CN112808312A

CN112808312A - Method for preparing nano metal-organic framework (MOFs) catalytic film

Info

Publication number: CN112808312A
Application number: CN201911116143.8A
Authority: CN
Inventors: 樊森清; 王艺霖; 仇博雅; 肖泽仪; 秦杨梅; 王宇阳
Original assignee: Sichuan University
Current assignee: Sichuan University
Priority date: 2019-11-15
Filing date: 2019-11-15
Publication date: 2021-05-18
Anticipated expiration: 2039-11-15
Also published as: CN112808312B

Abstract

The invention discloses a method for preparing a nano metal-organic framework (MOFs) catalytic film. Respectively percolating the precursor and the organic ligand through the porous base membrane, and preparing the nano MOFs catalytic membrane under the condition of synergy of flow and reaction. The metal nanoparticles or metal oxide nanoparticles can also be synthesized in the pores of the membrane by a percolation method, and the nano MOFs are modified. The pore structure of the base membrane is used as a synthesis reactor of MOFs, metal or metal oxide nanoparticles. The nanometer MOFs catalytic film prepared by the cooperation of the flow in the film hole and the reaction can effectively overcome the surface tension of liquid, so that the whole film hole can be filled with the reaction liquid. The catalytic membrane prepared by the method has the advantages of good catalyst dispersibility, good stability, high loading capacity, high catalytic efficiency and the like.

Description

Method for preparing nano metal-organic framework (MOFs) catalytic film

Technical Field

The invention relates to a method for preparing a nano metal-organic framework (MOFs) catalytic membrane, in particular to a nano MOFs catalytic membrane which is assembled by the cooperation of flowing and reacting in membrane pores.

Background

The MOFs and MOFs composite materials have large specific surface area, large porosity, regular cage channel structure and adjustable structure, so that the MOFs and MOFs composite materials show large application potential in the field of catalysis [1,2 ]. If the MOFs is prepared into the nano-scale powder material, the catalytic effect of the nano-scale powder material is remarkably enhanced due to small size, large specific surface area and many surface active sites. However, the powdered MOFs are difficult to recover, which hinders the practical application of the powdered MOFs. In addition, the MOFs powder is easy to agglomerate due to large surface energy, and the catalytic performance of the MOFs powder is also influenced. From the reactor point of view, the immobilization and dispersion of MOFs materials are critical in determining their successful applications. The porous membrane support has uniformly distributed pores with uniform pore diameters. If the nano MOFs catalyst is immobilized in the pore canal of the membrane support body, the immobilization and dispersion of the nano MOFs can be well realized. In addition, MOFs is arranged inside the pore channel of the membrane support body, so that catalytic reaction is carried out in the membrane pore with the micro-nano scale, concentration polarization can be reduced, and the catalytic reaction efficiency is improved.

The catalyst is immobilized on the surface of the membrane substrate, so that the mass transfer efficiency in the catalysis process can be improved, and the catalyst is a main structure of the current catalytic membrane. To increase the stability of the catalyst to the membrane substrate, the membrane substrate is often functionally modified and then bonded to the catalyst [3 ]. In addition, the stability of the catalyst and the membrane substrate can also be improved by depositing a layer of dopamine with adhesion on the membrane substrate and then loading the catalyst [4 ]. Due to the rigid nature of MOFs materials, there is still a greater risk of stabilization when the surface of the membrane substrate supports more MOFs. In addition, the problem of agglomeration of the nanocatalyst is difficult to solve by the surface immobilization of the membrane. In order to disperse and fix the catalyst inside the membrane pores, the catalyst is blended with the membrane casting solution by Sharpe and the like, and the catalyst is migrated to the surface of the membrane pores by utilizing the surface migration effect in the membrane forming process [5 ]. The method can well improve the solid-carrying stability of the catalyst. When the amount of the catalyst to be immobilized is large, a certain proportion of the catalyst is embedded in the membrane and cannot migrate to the surface of the membrane pores, so that the utilization efficiency of the catalyst is reduced.

