Metal-organic framework and porous graphene oxide crystalline hybrid membrane, and preparation method and application thereof

Abstract

The application discloses a kind of metal organic framework and porous graphene oxide crystalline hybrid film, the crystalline hybrid film includes metal organic framework (MOF) and porous graphene oxide (PGO), by co-deposition under direct current electric field ZIF-8 with negative charged two-dimensional PGO nanosheet preparation;In the preparation process, the ZIF-8 is grown on the base film, while two-dimensional PGO nanosheet is adsorbed by hydrogen bond, ionic bond and coordination bond Positive charged precursor, and are deposited on the base film together, then, the two-dimensional PGO nanosheet induces ZIF-8 nucleation and growth on the two-dimensional PGO nanosheet, to enhance the screening capacity and mechanical properties of film.The preparation process of the film mainly includes two steps of hydrothermal method preparation PGO nanosheet, co-deposition method preparation MOF-PGO crystalline hybrid film.The film is used for C3H6 / C3H8 system normal pressure and high pressure separation, has high permeation rate, high selectivity to C3H6 under different pressures, and the film has good high pressure stability and long-term stability.

Description

Technical Field

[0001] This invention relates to a metal-organic framework and a porous graphene oxide crystalline hybrid film, as well as their preparation and application, belonging to the field of crystalline hybrid film technology. Background Technology

[0002] Olefins are one of the most in-demand and produced basic chemical raw materials globally, with annual global production exceeding 300 million tons. Their downstream industrial chain is extensive, encompassing important industries such as plastics, resins, and pharmaceuticals. Statistics show that energy consumption for olefin / alkane separation accounts for approximately 0.3% of global energy consumption annually. Developing energy-efficient olefin and alkane separation technologies is a crucial prerequisite for the sustainable development of modern chemical industry. Membrane technology, due to its low energy consumption and zero pollutant emissions, is considered one of the most promising gas separation technologies. However, traditional membrane materials suffer from a trade-off between permeability and selectivity, and are limited by short service life, making it difficult to meet the demands of practical industrial separation tasks. Therefore, developing novel membrane materials with high permeability, high selectivity, high pressure stability, and good long-term stability has become a major demand for olefin / alkane separation.

[0003] Advanced molecular sieve membranes can effectively separate two molecules with similar kinetic diameters based on the principle of size sieving. Therefore, the development of molecular sieve materials and the design of molecular sieve membrane structures are among the most popular research topics in the field of molecular separation. Metal-organic frameworks (MOFs) are an emerging type of molecular sieve with… High-grade molecular sieving windows, due to their high crystallinity, have regular and orderly pores and good structural modification compatibility, offering significant advantages for separating small molecule mixtures of gases. A typical example is ZIF-8, with an effective molecular sieving range of [missing information - likely a specific range or size]. Located precisely between the molecular dynamic diameters of C3H6 and C3H8, ZIF-8 polycrystalline membranes demonstrate great potential for achieving efficient C3H6 / C3H8 separation. However, two problems still exist with ZIF-8 membrane materials: (1) the heterogeneous nucleation rate or density on the base membrane during polycrystalline membrane preparation does not match the crystal growth rate, easily leading to numerous grain boundary defects and resulting in less than ideal C3H6 / C3H8 selectivity; (2) insufficient material rigidity and poor membrane mechanical properties result in poor C3H6 / C3H8 separation performance and pressure stability under high pressure. Currently, there are no reports on preparing crystalline hybrid membranes to enhance the membrane's mechanical properties, thereby achieving good high-pressure separation performance and pressure stability. Therefore, developing simple, efficient, and scalable methods for ZIF-8 membrane preparation and membrane structure control is expected to promote the development of metal-organic framework molecular sieve membranes in the field of propylene / propane separation.

[0004] For the construction of the crystalline hybrid membrane by introducing other guest components, a key problem to be considered is that the matching between the currently introduced guest components and the host components is not high, the combination is poor, and the enhancement effect of the guest components on the mechanical properties of the crystalline hybrid membrane is not considered. Traditional polymers and covalent organic frameworks are commonly used as guest components of crystalline hybrid membranes. For traditional polymers, the chain segment is flexible and does not have a regular permanent mass transfer channel, which leads to a significant decrease in the gas permeation rate of the membrane after filling into the membrane, and the combination between the host and the guest is poor, which leads to poor selectivity improvement effect of the membrane. For the introduction of covalent organic framework, a new type of molecular sieve material, it is an effective strategy to realize high-efficiency C3H6 / C3H8 separation at normal pressure, but it significantly increases the raw material cost and time cost of the preparation process, and complicates the preparation process. For example, the cationic covalent organic framework is used as the guest component of the crystalline hybrid membrane in patent CN113713634B, and the ionic bond is used to enhance the matching and combination between the host and the guest, but due to the poor mechanical properties of the cationic covalent organic framework, the mechanical properties of the membrane have not been significantly improved, and this method is difficult to meet the needs of high-pressure separation.

