Porous metal complex-containing film, detection element having same, and method for producing porous metal complex-containing film

Abstract

Provided are: a porous metal complex-containing film which can be produced by a simple process, has a high yield during production, and has high sensitivity when used as a detection element; a detection element comprising the film; and a method for producing the porous metal complex-containing film. The porous metal complex-containing film includes a filter having voids therein and having light transmittance and air permeability, and a porous metal complex fixed to the voids, the porous metal complex containing a metal ion and an organic ligand coordinately bonded to the metal ion. The porous metal complex has a volume-based median diameter of 0.1 [mu] m or more and 3 [mu] m or less.

Description

Technical Field

[0001] The present disclosure relates to a porous metal complex-containing membrane, a detection element having the porous metal complex-containing membrane, and a method for producing the porous metal complex-containing membrane. Background Art

[0002] Porous metal complexes (also referred to as porous metal organic frameworks, metal organic structures, metal organic frameworks, etc., and sometimes referred to as MOFs hereinafter) are polymeric metal complexes in which metal ions are cross-linked by organic ligands.

[0003] In Japanese Patent Application Publication No. 2017-512891 (Patent Document 1), a porous membrane containing a porous metal organic framework material (MOF), a composition for modulating the membrane, and a method for using the same are disclosed. The porous membrane contains: a material containing at least one at least bidentate organic compound coordinated with at least one metal ion as 51% to 99.9% of the total mass of the membrane as at least one porous metal organic framework material; at least one fibrillated fluoropolymer accounting for 0.1% to 49% of the total mass of the membrane; and an additive component accounting for 0% to 48.9% of the total mass of the membrane. As a method of using the membrane, a method of using it as a sensor, a conductive membrane, a storage or separation device is disclosed. For example, a commercially available porous metal complex and a fluoropolymer powder are mixed to obtain a powder mixture, and then, in order to fibrillate the fluoropolymer contained in the powder mixture, a pestle is used for processing, and the obtained putty-like block is subjected to a calendering process to be thin-filmed, thereby manufacturing the membrane.

[0004] Japanese Patent Application Publication No. 2019-163228 (Patent Document 2) discloses a metal organic structure (MOF), a phosphor film, and a molecular detection device. The MOF is a metal organic structure that emits fluorescence and is deformed by interacting with target molecules. It has a layered pillar structure and contains metal ions, a tetradentate ligand bonded to the metal ions, and a bidentate ligand bonded to the metal ions. The layered pillar structure refers to a structure having a plurality of two-dimensional layered structures formed by metal ions and first ligands having carboxyl groups, and the layered structures are cross-linked by second ligands having pyridyl, imidazole or amino groups to form a three-dimensional structure. The MOF emits fluorescence excited by light from a light source and is deformed by interacting with target molecules as guest molecules. The emission spectrum of the fluorescence of the MOF changes according to the above deformation. Patent Document 2 discloses the use of the above phenomenon to construct molecular detection devices such as VOC sensors and explosive sensors. In addition, the layered pillar structure achieves high-sensitivity detection of target molecules.

[0005] In Japanese Patent Publication No. 2020-32325 (Patent Document 3), a selective gas permeation membrane having a metal organic structure (MOF) layer and a method for making the same are disclosed. In the selective gas permeation membrane, the gas permeation membrane is tightly arranged on both sides of the metal organic structure (MOF) particle layer having gas selectivity. In Patent Document 3, Cu(bim)2 is exemplified as a MOF capable of selectively separating and recovering CO2 from a CH4 / CO2 mixed gas. As a method for synthesizing Cu(bim)2 particles, it is disclosed that 30 mg of terephthalic acid and 30 mg of copper (II) nitrate trihydrate are added to a mixture of 4 ml of dimethylformamide and 4 ml of acetonitrile while stirring, and then placed in a thermostatic bath and allowed to stand at 40°C for 24 hours, and then centrifuged to obtain 50 mg of Cu(bim)2 particles with an average particle size of approximately 100 nm.

[0006] (Prior art literature)

[0007] (Patent Document)

[0008] Patent Document 1: Japanese Patent Application No. 2017-512891

[0009] Patent Document 2: Japanese Patent Application Publication No. 2019-163228

[0010] Patent Document 3: Japanese Patent Application Laid-Open No. 2020-32325 Summary of the Invention

[0011] (Problems to be solved by the invention)

[0012] The porous membrane disclosed in Patent Document 1 may be damaged by the shear stress in the fibrillation process, thereby causing the particle size distribution to broaden and the crystallinity to decrease. In addition, during beating in the fibrillation process, fine powder of the porous metal complex may enter the gaps between the fluoropolymer and the porous metal complex and block the gaps. Therefore, when the porous membrane is used as a sensor, highly sensitive detection cannot be performed.

[0013] The molecular detection device disclosed in Patent Document 2 uses multiple MOFs having a pillared structure with multiple two-dimensional layered structures, which complicates the process involved in molecular detection and may prevent stable and highly sensitive detection.

[0014] In the case of forming a MOF particle layer as in the selective gas permeation membrane disclosed in Patent Document 3, there is a method of synthesizing MOF particles and then performing centrifugal separation to obtain MOF particles. However, as shown in the synthesis method of Cu(bim)2 particles (MOF particles) disclosed in Patent Document 3, it requires crystal growth processes, centrifugal separation processes, etc., and the overall process is complicated, resulting in a low yield.

[0015] In view of the above-mentioned prior art, it is necessary to provide a highly sensitive porous metal complex-containing membrane that can be manufactured through simple processes with high yield and a method for manufacturing the same. Furthermore, it is necessary to provide a detection element using such a porous metal complex-containing membrane.