In order to further improve the dispersibility and stability of the nano-catalyst, the base film can be soaked in a precursor solution of the MOFs, so that the precursor solution fills the pores of the film and reacts and crystallizes in the pores of the film, thereby loading the MOFs in the pores of the film. The method realizes the purpose of in-situ synthesis of the loaded nano-catalyst in the membrane pores, and can well control the size of the nano-catalyst. Due to the action of the surface tension of the liquid, the speed of the liquid entering the membrane pores is slow, and the liquid is difficult to infiltrate into the membrane pores after a certain amount of MOFs is generated in the membrane pores. Based on the background, the MOFs precursor is adopted to seep in the base film, and nanometer MOFs is synthesized in situ in the holes, so that the nanometer MOFs catalytic film is constructed.

Disclosure of Invention

The invention provides a method for directly synthesizing and assembling a nano MOFs catalytic membrane in a base membrane in a seepage way in order to improve the stability of MOFs with catalytic activity and a composite material thereof and improve the catalytic performance of the MOFs, and the nano MOFs are synthesized by utilizing the microporous structure of the base membrane and assembled into a MOFs composite membrane.

The invention adopts the main technical scheme that: a method for assembling a nano MOFs catalytic membrane by seepage flow synthesis is characterized by comprising the following main steps.

(1) Introducing a precursor into the inner pore channel of the porous base membrane: and (3) infiltrating the precursor with a certain concentration through the porous base membrane, and taking out the membrane for drying after the infiltration is finished.

(2) Introducing an organic ligand into the inner pore channel of the porous base membrane: and (3) percolating an organic ligand solution with a certain concentration through the membrane in the step (1), and drying after the percolation is finished to prepare the nano MOFs catalytic membrane assembled by percolation synthesis.

(3) In order to prepare the catalytic membrane with more catalytic functions, the nano MOFs catalytic membrane prepared in the step (2) can be modified by introducing metal nanoparticles or metal oxide nanoparticles with catalytic action through seepage.

The specific process of introducing the metal nanoparticles or metal oxide nanoparticles with catalytic action by seepage comprises the following steps: introducing metal ions into the nano MOFs catalytic membrane from a metal salt solution with a certain concentration by adopting a seepage method, and drying to obtain the nano MOFs catalytic membrane modified by metal oxide nanoparticles; and then, carrying out seepage flow in the membrane to reduce the metal oxide into a metal simple substance by a reducing agent solution with a certain concentration, and drying to obtain the metal nanoparticle modified nano MOFs catalytic membrane.

The concentrations of the precursor and the organic ligand and the types of the solvents used for synthesizing the MOFs can be selected by referring to the disclosed traditional synthesis method of the MOFs; the concentrations of the metal salt solution and the reducing agent solution used for synthesizing the metal nanoparticles or metal oxide nanoparticles may be selected with reference to a conventional synthesis method of the metal or metal oxide, and the forms of the precursor and the organic ligand may be selected to be gaseous or liquid according to reaction characteristics.

In the fluid seepage process, the flow rate of the fluid can be controlled by controlling the driving force on two sides of the membrane: when the flow rate of the fluid is too high, the pushing force is reduced to prevent the fluid from staying for too short time; increasing the pushing force when the fluid flow rate is too slow prevents the fluid from failing to seep due to too much resistance.

In the preparation process of the catalytic film, the MOFs loading capacity in the catalytic film can be controlled by controlling the seepage frequency of the precursor and the organic ligand; and controlling the loading of metal nanoparticles and metal oxide nanoparticles in the nano MOFs catalytic membrane by controlling the seepage times of the metal salt solution and the reducing agent solution.

Compared with the prior art, the research has the following advantages.

