unequal sizes appeared on the surface, but these HKUST-1 seeds were more dispersed and discontinuous, probably because the ligand solution concentration was too low (2.5 mmol/L-5 mmol/L) resulting in slow crystal formation.
Example 2:
a preparation method for rapidly synthesizing a defect-free metal-organic framework (MOF) membrane material is prepared by the following steps:
(1) Sequentially coating Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane (M) PSf ) The specific procedure is the same as in step (1) of example 1;
(2) Using a low temperature solid phase synthesis method, using a ligand with a higher pKa and a metal salt in the step (1)In-situ synthesis of metal composite nano sheet membrane on the surface of water modified polysulfone membrane to obtain metal nano sheet membrane/hydrophilic modified polysulfone membrane (H) 4-F /M PSf ) The specific procedure is the same as in step (2) of example 1;
(3) Immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in methanol/water solution containing ligand with lower pKa reversely, standing at normal temperature for reaction fully to obtain flawless metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material (HKUST-1/H) 4-F /M PSf ) Except that the concentration of trimesic acid was 10 mmol/L, the procedure of step (3) of example 1 was followed.
The HKUST-1/H obtained above was examined by a scanning electron microscope 4-F /M PSf The surface and cross section of the film were characterized and the SEM image obtained is shown in figure 3.
FIG. 3 shows HKUST-1/H 4-F /M PSf The HKUST-1 crystal particles on the surface of the membrane are continuous and compact, and the formation of the HKUST-1 crystal layer on the surface of the membrane can be clearly seen, but the crystal size is not uniform, and compared with the concentration of the solution of 2.5mmol/L and 5mmol/L, the crystal continuity is remarkably improved.
Example 3:
a preparation method for rapidly synthesizing a defect-free metal-organic framework (MOF) membrane material is prepared by the following steps:
(1) Sequentially coating Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane (M) PSf ) The specific procedure is the same as in step (1) of example 1;
(2) Synthesizing a metal composite nano sheet membrane on the surface of the hydrophilic modified polysulfone membrane obtained in the step (1) by adopting a low-temperature solid-phase synthesis method to obtain a metal nano sheet membrane/hydrophilic modified polysulfone membrane (H) 4-F /M PSf ) The specific procedure is the same as in step (2) of example 1;
(3) Inversely immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in a methanol/water solution containing a ligand with lower pKaStanding at normal temperature to react fully to obtain a flawless metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material (HKUST-1/H) 4-F /M PSf ) Except that the concentration of trimesic acid was 15 mmol/L, the procedure of step (3) of example 1 was followed.
The HKUST-1/H obtained above was examined by a scanning electron microscope 4-F /M PSf The surface and cross section of the film were characterized and the SEM image obtained is shown in figure 4.
FIG. 4 shows HKUST-1/H 4-F /M PSf The HKUST-1 seed crystal particles on the surface of the membrane are continuous and compact, and the formation of the HKUST-1 crystal layer on the surface of the membrane can be clearly seen, and compared with the concentration of the solution of 10 mmol/L, the crystal continuity is remarkably increased, and the size is more uniform.
Example 4:
a preparation method for rapidly synthesizing a defect-free metal-organic framework (MOF) membrane material is prepared by the following steps:
(1) Sequentially coating Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane (M) PSf ) The specific procedure is the same as in step (1) of example 1;
(2) Synthesizing a metal composite nano sheet membrane on the surface of the hydrophilic modified polysulfone membrane obtained in the step (1) by adopting a low-temperature solid-phase synthesis method to obtain a metal nano sheet membrane/hydrophilic modified polysulfone membrane (H) 4-F /M PSf ) The specific procedure is the same as in step (2) of example 1;
(3) Immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in methanol/water solution containing ligand with lower pKa reversely, standing at normal temperature for reaction fully to obtain flawless metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material (HKUST-1/H) 4-F /M PSf ) Except that the concentration of trimesic acid was 20 mmol/L, the procedure of step (3) of example 1 was followed.