[0005] Based on the above analysis, the current polycrystalline membrane and crystalline hybrid membrane for C3H6 / C3H8 separation mainly face the following three problems: (1) it is necessary to select a guest component with a certain porosity to reduce the gas mass transfer resistance and improve the permeability; (2) it is necessary to select a guest component with strong adsorption and combination effect on the precursor of the MOF, and to design the structure, based on stronger and more stable coordination bonds and other interactions, to enhance the interface between the host and the guest and reduce defects, and to improve the selectivity of the membrane; (3) it is necessary to select a two-dimensional guest component with excellent mechanical properties to construct a bridging structure between the host and the guest, to enhance the mechanical properties of the membrane, and to ensure the high-pressure separation performance and pressure stability of the membrane. SUMMARY

[0006] In view of the prior art, the application provides a metal organic framework and porous graphene oxide crystal hybrid film and a preparation method and application thereof, the main component of the crystal hybrid film is metal organic framework ZIF-8, the guest component is porous graphene oxide PGO, and the crystal hybrid film is prepared by co-deposition of ZIF-8 and negatively charged two-dimensional porous graphene oxide nanosheets under a direct current electric field; in the preparation process, the ZIF-8 grows on a base film at the same time, the two-dimensional porous graphene oxide nanosheet absorbs positively charged precursors through hydrogen bonds, ionic bonds and coordination bonds, and is deposited on the base film together, then the two-dimensional porous graphene oxide nanosheet induces the ZIF-8 to nucleate and grow on the two-dimensional porous graphene oxide nanosheet, so that the metal organic framework and porous graphene oxide crystal hybrid film are obtained, and the thickness of the crystal hybrid film is 450-520 nm. The preparation method is simple and convenient, has strong expandability, the prepared crystal hybrid film shows ultra-high C3H6 / C3H8 separation performance, long-term stability and high-pressure stability for normal pressure and high-pressure separation of a C3H6 / C3H8 mixed system, and provides a platform for normal pressure and high-pressure separation applications for various separation systems.

[0007] The application provides a preparation method of a metal organic framework and porous graphene oxide crystal hybrid film, which mainly comprises the following steps: firstly, two-dimensional porous graphene oxide nanosheets are prepared by a hydrothermal method with graphene oxide nanosheets and hydrogen peroxide as reaction raw materials; then, the two-dimensional porous graphene oxide nanosheets are added into a ZIF-8 precursor solution of 2-methyl imidazole and Zn ions, and the solution is stirred uniformly to serve as a co-deposition solution of the metal organic framework and the two-dimensional porous graphene oxide nanosheets; subsequently, an anodized aluminum base film pre-sprayed with platinum is immersed into the co-deposition solution as a cathode of an electric field, and deposition is carried out under a constant current until the voltage remains basically stable; the obtained product is washed and soaked with deionized water and methanol, and is dried at room temperature, and finally the metal organic framework and porous graphene oxide crystal hybrid film are obtained. The specific steps are as follows:

[0008] In step one, two-dimensional porous graphene oxide nanosheets are prepared by hydrogen peroxide oxidation etching of graphene oxide nanosheets by a hydrothermal method: graphene oxide nanosheets are dispersed into deionized water to prepare a 0.5 mg / mL dispersion liquid, and ultrasonic treatment is carried out for 20 minutes; then, a hydrogen peroxide aqueous solution with a mass concentration of 1.1 g / mL is added, and the volume ratio of the hydrogen peroxide aqueous solution to the dispersion liquid is 1 / 40; the reaction system is kept at 100 DEG C for 4 hours under continuous stirring, two-dimensional sheets with a lateral size of 5-30 microns and a thickness of 3 nm±0.1 nm are collected after the reaction is completed, are put into a dialysis bag and are dialyzed in deionized water for 5 days, and finally two-dimensional porous graphene oxide nanosheets, namely two-dimensional PGO nanosheets, are obtained;

