JP7618927B2 - Gas Storage and Release Compounds - Google Patents

Description

The present invention relates to a gas storage and release compound capable of storing and releasing gas.

In order to solve environmental problems such as global warming, efforts are underway to develop clean energy sources to replace fossil fuels. Of these, hydrogen is considered one of the most promising energy sources because it is a diverse and abundant resource, has good combustion performance characteristics and heat generation, and has a low environmental impact as no carbon dioxide is emitted when generating electricity using fuel cells or internal combustion engines.

To use hydrogen as an energy source, it is necessary to build a hydrogen storage and release system that can flexibly respond to changing demand. For example, it is necessary to build a hydrogen supply chain that transports hydrogen obtained by electrolyzing water using surplus electricity to facilities where it will be used.
However, because hydrogen is a gas at room temperature and pressure, it is currently stored as high-pressure hydrogen gas in containers such as tanks and cylinders. Therefore, in order to use hydrogen, it was necessary to transport high-pressure hydrogen or liquefied hydrogen by tank truck. In addition, hydrogen storage facilities also required the development of large-scale infrastructure such as high-pressure hydrogen gas tanks.

Instead of using a high-pressure hydrogen gas storage/release system using a container, when using hydrogen on-site, a hydrogen storage/release system using a hydrogen storage material that can safely store and release a large amount of hydrogen at low pressure by the interaction between hydrogen and the material is being considered. A hydrogen storage material is a material that can selectively and reversibly store and release hydrogen. Hydrogen storage alloys are considered to be promising hydrogen storage materials, but they have problems with their hydrogen storage capacity. There is also room for improvement in terms of performance degradation due to impurity gases and increased costs associated with using rare metals and high-purity metals as raw materials. Furthermore, hydrogen storage alloys have poor workability, and the density of the titanium and manganese that make up the alloys is as high as 4 to 8 g/cm ^3, which makes the storage body heavy, and requires cooling when storing hydrogen and heating when releasing hydrogen, which is problematic in terms of handling.

Patent Document 1 describes a hydrogen storage material containing a carbon material in which a 3D structure is expressed from graphene and carbon nanotubes. However, the pressure range required for absorbing hydrogen into the hydrogen storage material is as high as 20 atm to 50 atm, and the material is not practical as a hydrogen storage adsorption material.
Patent Literature 2 describes a gas adsorption material that includes a porous metal-organic framework containing a plurality of metal clusters containing one or more metal ions and a plurality of charged multidentate bonding ligands bonding adjacent metal clusters, and a plurality of functional fullerenes or fullerides provided in the pores of the porous metal-organic framework, and that can adsorb 6% by weight of hydrogen at a temperature of 77 K. However, since the metal and the multidentate bonding ligands are not covalently bonded to each other in the porous metal-organic framework, but are bonded only by weak interactions, the crystal structure of the porous metal-organic framework is destroyed by moisture, causing a decrease in hydrogen storage capacity, making the material impractical.
Patent Document 3 describes a coated hydrogen storage pellet that includes a hydrogen storage material such as a borohydride compound and a coating that includes a hydrogen-permeable polymer. However, sodium borohydride, a typical borohydride compound, is not practical because it has a very high hydrogen release temperature of 300° C. or more and requires a long time to generate hydrogen.

Special Publication No. 2021-510364 Special Publication No. 2012-514530 Special table 2016-502968 publication

The problem to be solved by the present invention is to provide a novel gas storage/release compound that has excellent storage and release properties for various gases, and a gas storage/release material that contains the gas storage/release compound.

The present inventors have conducted extensive research to solve the above problems. As a result, they have found that a gas storage/release compound having a specific structural unit and a gas storage/release material containing the gas storage/release compound have excellent storage/release properties for various gases, particularly hydrogen, and that the above problems can be solved by using them.