The HKUST-1/H obtained above was examined by a scanning electron microscope 4-F /M PSf Surface of filmAnd cross-section characterization, the resulting SEM image is shown in figure 5.
FIG. 5 shows HKUST-1/H 4-F /M PSf The HKUST-1 seed crystal particles on the surface of the membrane are continuous and compact, the formation of the HKUST-1 crystal layer on the surface of the membrane can be clearly seen, the HKUST-1 continuously grows on the surface of the membrane, and the membrane thickness is uniform.
Example 5:
a preparation method for rapidly synthesizing a defect-free metal-organic framework (MOF) membrane material is prepared by the following steps:
(1) Sequentially coating Polydimethylsiloxane (PDMS) and polyvinyl alcohol (PVA) on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane (M) PSf ) The specific procedure is the same as in step (1) of example 1;
(2) Synthesizing a metal composite nano sheet membrane on the surface of the hydrophilic modified polysulfone membrane obtained in the step (1) by adopting a low-temperature solid-phase synthesis method to obtain a metal nano sheet membrane/hydrophilic modified polysulfone membrane (H) 4-F /M PSf ) The specific procedure is the same as in step (2) of example 1;
(3) Immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in methanol/water solution containing ligand with lower pKa reversely, standing at normal temperature for reaction fully to obtain flawless metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material (HKUST-1/H) 4-F /M PSf ) Except that the concentration of trimesic acid was 25 mmol/L, the procedure of step (3) of example 1 was followed.
The HKUST-1/H obtained above was examined by a scanning electron microscope 4-F /M PSf The surface and cross section of the film were characterized and the SEM image obtained is shown in figure 6.
FIG. 6 shows HKUST-1/H 4-F /M PSf The HKUST-1 crystal particles on the surface of the membrane are accumulated on the surface of the membrane in a cluster shape, are dispersed and discontinuous, and are rapidly generated due to the severe reaction caused by the too high concentration of the solution.
The above detailed description is only for explaining the technical solution of the present invention in detail, the present invention is not limited to the above examples, and it should be understood that those skilled in the art should all modifications and substitutions based on the above principles and spirit are within the scope of the present invention.
Claims (9)
1. A preparation method for rapidly synthesizing a metal-organic framework MOF membrane material without defects is characterized by comprising the following steps:
sequentially coating polydimethylsiloxane PDMS and polyvinyl alcohol PVA on the surface of the polysulfone membrane to prepare the hydrophilic modified polysulfone membrane M PSf ；
Step (2) adopts a low-temperature solid-phase synthesis method, and a ligand with higher pKa and metal salt are synthesized on the surface of the hydrophilic modified polysulfone membrane obtained in step (1) to obtain a metal composite nano-sheet membrane in situ, thus obtaining a metal nano-sheet membrane/hydrophilic modified polysulfone membrane H/M PSf ；
Step (3) inversely immersing the metal nano sheet membrane/hydrophilic modified polysulfone membrane prepared in the step (2) in methanol/water solution containing ligand with lower pKa, and standing at normal temperature for sufficient reaction to obtain a metal-organic framework membrane/metal nano sheet membrane/hydrophilic modified polysulfone membrane material MOF/H/M without defects PSf ；
The metal composite nano sheet membrane grows on the surface of the hydrophilically modified polysulfone membrane in situ, a metal source on the surface of the nano sheet membrane containing a ligand with higher pKa reacts with the ligand with lower pKa, and the defect-free metal-organic framework membrane is synthesized on the metal composite nano sheet membrane in situ; the higher pKa ligand is 4-fluorobenzoic acid pka=4.15, 4-chlorobenzoic acid pka=3.98, 4-bromobenzoic acid pka=3.96 or 4-iodobenzoic acid pka=4.00; the lower pKa ligand is trimesic acid pka=2.12 or terephthalic acid pka=3.51.
