Gas-sensitive material and gas detector

Abstract

The objective of the present disclosure is to provide a gas-sensitive material allowing for an enhanced degree of physical property change that occurs when said gas-sensitive material responds to a substance in a gas. A gas-sensitive material according to an embodiment of the present disclosure is used for gas detection. The gas-sensitive material contains a metal organic structure.

Description

Gas-sensitive materials and gas detectors

[0001] The present disclosure relates to gas sensitive materials and gas detectors, and more particularly to gas sensitive materials used for gas detection and gas detectors comprising gas sensitive materials.

[0002] Patent Document 1 discloses a chemiresistor including an electrically insulating substrate including a pair of conductive wires arranged in a circular pattern parallel to one another, a chemically sensitive polymer in contact with the pair of conductive wires, and carbon particles dispersed in the chemically sensitive polymer. In this chemiresistor, when the chemically sensitive polymer adsorbs volatile organic compounds or the like in a gas, a change in electrical resistance occurs. Using this chemiresistor, volatile organic compounds or the like in a gas can be detected based on the change in the electrical resistance of the chemiresistor.

[0003] U.S. Patent No. 7,189,360

[0004] An object of the present disclosure is to provide a gas-sensitive material that can improve the degree of change in physical properties that occurs when the material is sensitive to a substance in a gas, and a gas detector that includes this gas-sensitive material.

[0005] A gas-sensitive material according to one embodiment of the present disclosure is used for gas detection. The gas-sensitive material contains a metal-organic framework.

[0006] A gas detector according to one aspect of the present disclosure includes a sensitive portion containing the gas-sensitive material.

[0007] Fig. 1 is a cross-sectional view of a sensor unit in a gas detector according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view of a sensitive portion in the sensor unit. Fig. 3 is a cross-sectional view of another example of a sensitive portion in the sensor unit. Fig. 4 is a block diagram of the gas detector. Fig. 5 is a graph showing the results of a sensitivity test of an example. Fig. 6 is a graph showing the results of a sensitivity test of a comparative example.

[0008] Embodiments of the present disclosure will be described. Note that the following embodiments are merely a portion of various embodiments of the present disclosure. Furthermore, the following embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. The figures referred to below are schematic diagrams, and the shapes and dimensional ratios of the components in the figures do not necessarily reflect the actual shapes and dimensional ratios, etc. The mechanism of action of the embodiments may be described below, but this mechanism of action may be speculated. Furthermore, the present disclosure is not bound by the description of the mechanism of action shown below.

[0009] 1. Overview Fig. 1 shows a sensor section of a gas detector 10 using a gas-sensitive material according to an embodiment, and Fig. 2 and Fig. 3 each show an example of a sensitive section 2 including a gas-sensitive material in the sensor section. Fig. 4 shows a block diagram of the gas detector 10 using the gas-sensitive material according to an embodiment.

[0010] The gas-sensitive material of the embodiment is used for gas detection. Gas detection is the detection of an event that depends on a substance contained in the gas. The event may be a property of the gas itself, such as the type and concentration of a substance contained in the gas, or the smell of the gas. The event may also be an event derived from the property of the gas itself, such as the state of an object that emits a substance contained in the gas.

[0011] The gas-sensitive material contains a metal organic framework (MOF).

[0012] Metal-organic frameworks are also called porous coordination polymers. When a metal-organic framework comes into contact with a gas, it adsorbs molecules of a substance contained in the gas, and may undergo a large increase in its own volume due to the adsorption of the molecules of the substance contained in the gas. The metal-organic framework has a porous structure due to the inclusion of metal ions and organic ligands bridging the metal ions. Therefore, it is thought that the metal-organic framework exhibits gas adsorption properties when molecules of the substance are arranged in its pores, and that the arrangement of the molecules of the substance in the pores causes a change in the framework structure of the metal-organic framework, which in turn causes a large structural change and a large volume change in the metal-organic framework.

[0013] For this reason, when the gas-sensitive material comes into contact with a gas, the physical properties thereof change due to structural changes and volume changes of the metal-organic framework, and the degree of change in the physical properties may become large. Note that the physical properties of the gas-sensitive material include, for example, electrical properties such as electrical resistance, magnetic properties such as magnetic permeability, volume, mass, specific gravity, or resonant frequency. Because the physical properties of the gas-sensitive material change to a large extent when the gas-sensitive material comes into contact with a gas, the detection sensitivity of the gas-sensitive material can be improved when used for gas detection.

