Gas-adsorbing composite material substrate, gas sensor including the same and method for manufacturing gas-adsorbing composite material substrate

Abstract

To provide a gas-adsorbing composite material substrate capable of forming a gas sensor applicable to detection of trace amounts of VOCs (e.g., gas concentration: several tens ppm or less) and detection of gases that has not been applied previously, such as CO2 by firmly fixing a porous solid material onto a solid substrate without micropores being blocked.SOLUTION: A gas-adsorbing composite material substrate includes: a solid substrate; a thin film formed on the solid substrate, and comprising a sol-gel polycondensate of an organosilane compound having two or more trialkoxysilyl groups and having a circumscribed sphere diameter of 1 to 10 nm in a molecular structure from which a terminal alkoxy group has been eliminated; and a microporous solid material fixed on the thin film and having micropores and a BET specific surface area of 100 m2 / g or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a gas adsorbing composite material substrate, a gas sensor including the same, and a method for manufacturing a gas adsorbing composite material substrate. [Background technology]

[0002] Gas sensors using a sensitive material that adsorbs volatile organic compounds (VOCs) such as acetone have been known for some time. For example, Japanese Patent Application Laid-Open No. 2011-84487 (Patent Document 1) discloses a gas sensor in which a sensitive film made of a calixarene-based composite material, in which a calixarene derivative and polydimethylsiloxane are combined, is formed on a substrate. The sensitive film used in this gas sensor detects VOCs such as acetone by selectively adsorbing VOCs with specific functional groups, such as ketone molecules. However, the detection sensitivity of this sensor is approximately 500 ppm or higher, making it unsuitable for detecting trace amounts of gas.

[0003] Furthermore, JP 2019-537506 A (Patent Document 2) discloses a composite membrane having a mixed matrix membrane containing a gas-permeable polymer matrix and a filler such as metal-organic framework particles, zeolite particles, silica gel particles, or nanotubes that has high adsorption and selectivity for various gases. Furthermore, JP 2022-151869 A (Patent Document 3) discloses an organic-inorganic hybrid membrane containing a gas-permeable resin and a gas-selective zeolite. Although these membranes contain a filler such as zeolite that has high adsorption and selectivity for gases, they contain a gas-permeable polymer as the matrix, making them unsuitable as sensitive membranes (gas adsorption layers) for gas sensors.

[0004] On the other hand, gas sensors that detect CO2 by utilizing the infrared absorption of gas are known, but gas sensors that detect CO2 by adsorbing it onto a sensitive material were not known. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-84487 [Patent Document 2] Special Publication No. 2019-537506 [Patent Document 3] Japanese Patent Publication No. 2022-151869 Summary of the Invention [Problem to be solved by the invention]

[0006] First, the inventors focused on the high gas adsorption or selectivity of porous solid materials with micropores, such as metal-organic frameworks and zeolites. Such porous solid materials are typically powders, and their use as the sensitive film (gas adsorption layer) of a gas sensor requires immobilization on a substrate. However, the porous solid material powder alone cannot stably immobilize the material, making it difficult to stably detect the adsorbed gas. Furthermore, when immobilizing a solid powder on a substrate, a polymer or other matrix is ​​typically used. However, using a polymer or other matrix to immobilize the porous solid material powder results in the problem of blocking the micropores of the porous solid material powder. Furthermore, if the polymer used as the matrix reacts with the target gas or adsorbs gases other than the target gas, the gas sensor's performance may be impaired, making it impossible to accurately quantify trace amounts of the target gas.

[0007] The present invention has been made in view of the problems associated with the prior art described above, and has an object to provide a gas adsorbing composite material substrate in which a porous solid material is firmly fixed to a solid substrate without blocking the micropores, a gas sensor using the same, in particular a gas sensor applicable to the detection of trace amounts of VOCs (for example, gas concentrations of several tens of ppm or less) and gases not previously applicable, such as CO, and a method for manufacturing a gas adsorbing composite material substrate that can be firmly fixed to a solid substrate without blocking the micropores of the porous solid material. [Means for solving the problem]

[0008] As a result of intensive research conducted by the present inventors to achieve the above-mentioned object, they have found that by pressing a porous solid material having micropores onto a thin film made of a sol-gel polycondensation reactive composition of an organic silica compound having a plurality of polymerizable alkoxysilyl groups and a specific size, and then polycondensing the sol-gel polycondensation reactive composition, the porous solid material can be firmly fixed onto a solid substrate without blocking the micropores or being embedded in the thin film, with part of its surface exposed to the gas phase, and that the sol-gel polycondensate formed is non-porous and has low gas adsorption property, and therefore has almost no effect on the gas adsorption property of the porous solid material, thereby completing the present invention.