(1) The catalyst has better dispersibility: MOFs are assembled in the porous base film through seepage synthesis and are modified by metal nanoparticles or metal oxide nanoparticles, so that the pore space of the porous base film is fully utilized to disperse the MOFs, the metal nanoparticles or the metal oxide nanoparticles, the contact area of a catalyst and a reactant is greatly increased, and the catalytic activity is favorably improved.

(2) The catalyst has better stability and is convenient to recycle and operate: MOFs, metal nanoparticles and metal oxide nanoparticles are directly assembled inside pores of the porous base membrane through seepage synthesis, so that the powdery nano material is formed into a membrane, the stability of the catalyst is improved, the recovery operation with high energy consumption and a complex process is avoided, the loss of the catalyst in the reaction process is reduced, and the industrial production cost is reduced.

(3) The loading of the catalyst is controllable: the pores of the porous base membrane provide enough loading space for the catalyst, and the loading capacity of the catalyst in the catalytic membrane can be regulated and controlled by controlling the seepage frequency of the solution in the assembling process of the catalytic membrane, so that the catalytic membrane with different catalyst loading capacity, wider application range, higher assembling flexibility and higher controllability is obtained by assembling.

(4) The microporous structure of the porous base membrane provides a natural micro-reaction channel for MOFs, metal nanoparticles and metal oxide nanoparticles, and can be used as a membrane hole micro-reactor.

Drawings

FIG. 1 is a schematic illustration of a liquid phase fluid percolation process in accordance with the present invention.

FIG. 2 is a schematic view of the process of gas phase fluid percolation in the present invention.

FIG. 3 is an SEM cross-sectional representation of a ZIF-8/PES catalytic membrane prepared in example 1 of the invention.

FIG. 4 is a SEM cross-sectional representation of a Cu @ ZIF-8/PES catalytic membrane prepared in example 2 of the invention.

Detailed Description

The present invention will be described in detail below with reference to specific examples, but the present invention is not limited to the following examples, and various modifications and implementations are included within the technical scope of the present invention without departing from the content and scope of the present invention.

Example 1: ZIF-8/PES catalytic membrane was used for Knoevenagel reaction of benzaldehyde.

In the embodiment, a polyether sulfone (PES) membrane with the pore diameter of 0.45 mu m is selected as a catalytic membrane base membrane, the target MOFs is a zeolite imidazole framework ZIF-8 with catalytic activity, and the precursor and the organic ligand are both liquid phases. In order to test the catalytic performance of the catalytic membrane, Knoevenagel condensation reaction of benzaldehyde and ethyl isocyanoacetate is selected as a catalytic system. The specific implementation steps are as follows.

(1) Firstly, introducing Zn into PES basal membrane by percolation method²⁺The specific implementation process is as follows: weighing Polyethersulfone (PES) raw membrane, placing on a positive pressure filter disc with filter paper, then compacting the positive pressure filter, and pouring 50 mL of Zn (NO) with the concentration of 0.54 mol/L₃)₂The driving force of the precursor solution is the pressure difference between the two sides of the membrane, the precursor solution is realized by introducing inert gas into the filter, and the flow rate of the solution passing through the filter is controlled by controlling the pressure of the inert gas; and after about 20 min of filtration, sequentially taking out the membranes, drying in an electrothermal constant-temperature drying oven at 60 ℃ for 30 min, and weighing.

(2) Then introducing a 2-methylimidazole organic ligand into the membrane pores, and specifically comprising the following steps: placing the dried membrane in the step (1) on a positive pressure filter disc with filter paper, then pressing the positive pressure filter tightly, pouring 50 mL of 2-methylimidazole solution with the concentration of 0.95 mol/L, and controlling the flow rate of the solution passing through the filter by controlling the pressure of inert gas; after about 20 min of filtration, the membrane was taken out, dried in an electrothermal constant temperature drying oven at 60 ℃ for 30 min and weighed.