That is, the present invention for solving the above problems mainly includes the following configurations.
[Item 1]
A gas storage and release compound having a structural unit represented by formula (1) and a structural unit represented by formula (2).
(In formula (1), R ¹ to R ³ are each independently a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms. In formula (2), R ⁴ is a trivalent aromatic hydrocarbon group. Formulas (1) and (2) are bonded by an amide bond, and structural units of the same formula are not directly bonded.)
[Item 2]
Item 2. The gas storage and release compound according to item 1, wherein the gas storage and release compound has a network structure.
[Item 3]
A method for producing a gas storage/release compound, comprising reacting at least a tris(aminoalkyl)amine compound represented by formula (3) with an aromatic tricarboxylic acid represented by formula (4).
(In formula (3), R ¹ to R ³ are each independently a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms. In formula (4), R ⁴ is a trivalent aromatic hydrocarbon group, and X, Y, and Z are each independently OH, halogen, OR ⁵ (R ⁵ is an alkyl group having 1 to 6 carbon atoms, and when there are multiple R 5 s, they may be the same or different), or NHR ⁶ (R ⁶ is an alkyl group having 1 to 6 carbon atoms, and when there are multiple R 6 s, they may be the same or different).)
[Item 4]
Item 3. A gas storage and release material comprising the gas storage and release compound according to item 1 or 2.
[Item 5]
Item 5. The gas storage and release material according to item 4, wherein the gas is at least one selected from the group consisting of hydrogen, carbon dioxide, nitrogen, a rare gas, and a hydrocarbon gas.
[Item 6]
Item 6. The gas storage and/or release material according to item 4 or 5, wherein the gas is stored and/or released by a method including one or more means selected from the group consisting of pressurization, depressurization, temperature increase, temperature decrease, application of electric potential, and irradiation with energy waves.
[Item 7]
Item 7. The gas storage and release material according to any one of Items 4 to 6, wherein the gas storage and release material is in the form of particles, fibers, a film, a nonwoven fabric, a woven fabric, a porous body, or a molded body.

INDUSTRIAL APPLICABILITY The present invention provides a novel gas storage/release compound having excellent storage/release properties for various gases, and a gas storage/release material containing the gas storage/release compound.
The gas storage and release compound of the present invention and the gas storage and release material containing the gas storage and release compound have particularly excellent hydrogen storage and release properties.
The gas storage/release compound of the present invention and the gas storage/release material containing the gas storage/release compound can store larger amounts of hydrogen than hydrogen storage alloys and have a lower density, require less energy when cooling to store hydrogen or when heating to release hydrogen, and are easy to control the storage and release of hydrogen.
The gas storage/release compound and the gas storage/release material containing the gas storage/release compound of the present invention are inexpensive and highly versatile because they can be obtained by a simple synthesis method using commercially available compounds. In addition, since the compound is a polymer material with a lower density than hydrogen storage alloys, it is easy to handle and enables efficient hydrogen transportation. Furthermore, since the conditions for heating/cooling, pressurization/depressurization, etc. during hydrogen storage/release can be made mild, it can be used under low energy usage. Therefore, it is possible to safely and inexpensively build a hydrogen supply chain that transports hydrogen obtained from surplus electricity to utilization facilities.

FIG. 2 is a diagram showing the hydrogen storage and release characteristics of a gas storage and release material containing the gas storage and release compound of the present invention and a hydrogen storage alloy. FE-SEM (field emission scanning electron microscope) photograph of the surface of the gas storage and release compound of the present invention.

The gas storing and releasing compound and the gas storing and releasing material containing the same of the present invention will be described below.
[Gas storage and release compounds]
The gas storage and release compound of the present invention has a structural unit represented by formula (1) and a structural unit represented by formula (2).
(In formula (1), R ¹ to R ³ are each independently a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms. In formula (2), R ⁴ is a trivalent aromatic hydrocarbon group. Formulas (1) and (2) are bonded by an amide bond, and structural units of the same formula are not directly bonded.)
At least two of the three binding sites in the structural unit represented by formula (1) of the present invention are polymerized by bonding with the structural unit represented by another formula (2). Similarly, at least two of the three binding sites in the structural unit represented by formula (2) of the present invention are polymerized by bonding with the structural unit represented by another formula (1).

The structural unit represented by formula (1) can be obtained, for example, from a tris(aminoalkyl)amine compound represented by formula (3).
(In formula (3), R ¹ to R ³ each independently represent a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms.)

In formula (3), the divalent aliphatic hydrocarbon groups having 2 to 8 carbon atoms for R ¹ to R ³ are preferably, for example, each independently one or more groups selected from the group consisting of -(CH ₂ ) ₂ -, -(CH ₂ ) ₃ -, -(CH ₂ ) ₄ -, -(CH ₂ ) ₆ -, -(CH ₂ ) ₈ -, -(CH(CH ₃ )CH ₂ )-, etc. When R ¹ to R ³ are divalent aliphatic hydrocarbon groups having 2 to 8 carbon atoms, the surface area of the gas storage and release compound when granulated becomes appropriate, and the gas storage and release capacity can be increased.