[0009] That is, the present invention provides the following aspects. [1] A solid substrate; a thin film formed on the solid substrate and made of a sol-gel polycondensate of an organosilane compound having two or more trialkoxysilyl groups and a circumscribed sphere of a molecular structure from which a terminal alkoxy group has been eliminated, the sphere having a diameter of 1 to 10 nm; A microporous nanofiber having a BET specific surface area of ​​100 m2 is fixed on the thin film. 2 / g or more porous solid material; A composite substrate for gas adsorption comprising: [2] The composite material substrate for gas adsorption according to [1], wherein the solid substrate is an electrode substrate of a quartz crystal microbalance. [3] The composite material substrate for gas adsorption according to [1] or [2], wherein the porous solid material is a metal-organic framework. [4] A gas sensor comprising the gas adsorption composite material substrate according to any one of [1] to [3], wherein the composite film containing the thin film made of the sol-gel polycondensate of the organosilane compound and the porous solid material is a gas adsorption layer or a sensitive film. [5] forming a thin film on a solid substrate, the thin film being made of a sol-gel polycondensation reactive composition containing an organosilane compound having two or more trialkoxysilyl groups and a circumscribed sphere of a molecular structure from which a terminal alkoxy group has been eliminated, the diameter of which is 1 to 10 nm; The thin film has micropores and a BET specific surface area of ​​100 m 2 / g or more of a porous solid material; polycondensing the sol-gel polycondensation reactive composition to immobilize the porous solid material; A method for producing a composite substrate for gas adsorption, comprising: [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a gas adsorbing composite material substrate in which a porous solid material is firmly fixed to a solid substrate without its micropores being blocked and without being buried in a thin film, with part of its surface exposed to the gas phase, and a gas sensor using the same, particularly a gas sensor applicable to the detection of trace amounts (for example, gas concentrations of several tens of ppm or less) of VOCs and the detection of gases that have not been applicable to conventional methods, such as CO2. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a graph showing the X-ray diffraction spectrum of the Mg-MOF-74 powder obtained in Synthesis Example A1. [Figure 2] 1 is a scanning electron microscope photograph of Mg-MOF-74 powder obtained in Synthesis Example A1. [Figure 3] 1 is a graph showing the nitrogen adsorption / desorption isotherm of the Mg-MOF-74 powder obtained in Synthesis Example A1. [Figure 4] 1 is a graph showing the X-ray diffraction spectrum of the ZIF-90 powder obtained in Synthesis Example A2. [Figure 5] 1 is a scanning electron microscope photograph of ZIF-90 powder obtained in Synthesis Example A2. [Figure 6] 1 is a graph showing the X-ray diffraction spectrum of the ZIF-90 powder obtained in Synthesis Example A2. [Figure 7]1 is a graph showing the solid-state 29Si MAS NMR spectrum of the Ni-d-silica thin film obtained in Synthesis Example B1. [Figure 8] FIG. 1 is a diagram showing a molecular structure model in which an alkoxy group is eliminated from NI-d-Si. [Figure 9] 1 is a scanning electron microscope photograph of the surface of the Mg-MOF-74 / NI-d-silica composite film obtained in Example 1. [Figure 10] 1 is a scanning electron microscope photograph of a cross section of the Mg-MOF-74 / NI-d-silica composite membrane obtained in Example 1. [Figure 11] 1 is a graph showing the CO2 response characteristics of a composite material substrate for QCM having an Mg-MOF-74 / NI-d-silica composite film obtained in Example 1. [Figure 12] 1 is a scanning electron microscope photograph of the surface of the ZIF-90 / NI-d-silica composite membrane obtained in Example 2. [Figure 13] 1 is a scanning electron microscope photograph of a cross section of the ZIF-90 / NI-d-silica composite membrane obtained in Example 2. [Figure 14] 1 is a graph showing the acetone gas response characteristics of a composite material substrate for QCM having a ZIF-90 / NI-d-silica composite film obtained in Example 2. [Figure 15] 1 is a graph showing an X-ray diffraction spectrum of the Mg-MOF-74 particle film obtained in Comparative Example 1. [Figure 16] 1 is a scanning electron microscope photograph of the Mg-MOF-74 particle film obtained in Comparative Example 1. [Figure 17] 1 is a graph showing the CO 2 response characteristics of a QCM substrate having an Mg-MOF-74 particle film obtained in Comparative Example 1. [Figure 18] 1 is a graph showing the X-ray diffraction spectrum of the Mg-MOF-74 / NI-d-silica (1 / 1) composite film obtained in Comparative Example 2. [Figure 19] 1 is a graph showing the nitrogen adsorption / desorption isotherm of the Mg-MOF-74 / NI-d-silica (1 / 1) composite membrane obtained in Comparative Example 2. [Figure 20]1 is a scanning electron microscope photograph of a ZIF-90 particle film obtained in Comparative Example 3. [Figure 21] 10 is a graph showing the acetone gas response characteristics of a QCM substrate having a ZIF-90 particle film obtained in Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in detail below based on preferred embodiments thereof.

[0013] [Gas adsorption composite substrate] The gas adsorption composite material substrate of the present invention comprises: a solid substrate; a thin film (cured film) formed on the solid substrate and made of a sol-gel polycondensate of an organosilane compound having two or more trialkoxysilyl groups and a circumscribed sphere of a molecular structure from which a terminal alkoxy group has been eliminated, the sphere having a diameter of 1 to 10 nm; A microporous nanofiber having a BET specific surface area of ​​100 m2 is fixed on the thin film. 2 / g or more porous solid material; It is equipped with the following.

[0014] (solid substrate) The solid substrate used in the present invention is not particularly limited, and examples thereof include a quartz substrate, a silicon substrate, an electrode substrate, a glass substrate, etc. However, as will be described later, when the gas adsorbing composite material substrate of the present invention is used as a gas sensor, preferred examples include an electrode substrate for a quartz crystal microbalance (QCM), a substrate for a stress sensor, an electrode substrate for a capacitance sensor, etc. Among these, an electrode substrate for a quartz crystal microbalance is preferred from the viewpoint of being able to detect trace amounts of gas with high sensitivity.

[0015] (thin film) The thin film used in the present invention is a non-porous cured film made of a sol-gel polycondensate of an organosilane compound having a specific structure and size. Because the thin film is made of a non-porous sol-gel polycondensate, gas components are less likely to be adsorbed onto the thin film and do not affect gas adsorption into the microporous solid material, making it possible to obtain a gas sensor capable of detecting trace amounts of gas.

[0016] The organosilane compound used in the present invention has two or more (preferably 2 to 4, more preferably 3 to 4) alkoxysilyl groups. Examples of the alkoxysilyl groups include a methoxysilyl group, an ethoxysilyl group, a propoxysilyl group, an isopropoxysilyl group, and a butoxysilyl group.

[0017] Furthermore, in the organosilane compound, the diameter of the circumscribed sphere of the molecular structure from which the terminal alkoxy groups have been eliminated is 1 to 10 nm. By using an organosilane compound of this size, when preparing a composite film containing a thin film and a porous solid material, the organosilane compound is less likely to penetrate into the micropores of the microporous material, thereby preventing blockage of the micropores by the sol-gel polycondensate of the organosilane compound. On the other hand, if the diameter of the circumscribed sphere of the molecular structure from which the terminal alkoxy groups have been eliminated is less than the lower limit, the organosilane compound is more likely to penetrate into the micropores of the microporous material during preparation of the composite film, and the micropores are more likely to be blocked by the sol-gel polycondensate of the organosilane compound. On the other hand, if the diameter of the circumscribed sphere of the molecular structure from which the terminal alkoxy groups have been eliminated exceeds the upper limit, gas adsorption between organic groups is more likely to occur in the resulting thin film made of the sol-gel polycondensate. Furthermore, from the viewpoint that blocking of micropores by the sol-gel polycondensate of the organic silane compound is easily suppressed and gas adsorption between organic groups in a thin film made of the sol-gel polycondensate is less likely to occur, the diameter of the circumscribed sphere of the molecular structure from which the terminal alkoxy groups have been eliminated is preferably 1 to 8 nm, and more preferably 2 to 5 nm.