(3) Repeating the steps (1) and (2) twice, and passing Zn (NO) for 3 times in total₃)₂And soaking the solution and the 2-methylimidazole solution for 3 times in water for 12 hours, washing off impurities and dust on the surface of the membrane, and drying at the constant temperature of 60 ℃ for 24 hours to obtain the ZIF-8/PES catalytic membrane.

(4) The specific implementation steps of the ZIF-8/PES catalytic membrane catalytic experiment are as follows: a mixture of 50 mL of a 0.1 mol/L benzaldehyde solution and 50 mL of a 0.1 mol/L ethyl isocyanoacetate solution was prepared as a reaction solution. Sucking the reaction solution into a medical injector, pushing the reaction solution in the injector to flow through a membrane component provided with a catalytic membrane at a constant speed by using an injection pump, and collecting the solution passing through the membrane at the downstream by using a beaker. The collected downstream solutions were tested for reactant and reaction product concentrations using a gas chromatograph.

The catalytic experiment result shows that the conversion rate of benzaldehyde can reach 95-100% after normal-temperature catalysis by the ZIF-8/PES catalytic membrane, the yield of a target product is more than 99%, and the catalytic membrane can remarkably improve the reaction progress degree of benzaldehyde and ethyl cyanoacetate.

Example 2: the Cu @ ZIF-8/PES catalytic membrane degrades nitrophenol.

In the embodiment, a polyether sulfone (PES) membrane with the pore diameter of 0.45 mu m is selected as a catalytic membrane base membrane, the target MOFs is ZIF-8 with a zeolite imidazole framework, the precursor is a liquid phase, and the organic ligand is a gas phase. The main catalyst with catalytic action in the catalytic membrane is metal Cu nano-particles. In order to test the catalytic performance of the catalytic membrane, a strong reducing agent NaBH is selected₄The decomposition reaction of p-nitrophenol (4-NP) is used as a catalytic system. The specific implementation steps are as follows.

(1) Firstly, introducing ZnO nano-rods by a percolation method. The specific implementation process comprises the following steps: weighing a Polyethersulfone (PES) original membrane, placing the membrane on a positive pressure filter disc with filter paper, then compacting the positive pressure filter, pouring 100 mL of 70 mmol/L zinc acetate solution (the solvent is absolute ethyl alcohol), taking out the membrane after filtering is completed for about 40 min, and placing the membrane in an electric heating constant temperature drying oven for drying at 60 ℃ for 60 min and then weighing; then 100 mL of NaOH solution (solvent is absolute ethyl alcohol) with the concentration of 0.1 mmol/L is poured into the positive pressure filter by the same method; repeating the operation twice, wherein the film passes through a zinc acetate solution and a NaOH solution for 3 times in total, then is soaked in water for 12 hours, impurities and dust on the surface of the film are washed away, and the film is dried at a constant temperature of 60 ℃ for 24 hours; the dried membrane was taken out, placed in a positive pressure filter, and 500 mL of a 50 mmol/L zinc acetate solution and 500 mL of a 50 mmol/L hexamethylenetetramine solution were poured therein, subjected to hydrothermal reaction at 90 ℃ for 18 hours, and finally dried at 60 ℃.

(2) The gas phase organic ligand is then introduced by percolation. The specific implementation process comprises the following steps: and (2) taking out the dried membrane in the step (1), placing the membrane on a positive pressure filter disc, weighing 50 g of 2-methylimidazole, completely filling the 2-methylimidazole in a cavity of the positive pressure filter disc, converting the 2-methylimidazole into a gas phase at 125 ℃, percolating the gas from bottom to top through a composite membrane with ZnO nanorods attached inside, treating the gas phase for 24 hours, and drying the membrane at 60 ℃ to obtain the ZIF-8/PES membrane.

