A mixed matrix membrane for efficient ion separation and a method of making the same

Abstract

The application provides a mixed matrix membrane for efficient ion separation and a preparation method thereof, and belongs to the technical field of separation membranes.The application mixes an aluminum salt and sodium hydroxide in an organic solvent, then adds a heterocyclic organic ligand containing nitrogen to obtain a MOF precursor solution; adds polyimide into the MOF precursor solution to obtain a casting solution; pours the casting solution into a mold and performs vacuum heating, then performs peeling, soaks in ethanol, and then performs drying to obtain the mixed matrix membrane for efficient ion separation.The application realizes uniform dispersion of MOF-303 in the whole matrix by controlling the MOF loading, and constructs continuous ion channels by the uniformly dispersed MOF-303 crystal structure, so that the selectivity of the membrane to monovalent ions is further improved.The operation is simple, and the cost is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of separation membranes, in particular to a mixed matrix membrane for efficient ion separation and a preparation method thereof. BACKGROUND

[0002] The application of separation membranes in ion sieving is a key research and development field supported by China. The sieving of monovalent ions by separation membranes plays an irreplaceable role in the fields of seawater desalination and potassium therapy. Metal-organic frameworks (MOFs) have great application potential in ion sieving due to their uniform and tunable pore structures, which can form ordered sub-nanometer channels. Mixed matrix membranes are a kind of composite membrane materials that combine inorganic nanofillers (such as metal-organic framework materials MOFs, porous organic frameworks COFs, graphene oxide GO, etc.) with polymer matrices. This membrane structure combines the flexibility of polymers and the high selectivity of inorganic fillers, showing excellent separation performance and broad application prospects. In the field of ion separation, mixed matrix membranes can significantly improve the selective transport and separation efficiency of ions by optimizing the type, structure and distribution of fillers. MOF-based mixed matrix membranes have the combined advantages of solution processability of polymer matrices and target ability of nano-porous crystals, and as a feasible nanofluidic platform, however, it is still a great challenge to make mixed matrix membranes have both high selectivity and high permeability for ions. This is mainly because the dispersibility and continuity of MOF fillers can greatly affect the performance of mixed matrix membranes, limiting the separation performance of the membranes. Moreover, the differences in the physical and chemical properties of organic polymer matrices and inorganic fillers (such as MOFs and nanoparticles) can lead to interface defects (such as voids and cracks), reducing the integrity and selectivity of the membranes. The preparation process is complex and costly, and requires precise control of filler dispersion, interface modification and film formation conditions (such as solvent evaporation rate), which is complex and difficult to scale up.

[0003] Therefore, how to obtain a separation membrane with excellent separation performance and a simple preparation method is a technical problem to be solved at present. SUMMARY

[0004] The purpose of the present application is to provide a mixed matrix membrane for efficient ion separation and a preparation method thereof, to solve the above technical problems.

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

[0006] The present application provides a preparation method of a mixed matrix membrane for efficient ion separation, comprising the following steps:

[0007] 1) Mix aluminum salt and sodium hydroxide in an organic solvent, perform first stirring, then add nitrogen-containing heterocyclic organic ligand, perform second stirring, to obtain MOF precursor solution;

[0008] 2) adding polyimide into the MOF precursor solution, stirring for the third time and ultrasonic treatment, to obtain a casting solution;

[0009] 3) vacuum heating by pouring the casting solution into a mold, soaking in ethanol after peeling, and then drying to obtain a mixed matrix membrane for efficient ion separation.

[0010] Further, the aluminum salt comprises aluminum chloride; the nitrogen-containing heterocyclic organic ligand comprises pyrazole dicarboxylic acid.

[0011] Further, the organic solvent comprises dimethylformamide.

[0012] Further, the mass ratio of the aluminum salt, the nitrogen-containing heterocyclic organic ligand and sodium hydroxide is 2-4:2-3:1.

[0013] The mass ratio of the polyimide and sodium hydroxide is 0.1-0.8:1.

[0014] Further, the rotation speed of the first stirring is 40-60 r / min, and the first stirring time is 1-1.5 h.

[0015] Further, the rotation speed of the second stirring is 30-50 r / min, and the second stirring time is 15-25 min.

[0016] The rotation speed of the third stirring is 40-50 r / min, and the third stirring time is 1-3 h.

[0017] Further, the frequency of the ultrasonic treatment is 60-100 kHz, and the ultrasonic treatment time is 20-40 min.