[0009] Step two, preparing the co-deposition solution, including: preparing 2-methylimidazole aqueous solution of 1 mmol / mL, denoted as solution A; preparing Zn(CH3COO)2 aqueous solution of 0.083 mmol / mL, then adding two-dimensional PGO nanosheets, ultrasonic dispersion, to obtain solution B, wherein the mass ratio of the two-dimensional PGO nanosheets to Zn(CH3COO)2 is 6*10 -4 ~1*10 -2 ; mixing solution A and solution B in a volume ratio of 5:1 and stirring uniformly to obtain the co-deposition solution;

[0010] Step three, preparing the metal organic framework (MOF) and porous graphene oxide (PGO) crystal hybrid membrane by the co-deposition method: taking anodic aluminum oxide as a base film, performing platinum spraying treatment on the surface of the base film by an ion sputtering instrument, taking the base film after the platinum spraying treatment as a cathode, and taking hydrophilic carbon paper as an anode; immersing into the co-deposition solution, and depositing reaction under a direct current density of 0.13 mA cm -2 for 1 hour; rinsing and soaking the obtained product with deionized water and methanol respectively, and drying at room temperature to obtain the MOF-PGO crystal hybrid membrane finally.

[0011] Further, in step three of the preparation method, the process conditions for performing platinum spraying treatment on the surface of the base film by the ion sputtering instrument are as follows: current is 20 mA, argon atmosphere, and operation time is 200 s-300 s.

[0012] Compared with the prior art, the present application has the following beneficial effects:

[0013] (1) The present application provides a metal organic framework and porous graphene oxide crystal hybrid membrane and a preparation method thereof, and realizes efficient separation of C3H6 / C3H8 mixture. First, porous graphene oxide with certain porosity and strong mechanical properties is synthesized through a simple and fast synthesis process; second, the porous graphene oxide is introduced by an electrically driven co-deposition method, a large amount of metal organic framework precursors (metal ions) and small crystal nuclei are adsorbed based on multiple interactions, and the heterogeneous nucleation and crystal growth are promoted in a modular assembly and growth manner, so that the problem of many crystal boundary defects caused by the mismatch between the heterogeneous nucleation rate or density and the crystal growth rate is solved; finally, the porous graphene oxide is filled into the membrane to construct a bridging structure of metal organic framework-porous graphene oxide, which significantly enhances the mechanical properties of the membrane, thereby effectively improving the high-pressure separation performance and pressure stability of the membrane.

[0014] (2) The application guarantees the gas permeability of the film by oxidizing and etching the guest component with hydrogen peroxide; obtains high separation selectivity by reducing grain boundary defects; and obtains excellent mechanical properties by constructing a bridging structure, so that the prepared film has high gas permeability, high separation selectivity and strong pressure stability. The MOF-PGO crystalline hybrid film described in the application is used for normal pressure separation and / or high pressure separation of a C3H6 / C3H8 system, and has high permeation rate and high selectivity for C3H6 under different pressures, and the film has good high pressure stability and long-term stability. Under the conditions of 25 DEG C and a feed pressure of 1.1 bar, the C3H6 permeation rate is 83-131 GPU, and the C3H6 / C3H8 selectivity is 175-273; under the conditions of 25 DEG C and a feed pressure of 7 bar, the C3H6 permeation rate is 58-60 GPU, and the C3H6 / C3H8 selectivity is 185-234. The normal pressure and high pressure separation comprehensive performance all exceed the performance of the reported C3H6 / C3H8 separation film.

[0015] (3) The preparation method of the application is simple and controllable, and the guest component is simply filled by an electrically driven co-deposition method to enhance the mechanical properties of the film, so that normal pressure and high pressure efficient separation of the C3H6 / C3H8 system is realized, and the performance is more excellent than that of the pure ZIF-8 film and the reported crystalline hybrid film. The application can be used for propylene purification process, and has wide application prospect because of strong universality and can be expanded to other metal organic framework systems or other separation systems. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 Figure 1 is a cross-sectional electron microscope image of the film 1 prepared in Example 1.

[0017] Figure 2 Figure 2 is a cross-sectional electron microscope image of the film 2 prepared in Example 2.

[0018] Figure 3 Figure 3 is a cross-sectional electron microscope image of the film 3 prepared in Example 3.