[0014] The gas detector 10 of the embodiment includes a sensitive part 2 containing a gas-sensitive material. When the sensitive part 2 comes into contact with a gas, the gas-sensitive material in the sensitive part 2 adsorbs molecules of a substance contained in the gas, which may cause a change in the physical properties of the gas-sensitive material and the sensitive part 2. The gas can be detected based on this change in physical properties. In this case, gas detection is performed using the gas-sensitive material of the embodiment, and therefore detection sensitivity can be improved.

[0015] 2. Gas-Sensing Material As described above, the gas-sensitive material contains a metal-organic framework.

[0016] The metal-organic framework contains metal ions and organic ligands having multiple coordination sites in one molecule. The metal-organic framework is formed by repeating a structure in which multiple metal ions are crosslinked via the organic ligands. Therefore, the metal-organic framework has a fine porous structure.

[0017] When the metal-organic framework comes into contact with a gas, it can adsorb molecules of a substance contained in the gas into the pores within the metal-organic framework. This can cause the framework of the metal-organic framework to expand and the volume of the metal-organic framework to increase. This can cause changes in the physical properties of the metal-organic framework.

[0018] The metal organic framework can have various adsorption performances depending on the type of metal ion in the metal organic framework, the structure and crystallinity of the organic ligand, etc. In other words, the adsorption performance of the metal organic framework can be adjusted by controlling the type of metal ion in the metal organic framework, the structure and crystallinity of the organic ligand, etc.

[0019] The ligands constituting the metal-organic framework preferably include an organic ligand having a structure in which the ligand has at least two coordination sites that coordinate to different metal ions and a rotatable bond, and the positional relationship between the two coordination sites can be changed by rotating the bond. An example of such an organic ligand is an organic ligand in which a molecular chain connecting two coordination sites includes a rotatable single bond, an atom bonded to the single bond, and another atom bonded to the rotatable single bond, and the bond angle between the rotatable single bond and the bond connecting the two atoms is less than 180°. In this case, the rotation of the bond of the organic ligand bridging the metal ions in the metal-organic framework changes the structure of the framework bridging the metal ions, which can change the distance between the metal ions bonded via the organic ligand, as well as the angle and orientation of the bond between the metal ions. The structure of the entire metal-organic framework can change accordingly. The volume of the metal-organic framework can change in accordance with this change in the structure of the entire metal-organic framework. Therefore, when the metal-organic framework adsorbs molecules of a substance contained in a gas, the structure of the framework bridging between the metal ions changes so that the molecules are stably arranged in the pores of the metal-organic framework, which can result in a significant change in the volume of the metal-organic framework. For example, an increase in volume of about 1.5 to 2 times the metal-organic framework can be achieved. Furthermore, when the molecules are desorbed from the pores of the metal-organic framework, the structure of the framework bridging between the metal ions changes accordingly, and the structure of the metal-organic framework returns to its original state. As a result, the metal-organic framework can undergo a significant change in its physical properties in response to the adsorption of gas.

[0020] Furthermore, the metal-organic framework can have high thermal stability. Therefore, the metal-organic framework is less likely to deteriorate when high-temperature treatment is performed during the fabrication of the gas detector 10 using the metal-organic framework, or when the metal-organic framework is heated during gas detection. Therefore, the durability of the gas detector 10 using the metal-organic framework can be improved.

[0021] The ligand in the metal organic framework preferably includes at least one selected from the group consisting of 2-methylimidazole, 4-(1H-imidazol-1-yl)benzoic acid, terephthalic acid, fumaric acid, 4-amino-4H-1,2,4-triazole, bithiophenedicarboxylic acid, 1,4-benzenedipyrazolate, 1,4-diazabicyclo[2.2.2]octane, and 1,4-benzenedicarboxylate. In this case, the metal organic framework can undergo a greater change in its physical properties in response to the adsorption of molecules of a substance in the gas. However, the ligand in the metal organic framework is not limited to the above.

[0022] The ligand in the metal organic framework is μ ２ It is also preferable that it contains an —OH group. ２ An —OH group is an OH group bridging two metal ions. In this case, μ ２ The —OH group bonds with each of the two metal ions through hydrogen bonds, so that the two metal ions are bonded relatively strongly while the bridge structure between the metal ions is flexibly deformable. ２ The —OH group contributes to improving the flexibility of the metal-organic framework, and can promote a change in the framework of the metal-organic framework when the metal-organic framework adsorbs molecules of a substance contained in a gas, thereby further promoting a change in the physical properties of the metal framework.

[0023] The metal ions in the metal organic framework preferably include at least one selected from the group consisting of silver ions, copper ions, iron ions, zinc ions, aluminum ions, nickel ions, chromium ions, cobalt ions, cadmium ions, and manganese ions. In this case, the metal organic framework may undergo a greater change in physical properties in response to gas adsorption. However, the metal ions in the metal organic framework are not limited to the above.