[0018] The organic group in the organosilane compound is not particularly limited as long as the diameter of the circumscribed sphere of the molecular structure from which the terminal alkoxy groups have been eliminated falls within the above-mentioned range. Examples of the organic group include organic groups having an aromatic ring structure such as a naphthalimide ring, a triphenylamine ring, a pyrene ring, a diphenylpyrene ring, a tetraphenylpyrene ring, a perylene ring, a perylene bisimide ring, an acridone ring, a methylacridone ring, a styrylbenzene ring, a divinylbenzene ring, a fluorene ring, a quaterphenyl ring, an anthracene ring, an acridine ring, a phenylpyridine ring, a divinylpyridine ring, a porphine ring, a phthalocyanine ring, a diketopyrrolopyrrole ring, or a dithienylbenzothiazole ring, and an organic group having two or more of the aromatic ring structures is preferred.

[0019] The thin film used in the present invention is made of such a sol-gel polycondensate of an organic silane compound, and the condensation degree of the sol-gel polycondensate must be 40% or more. This suppresses the permeation of gas components into the thin film made of the sol-gel polycondensate, making it possible to form a highly sensitive gas sensor. On the other hand, if the condensation degree of the sol-gel polycondensate is below the lower limit, gas components will easily permeate into the thin film made of the sol-gel polycondensate, resulting in a deterioration in the performance of the resulting gas sensor. Furthermore, from the viewpoint of further suppressing the permeation of gas components into the thin film made of the sol-gel polycondensate, the condensation degree of the sol-gel polycondensate is preferably 45% or more. The upper limit of the condensation degree of the sol-gel polycondensate is 100%.

[0020] (Porous solid material) The porous solid material used in the present invention has micropores with a pore diameter of 2 nm or less (hereinafter also referred to as a "microporous solid material") and is preferably particulate. Porous solid materials with micropores have high gas adsorption properties and can form composite membranes with excellent gas adsorption properties. Such microporous solid materials are not particularly limited as long as they have gas adsorption properties, and examples include metal-organic frameworks (MOFs), covalent organic frameworks (COFs), zeolites, and activated carbon. These microporous solid materials may be used alone or in combination of two or more. Among these microporous solid materials, metal-organic frameworks and covalent organic frameworks are preferred from the viewpoint of easily selecting the specific surface area and the type of gas to be adsorbed by selecting the framework raw material.

[0021] The microporous solid material used in the present invention has a BET specific surface area of ​​100 m 2 / g or more. A microporous solid material having such a BET specific surface area has high gas adsorption properties and can form a composite membrane with excellent gas adsorption properties. From the viewpoint of improving the gas adsorption properties of the composite membrane, the BET specific surface area of ​​the microporous solid material is 200 m 2 / g or more is preferable, and 500m 2 The upper limit of the BET specific surface area of ​​the microporous solid material is not particularly limited, but is usually 5000 m 2 / g or less.

[0022] [Method for manufacturing a gas adsorption composite material substrate] The method for producing a gas adsorbing composite material substrate of the present invention includes the steps of: a step of forming a thin film on a solid substrate, the thin film being made of a sol-gel polycondensation reactive composition containing the organic silane compound (uncured thin film forming step); a step of pressing the microporous solid material onto the thin film (pressing step); a step (polycondensation step) of polycondensing the sol-gel polycondensation reactive composition to fix the porous solid material; By producing a composite material substrate for gas adsorption by this method, the porous solid material can be firmly fixed on the solid substrate without blocking its micropores and without being embedded in the thin film, with part of its surface exposed to the gas phase.

[0023] (Uncured thin film formation process) The uncured thin film forming step is a step of applying a sol-gel polycondensation reactive composition containing the organic silane compound onto the solid substrate to form an uncured thin film made of the sol-gel polycondensation reactive composition.

[0024] The sol-gel polycondensation reactive composition is not particularly limited as long as it contains the organosilane compound and is used in the sol-gel reaction of the organosilane compound, but is preferably an acidic or basic sol solution. Examples of such sol solutions include an alcohol solution containing an acid catalyst used in the sol-gel reaction of the organosilane compound, such as hydrochloric acid, an alcohol solution containing a basic catalyst used in the sol-gel reaction of the organosilane compound, such as ammonia, and an alcohol solution containing a strong acid, such as p-toluenesulfonic acid, and an amine. Among these sol solutions, an alcohol solution containing a strong acid and an amine is preferred from the viewpoint of easy control of curing of an uncured thin film.

[0025] The method for applying the sol-gel polycondensation reactive composition is not particularly limited, and examples thereof include spin coating, solution casting (drop casting), dip coating, and spraying.

[0026] The amount of the sol-gel polycondensation reactive composition to be applied is preferably an amount such that the thickness of the resulting thin film (cured film) made of the sol-gel polycondensate is 0.1 to 15 μm (more preferably 0.2 to 5 μm). If the thickness of the cured film is less than the lower limit, it tends to be difficult to firmly fix the microporous solid material. On the other hand, if the thickness of the cured film exceeds the upper limit, the microporous solid material tends to be buried in the cured film, and the gas adsorption properties of the resulting composite film tend to be reduced.

[0027] In the uncured thin film forming step, the formed uncured thin film may be semi-cured as needed. The semi-curing conditions (heating temperature, heating time, etc.) can be appropriately set in consideration of the complete curing conditions (heating temperature, heating time, etc.).

[0028] (Crimping process) The compression bonding step is a step of compressing the microporous solid material onto the uncured or semi-cured thin film made of the sol-gel polycondensation reactive composition produced in the uncured thin film forming step.

