KR101571622B1 - Method of preparation for mof membrane by electrospray deposition, membrane by using the same, and apparatus thereof - Google Patents

Abstract

The present invention relates to a method for manufacturing a MOF separation membrane by electrostatic spray deposition, a separation membrane manufactured by the method, and an apparatus therefor, and more particularly, to a method for forming a MOF separation membrane by electrostatic spray deposition, Moving the injected fine droplet through a thermal gradient zone to evaporate a portion of the solvent; And depositing and dispersing the fine droplets transferred through the thermal gradient region on the surface of the substrate, wherein the surface temperature of the substrate is at least the boiling point of the solvent, and the MOF separator Lt; / RTI > The method of the present invention is an electrostatic spraying method for producing ultrafine droplets by charging static electricity. Due to the nature of electrostatic spraying, the synthesis time and the consumption of the precursor can be drastically reduced, and the process is simple, It is also easy.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a MOF separator by electrostatic spray deposition,

The present invention relates to a process for producing an MOF separation membrane by electrostatic spray deposition, a separation membrane produced thereby, and an apparatus therefor.

BACKGROUND ART Metal organic frameworks (MOFs) are relatively new hybrid organic-inorganic materials, which are microporous crystal materials consisting of metal atoms or metal clusters and organic linkages connecting them via coordination bonds.

The pore size and physical / chemical properties of this material can be easily controlled by selection of suitable metal atoms and organic linkages. Because of this particular nature, the potential applications for gas storage and / or absorption, catalysis, and separation membranes have been demonstrated.

Zeolitic-imidazolate frameworks (ZIFs) are sub-concepts of metal organic structures and consist of metal nodes (usually zinc or cobalt) connected to an imidazolate (or imidazolate derivative) ligand . The metal-bond-metal bond angle (ca. 145 °) of ZIFs is close to the Si-O-Si bond angle found in many zeolites. ZIFs have been noted for their excellent thermal and chemical stability along with ultrafine porosity. Because of these properties, ZIFs are considered as potential candidates in the manufacture of high performance molecular sieve membranes.

ZIF-7 is of particular interest in the potential use of hydrogen separation due to its pore structure.

Because ZIF-7 is composed of zinc cations and benzimidazolate (bim) anions interconnected, forming a sodalite structure (SOD) with a pore size of about 0.3 nm, ZIF the pore size of -7 is molecular hydrogen (H ₂ (0.29㎚) and carbon dioxide (in the range between the size of the _{CO 2 (0.33㎚)), ZIF} -7 separator, minutes of high hydrogen and carbon dioxide molecules through the sieve effect It is expected that the degree of selectivity can be achieved.

The MOF separation membrane can be manufactured by various methods. As can be understood from the non-patent reference 1, the prior art is related to the above-mentioned prior art document in the specification of the present invention, ), Large in-situ method ( in situ method) and secondary (seeded growth method).

Conventional techniques for the in-situ method can be understood with reference to Non-Patent Documents 2 to 3 below. Thus, the non-patent documents 2 to 3 are the prior art documents in the specification of the present invention, and their contents are entirely incorporated. In Non-Patent Documents 2 and 3, ZIF-7 and ZIF-8 separation membranes were synthesized on an alumina support of disc type, respectively, by in-situ method.

Conventional techniques for the secondary growth method can be understood with reference to Non-Patent Documents 4 to 9 below. Thus, Non-Patent Documents 4 to 9 are related art documents in the specification of the present invention, and their contents are all incorporated. The secondary growth method is a method in which a seeding step such as a conventional dip coating is performed before the solvent thermal growth step even though the ZIF-7 and ZIF-8 membranes show a defect-free and uniform structure And can exhibit low reproducibility.