[0024] The metal organic framework can be synthesized by any suitable method, including known methods. Examples of methods for producing the metal organic framework include a solution method in which metal ions and organic ligands are mixed in a solvent at room temperature and normal pressure, a hydrothermal method in which a solution containing metal ions and organic ligands is subjected to a hydrothermal reaction at high temperature and high pressure, a microwave method in which a solution containing metal ions and organic ligands is irradiated with microwaves, an ultrasonic synthesis method in which a solution containing metal ions and organic ligands is irradiated with ultrasonic waves, and a solid-phase synthesis method in which metal ions and organic ligands are mechanically mixed without using a solvent. The structure of the metal organic framework can be identified by analysis using X-ray diffraction or the like.

[0025] The metal organic framework is, for example, MIL-53(Al) containing tetrafluoroterephthalic acid as an organic ligand and aluminum ions as metal ions, Cu(4,4'-bipyridine) ２ (BF ４ ) ２ ELM-11 represented by the formula ２ (2,6-naphthalenedicarboxylate) ２ In addition to the above, the metal organic framework may include, for example, Zn(MeIM) ２ [ZIF-8], Cd (IBA) ２ , Ag ２ [Ag ４ Tz ６ ], M ２ (μ ３ -O)(H ２ O) (dicarboxylate) ６ (M=Fe, Cr) [MIL-88], Ni II Ni III (μ ３ —OH) (L3) ３ , Fe(pz) [M II (CN) ４ ](M=Ni, Pd, Pt), Fe(azpy)[(M II (CN) ４ ] (M=Ni, Pd, Pt), Fe (bpac) [M (CN) ４ ] (M=Ni, Pd, Pt), M(OH) (bdc) (M=Al, Cr, Fe) [MIL-53], Zn２ (btdc) ３ (bpyy)、Co(3DP)、+n ２ (1,4-bdc) ２ (dabcoo)、Zn ２ (88) ２ -bdc) ２ (dabcoo)、Znn(2,5-､M･bdc) ２ (dabcoo)、3u(3D4riii)(M0)、ｺn ２ 843 ２ .000 ２ The ２ (bpydc) ３ (8) ２ 9) ３ Ln=NdddSmmuu、1d:4b,Dy,Hooorrr)、o. ３ (98) ２ (btca) ２ 、(PMI),---6y)(M=Znn,CddMnn)、 ３ (L)ietbipyy)LL=N,N,N,N-tetrakissppo honomethyl? hylenediamine)auu(ｬ) ２ (39) ４ )(3) ２ (1,4,4'-(1,4-(f) diyllbissss(1,2,4-triazolee)) ４ 9. ２ P(H) ２ ) １－ｘ (9) ２ PO((3H ２ ) ) ｎ 2009 ２ ) ) ｘ／２ 、La(ｨ ５ 4470)、3o ２ (epda) ２ (bpaa)(2 ２ 9) ２ The ２ (bpeb)(obc) ２ 、Co(5-82 ２ -bdc)(bpy) ０．５ (8) ２ O)、Cd ２(pzdc) ２ L (H ２ O) ２ (L-2,5-bis(2-hydroxyethoxy)-1,4-bis(4-pyridyl)benzene), Zn ２ (cpa) ２ (bpy), Cu(CN) ３ L(L-2,6-bis-((3,5-dimethyl-1H-pyrazol-4-yl)methyl)pyridine), [Me ２ NH ２ ] １．７５ [In(L)] １．７５ (L=biphenyl-3,3',5,5'-tetra(phenyl-4-carboxylic acid)), Cu ２ (bdc) ２ (bpy), Zn ２ (bdc) ２ (dpNDI), and Zn ２ (tp) ２ (L ２ ) and the like.

[0026] The gas-sensitive material may contain only a metal-organic framework. In this case, when the metal-organic framework adsorbs molecules of a substance in a gas, the molecules of the substance are arranged in the pores of the metal-organic framework, the framework structure of the metal-organic framework changes, the volume of the metal-organic framework changes, and so on, resulting in changes in the physical properties of the metal-organic framework. Gas detection can be performed based on these changes in physical properties.

[0027] The gas-sensitive material may contain a metal-organic framework and a substance other than the metal-organic framework. For example, the gas-sensitive material is a mixture of the metal-organic framework and the substance other than the metal-organic framework. In this case, gas detection can be performed based on a change in the physical properties of the gas-sensitive material involving not only the metal-organic framework but also the substance other than the metal-organic framework.