[0029] As a method for pressing the microporous solid material, a dispersion of the microporous solid material may be prepared, coated on the uncured or semi-cured thin film, and then pressure may be applied to the microporous solid material on the uncured or semi-cured thin film to press the uncured or semi-cured thin film and the microporous solid material together. However, from the viewpoint of being able to fix the microporous solid material even on an uncured or semi-cured thin film that has poor resistance to solvents, it is preferable to load a powdered microporous solid material on the uncured or semi-cured thin film without using a solvent, and then apply pressure to the microporous solid material on the uncured or semi-cured thin film to press the uncured or semi-cured thin film and the microporous solid material together.

[0030] There is no particular restriction on the amount of powdered microporous solid material to be loaded, but from the viewpoint of increasing the gas adsorption properties of the resulting composite membrane, it is preferable to use as large an amount as possible, and more preferably an amount that completely covers the surface of the uncured or semi-cured thin film.

[0031] The pressure applied to the microporous solid material on the uncured or semi-cured thin film is 0.1 to 10 kg / cm 2 is preferable, and 0.3 to 3 kg / cm 2 If the pressure applied to the microporous solid material is less than the lower limit, the fixing of the microporous solid material tends to become unstable, whereas if the pressure applied to the microporous solid material is more than the upper limit, the microporous solid material tends to be pulverized, making it difficult to stably form a composite material substrate for gas adsorption.

[0032] (Polycondensation process) The polycondensation step is a step of polycondensing the sol-gel polycondensation reactive composition constituting the uncured or semi-cured thin film to form a thin film (cured film) made of a sol-gel polycondensate, and immobilizing the microporous solid material on the thin film (cured film) made of the sol-gel polycondensate, thereby obtaining a composite film (cured composite film) in which the microporous solid material is immobilized on the thin film (cured film) made of the sol-gel polycondensate.

[0033] The polycondensation method of the sol-gel polycondensation reactive composition is not particularly limited, and any known method can be used, for example, a method of heating an uncured or semi-cured composite film obtained by pressure-bonding the uncured or semi-cured thin film and the microporous solid material. The heating conditions are not particularly limited as long as they are conditions under which the uncured or semi-cured thin film becomes a cured thin film, i.e., conditions under which the sol-gel polycondensation reactive composition becomes a sol-gel polycondensate.

[0034] Furthermore, in the polycondensation step, it is preferable to wash the obtained composite film (cured composite film) as necessary. This allows the removal of insufficiently fixed microporous solid material, resulting in a composite film that exhibits stable gas adsorption. The washing method is not particularly limited, but examples include washing with a solvent, blowing with air, and subjecting the composite film to ultrasonic treatment in a solvent. Of these, ultrasonic treatment in a solvent is preferred from the viewpoint of completely removing insufficiently fixed microporous solid material. The solvent used for washing is not particularly limited, but from the viewpoint of not damaging the composite film and being easy to dry, organic solvents with low boiling points are preferred, and ethanol, hexane, etc. are more preferred.

[0035] The thickness of the thin film (cured film) made of the sol-gel polycondensate thus obtained is preferably 0.1 to 15 μm, more preferably 0.2 to 5 μm. If the thickness of the cured film is less than the lower limit, it tends to be difficult to firmly fix the microporous solid material. On the other hand, if the thickness of the cured film exceeds the upper limit, the microporous solid material tends to be buried in the cured film, and the gas adsorption properties of the resulting composite film tend to decrease.

[0036] [Gas sensor] The gas sensor of the present invention comprises the gas adsorbing composite material substrate of the present invention, in which a composite film (cured composite film) containing a thin film (cured film) made of the sol-gel polycondensate of an organosilane compound and the microporous solid material acts as a gas adsorption layer or a sensitive film.

[0037] In the gas sensor of the present invention, the solid substrate is preferably an electrode substrate for a quartz crystal microbalance (QCM), a substrate for a stress sensor, an electrode substrate for a capacitance sensor, or the like, and an electrode substrate for a quartz crystal microbalance is preferred from the viewpoint of being able to detect trace amounts of gas with high sensitivity. [Example]

[0038] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. The metal-organic frameworks (MOFs) and organosilane compounds used in the Examples and Comparative Examples were synthesized by the following methods.

[0039] (Synthesis Example A1) <Synthesis of Mg-MOF-74> First, magnesium acetate tetrahydrate (Mg(OAc)2·4H2O, 428.9 mg, 2.00 mmol) was added to dimethylformamide (DMF, 2.0 ml), and stirred at room temperature until uniformly dissolved to prepare a DMF solution of magnesium acetate (Solution A). Separately, 2,5-dihydroxyterephthalic acid (H4DOBDC, 196.2 mg, 1.00 mmol) was added to DMF (2.0 ml), and further acetic acid (80 μl) and water (200 μl) were added. After stirring at 50 °C for 5 minutes until uniformly dissolved, it was cooled to room temperature to prepare a DMF solution of 2,5-dihydroxyterephthalic acid (Solution B).

[0040] Next, the Solution A and the Solution B were mixed, and the resulting mixture was heated at 120 °C for 10 minutes, then added to a DMF / ethanol / water mixed solvent (15 / 1 / 1 (volume ratio), 50 ml), and ultrasonic treatment was performed for 10 minutes. The resulting slurry was transferred to an autoclave, heated at 125 °C for 20 hours, and then cooled to room temperature. The generated solid component was collected by suction filtration, washed with methanol (about 50 ml), and then vacuum dried at 100 °C for 6 hours to obtain a powder (yield: 260 mg).

[0041] When the X-ray diffraction spectrum of the dried powder was measured, as shown in Figure 1, since it showed an X-ray diffraction pattern similar to that of the known magnesium organic framework (Mg-MOF-74), it was confirmed that the obtained powder was a powder (Mg-MOF-74 powder) having a crystalline skeleton peculiar to the magnesium organic framework (Mg-MOF-74).

[0042] After applying a Pt coating to this Mg-MOF-74 powder using an ion coater and observing it using a scanning electron microscope ("SU3500" manufactured by Hitachi High-Tech Corporation), as shown in Figure 2, it was confirmed that the obtained Mg-MOF-74 powder consists of particles with a diameter of 100 to 200 nm.