(3) And finally, modifying the ZIF-8/PES composite membrane by using Cu nanoparticles with catalytic activity to prepare the Cu @ ZIF-8/PES catalytic membrane. The specific implementation process comprises the following steps: firstly, 50 mL of Cu (NO) with a concentration of 0.15 mol/L₃)₂Pouring the solution into a positive pressure filter filled with a ZIF-8/PES membrane, controlling the pressure of the introduced inert gas to control the slow flow of the solution at a low speed, taking out the membrane after about 20 min, and drying at 60 ℃ for 1 h to change the membrane from colorless to blue. Then weighing the dried membrane, placing the membrane on a filter disc for compacting, and pouring 50 mL of freshly prepared 1 mol/LNaBH into the positive pressure filter₄Solution, NaBH₄As a strong reducing agent, Cu may be used²⁺Reducing the solution into a catalyst simple substance Cu, controlling the pressure of the introduced inert gas to control the solution to slowly flow out at a low speed, taking out the membrane after about 20 min, drying the membrane at the temperature of 60 ℃ for 1 h, and changing the blue color of the membrane into brownish black to obtain the Cu @ ZIF-8/PES catalytic membrane.

(4) The specific implementation steps for testing the catalytic performance of the Cu @ ZIF-8/PES catalytic membrane are as follows: 10 mL of 0.17 mol/L NaBH was mixed with 20 mL of 0.27 mmol/L4-NP solution₄Solution, adding NaBH₄Changing the 4-NP solution from light yellow to bright yellow after the solution is dissolved, uniformly stirring to obtain a reaction solution, sucking the reaction solution into a medical injector, pushing the reaction solution in the injector to flow through a membrane component provided with a catalytic membrane at a constant speed by using an injection pump, and collecting the solution passing through the membrane at the downstream by using a beaker. The spectrophotometry at 400 nm wavelength (reactant) and 300 nm wavelength (reaction product) of the initial solution and the downstream solution was measured with a spectrophotometer, and the standard solution was deionized water.

The above Experimental Process NaBH₄The solution is ready to use after being prepared and is operated in a fume hood to prevent NaBH₄H produced by reaction with water₂Gather in the small space, guarantee the experiment safety.

The catalytic experiment result shows that after being catalyzed by a Cu @ ZIF-8/PES catalytic membrane, the 400 nm spectral degree of the reaction solution is obviously reduced, the 300 nm spectral degree is obviously improved, the 4-NP conversion rate is over 99 percent, and the 4-NP decomposition reaction is more thorough under the catalysis of the catalytic membrane; the highest reaction rate of the injection method 4-NP decomposition reaction can reach 267 mmol L^-1min^-1The reaction rate constant can reach 878 min at most^-1The catalytic membrane can obviously improve the decomposition rate of 4-NP.

When the cumulative continuous service time of the Cu @ ZIF-8/PES catalytic membrane reaches 5 h, the conversion rate of 4-NP is still maintained to be more than 95%, and the catalytic membrane shows good stability.

Example 3: MnO₂@ ZIF-8/PES catalytic membrane degrades formaldehyde.

In the embodiment, a polyether sulfone (PES) membrane with the pore diameter of 0.45 mu m is selected as a catalytic membrane base membrane, the target MOFs is ZIF-8 with a zeolite imidazole framework, and a precursor and an organic ligand are both liquid phases. The main catalyst with catalytic action in the catalytic membrane is metal oxide MnO₂And (3) nanoparticles. In order to test the catalytic performance of the catalytic membrane, the decomposition reaction of formaldehyde is selected as a catalytic system. The specific implementation steps are as follows.