[0028] For example, the gas-sensitive material contains a metal-organic framework and a plurality of conductive particles 22. In this case, the gas-sensitive material is, for example, a mixture of the metal-organic framework and the plurality of conductive particles 22. In this case, too, when the metal-organic framework adsorbs molecules of a substance in a gas, the molecules of the substance are arranged in the pores of the metal-organic framework, the skeletal structure of the metal-organic framework changes, and the volume of the metal-organic framework changes, causing changes in the physical properties of the metal-organic framework. Gas detection can be performed based on this change in physical properties. Furthermore, when the metal-organic framework adsorbs molecules of a substance in a gas and the volume of the metal-organic framework increases, the spacing between the conductive particles 22 in the gas-sensitive material increases, causing changes in electrical properties such as the electrical resistance value of the gas-sensitive material. Gas detection can be performed based on this change in electrical properties. In the embodiment, the volume of the metal-organic framework can increase significantly when the metal-organic framework adsorbs molecules of a substance in a gas. Therefore, when the gas-sensitive material comes into contact with a gas, the volume of the gas-sensitive material increases significantly, resulting in a greater degree of change in the electrical properties of the gas-sensitive material, such as the electrical resistance value. Therefore, gases can be detected with high sensitivity using gas sensitive materials.

[0029] When the gas-sensitive material contains conductive particles 22, the conductive particles 22 may include at least one material selected from the group consisting of carbon materials, conductive polymers, metals, metal oxides, semiconductors, superconductors, and complex compounds. Examples of carbon materials include at least one material selected from the group consisting of carbon black, graphite, coke, carbon nanotubes, graphene, and fullerenes. Examples of conductive polymers include at least one material selected from the group consisting of polyaniline, polythiophene, polypyrrole, and polyacetylene. Examples of metals include at least one material selected from the group consisting of silver, gold, copper, platinum, and aluminum. Examples of metal oxides include at least one material selected from the group consisting of indium oxide, tin oxide, tungsten oxide, zinc oxide, and titanium oxide. Examples of semiconductors include at least one material selected from the group consisting of silicon, gallium arsenide, indium phosphide, and molybdenum sulfide. Examples of superconductors include at least one material selected from the group consisting of YBa2Cu3O7 and Tl2Ba2Ca2Cu3O. 10The complex compound includes at least one material selected from the group consisting of, for example, a complex compound of tetramethylparaphenylenediamine and chloranil, a complex compound of tetracyanoquinodimethane and an alkali metal, a complex compound of tetrathiafulvalene and a halogen, a complex compound of iridium and a halocarbonyl compound, and tetracyanoplatinum.

[0030] The conductive particles 22 have an average particle size of, for example, 10 nm to 300 nm, which is the arithmetic mean value of particle sizes of the conductive particles 22 based on the number thereof, determined from an electron microscope photograph of the conductive particles 22.

[0031] When the gas-sensitive material contains the conductive particles 22, the proportion of the conductive particles 22 is, for example, 25 parts by mass or more and 400 parts by mass or less per 100 parts by mass of the metal-organic framework in the gas-sensitive material.

[0032] 3. Sensitive Part The sensitive part 2 in the gas detector 10 includes a gas-sensitive material. The sensitive part 2 is, for example, a molded body made of the gas-sensitive material.

[0033] When the gas-sensing material contains only the metal-organic framework, the sensitive part 2 is, for example, a molded body obtained by molding the metal-organic framework. In this case, the sensitive part 2 is produced, for example, by dispersing the metal-organic framework in a liquid dispersion medium to prepare a dispersion, applying the dispersion to a molded body, and then drying the molded body.

[0034] When the gas-sensing material contains a metal-organic framework and a plurality of conductive particles 22, the sensitive part 2 is, for example, a molded body obtained by molding a mixture of the metal-organic framework and the plurality of conductive particles 22. In this case, as shown in Fig. 2, for example, the sensitive part 2 includes an adsorption phase 21 made of the metal-organic framework and a plurality of conductive particles 22 dispersed in the adsorption phase 21. In this case, the sensitive part 2 is produced, for example, by dispersing the metal-organic framework and the plurality of conductive particles 22 in a liquid dispersion medium to prepare a dispersion, and then applying or otherwise molding this dispersion, followed by drying.