[0016] The present disclosure is proposed in view of the above situation, and its purpose is to provide a porous metal complex-containing membrane that can be manufactured through simple processes, has a high yield during manufacturing, and has high sensitivity when used as a detection element, a detection element having the porous metal complex-containing membrane, and a method for manufacturing a porous metal complex-containing membrane.

[0017] (Measures taken to resolve the problem)

[0018] The porous metal complex-containing membrane according to the present disclosure for achieving the above-mentioned object comprises:

[0019] a filter having voids therein and being light-transmitting and air-permeable; and

[0020] a porous metal complex fixed in the voids,

[0021] The porous metal complex contains a metal ion and an organic ligand coordinated with the metal ion.

[0022] The porous metal complex has a volume-based median diameter of 0.1 μm or more and 3 μm or less.

[0023] The detection element of the present disclosure for achieving the above-mentioned object has:

[0024] The porous metal complex described above contains a membrane.

[0025] The method for producing a porous metal complex-containing membrane according to the present disclosure for achieving the above-mentioned object is the method for producing a porous metal complex-containing membrane described above, comprising:

[0026] a solution preparation step of mixing a first polar solvent, the organic ligand, and a metal salt to prepare a precursor solution of the porous metal complex;

[0027] an impregnation step of impregnating the filter with the precursor solution to obtain a precursor impregnated membrane;

[0028] an intermediate drying step of drying the precursor impregnated membrane to obtain a precipitated membrane; and

[0029] A washing step is performed in which the precipitated film is washed with a second polar solvent to obtain a washed film.

[0030] (Effects of the Invention)

[0031] According to the present disclosure, a porous metal complex-containing membrane that can be manufactured through simple processes, has a high manufacturing yield, and has high sensitivity when used as a detection element, a detection element having the porous metal complex-containing membrane, and a method for manufacturing the porous metal complex-containing membrane can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is an explanatory diagram of a device for measuring trace water concentration using the porous metal complex-containing membrane according to this embodiment as a detection element.

[0033] Figure 2 It is a bar graph showing the product yield of Examples and Comparative Examples. DETAILED DESCRIPTION

[0034] The porous metal complex-containing membrane, the detection element having the porous metal complex-containing membrane, and the method for producing the porous metal complex-containing membrane according to the present embodiment will be described with reference to the drawings.

[0035] First, the porous metal complex-containing membrane, the detection element having the porous metal complex-containing membrane, and the method for producing the porous metal complex-containing membrane according to the present embodiment will be briefly described.

[0036] The porous metal complex-containing membrane according to this embodiment includes: a filter having internal voids and being both light-transmissive and air-permeable; and a porous metal complex fixed within the voids. The porous metal complex contains metal ions and organic ligands coordinated with the metal ions. The porous metal complex has a volume-based median particle size of 0.1 μm or greater and 3 μm or less.

[0037] The detection element according to this embodiment includes the porous metal complex-containing membrane according to this embodiment.

[0038] As an example, the porous metal complex-containing membrane can be produced by the following production method. Specifically, the production method of the porous metal complex-containing membrane according to this embodiment includes: a solution preparation step of mixing a first polar solvent, an organic ligand, and a metal salt to prepare a precursor solution of the porous metal complex; an impregnation (impregnation) step of impregnating a filter with the precursor solution to obtain a precursor impregnated (impregnated) membrane; an intermediate drying step of drying the precursor impregnated membrane to obtain a precipitated membrane; and a washing step of washing the precipitated membrane with a second polar solvent to obtain a washed membrane.

[0039] The porous metal complex-containing film according to the present embodiment can be produced through simple steps, has a high production yield, and has high detection sensitivity when used as a detection element (sensor).

[0040] Hereinafter, the porous metal complex-containing membrane, the detection element having the porous metal complex-containing membrane, and the method for producing the porous metal complex-containing membrane according to the present embodiment will be described in detail.

[0041] The porous metal complex-containing membrane according to this embodiment includes: a filter having internal voids; and a porous metal complex (MOF) immobilized in the voids. The porous metal complex-containing membrane according to this embodiment can be suitably used as a detection element for, for example, detecting water contained in gas or measuring water concentration.

[0042] The filter is a substrate for forming the porous metal complex-containing membrane according to this embodiment.

[0043] The filter has both light-transmitting and air-permeable properties. The material (material) of the filter is not particularly limited. Examples of filter materials include metal, ceramic, glass, wood, resin, paper, cloth, and the like. Cellulose fiber, glass fiber, or polytetrafluoroethylene fiber are preferred as the filter material. Polytetrafluoroethylene fiber is particularly preferred as the filter material.

[0044] The filter may be formed in a plate or membrane shape. The thickness of the filter is not particularly limited, and the filter may be formed in a thin plate shape. The thickness of the filter may be, for example, not less than 100 μm and not more than 5 mm.

[0045] As described above, the filter has internal voids. As an example, the filter can be porous. The porosity of the filter can be determined by considering the physical properties of the porous metal complex-containing membrane required when the filter is used as a substrate to form the porous metal complex-containing membrane, such as flexibility and mechanical strength. Based on volume, the porosity of the filter can be greater than 50% and less than 95%.