 M. Shah, M.C. McCarthy, S. Sachdeva, A.K. Lee, H.-K. Jeong, Current Status of Metal-Organic Framework Membranes for Gas Separations: Promises and Challenges, Ind. Eng. Chem. Res., 51 (2012) 2179-2199.  S.-J. Noh, S.P. Yoon, J. Han, S. Park, J. Kim, Synthesis and characterization of ZIF-7 membranes by in situ method, Journal of Nanoscience and Nanotechnology, (2013) in press.  M. Shah, H.T. Kwon, V. Tran, S. Sachdeva, H.-K. Jeong, One step in situ synthesis of supported zeolitic imidazolate framework ZIF-8 membranes: Role of sodium formate, Microporous and Mesoporous Materials, 165 (2013) 63-69.  Y. Li, F. Liang, H. Bux, W. Yang, J. Caro, Zeolitic imidazolate framework ZIF-7 based molecular sieve membrane for hydrogen separation, Journal of Membrane Science, 354 (2010) 48-54.  Y.S. Li, H. Bux, A. Feldhoff, G.L. Li, W.S. Yang, J. Caro, Controllable synthesis of metal-organic frameworks: From MOF nanorods to oriented MOF membranes, Advanced Materials, 22 (2010) 3322-3326.  Y.S. Li, F.Y. Liang, H. Bux, A. Feldhoff, W.S. Yang, J. Caro, Molecular sieve membrane: supported metal-organic framework with high hydrogen selectivity, Angewandte Chemie, 122 (2010) 558-561.  M.C. McCarthy, V. Varela-Guerrero, G.V. Barnett, H.-K. Jeong, Synthesis of zeolitic imidazolate framework films and membranes with controlled microstructures, Langmuir, 26 (2010) 1463614641.  H. Bux, A. Feldhoff, J. Cravillon, M. Wiebcke, Y.-S. Li, J. Caro, Oriented Zeolitic Imidazolate Framework-8 Membrane with Sharp H2 / C3H8 Molecular Sieve Separation, Chemistry of Materials, 23 (2011) 2262-2269.  M.N. Shah, M.A. Gonzalez, M.C. McCarthy, H.-K. Jeong, An Unconventional Rapid Synthesis of High Performance Metal-Organic Framework Membranes, Langmuir, 29 (2013) 7896-7902.

In order to obtain a MOF film and a separation membrane which are uniform and unbound, both of the conventional in-situ method and the secondary growth method are required to be at least several hours.

Therefore, the present invention proposes a novel method capable of producing defect-free and uniform MOF membranes at normal pressure and in a relatively short time.

The present invention has been made to solve the problems of the prior art,

Forming a charged precursor microdroplet comprising a solvent and injecting it;

Moving the injected fine droplet through a thermal gradient zone to evaporate a portion of the solvent; And

And depositing and crystallizing the fine droplets transferred through the thermal gradient region on the surface of the substrate,

Wherein the surface temperature of the substrate is not lower than the boiling point of the solvent. The present invention also provides a method for producing a crystalline MOF separation membrane by electrostatic spray deposition.

Further, in the production method of the present invention, it is preferable that the thermal diffusivity is a linear or non-linear continuous gradient within the range of 2 to 5 DEG C / mm gradually increasing from the time of fine droplet jetting to the surface of the substrate surface. ≪ / RTI >

Also, in the production method of the present invention, the solvent includes DMF and methanol.

Further, in the production method of the present invention, the injection form of the charged fine droplets is a conjugate.

Also, in the manufacturing method of the present invention, the step of forming a charged precursor fine droplet including the solvent and spraying the precursor droplet may include spraying the precursor solution through the metal capillary to which the voltage is applied. .

Further, in the manufacturing method of the present invention, the metal capillary has an inner diameter within a range of 0.1 to 1 mm.

Also, in the manufacturing method of the present invention, the voltage applied to the metal capillary is in the range of 5 to 12 kV.

Further, in the manufacturing method of the present invention, the distance that the injected fine droplet travels through the thermal gradient region is 1 to 10 cm.

Also, in the production method of the present invention, the fine droplets are injected at a flow rate within a range of 0.5 to 2 ml / h.

Further, in the production method of the present invention, the substrate is at least one selected from porous Al ₂ O ₃ , ZrO ₂ , TiO ₂ , and SiO ₂ .

In the production method of the present invention, the substrate is heated to a temperature within the range of 160 to 200 ° C when the solvent is DMF and heated to within a range of 70 to 80 ° C when the solvent is methanol. to provide.

In the manufacturing method of the present invention, the MOF separation membrane is a ZIF-7 or ZIF-8 separation membrane.

Also, a MOF separation membrane produced by the production method of the present invention is provided.

A capillary to which a high voltage is applied to form a charged droplet by electrostatic repulsive force while spraying a precursor comprising a solvent; And

Wherein the charged fine droplet is deposited and deposited on the surface by applying electricity of an opposite polarity to electricity applied to the capillary,

And the surface temperature of the substrate is not lower than the boiling point of the solvent.