[0035] The sensitive part 2 may be an aggregate of a plurality of metal-organic framework particles 211 and a plurality of conductive particles 22. In this case, the sensitive part 2 includes, for example, an adsorption phase 21 consisting of a plurality of metal-organic framework particles 211, and a plurality of conductive particles 22 dispersed in the adsorption phase 21, as shown in FIG. 3 . In this case, the sensitive part 2 is produced, for example, by dispersing the plurality of metal-organic framework particles 211 and the plurality of conductive particles 22 in a liquid dispersion medium to prepare a dispersion, and then shaping the dispersion by coating or the like, followed by drying. The dispersion may contain a binder. In this case, the sensitive part 2 can be formed by binding the plurality of metal-organic framework particles 211 and the plurality of conductive particles 22 to each other in the sensitive part 2 by the binder.

[0036] The average particle size of the metal-organic framework particles 211 is, for example, 1 μm or more and 20 μm or less, but is not limited to this range. The average particle size of the conductive particles 22 is the number-based arithmetic mean value of particle sizes determined from an electron microscope photograph of the metal-organic framework particles 211.

[0037] The sensitive part 2 is, for example, in the form of a film. In this case, the thickness of the sensitive part 2 is, for example, 1 μm or more and 3 μm or less, but is not limited to this range. The shape of the sensitive part 2 is not limited to a film shape.

[0038] 4. Gas Detector The gas detector 10 of the embodiment includes a sensitive part 2 containing a gas-sensitive material. Therefore, gas detection can be performed based on changes in the physical properties of the sensitive part 2 when the gas-sensitive material in the sensitive part 2 adsorbs molecules of a substance in the gas.

[0039] The gas detector 10 further includes a transducer 11 that outputs a signal corresponding to, for example, the physical properties of the sensitive part 2. In this case, gas detection can be performed based on the signal output by the transducer 11.

[0040] The gas detector 10 of the embodiment includes a detection section 1 having a sensitive section 2, a transducer 11, a processing section 12, and an output section 15 (see FIG. 4).

[0041] As shown in FIG. 1, the detection unit 1 includes a sensor chamber 51, a sensitive part 2, a substrate 3, an inlet path 52, and an outlet path 53.

[0042] The sensor chamber 51 has an internal space. An inlet path 52 that leads to the internal space of the sensor chamber 51 and an outlet path 53 that leads to the internal space of the sensor chamber 51 are connected to the sensor chamber 51.

[0043] A substrate 3 and a sensitive part 2 are disposed in the sensor chamber 51. The sensitive part 2 is mounted on the substrate 3. In the embodiment, the detection unit 1 includes a plurality of sensitive parts 2 having different sensing characteristics from one another. That is, a plurality of sensitive parts 2 having different sensing characteristics from one another are mounted on the substrate 3. Different sensing characteristics means that the degree of change in physical properties when molecules of a substance in a gas are adsorbed is different. For example, if at least one of the type of metal organic framework, the type of conductive particles, and the ratio of metal organic framework to conductive particles is different between the plurality of sensitive parts 2, the sensitive characteristics may be different from one another.

[0044] As shown in FIG. 2 or 3 , the sensitive part 2 of the embodiment has an adsorption phase 21 made of a metal-organic framework and a plurality of conductive particles 22 dispersed in the adsorption phase 21 .

[0045] The substrate 3 is a wiring substrate provided with conductor wiring (not shown) and is provided with electrodes 4 electrically connected to the respective sensitive parts 2 (see FIG. 2 or FIG. 3).

[0046] As shown in FIG. 2 or 3 , the electrode 4 includes a first electrode 41 and a second electrode 42 , and the first electrode 41 and the second electrode 42 are electrically connected to the sensitive part 2 .

[0047] The transducer 11 is, for example, a measurement circuit that outputs a signal corresponding to the electrical resistance value of the sensitive part 2. More specifically, the transducer 11 is, for example, a measurement circuit that outputs a signal corresponding to the electrical resistance value between the first electrode 41 and the second electrode 42. The measurement circuit applies a constant voltage between the first electrode 41 and the second electrode 42, for example. A current corresponding to the electrical resistance value of the sensitive part 2 flows between the first electrode 41 and the second electrode 42. The measurement circuit outputs a signal corresponding to this current as a signal corresponding to the electrical resistance value of the sensitive part 2. In the embodiment, the detection unit 1 includes a plurality of sensitive parts 2, and therefore the transducer 11 outputs a signal corresponding to the electrical resistance value of each sensitive part 2.

[0048] The processing unit 12 controls the operation of the gas detector 10. The processing unit 12 processes the signal output by the detection unit 10, and outputs the result as a detection result.