[0046] The microparticles of the porous metal complex to be described later are fixed to the gaps of the filter. In addition, in the present embodiment, fixing refers to that the microparticles of the porous metal complex are captured by the gaps of the filter, and when the porous metal complex contains a membrane as a detection element, the microparticles of the porous metal complex will not be separated from the state of the filter (the porous metal complex contains a membrane). As a mode for fixing the microparticles of the porous metal complex to the gaps of the filter, the microparticles of the porous metal complex are included in the situation that the microparticles of the porous metal complex do not break away from the gaps in the steric hindrance in the gaps and the microparticles of the porous metal complex are carried on the surface without gaps by attachment, adhesion or spreading, etc. In addition, the size of the gaps of the filter can be about the size that the spherical particles with a diameter of more than 10 μm cannot pass through (i.e., capture).

[0047] A porous metal complex is a polymeric metal complex obtained by cross-linking metal ions with organic ligands. A porous metal complex is a porous substance having a plurality of pores connected to the outside. In this embodiment, the porous metal complex can be a structure in which metal ions or metal atoms are continuously bonded to an organic ligand having a bidentate or higher coordination functional group. Functional molecules and additives may be contained in the pores of the porous metal complex. When functional molecules and additives are contained in the pores of the porous metal complex, it is preferable to ensure that the gaps between the pores and the outside are not blocked.

[0048] An example of a metal ion or metal atom constituting a porous metal complex is a transition metal, aluminum, and magnesium. The metal ion or metal atom constituting a porous metal complex is not limited to one type. The metal ions or metal atoms constituting a porous metal complex may be two or more types.

[0049] The metal ions constituting the porous metal complex are particularly preferably copper ions.

[0050] The functional group of the organic ligand must be able to coordinate with the metal ion or metal atom. Examples of the functional group of the organic ligand that can coordinate with the metal ion or metal atom include hydroxyl, imidazole, sulfonic acid, amino, carboxyl, and amide groups.

[0051] The organic ligand is particularly preferably benzene-1,3,5-tricarboxylic acid (1,3,5-benzenetricarboxylate in a coordinated state).

[0052] In the porous metal complex-containing film according to this embodiment, the content of the porous metal complex is preferably 0.5% to 50% by mass, more preferably 1% to 30% by mass, and even more preferably 1% to 15% by mass.

[0053] The porous metal complex has a particle size with a median particle size (particle size at 50% cumulative density, i.e., d50) of 0.1 μm or more and 3 μm or less on a volume basis. The median particle size of the porous metal complex is preferably 0.1 μm or more and 2 μm or less. The particle size of the porous metal complex can be appropriately adjusted to ensure the response intensity when the porous metal complex-containing membrane is used as a detection element and to maintain the crystallinity of the porous metal complex particles.

[0054] As an example, as described above, the porous metal complex-containing membrane according to this embodiment can be produced by a manufacturing method comprising a solution preparation step, an impregnation step, an intermediate drying step, and a cleaning step. In this manufacturing method, the solution preparation step, the impregnation step, the intermediate drying step, and the cleaning step are performed in this order. In this manufacturing method, a drying step (described later) may be performed after the cleaning step. The intermediate drying step may include a humidification step (described later).

[0055] As described above, the solution preparation step is a step of mixing a polar solvent (an example of a first polar solvent, hereinafter referred to as a first polar solvent), an organic ligand, and a metal salt to prepare a precursor solution of a porous metal complex.

[0056] The precursor solution is prepared by adding an organic ligand and a metal salt and dissolving them in a polar solvent. During dissolution, the order in which the organic ligand and the metal salt are added to the polar solvent, the order in which they are dissolved, and the order in which they are mixed are not limited. For example, the metal salt can be dissolved in the polar solvent after the organic ligand is dissolved in the polar solvent. Alternatively, the organic ligand can be dissolved in the polar solvent after the metal salt is dissolved in the polar solvent. Furthermore, a solution obtained by dissolving the organic ligand in a polar solvent and a solution obtained by dissolving the metal salt in a polar solvent can be mixed to obtain a precursor solution of a porous metal complex.

[0057] The first polar solvent is not limited as long as it can dissolve the organic ligand and the metal salt. An example of the first polar solvent is tetrahydrofuran, acetonitrile, N,N-dimethylformamide, acetone, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol. The first polar solvent is preferably an organic solvent.

[0058] In particular, when copper nitrate is used as the metal salt and 1,3,5-carboxylic acid is used as the organic ligand, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol are preferably used. In particular, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, or 2-butanol is preferably used to obtain porous metal complex crystals with a small particle size distribution (small variation in particle size).

[0059] As described above, the impregnation step is a step of impregnating the filter with the precursor solution to obtain a precursor-impregnated membrane.

[0060] The precursor impregnated membrane is produced by impregnating a filter with a precursor solution. The method for impregnating the filter with the precursor solution is not particularly limited. As an example, the precursor solution can be filled into a container, and the filter can be immersed in the precursor solution in the container to impregnate the filter with the precursor solution. Alternatively, the precursor solution can be dripped into the filter to impregnate the filter with the precursor solution. Furthermore, during the impregnation, the surrounding gas can be reduced in pressure or heated. Furthermore, during the impregnation, the pressure can be reduced while heating.

[0061] When the precursor solution has difficulty penetrating into the voids of the filter, the filter can be pre-impregnated with a polar solvent different from the precursor solution (for example, a solvent selected from the first polar solvent mentioned above, hereinafter referred to as a third polar solvent), and then the filter can be impregnated with the precursor solution.

[0062] The intermediate drying step is a step for drying the precursor impregnated membrane to precipitate the porous metal complex. The method for drying the precursor impregnated membrane in the intermediate drying step is not particularly limited. For example, the precursor impregnated membrane can be dried under reduced pressure using a vacuum dryer. Alternatively, the membrane can be dried while heating. In the intermediate drying step, the precursor impregnated membrane is preferably heated to a temperature of 40°C to 100°C. During the intermediate drying step, the porous metal complex precipitates in the voids of the filter. Hereinafter, the precursor impregnated membrane after the intermediate drying step may be referred to as a precipitated membrane.