(1) Firstly, preparing a ZIF-8/PES composite membrane by a seepage method. The specific implementation process comprises the following steps: weighing Polyethersulfone (PES) raw membrane, placing on a positive pressure filter disc with filter paper, then compacting the positive pressure filter, and pouring 50 mL of Zn (NO) with the concentration of 0.54 mol/L₃)₂The solution, the flow rate of the solution passing through the filter is controlled by controlling the pressure of the inert gas; after about 20 min of filtration, taking out the membrane, drying in an electrothermal constant-temperature drying oven at 60 ℃ for 30 min, and weighing; then 50 mL of 2-methylimidazole solution with the concentration of 0.95 mol/L is poured into the positive pressure filter by adopting the same method; the above operation was repeated twice, and the film was passed 3 times of Zn (NO) in total₃)₂And soaking the solution and the 2-methylimidazole solution for 3 times in water for 12 hours, washing off impurities and dust on the surface of the membrane, and drying at the constant temperature of 60 ℃ for 24 hours to obtain the ZIF-8/PES composite membrane.

(2) Then with MnO having catalytic activity₂ZIF-8/PES composite membrane modified by metal oxide nano particles and preparedTo MnO₂@ ZIF-8/PES catalytic membrane. The specific implementation process comprises the following steps: firstly, 50 mL of 0.4 mol/L MnSO₄Pouring the solution into a positive pressure filter filled with a ZIF-8/PES membrane, controlling the pressure of the introduced inert gas to control the slow outflow of the solution at a low speed, taking out the membrane after about 20 min, and drying at 60 ℃ for 1 h. Then the dried membrane is weighed, placed on a filter disc to be compressed, and 50 mL of 0.1 mol/L KMnO is poured into the positive pressure filter₄Controlling the pressure of the introduced inert gas to control the slow outflow of the solution at a low speed, taking out the membrane after about 20 min, and drying at 60 ℃ for 1 h to obtain MnO₂@ ZIF-8/PES catalytic membrane.

（3）MnO₂The specific implementation steps of the test of the catalytic performance of the @ ZIF-8/PES catalytic membrane are as follows: injecting 30 mL of 74 mg/L liquid formaldehyde into a syringe, and making the initial solution pass through a syringe filled with MnO under the drive of a medical injection pump₂The membrane component of the @ ZIF-8/PES catalytic membrane can be used for measuring the spectrophotometry of a downstream solution, the degradation rate of formaldehyde can be calculated, and the injection speed can be adjusted by a medical injection pump.

(4) The results of catalytic experiments show that the catalyst is subjected to MnO₂After the @ ZIF-8/PES catalytic membrane is degraded at 85 ℃, the concentration of formaldehyde is reduced from 74 mg/L to 0.22 mg/L, the degradation rate reaches more than 99%, and good catalytic activity is shown.

Reference to the literature

[1] L. Jiao, Y. Wang, H.L. Jiang, Q. Xu, Metal-Organic Frameworks as Platforms for Catalytic Applications, Adv. Mater., 30 (2018) e1703663.

[2] J. Lee, O.K. Farha, J. Roberts, K.A. Scheidt, S.T. Nguyen, J.T. Hupp, Metal-organic framework materials as catalysts, Chem. Soc. Rev., 38 (2009) 1450-1459.

[3] R. Chen, Y. Jiang, W. Xing, W. Jin, Fabrication and Catalytic Properties of Palladium Nanoparticles Deposited on a Silanized Asymmetric Ceramic Support, Ind. Eng. Chem. Res., 50 (2011) 4405-4411.

[4] N. Li, G. Chen, J. Zhao, B. Yan, Z. Cheng, L. Meng, V. Chen, Self-cleaning PDA/ZIF-67@PP membrane for dye wastewater remediation with peroxymonosulfate and visible light activation, J. Membrane Sci., 591 (2019) 117341.