[0049] The processing unit 12 includes, for example, a computer system mainly composed of a processor serving as the control unit 13 and a memory serving as the storage unit 14 as hardware. The processor executes a program stored in the memory of the computer system to realize the functions of the processing unit 12. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided by being recorded on a non-transitory recording medium such as a memory card, optical disk, or hard disk drive that is readable by the computer system. The processor of the computer system is composed of one or more electronic circuits including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). The integrated circuits such as ICs and LSIs referred to here are called by different names depending on the degree of integration, and include integrated circuits called system LSIs, very large scale integration (VLSI), or ultra large scale integration (ULSI). Furthermore, a field-programmable gate array (FPGA), which is programmed after the LSI is manufactured, or a logic device capable of reconfiguring the connections within the LSI or the circuit partitions within the LSI, can also be employed as a processor. Multiple electronic circuits may be integrated into a single chip or distributed across multiple chips. Multiple chips may be integrated into a single device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller is also composed of one or more electronic circuits, including a semiconductor integrated circuit or a large-scale integrated circuit.

[0050] The detection result by the processing unit 12 is, for example, a result of identifying the type and concentration of a substance contained in the gas. Alternatively, the detection result may be an appropriate judgment result depending on the type and concentration of a substance contained in the gas. For example, the detection result may be a judgment result of the odor of the gas or a judgment result regarding the state of an object emitting the gas.

[0051] The processing unit 12 may generate and output detection results using a trained model, which is the result of machine learning using training data. In this case, the trained model is stored, for example, in the storage unit 14. When detection results are generated using the trained model based on signals respectively obtained from the multiple sensor units 2, highly accurate detection results can be obtained.

[0052] The output unit 15 outputs the processing result by the processing unit 12 in a manner that can be recognized by a person. For example, the output unit 15 is a monitor or a lamp that visually displays the processing result, or a speaker or a buzzer that audibly displays the processing result. Note that the processing result may not be output from the output unit 15 but may be stored in the storage unit 14 or transmitted wirelessly or via a wire to the outside of the gas detector 10.

[0053] Before gas detection is performed using the gas detector 10 of the embodiment, a reference gas is supplied into the sensor chamber 51 through the inlet path 52. The reference gas may be, for example, nitrogen or air, but is not limited to these. The reference gas flows into the sensor chamber 51 from the inlet path 52 and then flows out of the sensor chamber 51 through the outlet path 53.

[0054] When gas detection is performed, the gas to be detected is mixed with a reference gas and supplied into the sensor chamber 51 through the inlet path 52. The gas to be detected flows into the sensor chamber 51 from the inlet path 52 and then flows out of the sensor chamber 51 through the outlet path 53.

[0055] When a gas to be detected is supplied to the sensor chamber 51, the gas comes into contact with the sensitive parts 2, causing molecules of substances in the gas to be adsorbed onto each sensitive part 2. This increases the volume of the metal-organic framework in each sensitive part 2, and increases the electrical resistance value of the sensitive part 2. The transducer 11 sends a signal corresponding to the electrical resistance value of the sensitive part 2 to the control part 13. The control part 13 processes this signal to generate a detection result corresponding to the gas to be detected, and can output the detection result to the outside via the output part 15.

[0056] 5. Modifications The above-described embodiments are merely a part of various embodiments of the present disclosure. The above-described embodiments can be modified in various ways depending on the design, etc., as in the modifications listed below, as long as the object of the present disclosure can be achieved. In the following description of the modifications, detailed description of the same configurations as the above-described embodiments will be omitted.

[0057] Although the sensitive part 2 in the embodiment is in the form of a film, the sensitive part 2 may have any suitable shape other than the film shape.

[0058] The gas detector 10 in this embodiment has a plurality of sensitive parts 2, and although the number of sensitive parts 2 is 16 in Fig. 1, there is no limit to the number of sensitive parts 2. The number of sensitive parts 2 may be one, or an appropriate number of two or more. Although the sensitive parts 2 are arranged in a matrix in Fig. 1, the sensitive parts 2 may be arranged in a line, along the circumference of an imaginary circle, or along the circumference of multiple imaginary concentric circles.

[0059] The gas detector 10 in the embodiment includes an electrode 4 electrically connected to the sensitive part 2 and a transducer 11 that outputs a signal corresponding to the electrical resistance between the electrodes 4, but the gas detector 10 is not limited to this configuration as long as it can detect changes in the physical properties of the sensitive part 2 that occur due to the adsorption of substance molecules. For example, the transducer 11 may include a quartz crystal microbalance (QCM) that outputs a signal corresponding to the mass of the sensitive part 2. The transducer 11 may also include a field-effect transistor that outputs a signal corresponding to the characteristics of the sensitive part 2, such as the dielectric constant.