[0063] The intermediate drying step may include a humidification step of humidifying the dried precursor impregnated membrane by exposing it to a gas containing water vapor. Hereinafter, there is a case where the precursor impregnated membrane that has been dried at least once is referred to as a pre-precipitation membrane. In addition, in the following, there is a case where the treatment of humidifying the precursor impregnated membrane by exposing it to a gas containing water vapor is simply referred to as a humidification treatment. In addition, there is a case where the precursor impregnated membrane after the humidification treatment is referred to as a humidification treatment membrane. The particle size distribution of the porous metal complex fixed in the voids of the filter may become narrower (sharper) due to the humidification step.

[0064] When the humidification treatment is performed in the intermediate drying step, it is preferable to dry the humidification treated film again to form a precipitation film (precipitation film as the humidification treated film).

[0065] In addition, when the humidification treatment is not performed in the intermediate drying step, the pre-deposition film may become the deposition film. In the case where the humidification treatment is not performed in the intermediate drying step, the pre-deposition film may be further dried to form the deposition film.

[0066] That is, the intermediate drying step is a step of drying at least the precursor impregnated membrane to obtain a precipitation membrane in which the porous metal complex is precipitated in the gaps of the filter. The intermediate drying step further preferably includes a first intermediate drying step to obtain a pre-precipitated membrane, a humidification step to humidify the pre-precipitated membrane to obtain a humidified membrane, and a second intermediate drying step to dry the humidified membrane to obtain a precipitation membrane. The intermediate drying step may omit the humidification step and include a first intermediate drying step to obtain a pre-precipitated membrane and a second intermediate drying step to further dry the pre-precipitated membrane to obtain a precipitation membrane.

[0067] The second intermediate drying step can suppress changes in the particle size of the porous metal complex in the cleaning step described later. Furthermore, the second intermediate drying step may improve the efficiency of the cleaning step described later.

[0068] The first intermediate drying step, the second intermediate drying step, and the humidifying step in the intermediate drying step will be described in detail.

[0069] The method for drying the precursor impregnated film in the first intermediate drying step is not particularly limited. For example, the precursor impregnated film can be dried under reduced pressure in a vacuum dryer. The first intermediate drying step can be performed while heating the precursor impregnated film under a flow of carrier gas. The first intermediate drying step can be performed while heating the precursor impregnated film under reduced pressure under a flow of carrier gas. In the first heating step, the precursor impregnated film is preferably heated to a temperature of 60°C or higher and 80°C or lower.

[0070] The method for further drying the pre-deposited film or the method for drying the film after the humidification treatment in the second intermediate drying step is not particularly limited. For example, the precursor impregnated film can be dried under reduced pressure in a vacuum dryer. The second intermediate drying step can be performed while heating the precursor impregnated film under a flow of carrier gas. The second intermediate drying step can be performed while heating the precursor impregnated film under reduced pressure under a flow of carrier gas. In the second intermediate drying step, the pre-deposited film or the film after the humidification treatment is preferably heated to a temperature of 40°C or higher and 100°C or lower.

[0071] In the drying of the precursor impregnated film, pre-precipitated film or humidified film in the first intermediate drying step or the second intermediate drying step in the intermediate drying step, for example, there may be: a gas supply unit such as a gas cylinder for supplying a carrier gas; a processing container such as an eggplant-shaped flask having a processing chamber for accommodating the precursor impregnated film, pre-precipitated film or humidified film and supplied with a carrier gas from the gas supply unit; a heating unit having a heater, an oil bath or other heating equipment for heating the film accommodated in the processing chamber of the processing container; and a pump unit for reducing the pressure of the internal atmosphere of the processing chamber of the processing container.

[0072] An example of a preferable carrier gas in the first intermediate drying step and the second intermediate drying step is hydrogen, nitrogen, argon, oxygen, helium, carbon dioxide, hydrocarbons, or clean dry air.

[0073] The humidification treatment in the humidification step can be performed by exposing the pre-deposited film to a gas containing water vapor adjusted to a predetermined temperature and humidity. Specifically, for example, the pre-deposited film can be placed in a container (hereinafter referred to as a humidification container) whose internal atmosphere is adjusted to a predetermined temperature and humidity, and the cleaned film can be exposed to the gas containing water vapor. Alternatively, the pre-deposited film can be placed in the humidification container and the gas containing water vapor adjusted to a predetermined temperature and humidity can be passed through the container.

[0074] The humidification process can be performed using a thermo-hygrostat equipped with a device for circulating gas within a room and a device for controlling the temperature and humidity of the gas. Alternatively, a system can be used in which a supply pipe for temperature- and humidity-controlled gas and an exhaust pipe for exhausting the gas are connected to a container capable of accommodating the cleaned membrane, with the container serving as the humidification container. The supply pipe can be equipped with a gas flow control device, a temperature regulator (e.g., an electric heater or cooling device), and a humidity regulator (e.g., a water vapor generator such as a bubbler or a gas bypass pipe). The exhaust pipe can be equipped with a water trap as needed. For example, the temperature of the humidification container can be adjusted using a water bath or oil bath.

[0075] The gas before humidification (the carrier gas for transporting the water vapor) supplied to the humidification container is not particularly limited. Examples of the gas supplied to the humidification container include hydrogen, nitrogen, argon, oxygen, helium, carbon dioxide, clean dry air, and the like. In particular, an inert gas such as nitrogen or argon is preferably used.