The method of the present invention is an electrostatic spraying method for producing ultrafine droplets by charging static electricity. Due to the nature of electrostatic spraying, the synthesis time and the consumption of the precursor can be drastically reduced, and the process is simple, It is also easy.

1 is a schematic view showing an apparatus for a manufacturing method of the present invention.
FIG. 2 is a photograph showing various types of spray (spray) patterns according to the applied voltage under a supply flow rate of 1.5 ml / h ((a) dripping pattern at 5-8 kV, (b) In the form of multi-jet at 13-15 kV).
FIG. 3 is an SEM image of the ZIF-7 membrane obtained by electrostatic spray deposition under various temperatures ((a) 200 ° C., (b) 180 ° C., and (c) 160 ° C.).
4A is an XRD pattern of a ZIF-7 membrane at 200 DEG C, 180 DEG C, and 160 DEG C. Fig.
4B is an XRD pattern of a ZIF-8 membrane synthesized at 70 ° C.
Figure 5a is an SEM image of a ZIF-7 membrane (0.2 ml, (b) 0.3 ml, (c) 0.5 ml) by electrostatic spray deposition under various volumes of precursor solution.
FIG. 5B is a SEM photograph of the surface and cross section of the ZIF-8 membrane synthesized at 70 ° C. ((a) is a surface photograph).
6 is a graph showing the relationship between the volume of the precursor solution at 160 캜 and the thickness of the ZIF-7 separator.

The present invention is a research result of the basic research program of the Korean National Research Foundation under the Ministry of Education, Science and Technology of the Republic of Korea (2013R1A2A2A01014540).

The Specification The term "MOF" Acronym stands for Metal organic frameworks (MOFs) and includes zeolitic-imidazolate frameworks (ZIFs).

According to an aspect of the present invention,

Forming a charged precursor microdroplet comprising a solvent and injecting it;

Moving the injected fine droplet through a thermal gradient zone to evaporate a portion of the solvent; And

And depositing and dispersing the fine droplets transferred through the thermal gradient region on the surface of the substrate,

And the surface temperature of the substrate is not lower than the boiling point of the solvent. The present invention also relates to a method for producing an MOF separation membrane by electrostatic spray deposition.

Conventional heat-solvent-based in situ and secondary applications require at least several hours of process time in a closed autoclave to produce a well-intergrown, well-intergrown crystalline MOF layer, , MOF membranes with similar thicknesses can be produced by the electrostatic spray deposition method of the present invention within a much shorter time (< 20 min) under atmospheric pressure.

Although MOF crystals can be prepared by the thermal solvent method on DMF (Dimethylformamide) in an autoclave at a temperature equal to the temperature of the membrane deposition of the present invention, at least several hours , It is presumed that the main driving force is evaporation rather than the thermal effect, as in the case of separation membrane production, as is deduced from the fact that the deposition time magnitude for the separation membrane is 10 minutes or less.

The key to the process of continuously obtaining a MOF separator while controlling the rate of evaporation is achieved by optimization of the substrate temperature (deposition temperature), thereby forming a MOF separator with well-mutually-grown microstructure without defects.

In particular, in the present invention, the solvent includes DMF. In this case, the substrate is preferably heated to a temperature within the range of 160 to 200 ° C.

If too high a temperature (> T _b of DMF), most of the solvent of the electrostatically sprayed droplets will evaporate as it moves onto the substrate surface, so individual crystals will be deposited rather than forming a continuous layer. In the opposite case (&lt; Tb of DMF), the precursor solution will simply wet the substrate surface and penetrate into the pores of the substrate without forming sufficient crystals.

Figure 3 shows the topmost surface of the deposited separator at various temperatures. The membranes deposited at 180 占 폚 and 200 占 폚 exhibit discontinuous planes covered with individual crystals as expected, exhibiting exceptional diffraction peaks in the form of XRD not belonging to ZIF-7 (Fig. 4). This is presumably due to the decomposition of the precursor caused by the high deposition temperature.

On the other hand, the separator prepared at 160 ° C shows a continuous, defect-free and well-mutually grown crystal surface as well as a crystal phase of ZIF-7 accurately from XRD results.

That is, the temperature is close to the boiling point (153 ° C) of DMF, and the evaporation rate of the droplet is balanced with the crystal generation and growth, thereby enabling formation of a continuous separation membrane without defects.