[0019] Figure 4 Figure 4 is a cross-sectional electron microscope image of the film 4 prepared in Example 4.

[0020] Figure 5 Figure 5 is a cross-sectional electron microscope image of the pure ZIF-8 film prepared in Comparative Example 1.

[0021] Figure 6 Figure 6 is a normal pressure performance comparison diagram of the C3H6 permeation rate and the C3H6 / C3H8 selectivity of the films of Examples 1-4 and the pure ZIF-8 film of Comparative Example.

[0022] Figure 7 Figure 7 is a high pressure performance comparison diagram of the C3H6 flow rate and the C3H6 / C3H8 selectivity of the film 3 and the pure ZIF-8 film. DETAILED DESCRIPTION

[0023] The design idea of the metal organic framework and the porous graphene oxide crystalline hybrid film of the present application is that the crystalline hybrid film comprises a metal organic framework and porous graphene oxide, the metal organic framework is ZIF-8, and the porous graphene oxide is negatively charged two-dimensional PGO nanosheet, wherein the host for C3H6 / C3H8 molecular sieving function is ZIF-8, and the guest is PGO nanosheet, and the PGO nanosheet is prepared by a hydrothermal method. Under the action of an electric field, using the precursor of ZIF-8 and two-dimensional PGO nanosheet as basic raw materials, adopting a co-deposition method combining water phase electrodeposition and electrophoretic deposition under a direct current electric field, the ZIF-8 electrophoretically migrates to the cathode base film to nucleate and grow, while the PGO nanosheet adsorbs the positively charged precursor through hydrogen bond, ionic bond and coordination bond and is deposited on the base film together, and then the ZIF-8 is induced to rapidly nucleate and grow on the PGO nanosheet, so as to enhance the sieving capacity and mechanical properties of the film. The preparation process of the film mainly includes three steps of preparing PGO nanosheet by a hydrothermal method, preparing a co-deposition solution of MOF-PGO, and preparing a MOF-PGO crystalline hybrid film by a co-deposition method.

[0024] The technical solutions of the present application will be further described in detail below in combination with specific embodiments and the accompanying tables, and the specific embodiments described are only used to explain and illustrate the present application, and do not limit the present application.

[0025] Example 1, preparation of a MOF-PGO crystalline hybrid film (film 1), the steps are as follows:

[0026] Step one, preparation of two-dimensional PGO nanosheet:

[0027] 0.25 mg of graphene oxide nanosheet was dispersed into 50 mL of deionized water to obtain a dispersion liquid, and ultrasonic treatment was performed for 20 minutes; then 1.25 mL of hydrogen peroxide aqueous solution with a mass concentration of 1.1 g / mL was added thereto, and the hydrogen peroxide aqueous solution was used as an etching agent; the reaction system was kept at 100℃ for 4 hours under continuous stirring; after the reaction was completed, the two-dimensional sheet with a lateral size of 5-30 μm and a thickness of about 3 nm formed in the bottle was collected, was loaded into a dialysis bag and was dialyzed in deionized water for 5 days to obtain two-dimensional PGO nanosheet.

[0028] Step two, preparation of a co-deposition solution of MOF-PGO:

[0029] 4.105 g (50 mmol) of 2-methylimidazolium ligand (2-mIm) was dissolved in 50 mL of deionized water to obtain solution A; 0.1523 g (0.83 mmol) of Zn(CH3COO)2 was dissolved in 10 mL of deionized water, and 0.1 mg of PGO nanosheets were added and ultrasonically dispersed to obtain solution B; solution A and solution B were mixed and stirred evenly to form a co-deposition solution for preparing MOF-PGO crystalline hybrid film.

[0030] Step 3: Preparation of MOF-PGO crystalline hybrid film:

[0031] Using anodic aluminum oxide (AAO) as the base film, the AAO surface was platinum-sputtered using an ion sputtering system. The process conditions were: 20 mA current, argon atmosphere, and 200 s operation time. The platinum-sputtered AAO base film was used as the cathode, and hydrophilic carbon paper was used as the anode. In this embodiment, Toray 060 hydrophilic conductive carbon paper from Japan was selected. The platinum-sputtered AAO base film and the hydrophilic conductive carbon paper were immersed in the co-deposition solution described above. At 0.13 mA cm⁻¹ -2 The deposition reaction was carried out for 1 hour at a DC current density. The prepared MOF-PGO crystalline hybrid film was thoroughly rinsed and soaked with deionized water and methanol, respectively, and finally dried at room temperature. This film is referred to as film 1. Figure 1 A cross-sectional electron microscope image of film 1 is shown, which shows that the thickness of film 1 is approximately 510 nm.