[0076] The flow control device can be any device capable of controlling the gas flow rate. As an example of a flow control device, a mass flow controller, a needle valve, or a diaphragm valve can be used. In the case where more precise control is required, a mass flow controller is preferably used.

[0077] The water vapor generator is not particularly limited, as long as it can generate any amount of water vapor. Examples of water vapor generators include the aforementioned bubblers and boilers. Furthermore, a bubbler is a device or apparatus that generates a gas containing water vapor by releasing (bubbling) gas into water stored in a container. To precisely control the amount of water vapor contained in the gas, the bubbler preferably can arbitrarily control the temperature of the gas used for bubbling or the water stored in the container.

[0078] The pre-deposition film is exposed to a water vapor atmosphere, i.e., the temperature of the water vapor-containing gas is preferably 30°C to 70°C. Furthermore, when relative humidity is used, the humidity of the water vapor-containing gas is preferably 20% to 70%. In the following description, humidity is described based on relative humidity. The temperature and humidity of the water vapor-containing gas are more preferably 40°C to 60°C and 30% to 70%, and further preferably 50°C to 60°C and 40% to 60%.

[0079] The time for exposing the pre-precipitated film to the gas containing water vapor is preferably 12 to 72 hours, more preferably 12 to 24 hours.

[0080] The washing step is a step of washing the deposited film with a polar solvent (an example of the second polar solvent, hereinafter referred to as the second polar solvent) to obtain a washed film.

[0081] The precipitation membrane is washed with a second polar solvent to remove the porous metal complex particles not fixed in the gaps of the filter and the raw materials of the porous metal complex (metal ions and organic ligands) that have not been crystallized.

[0082] The second polar solvent can be selected from the solvents described above as an example of the first polar solvent. The second polar solvent can be the same as or different from the solvent used as the first polar solvent. The second polar solvent is preferably ethanol, methanol, or acetone.

[0083] The precipitated film can be cleaned by immersing the precipitated film in a second polar solvent or dripping the second polar solvent into the precipitated film so that the second polar solvent flows through the precipitated film. During the cleaning of the precipitated film, the second polar solvent can be heated or heated. For example, the precipitated film can be cleaned while heating and refluxing the second polar solvent.

[0084] The particle size distribution of the porous metal complex fixed in the gaps of the filter can be determined by image analysis using a scanning electron microscope (SEM).

[0085] The particle size distribution and median diameter of the porous metal complex in this embodiment are obtained by measuring the maximum diameter of the porous metal complex crystals present in an image captured using a scanning electron microscope and determining the volume-based particle size distribution based on the maximum diameter.

[0086] In this embodiment, the yield rate of manufacturing the porous metal complex-containing membrane can be determined based on whether the porous metal complex-containing membrane can have a predetermined detection sensitivity or higher when used as a detection element. That is, in this embodiment, the yield rate of manufacturing the porous metal complex-containing membrane is the ratio of the number of porous metal complex-containing membranes having the predetermined detection sensitivity to the total number of porous metal complex-containing membranes manufactured in a batch.

[0087] One example of a device that can use the porous metal complex-containing film according to this embodiment as a detection element is a device for measuring a trace amount of water concentration in a gas.

[0088] Figure 1 An example of a device 100 for measuring trace water concentration that can use the porous metal complex-containing membrane according to this embodiment as a detection element is shown. Figure 1 , the measuring unit 1 of the measuring device 100 is shown as a schematic cross-sectional structure in order to explain the internal structure.

[0089] The measurement unit 1 is composed of three metal blocks: a central block 7 forming a sample gas path C through which the sample gas G to be measured flows; a light source side block 5 arranged on one side of the sample gas path C; and a light receiving side block 6 arranged on the other side of the sample gas path C.

[0090] The central block 7 is provided with a sample gas inflow path C1 for introducing the sample gas G, a sample gas outflow path C2 for discharging the sample gas G, and a detection element holding portion 10 for holding the detection element 2 which is a porous metal complex-containing membrane.

[0091] The light source side block 5 has a measurement light path P with a light source 3 provided at its open end. The light receiving side block 6 has a light receiving path L with a light receiving element 4 as a light receiving portion provided at its open end. The light receiving path L is arranged on the axis relative to the measurement light path P. A convex light-transmitting member 9 and an annular packing 9A are sandwiched between the light source side block 5 and the central block 7.

[0092] A flat light-transmitting member 8 and an annular gasket 8A are sandwiched between the light-receiving side block 6 and the center block 7. The convex light-transmitting member 9 and the flat light-transmitting member 8 are both light-transmitting and air-impermeable. By disposing the annular gaskets 8A and 9A between the convex light-transmitting member 9 and the flat light-transmitting member 8 and the center block 7, airtightness is achieved that prevents the sample gas G from leaking from the sample gas path C to the outside and preventing external gas from intruding into the sample gas path C.

[0093] As an example, a light source capable of emitting measurement light with a wavelength of 200 nm to 800 nm can be used as the light source 3. The light source 3 may be an LED light source or a laser light source.

[0094] The light receiving element 4 measures the intensity of the measurement light that has passed through the detection element 2 from the sample gas path C and reached the light receiving path L, converts the intensity into a voltage signal, and outputs the voltage signal. Any light receiving element capable of measuring the intensity of the measurement light can be used as the light receiving element 4. Examples of the light receiving element 4 include a photodiode and a photomultiplier tube.