[0018] Further, the vacuum heating temperature is 90-110 DEG C, and the vacuum heating time is 0.5-2 h; the drying temperature is 50-70 DEG C, and the drying time is 30-50 min.

[0019] The application further provides a mixed matrix membrane for efficient ion separation, wherein the loading amount of MOF in the mixed matrix membrane for efficient ion separation is 9-40%.

[0020] The application has the following beneficial effects:

[0021] The mixed matrix membrane for efficient ion separation has the advantages that MOF-303 is uniformly dispersed in a polyimide matrix by a flow casting method, and ion channels are formed through the upper surface and the lower surface of the mixed matrix membrane by in-situ growth, and the mixed matrix membrane has high selectivity for monovalent ions.

[0022] The technical scheme of the application comprises three stirring operations and one ultrasonic operation in sequence, wherein stirring is performed each time a reagent is added to the reaction system, so that the reaction system is more uniform. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 SEM images of the surface, the cross section and the bottom surface of MOF-303 / PI-X mixed matrix membranes with different MOF-303 loadings;

[0024] Figure 2 XRD patterns of pure PI membranes and MOF-303 / PI-X mixed matrix membranes with different MOF-303 loadings;

[0025] Figure 3 FT-IR patterns of pure PI membranes and MOF-303 / PI-X mixed matrix membranes with different MOF-303 loadings;

[0026] Figure 4 I-V curves of MOF-303 / PI-X mixed matrix membranes with different MOF-303 loadings;

[0027] Figure 5 Ion conductivity and ion selectivity curves of MOF-303 / PI-X mixed matrix membranes with different MOF-303 loadings;

[0028] Figure 6 I-V curves of MOF-303 / PI-2 membranes prepared in Example 2 under different voltages, (a) 0.1 V, (b) 0.4 V, (c) 1.5 V, (d) 1 V, (e) 2 V;

[0029] Figure 7is a plot of (a) ion conductivity and (b) ion selectivity of the MOF-303 / PI-2 membrane prepared in Example 2 of the present application at different voltages;

[0030] Figure 8 is a plot of I-V curves of the MOF-303 / PI-2 membrane prepared in Example 2 of the present application at different effective test diameters: (a) Φ 2 cm, (b) Φ 4 cm, (c) Φ 6 cm;

[0031] Figure 9 is a plot of (a) ion conductivity and (b) ion selectivity of the MOF-303 / PI-2 membrane prepared in Example 2 of the present application at different effective test diameters;

[0032] Figure 10 is a schematic diagram of the H-type electrolytic cell used in the present application. DETAILED DESCRIPTION

[0033] The present application provides a preparation method of a mixed matrix membrane for efficient ion separation, comprising the following steps:

[0034] 1) mixing an aluminum salt and sodium hydroxide in an organic solvent, performing first stirring, then adding a nitrogen-containing heterocyclic organic ligand, performing second stirring, to obtain a MOF precursor solution;

[0035] 2) adding a polyimide to the MOF precursor solution, performing third stirring and ultrasonic treatment, to obtain a casting solution;

[0036] 3) pouring the casting solution into a mold and vacuum heating, then peeling off and soaking in ethanol, and then drying to obtain a mixed matrix membrane for efficient ion separation.

[0037] In the present application, the mixed matrix membrane for efficient ion separation is denoted as MOF-303 / PI-X membrane.

[0038] In the present application, the aluminum salt is preferably aluminum chloride; and the nitrogen-containing heterocyclic organic ligand is preferably pyrazole dicarboxylic acid.

[0039] In the present application, the organic solvent is preferably dimethylformamide.

[0040] In the present application, the mass ratio of the aluminum salt, the nitrogen-containing heterocyclic organic ligand and sodium hydroxide is 2-4:2-3:1, preferably 3:2.2:1.

[0041] The mass ratio of the polyimide and sodium hydroxide is 0.1-0.8:1, preferably 0.175-0.7:1, and further preferably 0.35-0.6:1.

[0042] In the present application, the polyimide is preferably in the form of a powder.

[0043] In the present application, the rotation speed of the first stirring is 40-60 r / min, preferably 50 r / min; the time of the first stirring is 1-1.5 h, preferably 1 h.

[0044] In the present application, the rotation speed of the second stirring is 30-50 r / min, preferably 40 r / min; the time of the second stirring is 15-25 min, preferably 20 min.

[0045] The rotation speed of the third stirring is 40-50 r / min, preferably 50 r / min; the time of the third stirring is 1-3 h, preferably 2 h.