[0032] Membrane 1 was used for atmospheric pressure separation of the C3H6 / C3H8 system. Under conditions of 25°C and a feed pressure of 1.1 bar, the C3H6 permeation rate was 121 GPU, and the C3H6 / C3H8 selectivity was 175. The testing equipment in this invention was a 9790II gas chromatograph manufactured by Zhejiang Fuli Analytical Instrument Co., Ltd.

[0033] Example 2: Preparation of MOF-PGO crystalline hybrid film (film 2). The preparation steps are basically the same as in Example 1, except that in step two, the mass of two-dimensional PGO nanosheets added to the co-deposition solution is changed from 0.1 mg to 0.3 mg, finally obtaining a MOF-PGO crystalline hybrid film (film 2) with a thickness of approximately 500 nm. Figure 2 A cross-sectional electron microscope image of membrane 2 is shown.

[0034] Membrane 2 was used for atmospheric and high-pressure separation of the C3H6 / C3H8 system. At 25°C and a feed pressure of 1.1 bar, the C3H6 permeation rate was 104 GPU, and the C3H6 / C3H8 selectivity was 219. At 25°C and a feed pressure of 7 bar, the C3H6 permeation rate was 60 GPU (corresponding to a flow rate of 1.3 × 10⁻⁶). -2 mol m -2s -1 ), C3H6 / C3H8 selectivity of 185.

[0035] Example 3, preparation of MOF-PGO crystalline hybrid membrane (membrane 3), the preparation steps are basically the same as those of Example 1, except that in step two, the mass of two-dimensional PGO nanosheets added to the co-deposition solution is changed from 0.1 mg to 0.9 mg, and finally a MOF-PGO crystalline hybrid membrane (membrane 3) with a thickness of about 470 nm is obtained, Figure 3 A cross-sectional electron micrograph of membrane 3 is shown.

[0036] Membrane 3 is used for C3H6 / C3H8 system separation at normal pressure and high pressure, at 25°C, under the condition of feed pressure of 1.1 bar, the C3H6 permeation rate is 131 GPU, and the C3H6 / C3H8 selectivity is 273; at 25°C, under the condition of feed pressure of 7 bar, the C3H6 permeation rate is 58 GPU, and the C3H6 / C3H8 selectivity is 234.

[0037] Example 4, preparation of MOF-PGO crystalline hybrid membrane (membrane 4), the preparation steps are basically the same as those of Example 1, except that in step two, the mass of two-dimensional PGO nanosheets added to the co-deposition solution is changed from 0.1 mg to 1.5 mg, and finally a MOF-PGO crystalline hybrid membrane (membrane 4) with a thickness of about 450 nm is obtained, Figure 4 A cross-sectional electron micrograph of membrane 4 is shown.

[0038] Membrane 4 is used for C3H6 / C3H8 system separation at normal pressure, at 25°C, under the condition of feed pressure of 1.1 bar, the C3H6 permeation rate is 89 GPU, and the C3H6 / C3H8 selectivity is 245.

[0039] Comparative Example 1, preparation of pure MOF membrane, the steps are as follows:

[0040] An anodic aluminum oxide (AAO) is used as a base film, and the surface of the AAO is treated with platinum spraying by an ion sputtering instrument; then an electrodeposition solution of ZIF-8 is prepared: 50 mmol of 2-methyl imidazole ligand (2-mIm) is dissolved in 50 mL of deionized water to obtain solution A; 0.83 mmol of Zn(CH3COO)2 is dissolved in 10 mL of deionized water to obtain solution B. Solution A and solution B are mixed and stirred uniformly to form an electrodeposition solution for preparing a pure ZIF-8 membrane. The platinum-sprayed AAO base film is used as a cathode, and a hydrophilic carbon paper is used as an anode, which are immersed in the above electrodeposition solution. Under a direct current density of 0.13 mA cm -2 The deposition reaction is carried out for 1 hour; a pure MOF membrane is prepared. The above pure ZIF-8 membrane is washed and soaked with deionized water and methanol, respectively, and finally dried at room temperature. Figure 5is a cross-sectional electron microscope image of a pure ZIF-8 membrane prepared in Comparative Example 1, and the thickness of the pure ZIF-8 membrane is about 520 nm.