[0095] A voltage measuring unit 11 is connected to the light receiving element 4 for measuring the voltage signal output from the light receiving element 4. A calculation unit 12 is connected to the voltage measuring unit 11 for performing various calculations based on the measured voltage signal. The calculation unit 12 can calculate the temporal change in the optical characteristics of the detection element 2 based on the change in the intensity of the measurement light that has passed through the detection element 2 and reached the light receiving path L, and use this temporal change to accurately calculate the concentration of the gaseous impurity component (e.g., the water concentration).

[0096] When using the measurement device 100 to measure the concentration of gaseous impurities in the sample gas G, the sample gas inflow path C1 is connected to the upstream side of the sample gas path C through which the sample gas G flows, and the sample gas outflow path C2 is connected to the downstream side of the sample gas path C. Thus, the sample gas G flowing into the sample gas inflow path C1 from the upstream gas path is introduced into the sample gas path C, and the sample gas G that has passed through the detection element 2 is discharged from the sample gas outflow path C2 to the downstream gas path. As a result, the sample gas G is constantly flowing within the sample gas path C.

[0097] While the sample gas G is flowing, the light source 3 is operated to irradiate the sample gas path C with a predetermined intensity of measurement light from the measurement light path P via the convex light-transmitting member 9. Simultaneously, the measurement light, which has passed through the detection element 2 and the flat light-transmitting member 8, is received by the light-receiving element 4 and converted into a measurement voltage corresponding to the intensity of the received measurement light. This voltage is then output to the voltage measuring unit 11, which then outputs the voltage information to the calculation unit 12. Based on this voltage information, the calculation unit 12 outputs the gaseous impurity concentration (detection result) to a display device such as a monitor or printer (not shown). The calculation unit 12 can calculate the precise concentration of the gaseous impurity using a pre-established relationship between the intensity (voltage) of the measurement light at the light-receiving element 4 and the concentration of the gaseous impurity (e.g., water concentration).

[0098] Example

[0099] Hereinafter, the porous metal complex-containing membrane, the detection element having the porous metal complex-containing membrane, and the method for producing the porous metal complex-containing membrane according to the present embodiment will be described based on examples.

[0100] (Example 1)

[0101] First, a precursor solution was prepared as follows.

[0102] First, ethanol (grade: special reagent grade) manufactured by Kanto Chemical Co., Ltd. was weighed into a 25 mL container (made from perfluoroalkoxyalkane) as the first polar solvent. Trimesic acid (benzene-1,3,5-tricarboxylic acid) manufactured by Kanto Chemical Co., Ltd. was added and stirred to dissolve. Copper nitrate trihydrate manufactured by Kanto Chemical Co., Ltd. was then added and stirred to dissolve, thereby preparing a precursor solution. Copper nitrate trihydrate was added at a molar ratio of 1.81 between copper nitrate trihydrate and benzene-1,3,5-tricarboxylic acid. The atmosphere (environment) during mixing was 20°C and 60% relative humidity.

[0103] The filter was then cut into a desired shape and impregnated with the precursor solution. First, a 7mm-diameter punch was used to punch out a 1mm-thick, 70mm-diameter, circular polytetrafluoroethylene filter (PF100, manufactured by ADVANTEC) to obtain a 7mm-diameter circular filter. The cut filter was then impregnated with the same ethanol as the first polar solvent, serving as a third polar solvent, and then with the precursor solution, resulting in a precursor impregnated membrane.

[0104] Then, the precursor impregnated membrane was placed in a petri dish made of perfluoroalkoxyalkane and heated and dried at 80°C for 2 hours (first intermediate drying step). Then, the precursor impregnated membrane (pre-precipitated membrane) was transferred to a 100 mL glass eggplant flask. Then, the opening of the eggplant flask was sealed with a silicone stopper connected to a vacuum tube, and the vacuum tube was connected to a rotary oil pump. Then, the eggplant flask was heated to 100°C in an oil bath, and the inside of the eggplant flask was evacuated with a vacuum pump to create a vacuum, and vacuum heated for 2 hours and dried (second intermediate drying step) to obtain a precipitated membrane.

[0105] The precipitated membrane was then removed from the eggplant-shaped flask used for vacuum heating and transferred to another 100 mL eggplant-shaped flask. 20 mL of ethanol (produced by Kanto Chemical Co., Ltd.) was then added to the flask as a secondary polar solvent. The filter was then heated to 88°C in an oil bath and refluxed to clean the filter. This cleaning process was repeated three times, replacing the ethanol, to obtain a cleaned membrane. Each cleaning cycle lasted 30 minutes.

[0106] After washing, the filter was further dried in an eggplant-shaped flask set at 80° C. for 12 hours to obtain a dry film (drying step). This dry film was used as the porous metal complex-containing film according to Example 1.

[0107] The particle size distribution of the porous metal complex contained in the porous metal complex-containing membrane was determined by image observation using a scanning electron microscope. The width of the particle size distribution was found to be in the range of 0.1 μm to 2.5 μm, and the d50 was 1.0 μm. Therefore, it was found that the porous metal complex-containing membrane of this example contained a porous metal complex having fine crystals and a narrow (sharp) particle size distribution.

[0108] Then, 30 porous metal complex-containing membranes according to this example were used as detection elements for measuring gas concentration, and the detection lower limit was confirmed.

[0109] As described below, the product yield calculated based on the detection lower limit was 90%. Thus, it can be seen that the production method described in this embodiment can produce a porous metal complex-containing membrane with high detection sensitivity when used as a detection element with good reproducibility (i.e., high yield).

[0110] By using Figure 1 In the measuring device 100 shown, when the porous metal complex-containing membrane involved in this embodiment is used as a detection element 2 for detecting the trace moisture concentration in the sample gas, whether the detection element 2 has a detection sensitivity above the specified value (the detection lower limit is below the specified value) is used to determine the evaluation of the product yield.