Accordingly, it is preferable that the tear film has a linear or non-linear continuous gradient within the range of 2 to 5 占 폚 / mm, which gradually increases from the fine droplet jetting point to the surface of the substrate surface.

The injection form of the charged fine droplets is preferably a convey jet.

Depending on the fluid properties (e.g. electrical conductivity of the solvent, dielectric constant, viscosity) and other parameters (e.g. electrical potential applied to the capillary, geometry of the capillary, flow rate of the solution) , Largely dripping, cone-jet, and multi-jet types.

Of these forms, the condet form is preferred for coating purposes because it can completely cover the surface of the substrate by forming a uniform and circular deposition area compared to other forms. As mentioned above, since there are too many variables affecting the spray shape, the optimization process is simplified by fixing the properties of the fluid (concentration of the solvent and the precursor) and the area of the capillary, and the final conduction type is the electrical potential (Voltage) of 5 to 15 kV, and the precursor flow rate of 0.5 to 2 mL / h.

Figure 2 shows an observed photograph of the spray pattern obtained under various operating conditions. That is, for a given flow rate, the shape is gradually changed in the order of dripping, cusp, and multi-jet as the voltage is increased.

Also, for a fixed voltage, the shape of the droplet is mainly observed at low flow rates, while the shape of the mullet is generated at high flow rates. As a result, the inventors of the present application have found that various combinations of flow rates and voltages are tested several times to find that the optimum conditions for forming a stable conduction type are a supply rate of 1.5 mL / h and a voltage of 12 kV.

The manufacturing method of the present invention can easily adjust the thickness of the MOF separator by adjusting the thickness of the MOF membrane by simply increasing the electrostatic spray volume. For example, by increasing the electrostatic spray volume from 0.2 ml to 0.5 ml, the thickness of the MOF separator can be increased linearly from 4 to 22 占 퐉.

According to another aspect of the present invention,

And is a MOF separation membrane produced by the manufacturing method of the present invention described above.

The separator of the present invention has a special microstructure as compared with that produced by the conventional in situ process.

Figure 5 shows a cross section of a ZIF-7 membrane deposited at 160 캜 by electrostatic sprayed volume change of the precursor solution.

The separator of the present invention is composed of small grains with an unclear facet, which probably appears to be dynamically freeze due to the rapid formation rate.

Another distinguishing feature of the inventive separator is the substantial growth of MOF crystals within the substrate, such as the cross section of the ZIF-7 separator in Fig.

Since the droplet ejected by the method of the present invention still contains the solvent in the droplet, the ejected droplet is impinged after impacting on the substrate, which aids in the layer formation range on the substrate (due to the penetration effect, As shown, the membrane thickness increases somewhat slowly from the initial stage of deposition until the electrostatic spray volume reaches 0.2 ml, but once the alumina-based voids are filled with crystals, the membrane thickness Increasing proportionally as a function of deposition time).

Also, the portion of the separation membrane grown inside the substrate is beneficial in achieving excellent mechanical strength of the separation membrane, despite the sacrifice of gas flux due to the reduced effective separation area.

Furthermore, the membranes under the optimized conditions exhibit a remarkable improvement in H ₂ permeability (approximately 3 to 20 times higher than conventional known ZIF-7 membranes). It is believed that this is due to the deposition temperature of 160 [deg.] C above the general boiling point of DMF, which leads to a simultaneous activation step during the deposition of the ZIF-7 separator. More specific details thereof will be understood with reference to the following Examples and Experimental Examples.

According to another aspect of the present invention,

A capillary to which electricity is applied to form a charged droplet by electrostatic repulsive force while spraying a precursor comprising a solvent; And

Wherein the charged fine droplet is deposited and deposited on the surface by applying electricity of an opposite polarity to electricity applied to the capillary,

And the surface temperature of the substrate is not less than the boiling point of the solvent.

Hereinafter, the present invention will be described in more detail with reference to examples. It is to be understood that the following embodiments are for the purpose of illustration only and are not intended to limit the scope of the present invention.

Example

Example  One - ZIF -7 Preparation of Membrane

[Preparation of Precursor Solution]

6.12 g of zinc nitrate hydrate (Zn (NO ₃ ) ₂ .H ₂ O), 98% Sigma-Aldrich) was added to 80 ml of dimethylformamide (HCON (CH ₃ ) ₂ , 99.8%, Sigma-Aldrich; DMF) Lt; / RTI &gt;

At the same time, sodium formate (HCOONa, 99%, Sigma- Aldrich) 0.6g and benzimidazole _{(C 7 H 6 N 2,} 98%, Sigma-Aldrich) in dimethylformamide _{(HCON (CH 3) 2,} 99.8 %, Sigma-Aldrich; DMF) for 30 minutes.