[0043] Furthermore, the nitrogen adsorption / desorption isotherm of the obtained Mg-MOF-74 powder was measured at a temperature of 77 K using a specific surface area and pore size distribution measuring device ("Quadrasorb SI" manufactured by Quantachrome). The results are shown in Figure 3. Based on the obtained nitrogen adsorption / desorption isotherm (Figure 3), when the specific surface area was determined by the BET (Brunauer-Emmett-Teller) method in the range of relative pressure of 0.05 to 0.2, the BET specific surface area of the obtained Mg-MOF-74 powder was 1204 m 2 / g, and it was confirmed that the obtained Mg-MOF-74 powder has a high BET specific surface area.

[0044] (Synthesis Example A2) <Synthesis of ZIF-90> First, zinc nitrate hexahydrate (Zn(NO3)2·6H2O, 1.07 g, 3.60 mmol) was added to methanol (50 ml), stirred at room temperature until uniformly dissolved, and a methanol solution of zinc nitrate (Solution A) was prepared. Separately, 1H-imidazole-2-carboxaldehyde (C3H3N2CHO, 1.38 g, 14.4 mmol) was added to methanol (100 ml), stirred at 50 °C for 60 minutes until uniformly dissolved, and then cooled to room temperature to prepare a methanol solution of 1H-imidazole-2-carboxaldehyde (Solution B). Furthermore, separately, triethylamine (1.457 g, 14.4 mmol) was added to methanol (50 ml), stirred at room temperature until uniformly dissolved, and a methanol solution of triethylamine (Solution C) was prepared.

[0045] Next, while stirring with a magnetic stirrer, Solution A and Solution B were mixed, and about 1 minute later, Solution C was quickly added, and particle precipitation was observed immediately. This dispersion was stirred at room temperature for 3 hours, and then the precipitate was collected by suction filtration. The collected precipitate was redispersed in ethanol (approximately 50 ml), and then filtered and washed again. This washing procedure was repeated twice, and the resulting solid component was vacuum dried at 120°C for 6 hours to obtain a powder (yield: 0.89 g).

[0046] When the X-ray diffraction spectrum of the dried powder was measured, it showed an X-ray diffraction pattern similar to that of the known zinc organic framework (ZIF-90), as shown in Figure 4, and therefore the obtained powder was confirmed to be zinc organic framework (ZIF-90) powder.

[0047] Furthermore, when this ZIF-90 powder was observed using a scanning electron microscope in the same manner as in Synthesis Example A1, it was confirmed that the obtained ZIF-90 powder consisted of particles having a diameter of 0.5 to 1.0 μm, as shown in FIG.

[0048] Furthermore, the nitrogen adsorption / desorption isotherm of the obtained ZIF-90 powder was measured in the same manner as in Synthesis Example A1. The results are shown in Figure 6. Furthermore, based on the obtained nitrogen adsorption / desorption isotherm (Figure 6), the BET specific surface area of ​​the obtained ZIF-90 powder was calculated in the same manner as in Synthesis Example A1, and was found to be 1149 m 2 / g, and it was confirmed that the obtained ZIF-90 powder had a high BET specific surface area.

[0049] (Synthesis Example B1) <Synthesis of organosilane compounds> First, under a nitrogen atmosphere, 1,8-naphthalic anhydride (7.93 g, 40.0 mmol), ethylenediamine (1.20 g, 20.0 mmol), and pyridine (80 ml) were mixed and stirred while heating at 110° C. for 72 hours to obtain a compound represented by the following formula:

[0050] [ka]

[0051] The reaction shown in the following formula was carried out. After the resulting solution was cooled to room temperature, water (150 ml) was added and stirred, and the resulting precipitate was collected by suction filtration. The resulting precipitate was redispersed in ethanol (60 ml), and the resulting dispersion was stirred at 60°C for 10 minutes. The precipitate was then collected by suction filtration, thoroughly washed with ethanol, and vacuum dried to obtain a pale yellow solid (yield: 6.87 g, 82%).

[0052] The obtained pale yellow solid was dissolved in deuterated chloroform (CDCl3), and the NMR measurement was performed using a JEOL "JNM-ECX400P" NMR spectrometer. 1 The H-NMR spectrum was measured and identified to be a naphthalimide dimer (NI-d). The results are shown below. 1 H-NMR (CDCl3,δ in ppm): 4.68(s,4H), 7.68(dd,J=7.2,8.3Hz,4H), 8.17(d,J=8.3Hz,4H), 8.45(d,J=7.2Hz,4H).

[0053] Next, under a nitrogen atmosphere, naphthalimide dimer (NI-d) (2.52 g, 6.00 mmol), carbonyldihydridotris(triphenylphosphine)ruthenium [RuH2(CO)(PPh3)3] (330.5 mg, 0.36 mmol), triisopropoxyvinylsilane (11.62 g, 50.0 mmol), and mesitylene (70 ml) that had been previously treated with nitrogen bubbling for at least 5 minutes were mixed, and the mixture was stirred while heating at 160°C for 8 hours to obtain a compound of the following formula:

[0054] [ka]

[0055] The reaction represented by the formula (1) was carried out. The resulting solution was cooled to room temperature and purified using neutral silica gel column chromatography (developing solvent: chloroform / hexane = 1 / 1 (v / v) → chloroform / ethanol = 10 / 1 (v / v)) to obtain a fraction containing a naphthalimide ring-containing organosilane compound. The solvent was removed from this fraction using a rotary evaporator, followed by vacuum drying to obtain a purple crude product. This crude product was dissolved in chloroform (200 ml), and then a metal scavenger ("SiliaMetS(R)DMT" manufactured by SiliCycle) (20 g) was added. The mixture was stirred at room temperature for 72 hours to remove residual RuH2(CO)(PPh3)3. The metal scavenger was then removed by suction filtration, and the solvent was further removed using a rotary evaporator. The resulting solid was purified by recrystallization using cold acetonitrile to obtain a white solid (yield: 7.71 g, 95%).