[0046] In the present application, the stirring mode in the preparation method is carried out by cantilever electric mixer at room temperature.

[0047] In the present application, the mold is preferably a polytetrafluoroethylene mold; the mode of peeling the film from the mold is preferably peeling by soaking the mold in deionized water; the mode of ethanol soaking is preferably soaking three times, each time for 5 min.

[0048] In the present application, the frequency of the ultrasonic treatment is 60-100 kHz, preferably 80 kHz; the time of the ultrasonic treatment is 20-40 min, preferably 30 min.

[0049] Further, the temperature of the vacuum heating is 90-110℃, preferably 100℃; the time of the vacuum heating is 0.5-2 h, preferably 1 h; the temperature of the drying is 50-70℃, preferably 60℃; the time of the drying is 30-50 min, preferably 40 min.

[0050] In the present application, there are three times of stirring and once of ultrasonic treatment in the above preparation method in sequence, which aims to make the reaction system uniformly dispersed; the purpose of using the film casting method in step 3) is to make MOF-303 more uniformly dispersed, and after film formation, the ion channels formed by MOF-303 can be continuously distributed on the substrate; the effect of soaking the mold in deionized water in step 3) is easy to peel the film, and soaking in ethanol three times is used to remove unreacted ligands and impurities that are not easy to volatilize.

[0051] The application aims to provide a polyimide-based mixed matrix membrane with a through-type MOF-303 ion channel and a preparation method thereof, and solve the problems in the prior art that the dispersion of the MOF filler in the substrate is poor, the MOF cannot construct a continuous ion channel in the substrate, the separation performance of the separation membrane for monovalent ions is poor, and the interface compatibility of the filler and the matrix is poor, resulting in defects at the interface; and the unique in-situ heat-assisted flow casting method of polytetrafluoroethylene mold is simple to operate, low in cost, and greatly reduces the difficulty of film formation.

[0052] The application also provides a mixed matrix membrane for efficient ion separation, wherein the loading amount of the MOF in the mixed matrix membrane for efficient ion separation is 9-40%, preferably 10-30%, and further preferably 17.54%.

[0053] In the application, the mixed matrix membrane for efficient ion separation can be used for the screening of monovalent ions.

[0054] The technical solutions provided by the application are described in detail below in combination with examples, but they should not be understood as limitations on the protection scope of the application.

[0055] Example 1

[0056] Step 1): 0.03625 g of aluminum chloride hexahydrate (AlCl3·6H2O) and 0.012 g of sodium hydroxide (NaOH) were dissolved in 7 ml of dimethylformamide (DMF), stirred at a speed of 50 r / min for 1 h at room temperature, and then 0.0262 g of pyrazole dicarboxylic acid (PZDC) was added and stirred at a speed of 40 r / min for 20 min at room temperature to make it uniformly dispersed, to obtain a MOF precursor solution.

[0057] Step 2): 0.7 g of polyimide (PI) powder was added to the MOF precursor solution, stirred at a speed of 50 r / min for 2 h at room temperature, and then ultrasonically treated at a frequency of 80 kHz for 30 min to eliminate air bubbles, to obtain a uniformly dispersed casting solution.

[0058] Step 3): The casting solution was poured into a polytetrafluoroethylene mold, the mold was placed in a vacuum oven, heated at 100℃ for 1 h, naturally cooled to room temperature, then the mold was immersed in deionized water, the film was peeled off from the mold and immersed in ethanol for three times, each time for 5 min, and then vacuum dried at 60℃ for 40 min, to obtain a MOF-303 / PI-1 film with a MOF loading amount of 9.61%.

[0059] Example 2

[0060] Step 1): 0.0725 g of aluminum chloride hexahydrate (AlCl3·6H2O) and 0.024 g of sodium hydroxide (NaOH) were dissolved in 7 ml of dimethylformamide (DMF), stirred at a speed of 50 r / min for 1 h at room temperature, and then 0.0524 g of pyrazole dicarboxylic acid (PZDC) was added and uniformly dispersed by stirring at a speed of 40 r / min for 20 min at room temperature to obtain a MOF precursor solution.

[0061] Step 2): 0.7 g of polyimide (PI) powder was added to the MOF precursor solution, stirred at a speed of 50 r / min for 2 h at room temperature, and then ultrasonic treatment was performed at a frequency of 80 kHz for 30 min to eliminate bubbles to obtain a uniformly dispersed casting solution.