[0060] The gas detector 10 of the embodiment includes the detection unit 1, the transducer 11, the processing unit 12, and the output unit 15. However, for example, the gas detector 10 may be configured to include the detection unit 1, the transducer 11, and a transmission unit, and the transmission unit may transmit a signal output by the transducer 11 to an external device of the gas detector 10 via a wired or wireless connection. In this case, the transmission unit may include, for example, an appropriate interface or a wireless transmitter that transmits a signal.

[0061] Furthermore, it is not essential that the multiple functions of the gas detector 10 are integrated into one housing. The components of the gas detector 10 may be distributed across multiple housings.

[0062] Furthermore, a gas detection system may be constructed by implementing at least some of the functions of the gas detector 10, for example, at least some of the functions of the processing unit 12, using the cloud (cloud computing) or the like. For example, in the embodiment, when a trained model is used, the trained model is stored in the memory unit 14, but the control unit 13 may generate detection results using a trained model stored on the cloud. In this case, it can be said that the gas detector 10 including the sensing unit 2 constitutes part of the gas detection system.

[0063] More specific examples of the embodiments will be presented below, but the present disclosure is not limited to the following examples.

[0064] 1. Example As particles of a metal organic framework, MIL-53 (Al) having an average particle size of 10 μm was prepared.

[0065] Carbon black having an average particle size of 20 μm was prepared as the conductive particles.

[0066] Polytetrafluoroethylene was used as the binder.

[0067] The metal organic framework, the conductive particles, and the binder were blended in a mass ratio of 3:7:1, and these were dispersed in ethanol, which was a dispersion medium, so that the solid content was 30 mg / mL, thereby preparing a dispersion liquid.

[0068] The dispersion liquid was applied to a substrate having two comb-shaped electrodes so as to cover the two comb-shaped electrodes, and then dried to produce a membranous sensitive part having a circular shape with a diameter of 10 mm in plan view and a thickness of 2 μm.

[0069] 2. Comparative Example Polystyrene was prepared as a gas adsorbent resin.

[0070] Carbon black having an average particle size of 20 μm was prepared as the conductive particles.

[0071] Polytetrafluoroethylene was used as the binder.

[0072] A gas-adsorbing resin, conductive particles, and a binder were mixed in a mass ratio of 10:10:1, and these were added to hexyl acetate to dissolve the polystyrene and disperse the conductive particles to a concentration of 30 mg / mL, thereby preparing a dispersion liquid.

[0073] Using this dispersion, a membranous sensitive part having a circular shape with a diameter of 10 mm in plan view and a thickness of 2 μm was prepared in the same manner as in the example.

[0074] 3. Sensitivity Test Nitrogen gas was used as the reference gas, and the sensitive part of each of the Examples and Comparative Examples was exposed to a flow of the reference gas at a flow rate of 150 mL / min. Subsequently, benzaldehyde, the detection target, was mixed into the reference gas flow to a concentration of 5 ppm. The mixing of benzaldehyde was continued for 5 minutes, and then the mixing of benzaldehyde was stopped.

[0075] During the above test, the electrical resistance between the electrodes on the substrate was continuously measured. The measurement results for the example are shown in FIG. 5, and the measurement results for the comparative example are shown in FIG. 6. In each of the graphs in FIG. 5 and FIG. 6, the vertical axis represents the response value proportional to the electrical resistance, and the horizontal axis represents the elapsed time. In each graph, the section between the dashed lines represents the section in which benzaldehyde was mixed into the nitrogen gas flow.

[0076] As shown in Figures 5 and 6, it is observed that the electrical resistance of the sensitive part increases while the sensitive part is exposed to the airflow containing benzaldehyde. As is clear from a comparison between Figures 5 and 6, the degree of change in electrical resistance in the example is significantly greater than that in the comparative example. The electrical resistance (R ０ ) and the electrical resistance (R １ ) to [(R １ -R ０ ) / R ０ ] × 100 (%), the sensitivity of the comparative example was 2.00 × 10 －１ (%), whereas the sensitivity of the example was 2.70 × 10 ０ (%).

[0077] [Aspects] As shown in the above embodiments and examples, the present disclosure includes the following aspects.

[0078] The sensitive material of the first aspect is used for gas detection. The gas sensitive material contains a metal organic framework.

[0079] According to this embodiment, the degree of change in the physical properties of the gas sensitive material that occurs when the gas sensitive material is sensitive to the gas can be improved.

[0080] In the second aspect, the ligand constituting the metal organic framework in the first aspect includes an organic ligand having a structure in which the ligand has at least two coordination sites that form coordinate bonds with different metal ions and a rotatable bond, and the positional relationship between the two coordination sites is variable by rotation of the bond.