[0056] The obtained white solid was dissolved in deuterated chloroform (CDCl3), and the NMR measurement was performed using an NMR measurement device (JEOL Ltd., "JNM-ECX400P") 1 The H-NMR spectrum was measured and identified, and it was confirmed to be the reaction product of naphthalimide dimer and triisopropoxyvinylsilane (NI-d-Si). The results are shown below. 1 H-NMR (CDCl3,δ in ppm): 0.89(m,8H), 1.11(d,J=6.0Hz,72H), 3.24(m,8H), 4.13(m,12H), 4.62(s,4H), 7.45(d,J=8.2Hz,4H), 7.94(d,J=8.2Hz,4H).

[0057] <Preparation of sol solution> Next, 2-methoxyethanol (0.3 g) and p-toluenesulfonic acid monohydrate (PTSA, 2.0 mg) were added to the NI-d-Si (100 mg, 0.074 mmol). The resulting mixture was heated at 130 °C for 20 minutes to prepare a transesterified sol solution (NI-d-Si concentration: 25 wt%). The resulting sol solution was then cooled to room temperature. Triethylamine (10 μl) was added to the resulting sol solution and mixed uniformly. Further, 2-methoxyethanol (0.8 g or 1.6 g) was added as necessary to prepare sol solutions with NI-d-Si concentrations of 5 wt%, 10 wt%, or 25 wt%.

[0058] <Preparation of Sol-Gel Polycondensate Thin Film> The obtained sol solutions of each NI-d-Si concentration were used to form the substrates by spin coating (1000 rpm or 2000 rpm, 30 seconds) or drop casting (5 μl / cm 2 ) was used to form uncured thin films on silicon substrates, quartz substrates, and quartz crystal microbalance (QCM) substrates. These uncured thin films did not harden even after 10 minutes or more had passed since application, when most of the solvent had evaporated. However, when heated at 100°C for 5 minutes, they formed the following compounds:

[0059] [ka]

[0060] The reaction proceeded rapidly, and a cured film (a thin film of polycondensation product of NI-d-Si (NI-d-silica)) was obtained. The thickness of the obtained cured film is shown in Table 1.

[0061] [Table 1]

[0062] <Condensation Degree of Sol-Gel Polycondensate Thin Film> Solid state of the obtained cured film 29 The Si MAS NMR spectrum was measured using a nuclear magnetic resonance spectrometer (Bruker "AVANCE400"), and as shown in Figure 7, T1 Species (R-Si(OSi)1(OH)2, -49.8 ppm) and T 2 Signals of species (R-Si(OSi)2(OH)1, -58.9 ppm) were detected. Using the intensities of these signals, the following formula: Degree of condensation [%] = (T 1 + 2×T 2 + 3×T 3 ) / 3ΣT n × 100 [where T i represents the signal intensity of species T i (R-Si(OSi) i (OH) 3-i ), (i = 1, 2, 3)] was used to determine the degree of condensation of NI-d-silica, which was found to be 48%, indicating that the curing reaction had proceeded sufficiently.

[0063] <Diameter of the circumscribed sphere of the organosilane compound> A molecular structure model in which alkoxy groups were eliminated from NI-d-Si by hydrolysis was created using BIOVIA Materials Studio 2023 (manufactured by Dassault Systèmes). As shown in Fig. 8, the diameter of the circumscribed sphere of the said molecular structure was estimated to be approximately 2.1 nm.

[0064] (Example 1) <Fabrication of the composite material substrate for QCM> Using the sol solution with a NI-d-Si concentration of 5 mass% prepared in Synthesis Example B1, an uncured thin film was formed on the Au electrode of a quartz crystal microbalance (QCM) substrate (「QA-A9M-AU」 manufactured by Seiko EG&G) by the drop-casting method (5 μl / cm 2 ). This uncured thin film was heated at 100 °C for 30 seconds to produce a semi-cured thin film, and then the Mg-MOF-74 powder synthesized in Synthesis Example A1 was loaded until the semi-cured thin film was completely covered. The obtained laminated film was about 1000 g / cm 2Pressurize at the pressure of for 3 minutes to press the Mg-MOF-74 powder onto the semi-cured thin film, and then heat at 100 °C for 10 minutes to further cure the semi-cured thin film. The obtained cured film was immersed in hexane and subjected to ultrasonic treatment for 10 seconds to remove the unimmobilized Mg-MOF-74 powder, and then vacuum-dried while heating at 80 °C to obtain a composite material substrate for QCM in which a composite film of Mg-MOF-74 powder and NI-d-silica thin film (Mg-MOF-74 / NI-d-silica composite film) was formed on the electrode of the QCM substrate.

[0065] <Electron Microscopic Observation of Composite Film> After applying a Pt coat to the surface of the Mg-MOF-74 / NI-d-silica composite film of the obtained composite material substrate for QCM using an ion coater, observation was carried out using a scanning electron microscope ("SU3500" manufactured by Hitachi High-Tech Corporation). FIG. 9 is a scanning electron micrograph of the surface of the Mg-MOF-74 / NI-d-silica composite film, and FIG. 10 is a scanning electron micrograph of the cross-section of the Mg-MOF-74 / NI-d-silica composite film. As shown in FIGS. 9 and 10, it was found that the Mg-MOF-74 powder was immobilized in a state where a part thereof was exposed in the gas phase on the surface of the NI-d-silica thin film (the surface opposite to the QCM substrate).

[0066] <Gas Sensing Characteristics of Composite Material Substrate for QCM> The obtained composite material substrate for QCM was installed in the measurement chamber in the gas flow path and electrically connected to a QCM measuring device ("QCM922A" manufactured by Seiko EG&G Corporation). Nitrogen gas and nitrogen gas containing CO2 at various concentrations were alternately passed through the gas flow path at regular intervals, and the resonance frequency of the composite material substrate for QCM at this time was measured with the QCM measuring device. The results are shown in FIG. 11. As shown in FIG. 11, it was found that the change in the resonance frequency increased with an increase in the CO2 concentration in the flowing gas. This is considered to be due to the adsorption of CO2 on the Mg-MOF-74 / NI-d-silica composite membrane during CO2 flow, and it was confirmed that the QCM substrate with the surface of the electrode substrate coated with the Mg-MOF-74 / NI-d-silica composite membrane clearly responds to the presence of CO2 in the gas phase. Also, as shown in FIG. 11, the QCM substrate with the surface of the electrode substrate coated with the Mg-MOF-74 / NI-d-silica composite membrane also accurately responds to the ON / OFF of CO2 flow and changes in the CO2 flow time, and it was confirmed that it is useful as a sensor chip for gas sensing.