After the two solutions prepared above were mixed for 30 minutes, the mixed solution was prepared as an electrostatic atomization precursor solution.

The molar ratio of the final precursor solution was Zn ^{2 +} / bim / sodium formate / DMF = 1: 1.33: 0.5: 101.

[Electrostatic spray deposition]

1 is a schematic view showing an apparatus for a manufacturing method of the present invention.

Alumina substrate (diameter: 20 mm, thickness: 2 mm, average pore diameter: 0.12 m, porosity: 40%) was heated to a set temperature in the range of 160 to 200 占 폚 prior to the start of electrostatic spray deposition.

The precursor solution was supplied at a flow rate of 0.5 to 2 mL / h by a syringe pump through a metal capillary (22G, internal diameter = 0.413 mm) to which a high electrical potential was applied.

The voltage applied to the capillary was varied from 5 to 12 kV.

The distance between the capillary tip and the substrate was about 4 cm to allow the spray area to completely cover the substrate surface.

The sprayed volume of the precursor solution varied between 0.05 and 0.5 ml depending on the thickness of the separator.

After the raising, the separator was cooled to room temperature at a cooling rate of 1 占 폚 / min in order to reduce the thermal stress that would form a crack due to the difference in thermal expansion coefficient between the a-alumina substrate and the ZIF-7 separator.

The ZIF-7 membrane prepared above was activated by solvent substitution to remove bulk DMF molecules trapped inside the pores of the ZIF-7 structure. The ZIF-7 membrane was immersed in methanol for 1 hour. Thereafter, it was slowly dried overnight at 45 캜 under saturated conditions.

Example  2 - ZIF -8 Preparation of Membrane

[Preparation of Precursor Solution]

A solution of 0.60 g of zinc nitrate hexahydrate (ZnNO ₃ .6H ₂ O, 98%, Sigma-Aldrich) in 10 mL of methanol and 0.24 g of 2-methylimidazole (C ₄ H ₆ N _{2 ,} 99%, Sigma-Aldrich ) And 0.136 g of sodium formate (HCOONa, 99%, Sigma-Aldrich) in 10 mL of methanol are stirred for 30 minutes at room temperature. The two solutions were then mixed and stirred for 20 minutes to prepare a precursor solution for electrostatic spraying.

[Electrostatic spray deposition]

The precursor solution was injected into the nozzle at a flow rate of 0.7 mL / h using a syringe pump. The voltage applied to the nozzle was 8 kV. The distance between the nozzle tip and the support was maintained at 2 cm. The substrate was porous alumina And ZIF-8 membranes were synthesized by performing electrostatic spray deposition basically in the same manner as in Example 1, except that the substrate was heated to about 70 ° C.

Experimental Example  - Evaluation of membrane property

The ZIF-7 and ZIF-8 membranes prepared in Examples 1 and 2 were characterized by XRD, FE-SEM, and single gas permeation tests.

Crystalline identification

To confirm the crystal phase, XRD (M18XHF-SRA, Mac Science, Japan). The results were as shown in Figs. 4A and 4B.

Membrane shape and thickness measurement

The shape and thickness of the ZIF-7 membrane prepared in Example 1 were observed using a field emission scanning electron microscope (Leo-Supra 55, Carl Zeiss STM, Germany). The result was as shown in Fig.

On the other hand, the surface and the cross-section of the ZIF-8 membrane prepared in Example 2 were as shown in the SEM photograph shown in Fig. 5B.

Measurement of membrane gas permeability

The gas permeability through the separator was measured using a single gas permeation method of 25, 50, and 75 ° C that were directly manufactured.

The gas flow was measured using a soap-bubble flowmeter.

The inlet pressure was 17 psia and the outlet pressure was atmospheric, or 14.6 psia.

The gas i permeance F _i of the separation membrane is defined by the following equation (1).

Where Ni is the molar flow rate of the gas i (mol / s), Pi is the separation membrane permeation pressure difference of gas i, and A is the separation membrane area (m 2). The ideal selectivity was calculated as the ratio of H ₂ and CO ₂ single gas permeability.