The tris(aminoalkyl)amine compound represented by formula (3) may be a commercially available product or may be obtained by synthesis. In the present invention, it is preferable to use one or more types selected from the group consisting of tris(2-aminoethyl)amine, tris(3-aminotrimethylene)amine, tris(4-aminobutyl)amine, tris(6-aminohexyl)amine, tris(aminopropyl)amine, etc.

The structural unit represented by formula (2) can be obtained, for example, from an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof.
(In formula (4), R ⁴ is a trivalent aromatic hydrocarbon group, and X, Y, and Z each independently represent OH, a halogen, OR ⁵ (R ⁵ is an alkyl group of 1 to 6, and when there are multiple R 5s, they may be the same or different), or NHR ⁶ (R ⁶ is an alkyl group of 1 to 6, and when there are multiple R 6s, they may be the same or different).)

The trivalent aromatic hydrocarbon group R ⁴ in the formula (4) is, for example, an aromatic hydrocarbon group having 6 to 30 carbon atoms. Among these, trimellitic acid, 1,2,3-benzenetricarboxylic acid, trimesic acid, hemillitic acid, 1,2,4-naphthalenetricarboxylic acid, 1,4,5-naphthalenetricarboxylic acid, 1,3,6-naphthalenetricarboxylic acid or 2,3,6-naphthalenetricarboxylic acid, 1,2,8-naphthalenetricarboxylic acid, 2,3,6-anthracenetricarboxylic acid, 3,4,4'-benzophenonetricarboxylic acid, 3,4,4'-biphenylethertricarboxylic acid, 3,4,4'-biphenyltricarboxylic acid, 2,3,2'-biphenyltricarboxylic acid, 3,4,4'-biphenylmethanetricarboxylic acid, 3,4,4'-biphenylsulfonetricarboxylic acid, and reactive derivatives of these aromatic tricarboxylic acids (acid halides, acid anhydrides, esterified products, amidated products, etc.), and the like, are preferably groups derived from one or more trivalent aromatic tricarboxylic acids selected from the group consisting of these.

The gas storage/release compound of the present invention may contain copolymer units in addition to the structural units represented by formulas (1) and (2).
Copolymerization units that may be contained in the gas storage/release compound of the present invention include, for example, those represented by the following formulas (5) to (7), other than the structural units represented by formula (1) or (2).
-HN-R ⁷ (-NH-) _w ...(5)
-OC-R ⁸ (-CO-) _x ...(6)
(-CO-) _y R ⁹ (-CO-) _z ...(7)
(In formulas (5) to (7), w is an integer of 1 to 3, x is an integer of 1 to 3, y is 1 or 2, z is 1 or 2, ^R7 is an organic group having a valence of w+1, ^R8 is an organic group having a valence of x+1, and ^R9 is an organic group having a valence of y+z.)
The structural units represented by formula (1), formula (2), and formulas (5) to (7) are bonded together by forming an amide bond (-HN-CO- or >N-CO-).
In the present invention, the structural unit represented by formula (5) can be obtained from a polyamine compound that does not constitute a structural unit represented by formula (1), the structural unit represented by formula (6) can be obtained from a polycarboxylic acid or a reactive derivative thereof that does not constitute a structural unit represented by formula (2), and the structural unit represented by formula (7) can be obtained from a (di)amino(di)carboxylic acid, a reactive derivative thereof, or a lactam.

R ⁷ , R ⁸ and R ⁹ each independently include, for example, a divalent aliphatic hydrocarbon group having 2 to 20 carbon atoms, a divalent alicyclic hydrocarbon group having 3 to 20 carbon atoms, a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and an aromatic heterocyclic group having 6 to 20 carbon atoms and containing N and/or O and/or S. Preferred examples thereof include an alkylene group, a phenylene group, etc. having 2 to 6 carbon atoms.

R is an organic group having a valence of w+1 in formula (5). Examples of the compound ⁷ include aromatic diamines such as 1,4-diaminobenzene, 1,3-diaminobenzene, 1,2-diaminobenzene, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene, 2,6-diaminotoluene, 2,4-diaminotoluene, 3,4-diaminotoluene, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylether, 4,4'-diaminodiphenylether, 4,4'-diamino-1,2-diphenylethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, and 3,3'-diaminodiphenylsulfone; ethylenediamine, 1,3-propanediamine, 1,4-butanediamine, and 1,6-hexaaminodiamine. aliphatic diamines such as isophorone diamine, norbornane diamine, 1,2-cyclohexane diamine, 1,3-cyclohexane diamine, 1,4-cyclohexane diamine, 4,4'-diaminodicyclohexylmethane, piperazine, and the like; polyamine phenols such as 2,2-bis(3-amino-4-hydroxyphenyl)propane, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and polyfunctional amines such as 1,2,4-triaminobenzene and 3,4,4'-triaminodiphenyl ether, and the like.