[0111] The conditions of this evaluation test are as follows.

[0112] An LED lamp (OSB5XNE1C1E, manufactured by OptoSupply) was used as the light source 3 , and a photosensor (TSL-257, manufactured by AMS-TAOS USA) was used as the light receiving element 4 .

[0113] As the sample gas, high-purity nitrogen (water concentration <1 vppb (volume ppb)) and standard gas (base gas: nitrogen, water concentration: 10 vppm (volume ppm); manufactured by Taiyo Nippon Sanso Co., Ltd.) were used.

[0114] In the evaluation test, high-purity nitrogen gas and a gas obtained by adding a certain amount of standard gas to high-purity gas were switched at regular intervals and supplied as sample gas G to the measurement cell 1 , while the output of the water concentration detection result was observed.

[0115] When a standard gas is supplied, the absorbance of the porous metal complex, acting as a respondent, varies with the water concentration in the gas. When a peak output corresponding to the water concentration is observed, the detection limit (unit: vppb) is calculated based on the ratio of the voltage increase when switching from high-purity nitrogen to the standard gas to the noise. This detection limit is then confirmed to be below a certain value (10 vppb in this example) (above a specified detection sensitivity). The number of detection elements 2 (porous metal complex-containing membranes) with a detection sensitivity above the specified sensitivity is determined, and the yield rate is calculated based on this number. The yield rate of the porous metal complex-containing membrane in this example, thus determined, is 90%, as described above.

[0116] (Example 2)

[0117] The difference between this embodiment and Example 1 is that, in Example 1, ethanol is used as the first polar solvent, while in this embodiment, 2-propanol (reagent special grade) manufactured by Kanto Chemical Co., Ltd. is used as the first polar solvent. Other than this, the porous metal complex-containing membrane is manufactured and evaluated in the same manner as in Example 1.

[0118] The particle size distribution of the porous metal complex contained in the porous metal complex-containing membrane of this example was determined by image observation using a scanning electron microscope. The width of the particle size distribution was found to be in the range of 0.05 μm to 0.7 μm, and the d50 was 0.4 μm. Therefore, it was found that the porous metal complex-containing membrane of this example contained a porous metal complex having fine crystals and a narrow particle size distribution.

[0119] In addition, the product yield calculated based on the detection limit is as high as 78%.

[0120] (Example 3)

[0121] The difference between this embodiment and the first embodiment is that the precipitation film in the first embodiment is used as a pre-precipitation film, the pre-precipitation film is subjected to a humidification treatment (humidification process) and further subjected to vacuum heating (second intermediate drying process). Otherwise, the porous metal complex-containing film is manufactured and evaluated in the same manner as in the first embodiment.

[0122] That is, the precursor impregnation membrane manufactured in the same manner as in Example 1 is heated and dried in the same manner as in Example 1, and then the precursor impregnation membrane is vacuum-heated and dried in the same manner as in Example 1 to obtain a pre-precipitated membrane (the above is the first intermediate drying process). Then, dry argon gas is passed into a heating container filled with ultrapure water, thereby modulating the argon gas containing water vapor to a temperature of 60°C and a relative humidity of 40%, and continuously supplying it to the eggplant-shaped flask containing the pre-precipitated membrane and evacuating (decompressing) it by a vacuum pump, thereby humidifying the pre-precipitated membrane (humidification process). Then, the supply of argon gas containing water vapor is stopped, and the eggplant-shaped flask is heated to 100°C again by an oil bath, and the eggplant-shaped flask is evacuated by a vacuum pump to make it vacuum, and vacuum heating is performed for 2 hours (the second intermediate drying process) to obtain a precipitated membrane. After obtaining the precipitated membrane, a porous metal complex-containing membrane is manufactured and evaluated in the same manner as in Example 1.

[0123] The particle size distribution of the porous metal complex contained in the porous metal complex-containing membrane of this example was determined by image observation using a scanning electron microscope. The distribution width was found to be in the range of 0.1 μm to 0.5 μm, and the d50 was 0.3 μm. Therefore, it was found that the porous metal complex-containing membrane of this example contained a porous metal complex having fine crystals and a narrow particle size distribution.

[0124] In addition, the product yield calculated based on the detection limit is as high as 93%.

[0125] (Comparative Example 1)

[0126] The difference between this comparative example and Example 1 is that, in Example 1, ethanol was used as the first polar solvent and the third polar solvent, whereas in this comparative example, dimethyl sulfoxide (grade, purity: >99.5%) manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. was used as the first polar solvent, and acetone (for high performance liquid chromatography) manufactured by Kanto Chemical Co., Ltd. was used as the third polar solvent. Other than this, the porous metal complex-containing membrane was manufactured and evaluated in the same manner as in Example 1.

[0127] Scanning electron microscopic observation of the particle size distribution of the porous metal complex-containing membrane of this comparative example revealed a distribution width ranging from 0.2 μm to 11 μm, with a d50 of 3.5 μm. Therefore, it can be seen that the porous metal complex-containing membrane of this example contains a porous metal complex with larger crystals and a wider particle size distribution than those of Examples 1 and 2.

[0128] In addition, the product yield calculated based on the detection lower limit is 30%, which is lower than that of the above embodiments.