[0062] Step 3): The casting solution was poured into a polytetrafluoroethylene mold, the mold was placed in a vacuum oven, heated at 100°C for 1 h, naturally cooled to room temperature, then the mold was immersed in deionized water, the film was peeled off from the mold and immersed in ethanol for three times, each for 5 min, and then vacuum dried at 60°C for 40 min to obtain a MOF-303 / PI-2 film with a MOF loading amount of 17.54%.

[0063] Example 3

[0064] Step 1): 0.0725 g of aluminum chloride hexahydrate (AlCl3·6H2O) and 0.024 g of sodium hydroxide (NaOH) were dissolved in 7 ml of dimethylformamide (DMF), stirred at a speed of 50 r / min for 1 h at room temperature, and then 0.0524 g of pyrazole dicarboxylic acid (PZDC) was added and uniformly dispersed by stirring at a speed of 40 r / min for 20 min at room temperature to obtain a MOF precursor solution.

[0065] Step 2): 0.7 g of polyimide (PI) powder was added to the MOF precursor solution, stirred at a speed of 50 r / min for 2 h at room temperature, and then ultrasonic treatment was performed at a frequency of 80 kHz for 30 min to eliminate bubbles to obtain a uniformly dispersed casting solution.

[0066] Step 3): The casting solution was poured into a polytetrafluoroethylene mold, the mold was placed in a vacuum oven, heated at 100°C for 1 h, naturally cooled to room temperature, then the mold was immersed in deionized water, the film was peeled off from the mold and immersed in ethanol for three times, each for 5 min, and then vacuum dried at 60°C for 40 min to obtain a MOF-303 / PI-2 film with a MOF loading amount of 17.54%.

[0067] Example 4

[0068] Step 1): 0.02175 g of aluminum chloride hexahydrate (AlCl3·6H2O) and 0.072 g of sodium hydroxide (NaOH) were dissolved in 7 ml of dimethylformamide (DMF), stirred at a speed of 50 r / min for 1 h at room temperature, and then 0.1572 g of pyrazole dicarboxylic acid (PZDC) was added and uniformly dispersed by stirring at a speed of 40 r / min for 20 min at room temperature to obtain a MOF precursor solution.

[0069] Step 2): 0.7 g of polyimide (PI) powder was added to the MOF precursor solution, stirred at a speed of 50 r / min for 2 h at room temperature, and then ultrasonically treated at a frequency of 80 kHz for 30 min to eliminate air bubbles, to obtain a uniformly dispersed casting solution.

[0070] Step 3): The casting solution was poured into a polytetrafluoroethylene mold, the mold was placed in a vacuum oven, heated at 100℃ for 1 h, naturally cooled to room temperature, then immersed in deionized water, the film was peeled off from the mold and immersed in ethanol for three times, each time for 5 min, and then vacuum dried at 60℃ for 40 min to obtain a MOF-303 / PI-4 film with a MOF loading of 38.95%.

[0071] The MOF loading in each of the above examples refers to the percentage of the mass of MOF-303 in the total mass of the MOF-303 / PI-X film.

[0072] Test Example:

[0073] The ion transport test of the single solution of the present application was tested under an electrochemical workstation, the prepared film was sealed in the middle of a silica gel gasket with a diameter of 4 mm, then clamped in the center of an H-type electrolytic cell, and a transmembrane voltage was applied through an Ag / AgCl electrode. In order to study the ion transmembrane transport behavior of the film in different salt solutions, 5 ml of 0.1M of the same salt solution was added to the chambers on both sides of the H-type electrolytic cell, including KCl, NaCl, LiCl and MgCl2. The working electrode and the counter electrode were placed on both sides, and the two electrodes were as close to the film surface as possible to reduce the solution resistance. By recording the ion current in the potential scanning process generated by the ion transmembrane transport, the selectivity of the cation was studied. Once the measurement series of different cations is completed, the cell is thoroughly washed with deionized water to remove residual salt. Repeat this process until the film shows the conductivity characteristics of pure deionized water. After cleaning, the film is stored in pure deionized water and then measured with other cations.

[0074] Table 1 Ion separation performance of MOF-303 / PI-X mixed matrix membranes with different loadings

[0075]

[0076]

[0077] Table 1 shows the K values ​​of the MOF-303 / PI-X films prepared in Examples 1-4. + Comparison of permeation flux and selectivity for different ions. Table 1 shows that the MOF-303 / PI-X membranes prepared according to this invention, with MOF loading controlled at 15%-30%, exhibit both high selectivity and high permeability. The MOF-303 / PI-2 membrane prepared in Example 2 with a MOF loading of 17.54% shows extremely high selectivity for monovalent ions. For conductivity and selectivity data and error ranges of MOF-303 / PI-X membranes with different MOF loadings, please refer to [reference needed]. Figure 5 .