[0081] According to this embodiment, the degree of change in the physical properties of the gas-sensitive material that occurs when the gas-sensitive material is sensitive to a gas can be further improved.

[0082] In a third aspect, in the first or second aspect, the ligand constituting the metal organic framework comprises at least one selected from the group consisting of 2-methylimidazole, 4-(1H-imidazol-1-yl)benzoic acid, terephthalic acid, fumaric acid, 4-amino-4H-1,2,4-triazole, bithiophenedicarboxylic acid, 1,4-benzenedipyrazolate, 1,4-diazabicyclo[2.2.2]octane, and 1,4-benzenedicarboxylate.

[0083] According to this embodiment, the degree of change in the physical properties of the gas-sensitive material that occurs when the gas-sensitive material is sensitive to a gas can be further improved.

[0084] In a fourth aspect, in any one of the first to third aspects, the ligand constituting the metal organic framework is ２ Contains an —OH group.

[0085] According to this embodiment, the degree of change in the physical properties of the gas-sensitive material that occurs when the gas-sensitive material is sensitive to a gas can be further improved.

[0086] In a fifth aspect, in any one of the first to fourth aspects, the metal ions in the metal organic framework include at least one selected from the group consisting of silver ions, copper ions, iron ions, zinc ions, aluminum ions, nickel ions, chromium ions, cobalt ions, cadmium ions, and manganese ions.

[0087] According to this embodiment, the degree of change in the physical properties of the gas-sensitive material that occurs when the gas-sensitive material is sensitive to a gas can be further improved.

[0088] In a sixth aspect, in any one of the first to fifth aspects, the gas-sensitive material further contains a plurality of conductive particles (22).

[0089] According to this embodiment, the degree of change in the electrical properties of the gas-sensitive material that occurs when the gas-sensitive material is sensitive to a gas can be improved.

[0090] A gas detector (10) according to a seventh aspect comprises a sensitive part (2) containing the gas-sensitive material according to any one of the first to sixth aspects.

[0091] According to this embodiment, by using the gas detector (10), gas detection can be performed with high sensitivity based on changes in the physical properties of the sensitive part (2).

[0092] In an eighth aspect, the gas detector (10) of the seventh aspect further comprises an electrode (4) electrically connected to the sensitive part (2).

[0093] According to this embodiment, by using the gas detector (10), gas detection can be performed with high sensitivity based on changes in the electrical properties of the sensitive part (2).

[0094] In a ninth aspect, the gas detector (10) in the seventh or eighth aspect further comprises a transducer (11) that outputs a signal according to the physical properties of the sensitive part (2).

[0095] According to this embodiment, by using the gas detector (10), gas detection can be performed with high sensitivity based on the signal output from the transducer (11).

[0096] REFERENCE SIGNS LIST 1 Detecting section 10 Gas detector 11 Transducer 2 Sensing section 22 Conductive particles 4 Electrode

Claims

1. A gas-sensitive material used for gas detection, the gas-sensitive material containing a metal-organic framework.

2. The gas-sensing material according to claim 1, wherein the ligands constituting the metal-organic framework comprise an organic ligand having a structure in which the ligands have at least two coordination sites that form coordinate bonds with different metal ions and a rotatable bond, and the positional relationship between the two coordination sites is variable by rotating the bond.

3. The gas-sensitive material according to claim 1, wherein the ligand constituting the metal-organic framework comprises at least one selected from the group consisting of 2-methylimidazole, 4-(1H-imidazol-1-yl)benzoic acid, terephthalic acid, fumaric acid, 4-amino-4H-1,2,4-triazole, bithiophenedicarboxylic acid, 1,4-benzenedipyrazolate, 1,4-diazabicyclo[2.2.2]octane, and 1,4-benzenedicarboxylate.

4. The ligand constituting the metal organic framework is μ ２ The gas-sensitive material according to claim 1 , comprising an —OH group.

5. The gas-sensitive material according to claim 1, wherein the metal ions in the metal organic framework include at least one selected from the group consisting of silver ions, copper ions, iron ions, zinc ions, aluminum ions, nickel ions, chromium ions, cobalt ions, cadmium ions, and manganese ions.

6. The gas-sensitive material according to claim 1, further comprising a plurality of conductive particles.

7. A gas detector comprising a sensitive part containing the gas sensitive material according to any one of claims 1 to 6.

8. The gas detector according to claim 7, further comprising an electrode electrically connected to the sensitive portion.

9. The gas detector according to claim 7, further comprising a transducer that outputs a signal according to the physical properties of the sensitive part.

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