2. The method for preparing the rapid synthesis defect-free metal-organic framework MOF membrane material according to claim 1, which is characterized in that: the polysulfone in the step (1) is a commercial ultrafiltration polysulfone membrane with an average pore size of 20-50 nm.
3. The method for preparing the rapid synthesis defect-free metal-organic framework MOF membrane material according to claim 1, which is characterized in that: the structural formula of the polydimethylsiloxane in the step (1) is
Wherein n is 300-500; the polyvinyl alcohol has a polymerization degree=1700 and an alcoholysis degree=87-89%.
4. The method for preparing the rapid synthesis defect-free metal-organic framework MOF membrane material according to claim 1, which is characterized in that: the metal salt in the step (2) is anhydrous copper acetate.
5. The method for preparing the rapid synthesis of metal-organic framework MOF membrane material without defects according to claim 1, which is characterized in that: the volume ratio of the methanol to the aqueous solution in the step (3) is 99:1-1:50.
6. the method for preparing a rapid synthesis defect-free metal-organic framework MOF membrane material according to claim 1 or 2 or 3 or 4 or 5, wherein the hydrophilic modified polysulfone membrane has a thickness of 50-100nm, the metal composite nanosheet has a thickness of 50-800 nm, and the metal-organic framework MOF membrane has a thickness of 100-5000 nm, and the metal-organic framework MOF membrane thickness can be adjusted according to the growth density of the metal composite nanosheet on the surface of the hydrophilic modified polysulfone membrane.
7. The method for preparing a rapid synthesis of defect-free metal-organic framework MOF membrane material according to claim 1, wherein the step (1) is implemented by the following steps:
firstly, preparing a Polydimethylsiloxane (PDMS)/n-heptane solution with the concentration of 0.1-1.0 wt%, coating the PDMS/n-heptane solution on the surface of polysulfone by using a scraper, wherein the coating thickness is 0.03 mu m-1.00 mu m, and then drying under the conditions of 60 ℃ and 40% RH of humidityDrying for 16-24h to obtain a polysulfone membrane coated with PDMS; secondly, preparing a polyvinyl alcohol PVA aqueous solution with the concentration of 0.01 to 0.5 weight percent, soaking the polysulfone coated with PDMS in the PVA/aqueous solution, reacting for 0.5 to 4 hours, and continuously drying for 4 to 12 hours at the temperature of 30 ℃ and 40 percent RH to obtain the hydrophilic modified polysulfone membrane M PSf 。
8. The method for preparing a rapid synthesis of defect-free metal-organic framework MOF membrane material according to claim 1, wherein the step (2) is implemented by the following steps:
uniformly coating a higher pKa ligand/methanol solution with the concentration of 5-150mmol/L on the surface of the hydrophilic modified polysulfone obtained in the step (1) to a thickness of 20-200 nm, and then drying for 4-8h at 30 ℃ and 40% RH to obtain a hydrophilic modified polysulfone membrane coated with the higher pKa ligand; secondly, soaking the hydrophilic modified polysulfone membrane coated with the ligand with higher pKa in a metal salt/water solution with the concentration of 0.25wt% for 0.5-H-2H, and then drying for 24H at 30 ℃ and 40% RH to obtain the metal composite nano-sheet membrane/hydrophilic modified polysulfone membrane H/M PSf 。
9. The method for preparing a rapid synthesis of defect-free metal-organic framework MOF membrane material according to claim 1, wherein the step (3) is implemented by the following steps:
firstly preparing a methanol/water solution with the concentration of 0.1mmol/L-100mmol/L of a ligand with lower pKa, inversely immersing the metal composite nano-sheet membrane/hydrophilic modified polysulfone membrane obtained in the step (2) into the methanol/water solution of the ligand with lower pKa, standing for reaction for 4-24 hours at normal temperature, fully cleaning the surface of the membrane with methanol for 2 times, and then drying for 24 hours at 30 ℃ and 40% RH to obtain a metal-organic framework membrane/metal nano-sheet membrane/hydrophilic modified polysulfone membrane material MOF/H/MPSF without defects.
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