[0067] (Example 2) <Preparation of Composite Material Substrate for QCM> A composite material substrate for QCM in which a composite membrane (ZIF-90 / NI-d-silica composite membrane) of ZIF-90 powder and NI-d-silica thin film was formed on the electrode of the QCM substrate was obtained in the same manner as in Example 1, except that the ZIF-90 powder synthesized in Synthesis Example A2 was used instead of the Mg-MOF-74 powder.

[0068] <Electron Microscopic Observation of Composite Membrane> The obtained ZIF-90 / NI-d-silica composite film on the composite material substrate for QCM was observed using a scanning electron microscope in the same manner as in Example 1. FIG. 12 is a scanning electron micrograph of the surface of the ZIF-90 / NI-d-silica composite film, and FIG. 13 is a scanning electron micrograph of the cross-section of the ZIF-90 / NI-d-silica composite film. As shown in FIGS. 12 and 13, it was found that the ZIF-90 powder was immobilized in a state where a part of it was exposed in the gas phase on the surface of the NI-d-silica thin film (the surface opposite to the QCM substrate).

[0069] <Gas sensing characteristics of the composite material substrate for QCM> The resonance frequency of the obtained composite material substrate for QCM was measured in the same manner as in Example 1, except that nitrogen gas containing acetone (acetone concentration: 20 ppm) was used instead of nitrogen gas containing CO2. The results are shown in FIG. 14. As shown in FIG. 14, it was found that the resonance frequency changed between the flow of nitrogen gas and the flow of nitrogen gas containing acetone. This is considered to be due to the adsorption of acetone on the ZIF-90 / NI-d-silica composite film during the flow of acetone. It was confirmed that the QCM substrate with the surface of the electrode substrate coated with the ZIF-90 / NI-d-silica composite film clearly responds to the presence of acetone in the gas phase. Also, as shown in FIG. 14, although a peak appears in the change of the resonance frequency when the valve is switched during the introduction of acetone for the QCM substrate with the surface of the electrode substrate coated with the ZIF-90 / NI-d-silica composite film, it was also confirmed that it accurately responds to the ON / OFF of the acetone flow and the change in the acetone flow time, and is useful as a gas sensing sensor chip.

[0070] (Comparative Example 1) <Fabrication of the substrate for QCM> Magnesium nitrate hexahydrate (Mg(NO3)2·6H2O, 58.5 mg, 0.23 mmol) and 2,5-dihydroxyterephthalic acid (H4DOBDC, 14.0 mg, 0.07 mmol) were added to a DMF / ethanol / water mixed solvent (15 / 1 / 1 (volume ratio), 50 ml), and ultrasonic treatment was performed for 10 minutes. The resulting solution was transferred to an autoclave, and after immersing a quartz crystal microbalance (QCM) substrate (「QA-A9M-AU」 manufactured by Seiko EG&G Corporation), it was heated at 125 °C for 23 hours and then cooled to room temperature. Thereafter, the QCM substrate was taken out and immersed in methanol for 4 hours for washing, and vacuum dried at 120 °C for 3.5 hours to obtain a QCM substrate with powder deposited on its surface.

[0071] When the X-ray diffraction spectrum of the powder deposited on the surface of the QCM substrate was measured, as shown in Fig. 15, since it showed an X-ray diffraction pattern similar to that of a known magnesium organic structure (Mg-MOF-74), it was confirmed that the obtained powder was a powder (Mg-MOF-74 powder) having a crystalline skeleton peculiar to the magnesium organic structure (Mg-MOF-74). That is, it was found that a Mg-MOF-74 particle film was formed on the surface of the QCM substrate.

[0072] <Electron microscopic observation of Mg-MOF-74 particle film> After applying a Pt coat to the Mg-MOF-74 particle film on the QCM substrate using an ion coater and observing it using a scanning electron microscope (「SU3500」 manufactured by Hitachi High-Technologies Corporation), as shown in Fig. 16, it was confirmed that the obtained Mg-MOF-74 particle film was composed of particles with a diameter of 1 to 2 μm.

[0073] <Gas sensing characteristics of the substrate for QCM> The resonant frequency of the obtained QCM substrate was measured in the same manner as in Example 1. The results are shown in Figure 17. As shown in Figure 17, there was a tendency for the change in resonant frequency to increase as the CO2 concentration in the flowing gas increased, but the amount of change in resonant frequency did not accurately correspond to the increase in CO2 concentration. This indicates that the QCM substrate with Mg-MOF-74 powder deposited on its surface is strongly affected by factors other than the CO2 concentration and does not respond accurately to the presence of CO2 in the gas phase.

[0074] (Comparative Example 2) <Preparation of sol solution> The organosilane compound NI-d-Si (100 mg, 0.074 mmol) synthesized in Synthesis Example B1, 2-methoxyethanol (0.9 g), and 2 M hydrochloric acid (12 μl) were mixed and stirred at room temperature for 1 hour to prepare a hydrochloric acid acidic sol solution.

[0075] <Preparation of raw material dispersion> The hydrochloric acid sol solution (0.50 g) was mixed with the Mg-MOF-74 powder (50 mg) synthesized in Synthesis Example A1, and 2-methoxyethanol (0.45 g) was added. The mixture was then subjected to ultrasonic treatment for 30 minutes to prepare a uniform raw material dispersion (1.0 g) in which the raw material mass ratio of Mg-MOF-74 powder to NI-d-Si was 1:1 and the total raw material content of Mg-MOF-74 powder and NI-d-Si was 10 mass%.