[5] R. Xie, F. Luo, L. Zhang, S.F. Guo, Z. Liu, X.J. Ju, W. Wang, L.Y. Chu, A Novel Thermoresponsive Catalytic Membrane with Multiscale Pores Prepared via Vapor-Induced Phase Separation, Small, 14 (2018) e1703650。

Claims

1. A method for preparing a nano metal-organic framework (MOFs) catalytic membrane is characterized in that the preparation of the catalytic membrane comprises the following steps:

(1) loading a metal precursor in a pore channel in the porous base membrane, percolating the precursor with a certain concentration from one side of the membrane to the other side of the membrane by adopting a percolation method, and taking out the membrane for drying after the percolation is finished;

(2) introducing an organic ligand into the pore channel inside the porous base membrane, and assembling and synthesizing the nano metal-organic framework material membrane: infiltrating an organic ligand with a certain concentration from one side of the membrane to the other side of the membrane loaded with the metal precursor by adopting a percolation method, and synthesizing the metal precursor and the organic ligand into a metal organic-framework material in a membrane hole;

2. The precursor and the organic ligand with certain concentration according to claim 1, wherein the concentration and the solvent type of the precursor and the organic ligand can be selected according to the concentration and the solvent type of the solution in the conventional MOFs preparation method, and the prepared MOFs include, but are not limited to IRMOF series materials, MIL series materials, ZIF series materials, UiO series materials, and the like; and the forms of the precursor and the organic ligand can be selected to be gas phase or liquid phase according to the reaction characteristics.

3. The porous basement membrane according to claim 1, wherein the size of the MOFs prepared can be adjusted and controlled according to the pore size of the selected porous basement membrane, and the porous basement membrane includes, but is not limited to, Polyethersulfone (PES), Polytetrafluoroethylene (PTFE), Polyamide (PA), ceramic membrane, and the like.

4. Percolation introducing precursor and organic ligands according to claim 1, characterised in that the MOFs immobilization within the catalytic film can be controlled by controlling the number of percolates of precursor and organic ligands.

5. The percolation induced precursor and organic ligand of claim 1, wherein the percolation rate of the fluid can be controlled by controlling the amount of pushing force on both sides of the basement membrane: when the fluid flow rate is too fast, the driving force is reduced to prevent the fluid from staying for too short time to lead precursor ions or organic ligands not to be introduced into the film; increasing the pushing force when the fluid flow rate is too slow prevents the fluid from failing to seep due to too much resistance of the basement membrane.

6. The driving force across the basement membrane of claim 5, including, but not limited to, pressure difference across the basement membrane, concentration difference, electric field, and the like.

7. The method of claim 1, wherein the metal nanoparticles or metal oxide nanoparticles having catalytic activity are introduced into the nano-MOFs catalytic membrane by percolation, wherein metal ions are introduced into the nano-MOFs catalytic membrane from a metal salt solution with a certain concentration by the percolation method, and the nano-MOFs catalytic membrane modified by the metal oxide nanoparticles is obtained after drying; then, a reducing agent solution with a certain concentration is introduced into the seepage flow to reduce the metal oxide into a metal simple substance, and the metal simple substance is dried to prepare the nano MOFs catalytic film modified by the metal nano particles.

8. The concentrated metal salt solution and reducing agent solution of claim 7, wherein the metal salt solution and solution concentration are selected with reference to the solution concentration in conventional metal particle or metal oxide particle preparation methods, and the prepared metal nanoparticles or metal oxides include, but are not limited to, Au, Ag, Cu, Fe, Zn, Mn, CuO, ZnO, MnO₂，TiO₂And the solid loading of the metal nanoparticles and the metal oxide nanoparticles in the nano MOFs catalytic film can be controlled by controlling the seepage times of the metal salt solution and the reducing agent solution.

9. The percolation induced metal nanoparticles and metal oxide nanoparticles of claim 7, wherein the flow rate of the solution can be controlled by controlling the magnitude of the pushing force across the membrane: when the solution flow rate is too high, the driving force is reduced to prevent the solution from staying for too short to cause no metal ions to be introduced into the membrane or insufficient reduction; when the flow rate of the solution is too slow, the pushing force is increased to prevent the solution from being incapable of seepage due to too large resistance of the basement membrane.

10. The driving force across the membrane of claim 9 including, but not limited to, pressure differential across the membrane, concentration differential, electric field, and the like.