The results are shown in Table 1 below. Table 1 below shows the H ₂ permeability and selectivity performance over H ₂ / CO ₂ comparing the membrane of the example with the other ZIF-7 membrane.

As can be seen from Table 1, the embodiment of the separation membrane is a very much increased ^{1.34X10 -6 mol / m 2 · s} · Pa (25 ℃) Fig (Knudsen or more H ₂ / CO ₂ of 9.5, selection with H ₂ permeability separation factor of H ₂ / CO ₂ , 4.7). This is a result of the molecular sieve effect by the pore size of 0.3 nm of ZIF-7 located between the kinetic diameter of H ₂ of 0.29 nm and the kinetic diameter of CO ₂ of 0.33 nm.

During the separation experiment, the clear boundary between the two gas molecules seems to have probably not been observed, probably due to the flexibility of the ZIF structure (most probably the flip movement of the ligand), as reported previously in the prior art.

The permeability and the selectivity over H ₂ / CO ₂ of the ZIF-8 membrane prepared in Example 2 were as shown in Table 2 below.

As described above, by the electrostatic spraying, a defect-free and well-grown crystalline MOF separator can be produced on porous a-alumina substrate in a simple and time-efficient manner under normal pressure.

The thickness of the MOF separator (in the case of ZIF-7) could be adjusted to 2 to 22 탆, respectively, by adjusting the amount of the precursor solution to be electrostatically sprayed to 0.05 to 0.5 ml.

In particular, the MOF separator (in the case of ZIF-7) has a very high H ₂ / CO ₂ selectivity of more than 9.5 with a 1.34 × 10 ^-6 mol / m 2 · s · Pa (25 ° C.) H ₂ permeability factor of H ₂ / CO ₂ , 4.7). This is almost 3 to 30 times higher than conventional ZIF-7 membranes.

Considering particular properties, such as the dramatic reduction of production time and precursor consumption, simplification of the activation process, and potential expansion, the present invention provides specific opportunities for commercial applications of ZIF separators.

Claims (14)

Forming a charged precursor microdroplet comprising a solvent and injecting it;
Moving the injected fine droplet through a thermal gradient zone to evaporate a portion of the solvent; And
Depositing and crystallizing the fine droplets transferred through the thermal gradient region on the substrate surface to form a MOF separation membrane,
The surface temperature of the substrate is determined by the boiling point of the solvent. When the solvent is DMF, it is heated to a temperature within the range of 160 to 200 ° C. When the solvent is methanol,
Wherein the MOF separation membrane is a ZIF-7 or ZIF-8 separation membrane. The method according to claim 1, wherein the tropospheric line is a linear or non-linear continuous gradient within a range of 2 to 5 占 폚 / mm gradually increasing from the time of fine droplet jetting to the surface of the substrate. The method according to claim 1, wherein the solvent comprises DMF and methanol. The method for producing a MOF separation membrane according to claim 1, wherein the injection form of the charged fine droplets is a condensate. The method of claim 1, wherein forming the charged precursor microdroplets comprising the solvent and spraying the precursor microdroplets comprises spraying a precursor solution through the metal capillary to which the voltage is applied. [6] The method according to claim 5, wherein the metal capillary has an inner diameter within a range of 0.1 to 1 mm. The method of claim 5, wherein the voltage applied to the metal capillary is in the range of 5 to 12 kV. [2] The method of claim 1, wherein the injected fine droplets travel through the heat gradient zone at a distance of 1 to 10 cm. The method according to claim 1, wherein the fine droplets are injected at a flow rate within a range of 0.5 to 2 ml / h. The method according to claim 1, wherein the substrate is at least one selected from porous Al ₂ O ₃ , ZrO ₂ , TiO ₂ , and SiO ₂ . delete delete A MOF membrane produced by the method of claim 1. A capillary to which electricity is applied to form a charged droplet by electrostatic repulsive force while spraying a precursor comprising a solvent; And
And a substrate to which an electric charge of an opposite polarity to electricity applied to the capillary is applied to cause the charged fine droplet to be deposited and dispersed to form a MOF separator on the surface,
The surface temperature of the substrate is determined by the boiling point of the solvent. When the solvent is DMF, it is heated to a temperature within the range of 160 to 200 ° C. When the solvent is methanol,
Wherein the MOF separation membrane is a ZIF-7 or ZIF-8 separation membrane.

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