[0078] As shown in the data from Example 1, when the MOF loading is low, the membrane separation performance is poor because the MOF cannot construct continuous ion channels in the substrate. As shown in the data from Examples 3 and 4, the separation performance decreases with a higher MOF loading, which is attributed to the aggregation of the packing material leading to a decline in membrane performance. This invention further tests the MOF-303 / PI-2 membrane prepared in Example 2 with a MOF loading of 17.54%, and its separation performance under different voltages and effective test diameters is as follows: Figure 7 and Figure 9 As shown.

[0079] (1) SEM morphology analysis. For example... Figure 1 As shown, with increasing MOF content, more and more MOF-303 particles are exposed on the membrane surface, while the bottom exhibits a loose and porous structure. This asymmetric structure arises from solidification and solvent evaporation during phase transformation. The dense MOF layer on the membrane surface serves as the primary separation layer, mainly used for selective filtration of target valence ions, while the porous bottom layer acts as a support layer, providing mechanical strength and offering more open channels for ions passing through the selective layer, thus accelerating the rapid transport of target ions. Notably, in the cross-sectional view, we observed a unique structure unlike other mixed matrix membranes. In the portion between the surface selective layer and the bottom support layer, we observed more MOF-303 particles. Compared to the membrane surface, the MOF particles in this portion are smaller, reaching the nanometer scale, and are more numerous and uniformly distributed. This portion can serve as a second selective layer, performing secondary sieving of interfering ions when the surface selective layer fails to sieve them.

[0080] (2) XRD analysis. For example... Figure 2As shown, compared with the simulated standard XRD pattern of MOF-303, the characteristic diffraction peaks of MOF-303 appeared in the mixed matrix films with different contents. This proves that MOF-303 crystals were successfully synthesized during the in-situ growth process and can exist stably in the mixed matrix film, further confirming the chemical stability of MOF-303. With the increase of loading, the intensity of the MOF characteristic diffraction peaks of the mixed matrix film gradually increased.

[0081] (3) FT-IR analysis. For example... Figure 3 As shown, characteristic peaks of PI were found in mixed matrix membranes with different contents, such as at 1778 cm⁻¹. -1 The characteristic absorption peak of the asymmetric stretching vibration of C=O appears at 1720 cm⁻¹. -1 A characteristic absorption peak for the symmetrical stretching vibration of C=O appears at 1376 cm⁻¹. -1 The absorption peak at 725 cm⁻¹ is a characteristic absorption peak of the C=N stretching vibration of the imide group. -1 The absorption peak at the point is attributed to the out-of-plane bending vibration absorption of the CNC in the imide group. Due to the low MOF loading, the characteristic absorption peak intensity of MOF-303 in the mixed matrix membrane is also weak. Overall, the results indicate that due to the good compatibility between the filler (MOF-303) and the matrix (PI), in-situ growth of MOF in the matrix does not affect or destroy the structure of PI.

[0082] (4) Analysis of ion separation performance of MOF-303 / PI-X mixed matrix membranes with different MOF-303 loadings. For example... Figure 4 and Figure 5 As shown, the slope of the IV curve increases with increasing MOF-303 loading, and its slope corresponds to the ionic conductivity. For the tested membrane, a larger slope indicates a faster ion transmembrane rate. MOF-303 / PI-2 exhibits the highest ion selectivity, K... + / Mg 2+ The ion selectivity can reach 15.65, but as the MOF-303 loading continues to increase, the ion selectivity decreases sharply. These results indicate that adding an appropriate amount of MOF-303 can simultaneously improve ion permeability and selectivity. However, at higher loadings, the aggregation of MOF-303 particles creates non-selective ion transport pathways in the membrane, thereby reducing ion selectivity.