[0129] As a reference for understanding this embodiment, etc., Figure 2 A bar graph showing the product yields of Examples 1 to 3 and Comparative Example 1 is shown. Figure 2 As shown. The product yields of Example 1, Example 2 and Example 3 are significantly higher than the product yield of Comparative Example 1. In other words, according to the manufacturing method of these embodiments, a high-quality porous metal complex containing membrane as a detection element can be manufactured with high reproducibility. The reason is that in these embodiments, compared with the situation of Comparative Example 1, the particle size distribution of the porous metal complex can be narrowed and the particle size can be reduced, so that the porous metal complex containing membrane can be homogenized, thereby reducing the batch-to-batch error in the manufacturing process. In particular, in Example 3, it is possible to make the particle size distribution of the porous metal complex narrower than that of Example 1 and Example 2 while reducing the particle size, so that the porous metal complex containing membrane can be made more uniform, thereby further reducing the batch-to-batch error in the manufacturing process.

[0130] Above, as shown in each embodiment, according to the manufacture method involved in the present embodiment, the porous metal complex involved in the present embodiment can be manufactured by a simple process to contain a film. For example, when manufacturing the porous metal complex to contain a film, there is no need for a process such as centrifugation, a process for applying shear stress, a process for fibrillation, or a complex process such as using a polar organic solvent and water to synthesize crystals or to grow crystals. In addition, when the porous membrane is used as a sensor, the porous metal complex involved in the present embodiment contains a film with high sensitivity, i.e., high detection sensitivity, and high response intensity. Therefore, the porous metal complex involved in the present embodiment is very useful as a detection element.

[0131] As described above, a highly sensitive porous metal complex-containing membrane that can be produced through simple steps and has a high production yield and a method for producing the same can be provided. Furthermore, a detection element using the porous metal complex-containing membrane can be provided.

[0132] In addition, the configuration disclosed in the above-mentioned embodiment (including other embodiments, the same below) can be used in combination with the configuration disclosed in other embodiments as long as no conflict occurs. Moreover, the embodiments disclosed in this specification are examples, and the embodiments of the present disclosure are not limited thereto and can be appropriately modified within the scope of the purpose of the present disclosure.

[0133] (Industrial Applicability)

[0134] The present disclosure is applicable to a porous metal complex-containing membrane, a detection element having the porous metal complex-containing membrane, and a method for producing a porous metal complex-containing membrane.

[0135] (Explanation of Reference Numerals)

[0136] 1: measuring unit; 10: detection element holding portion; 100: measuring device;

[0137] 11: Voltage measurement unit; 12: Calculation unit; 2: Detection element; 4: Light receiving element;

[0138] 5: Light source side block; 6: Light receiving side block; 7: Central block; 8: Flat light-transmitting component;

[0139] 8A: annular gasket; 9: convex light-transmitting component; 9A: annular gasket; C: sample gas path;

[0140] C1: sample gas inflow path; C2: sample gas outflow path; G: sample gas;

[0141] L: light receiving path; P: light measuring path

Claims

1. A porous metal complex containing membrane comprising: A filter having voids inside and being light-transmitting and air-permeable; as well as a porous metal complex fixed in the voids, The porous metal complex comprises a metal ion and an organic ligand coordinated with the metal ion. The porous metal complex has a volume-based median diameter of 0.1 μm or more and 3 μm or less.

2. The porous metal complex-containing film according to claim 1, wherein The metal ion is a copper ion, The organic ligand is benzene-1,3,5-tricarboxylic acid.

3. The porous metal complex-containing film according to claim 1, wherein The filter is made of cellulose fiber, glass fiber or polytetrafluoroethylene fiber.

4. A detection element, wherein: The detection element comprises the porous metal complex-containing membrane according to any one of claims 1 to 3.

5. A method for producing a porous metal complex-containing membrane, which is the method for producing a porous metal complex-containing membrane according to any one of claims 1 to 3, comprising: a solution preparation step of mixing a first polar solvent, the organic ligand, and a metal salt to prepare a precursor solution of the porous metal complex; an impregnation step of impregnating the filter with the precursor solution to obtain a precursor impregnated membrane; An intermediate drying step of drying the precursor impregnated membrane under reduced pressure to obtain a precipitated membrane; and A washing step is performed in which the precipitated film is washed with a second polar solvent to obtain a washed film.

6. The method for producing a porous metal complex-containing film according to claim 5, wherein: The first polar solvent is methanol, ethanol, 1-propanol, 2-propanol, 1-butanol or 2-butanol.

7. The method for producing a porous metal complex-containing film according to claim 5, wherein: The metal salt is copper nitrate.

8. The method for producing a porous metal complex-containing film according to claim 5, wherein: The intermediate drying step includes a humidifying step of humidifying the precursor impregnated film.

9. The method for producing a porous metal complex-containing film according to claim 8, wherein: In the humidification step, the precursor impregnated film is exposed to a gas containing water vapor to humidify the precursor impregnated film.

10. The method for producing a porous metal complex-containing film according to claim 9, wherein: The carrier gas for transporting water vapor in the gas containing water vapor is argon, nitrogen and air.

11. The method for producing a porous metal complex-containing film according to claim 9, wherein: The temperature of the gas containing water vapor is higher than 40° C. and lower than 60° C., and the relative humidity is higher than 30% and lower than 70%.

12. The method for producing a porous metal complex-containing film according to claim 9, wherein: In the humidification step, the precursor impregnated membrane is exposed to the gas containing water vapor for a period of 12 hours to 24 hours.

13. The method for producing a porous metal complex-containing film according to claim 5, wherein: The intermediate drying process comprises: A first intermediate drying step of drying the precursor impregnated film to obtain a pre-precipitated film; a humidification step of humidifying the pre-precipitated film to obtain a humidified film; and A second intermediate drying step is performed in which the humidified film is dried to obtain the precipitated film.

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