R is an organic group having a valence of x+1 in formula (6). As ⁸ , for example, aromatic dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 2,7-pyrene dicarboxylic acid; aliphatic dibasic acids such as oxalic acid, methylmalonic acid, maleic acid, fumaric acid, malic acid, tartaric acid, thiomalic acid, and diglycolic acid; alicyclic dibasic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, dicyclohexanemethane-4,4'-dicarboxylic acid, and norbornanedicarboxylic acid; hydrogenated trimellitic acid, pyromellitic acid, hydrogenated pyromellitic acid, and benzophenonetetracarboxylic acid; or a group derived from one or more polycarboxylic acid compounds or reactive derivatives thereof (acid halides, esters, amidations, acid anhydrides, etc.) selected from the group consisting of these.

As R ⁹ which is an organic group having a valence of y+1 in formula (7), for example, one or more kinds of (di)amino(di)carboxylic acids selected from the group consisting of 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminocapric acid, 11-aminoundodecanoic acid, aminobenzoic acid, ε-caprolactam, ω-enantholactam, ω-undecalactam, ω-laurolactam, α-pyrrolidone, α-piperidone, etc., or reactive derivatives thereof, or groups derived from lactams are preferred.

The gas storage/release compound of the present invention may be composed only of the structural unit represented by formula (1) and the structural unit represented by formula (2). In addition to the structural unit represented by formula (1) and the structural unit represented by formula (2), the gas storage/release compound may contain one or more structural units represented by formulas (5) to (7).
The content of the structural unit represented by formula (1) relative to the total amount of all structural units in the gas storage/release compound (structural units represented by formula (1), structural units represented by formula (2), structural units represented by formula (5), structural units represented by formula (6) and structural units represented by formula (7), hereinafter, these may be collectively referred to as "all structural units") is 1 to 60 mol%, preferably 5 to 60 mol%, more preferably 10 to 50 mol%. If it is less than 1 mol% or more than 60 mol%, the gas storage/release properties may be reduced.

The content of the structural unit represented by formula (2) relative to the total amount of all structural units in the gas storage/release compound is 1 to 60 mol%, preferably 5 to 60 mol%, and more preferably 10 to 50 mol%. If it is less than 1 mol% or more than 60 mol%, the gas storage/release properties may be reduced.

The content of the structural unit represented by formula (5) relative to the total amount of all structural units in the gas storage/release compound is 0 to 30 mol%, preferably 0 to 20 mol%, more preferably 0 to 10 mol%. If it exceeds 30 mol%, the gas storage/release properties may be deteriorated.
The content of the structural unit represented by formula (6) relative to the total amount of all structural units in the gas storage/release compound is 0 to 30 mol%, preferably 0 to 20 mol%, more preferably 0 to 10 mol%. If it exceeds 30 mol%, the gas storage/release properties may be deteriorated.
The content of the structural unit represented by formula (7) relative to the total amount of all structural units in the gas storage/release compound is 0 to 40 mol%, preferably 0 to 20 mol%, more preferably 0 to 10 mol%. If it exceeds 40 mol%, the gas storage/release properties may be deteriorated.

The weight average molecular weight of the gas storage and release compound of the present invention is not particularly limited, but is 10,000 to 300,000, preferably 50,000 to 200,000, and more preferably 80,000 to 180,000.

[Method of producing gas storage and release compound]
The gas storage and release compound of the present invention can be obtained by reacting at least a polyamine component containing a tris(aminoalkyl)amine compound represented by formula (3) with a polycarboxylic acid component containing an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof, using a known polyamide polymerization reaction means.

(In formula (3), R ¹ to R ³ each independently represent a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms.)

(In formula (4), R ⁴ is a trivalent aromatic hydrocarbon group, and X, Y, and Z each independently represent OH, a halogen, OR ⁵ (R ⁵ is an alkyl group of 1 to 6, and when there are multiple R 5s, they may be the same or different), or NHR ⁶ (R ⁶ is an alkyl group of 1 to 6, and when there are multiple R 6s, they may be the same or different).)