[0041] The above pure MOF membrane was used for atmospheric separation and high-pressure separation of a C3H6 / C3H8 system. At 25℃ and a feed pressure of 1.1 bar, the C3H6 permeation rate was 111 GPU, and the C3H6 / C3H8 selectivity was 110; at 25℃ and a feed pressure of 7 bar, the C3H6 permeation rate was 40 GPU (corresponding to a flow rate of 9.5 x 10 -3 mol m -2 s -1 ), and the C3H6 / C3H8 selectivity was 2.

[0042] Table 1 shows the C3H6 permeation rate and C3H6 / C3H8 selectivity of membranes 1-4 and the pure MOF membrane for atmospheric separation and high-pressure separation of a C3H6 / C3H8 system.

[0043] Table 1

[0044]

[0045] By comparing membranes 1-4 with the pure MOF membrane, it can be seen that the addition of PGO nanosheets in step two of the preparation method has a great contribution to the atmospheric and high-pressure separation performance of the membrane, such as the improvement of the C3H6 permeation rate and the C3H6 / C3H8 selectivity. By changing the amount of PGO added in step two, the C3H6 rate can reach 83-131 GPU, and the C3H6 / C3H8 selectivity is 175-273, wherein when the amount of PGO added is 0.9 mg (i.e., the mass ratio of PGO to Zn(CH3COO)2 is about 6 x 10 -3 ), the C3H6 / C3H8 atmospheric separation performance of membrane 3 reaches the highest, the permeation rate is 131 GPU, and the C3H6 / C3H8 selectivity is 275, as shown in Figure 6 ; at a feed pressure of 7 bar, the C3H6 permeation rate of membrane 3 is 58 GPU, and the C3H6 / C3H8 selectivity is 234, which is much higher than that of the comparative example. As Figure 7As shown, the present application lists the performance of the C3H6 / C3H8 separation membrane under the condition that the feed pressure is not less than 3 bar, and draws a performance coordinate graph, wherein the more the performance corresponding point is close to the right upper corner of the graph, the better the comprehensive separation performance of the membrane is, and the MOF-PGO crystalline hybrid membrane (membrane 3) prepared according to the preparation method of the present application has the corresponding separation performance located in the right upper corner of the graph under the condition that the feed pressure is 3 bar and 7 bar, which exceeds the existing membrane; as a comparison, the C3H6 / C3H8 selectivity of the pure ZIF-8 membrane prepared in the comparative example decays seriously under the condition that the feed pressure is 7 bar, and is located in the right lower corner of the performance coordinate graph, which indicates that the high-pressure separation performance and pressure stability of the MOF-PGO crystalline hybrid membrane relative to the pure ZIF-8 membrane are obviously improved.

[0046] According to the preparation method of the present application, by adjusting the proportion content of the PGO nanosheet in the co-deposition solution, the adsorption amount of the PGO to the metal organic framework precursor can be controlled, thereby affecting the modular assembly and growth behavior of the crystalline hybrid membrane. By adsorbing the precursor, the PGO nanosheet changes from negative to positive and moves to the cathode base film, thereby providing a supporting role for enhancing the rigidity of the screening channel and the overall mechanical performance of the membrane in the crystalline hybrid membrane, so as to realize the normal pressure and high pressure separation of the MOF-PGO crystalline hybrid membrane to the C3H6 / C3H8 system, and exhibit good pressure stability and long-term stability.

[0047] Although the present application is described above in combination with the drawings, the present application is not limited to the above-described specific embodiments, and the above-described specific embodiments are only illustrative but not limiting, and a person of ordinary skill in the art can make many modifications under the inspiration of the present application without departing from the purpose of the present application: other metal organic frameworks such as ZIF-67 and MOF-801 are used; other two-dimensional nanosheet materials such as graphene oxide, covalent organic framework and metal organic framework two-dimensional nanosheet are used; these all belong to the protection of the present application.