[0083] (5) Analysis of the ion separation performance of the MOF-303 / PI-2 membrane prepared in Example 2 of this invention under different voltages. For example... Figure 6 and Figure 7As shown, the ion current increases significantly with the increase of the voltage bias. This is because the increase of the applied voltage directly leads to the increase of the ion current, and may enhance the electric field strength, thus accelerating the migration rate of ions. Excessive bias voltage may cause a certain degree of damage to the mixed matrix membrane and form a larger leakage current. Therefore, the ion selectivity decreases sharply after ±0.4V, K + / Mg 2+ decreases from 15.65 to 5.07. These results all show that appropriate applied voltage is conducive to ion separation, and excessive voltage has a certain negative effect on the ion selectivity of the mixed matrix membrane.

[0084] (6) Analysis of ion separation performance of the MOF-303 / PI-2 membrane prepared in Example 2 of the present application under different effective test diameters. As shown in Figure 8 and Figure 9 shown, the current of all ions gradually increases with the increase of the effective test diameter, because the increase of the effective area of the membrane increases the path of ions entering the membrane channel, and the ion flux also increases accordingly. By calculating the ion conductance under different effective diameters, we can see that all ions correspondingly show an increasing trend, and the K+ conductance of the mixed matrix membrane with a test diameter of 6mm reaches 8.22μs, which is about 4.7 times larger than that of the mixed matrix membrane with a test diameter of 2mm, and for Na + , Li + and Mg 2+ , also increases by a similar proportion. It is worth noting that the ion selectivity of the three effective test diameters hardly changes, which shows that the surface of the prepared MOF-303 / PI-2 mixed matrix membrane is uniform and has no defects, and the size of the effective test diameter will not have a negative effect on the ion selectivity.

[0085] From the above examples, the present application provides a mixed matrix membrane for efficient ion separation and a preparation method thereof. The mixed matrix membrane for efficient ion separation provided by the present application has the advantages that the MOF-303 is uniformly dispersed in the polyimide matrix by the flow casting method, and the ion channels penetrating the upper surface and the lower surface of the mixed matrix membrane are formed in situ, and has high selectivity for monovalent ions. The present application realizes the uniform dispersion of MOF-303 in the whole substrate by controlling the MOF loading amount, and constructs a continuous ion channel from the uniformly dispersed MOF-303 crystal structure, further improving the selectivity of the membrane to monovalent ions. The method of the present application is simple to operate and has low cost.

[0086] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and refinements can be made without departing from the principles of the present application, and these improvements and refinements should also be considered as falling within the protection scope of the present application.

Claims

1. A method for the preparation of a mixed matrix membrane for efficient ion separation, characterized in that, The method comprises the following steps: 1) mixing an aluminum salt and sodium hydroxide in an organic solvent, performing first stirring, then adding a nitrogen-containing heterocyclic organic ligand, performing second stirring, to obtain a MOF precursor solution; 2) adding a polyimide to the MOF precursor solution, performing third stirring and ultrasonic treatment, to obtain a casting solution; 3) pouring the casting solution into a mold and vacuum heating, then soaking in ethanol after peeling, and then drying to obtain a mixed matrix membrane for efficient ion separation; The nitrogen-containing heterocyclic organic ligand comprises a pyrazole dicarboxylic acid; The mass ratio of the aluminum salt, the nitrogen-containing heterocyclic organic ligand and sodium hydroxide is 2-4:2-3:1; The mass ratio of the polyimide and sodium hydroxide is 0.1-0.8:1; The loading amount of the MOF in the mixed matrix membrane for efficient ion separation is 9-40%; the aluminum salt comprises aluminum chloride; and the organic solvent comprises dimethylformamide. The first stirring time is 1-1.5 h, the second stirring time is 15-25 min, and the third stirring time is 1-3 h. The loading amount of the MOF is the percentage of the mass of MOF-303 in the total mass of the mixed matrix membrane.

2. The production method according to claim 1, characterized by, The first stirring speed is 40-60 r / min.

3. The preparation method according to claim 2, characterized in that, The second stirring speed is 30-50 r / min, and the third stirring speed is 40-50 r / min.

4. The production method according to claim 1 or 3, characterized by, The ultrasonic treatment frequency is 60-100 kHz, and the ultrasonic treatment time is 20-40 min.

5. The preparation method according to claim 4, characterized in that, The vacuum heating temperature is 90-110℃, and the vacuum heating time is 0.5-2 h; the drying temperature is 50-70℃, and the drying time is 30-50 min.

6. The mixed matrix membrane for efficient ion separation produced by the production method according to any one of claims 1 to 5, characterized in that, The loading amount of the MOF in the mixed matrix membrane for efficient ion separation is 9-40%, and the loading amount of the MOF is the percentage of the mass of MOF-303 in the total mass of the mixed matrix membrane.

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