[0076] <Preparation of composite substrate> Using the obtained raw material dispersion, an uncured thin film was formed on a quartz substrate by spin coating (3000 rpm, 30 seconds). This uncured thin film was then vacuum dried for 2 hours while heating at 80°C to obtain a composite material substrate on which a composite film of Mg-MOF-74 powder and NI-d-silica (Mg-MOF-74 / NI-d-silica (1 / 1) composite film) was formed on the quartz substrate.

[0077] When the X-ray diffraction spectrum of the Mg-MOF-74 / NI-d-silica (1 / 1) composite film on this composite material substrate was measured, as shown in FIG. 18, the diffraction intensity was overall very weak. In particular, compared with the Mg-MOF-74 powder synthesized in Synthesis Example A1 (FIG. 1), a decrease in the peak intensity at 2θ = 6.8° was observed, suggesting that Mg-MOF-74 was decomposed in the Mg-MOF-74 / NI-d-silica (1 / 1) composite film.

[0078] Also, when the nitrogen adsorption / desorption isotherm of the Mg-MOF-74 / NI-d-silica (1 / 1) composite film was measured in the same manner as in Synthesis Example A1, the results shown in FIG. 19 were obtained. The BET specific surface area of the Mg-MOF-74 / NI-d-silica (1 / 1) composite film was below the detection limit. From this result, it was found that micropores were not retained in the Mg-MOF-74 / NI-d-silica (1 / 1) composite film.

[0079] From the above results, it was difficult to obtain a porous film having micropores applicable to a gas sensor by the composite of Mg-MOF-74 and NI-d-silica using a normal acidic sol solution.

[0080] (Comparative Example 3) <Preparation of raw material dispersion liquid> After adding 2-methoxyethanol (0.18 g) to the ZIF-90 powder (20 mg) obtained in Synthesis Example A2, ultrasonic treatment was carried out for about 30 minutes to prepare a uniform raw material dispersion liquid (0.2 g) containing 10% by mass of ZIF-90 powder.

[0081] <Fabrication of QCM substrate> Using the obtained raw material dispersion liquid, a thin film made of ZIF-90 powder was formed on the Au electrode of a quartz crystal microbalance (QCM) substrate (「QA-A9M-AU」 manufactured by Seiko EG&G Corporation) by spin coating (3000 rpm, 30 seconds), and vacuum dried while heating at 70 °C to obtain a QCM substrate on which a thin film made of ZIF-90 powder (ZIF-90 particle film) was formed on the electrode of the QCM substrate.

[0082] <Electron Microscopic Observation of ZIF-90 Particle Film> After applying a Pt coat to the ZIF-90 particle film formed on the electrode of the QCM substrate using an ion coater, observation was carried out using a scanning electron microscope ("SU3500" manufactured by Hitachi High-Technologies Corporation). As shown in Fig. 20, it was confirmed that the obtained ZIF-90 particle film consists of particles with a diameter of 4 to 5 μm.

[0083] <Gas Sensing Characteristics of Substrate for QCM> The resonance frequency of the obtained QCM substrate was measured in the same manner as in Example 1, except that nitrogen gas containing acetone (acetone concentration: 20 ppm) was used instead of nitrogen gas containing CO2. The results are shown in Fig. 21. As shown in Fig. 21, while the resonance frequency decreased by about 30 Hz while the nitrogen gas containing acetone was flowing, a noise signal of the same level was also measured, and no clear response to the presence of acetone in the gas phase was observed in the QCM substrate with the surface of the electrode substrate coated with the ZIF-90 particle film.

Industrial Applicability

[0084] As described above, according to the method for manufacturing the composite material substrate for gas adsorption of the present invention, a porous solid material can be firmly fixed on a solid substrate in a state where a part of its surface is exposed to the gas phase without blocking its micropores and without being buried in a thin film. That is, in the composite material substrate for gas adsorption of the present invention, the porous solid material is firmly fixed on the solid substrate in a state where a part of its surface is exposed to the gas phase without blocking its micropores and without being buried in a thin film, and is provided with a composite film having excellent gas adsorption properties.

[0085] Therefore, a gas sensor comprising such a composite material substrate for gas adsorption of the present invention is useful in that it can stably detect adsorbed gas components, and thus can also be used in the detection of trace amounts (for example, gas concentration: several tens of ppm or less) of gases and the detection of gases that have not been conventionally applied.

[0086] In particular, in the gas sensor of the present invention, the microporous solid material is firmly fixed to the solid substrate without its micropores being blocked, without being buried in a thin film, and with part of its surface exposed to the gas phase. Therefore, the microporous solid material particles are firmly bonded to the solid substrate and to each other, and trace amounts of gas components can be stably detected. Therefore, the gas sensor of the present invention is particularly useful as a quartz crystal microbalance (QCM) gas sensor that detects gas adsorption into the microporous solid material as a change in resonant frequency due to an increase in mass.

Claims

1. a solid substrate; a thin film formed on the solid substrate and made of a sol-gel polycondensate of an organosilane compound having two or more trialkoxysilyl groups and a circumscribed sphere of a molecular structure from which a terminal alkoxy group has been eliminated, the sphere having a diameter of 1 to 10 nm; A microporous film having a BET specific surface area of ​​100 m2 is fixed on the thin film. ２ / g or more porous solid material; A composite material substrate for gas adsorption, comprising:

2. 2. The composite material substrate for gas adsorption according to claim 1, wherein the solid substrate is an electrode substrate of a quartz crystal microbalance.

3. 2. The gas adsorbing composite substrate according to claim 1, wherein the porous solid material is a metal-organic framework.

4. 2. A gas sensor comprising the gas adsorbing composite material substrate according to claim 1, wherein the composite film containing the thin film made of the sol-gel polycondensate of the organic silane compound and the porous solid material is a gas adsorption layer or a sensitive film.

5. forming a thin film on a solid substrate, the thin film being made of a sol-gel polycondensation reactive composition containing an organosilane compound having two or more trialkoxysilyl groups and a circumscribed sphere of a molecular structure from which a terminal alkoxy group has been eliminated, the diameter of which is 1 to 10 nm; The thin film has micropores and a BET specific surface area of ​​100 m ２ / g or more; polycondensing the sol-gel polycondensation reactive composition to immobilize the porous solid material; 1. A method for producing a gas adsorbing composite material substrate, comprising:

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