Claims

1. A metal organic framework and porous graphene oxide crystalline hybrid membrane, characterized in that, The crystalline hybrid film is prepared by co-deposition of ZIF-8 and negatively charged two-dimensional porous graphene oxide nanosheets under a direct current electric field; during the preparation process, the ZIF-8 grows on the base film, at the same time, the two-dimensional porous graphene oxide nanosheets adsorb positively charged precursors through hydrogen bonds, ionic bonds and coordination bonds, and are deposited on the base film together, then the two-dimensional porous graphene oxide nanosheets induce the nucleation and growth of ZIF-8 on the two-dimensional porous graphene oxide nanosheets, thereby obtaining a metal organic framework and porous graphene oxide crystalline hybrid film, the thickness of the crystalline hybrid film is 450-520 nm, and the preparation of the hybrid film is as follows: Firstly, two-dimensional porous graphene oxide nanosheets are prepared by a hydrothermal method using graphene oxide nanosheets and hydrogen peroxide as raw materials; Then, the two-dimensional porous graphene oxide nanosheets are added into a ZIF-8 precursor solution of 2-methyl imidazole and Zn ions, and the mixture is stirred uniformly to obtain a co-deposition solution of metal organic framework and two-dimensional porous graphene oxide nanosheets; Subsequently, an anodized aluminum film pre-sprayed with platinum is immersed into the co-deposition solution as a cathode of an electric field, and deposition is carried out under a constant current until the voltage remains stable, then the obtained product is washed and soaked in deionized water and methanol, and is dried at room temperature, and finally a metal organic framework and porous graphene oxide crystalline hybrid film is obtained.

2. A method of preparing a metal organic framework and porous graphene oxide crystal hybrid membrane according to claim 1, characterized by, The specific steps are as follows: Step one, preparation of two-dimensional porous graphene oxide nanosheets by a hydrothermal method: The graphene oxide nanosheets are dispersed in deionized water to prepare a dispersion liquid with a concentration of 0.5 mg / mL, and are ultrasonically treated for 20 minutes; then, a hydrogen peroxide aqueous solution with a mass concentration of 1.1 g / mL is added, and the volume ratio of the hydrogen peroxide aqueous solution to the dispersion liquid is 1 / 40; the reaction system is kept at 100 DEG C for 4 hours under continuous stirring, and then the two-dimensional sheets with a lateral size of 5-30 microns and a thickness of 3 nm±0.1 nm are collected, are put into a dialysis bag, and are dialyzed in deionized water for 5 days to obtain two-dimensional porous graphene oxide nanosheets; Step two, preparation of a co-deposition solution, including: A 2-methylimidazole aqueous solution with a concentration of 1 mmol / mL is prepared, and is denoted as solution A; a Zn(CH3COO)2 aqueous solution with a concentration of 0.083 mmol / mL is prepared, and then two-dimensional porous graphene oxide nanosheets are added and ultrasonically dispersed to obtain solution B, wherein the mass ratio of the two-dimensional porous graphene oxide nanosheets to Zn(CH3COO)2 is 6 x 10 -4 -1 x 10 -2 -2; solution A and solution B are mixed at a volume ratio of 5:1 and uniformly stirred to obtain a co-deposition solution; Step three, preparation of a crystalline hybrid film by a co-deposition method: With anodic aluminum oxide as a base film, the surface of the base film was treated with platinum spraying by an ion sputtering instrument, the above base film treated with platinum spraying was used as a cathode, hydrophilic carbon paper was used as an anode, and the above co-deposition solution was immersed, a deposition reaction was carried out at a direct current density of 0.13 mA cm -2 for 1 hour; the obtained product was washed and soaked with deionized water and methanol respectively, and was dried at room temperature to obtain a metal organic framework and porous graphene oxide crystal hybrid film.

3. The preparation method according to claim 2, characterized in that, In step three, the process conditions for spraying platinum on the surface of the base film by an ion sputtering instrument are as follows: the current is 20 mA, the argon atmosphere is used, and the operation time is 200-300 seconds.

4. Use of the MOF and porous graphene oxide crystalline hybrid film according to claim 1 or of the MOF and porous graphene oxide crystalline hybrid film produced according to the method of any one of claims 2 to 3, characterized in that, The crystalline hybrid film is used for normal pressure separation or high pressure separation of a C3H6 / C3H8 system, and includes: Under the conditions of 25 DEG C and a feed pressure of 1.1 bar, the C3H6 permeation rate is 83-131 GPU, and the C3H6 / C3H8 selectivity is 175-273; Under the conditions of 25 DEG C and a feed pressure of 7 bar, the C3H6 permeation rate is 58-60 GPU, and the C3H6 / C3H8 selectivity is 185-234.

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