<Polyamine component>
In the tris(aminoalkyl)amine compound represented by formula (3) contained in the polyamine component, the divalent aliphatic hydrocarbon groups having 2 to 8 carbon atoms for R ¹ to R ³ in formula (3) are preferably, for example, each independently one or more groups selected from the group consisting of -(CH ₂ ) ₂ -, -(CH ₂ ) ₃ -, -(CH ₂ ) ₄ -, -(CH ₂ ) ₆ -, -(CH ₂ ) ₈ -, -(CH(CH ₃ )CH ₂ )-, etc. When R ¹ to R ³ are divalent aliphatic hydrocarbon groups having 2 to 8 carbon atoms, the surface area of the gas storage and release compound when granulated becomes appropriate, and the gas storage and release capacity can be increased.

The tris(aminoalkyl)amine compound represented by formula (3) may be a commercially available product or may be obtained by synthesis. In the present invention, it is preferable to use one or more types selected from the group consisting of tris(2-aminoethyl)amine, tris(3-aminotrimethylene)amine, tris(4-aminobutyl)amine, tris(6-aminohexyl)amine, tris(aminopropyl)amine, etc.

In the present invention, the polyamine component may contain a polyamine other than the tris(aminoalkyl)amine compound represented by formula (3) or a reactive derivative thereof. Examples of such polyamines include diamines, polyamine phenols, and other polyamines.
Examples of diamines include aromatic diamines such as 1,4-diaminobenzene, 1,3-diaminobenzene, 1,2-diaminobenzene, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,3-diaminonaphthalene, 2,6-diaminotoluene, 2,4-diaminotoluene, 3,4-diaminotoluene, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylether, 4,4'-diaminodiphenylether, 4,4'-diamino-1,2-diphenylethane, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminobenzophenone, 4,4'-diaminodiphenylsulfone, 3,3'-diaminobenzophenone, and 3,3'-diaminodiphenylsulfone; ethylenediamine, 1,3-propanediamine, and 1,4-butanediamine. One or more selected from the group consisting of aliphatic diamines such as 1,6-hexanediamine, 1,7-heptanediamine, 1,9-nonanediamine, 1,12-dodecamethylenediamine, and metaxylenediamine; alicyclic diamines such as isophoronediamine, norbornanediamine, 1,2-cyclohexanediamine, 1,3-cyclohexanediamine, 1,4-cyclohexanediamine, 4,4'-diaminodicyclohexylmethane, and piperazine; polyamine phenols such as 2,2-bis(3-amino-4-hydroxyphenyl)propane, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, and 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane; and polyfunctional amines such as 1,2,4-triaminobenzene and 3,4,4'-triaminodiphenyl ether can be used.
The polyamine other than the tris(aminoalkyl)amine compound represented by formula (3) or a reactive derivative thereof is a monomer that constitutes a copolymerization unit, which is a structural unit represented by formula (5).

The content of the tris(aminoalkyl)amine compound represented by formula (3) in the polyamine component is 10 to 100 mol %, preferably 50 to 100 mol %. If it is less than 10 mol %, the gas storage space in the polymer structure will shrink, which may result in a decrease in gas storage and release characteristics.

<Polycarboxylic Acid Component>
The aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof contained in the polycarboxylic acid component is a monomer that constitutes the structural unit represented by formula (2).

The aromatic tricarboxylic acid compound represented by formula (4) used in the present invention or a reactive derivative thereof is, for example, trimellitic acid, 1,2,3-benzenetricarboxylic acid, trimesic acid, hemillitic acid, 1,2,4-naphthalenetricarboxylic acid, 1,4,5-naphthalenetricarboxylic acid, 1,3,6-naphthalenetricarboxylic acid or 2,3,6-naphthalenetricarboxylic acid, 1,2,8-naphthalenetricarboxylic acid, 2,3,6-anthracenetricarboxylic acid, 3,4,4'-benzophenonetricarboxylic acid, 3,4,4'-biphenylethertricarboxylic acid, 3,4,4'-biphenyltricarboxylic acid, 2,3,2'-biphenyltricarboxylic acid, 3,4,4'-biphenylmethanetricarboxylic acid, 3,4,4'-biphenylsulfonetricarboxylic acid, reactive derivatives of these aromatic tricarboxylic acids (acid halides, acid anhydrides, esterified products, amidated products, etc.), and the like. A group derived from one or more trivalent aromatic tricarboxylic acids selected from the group consisting of such is preferred.
In the present invention, it is preferable to use an aromatic tricarboxylic acid halide as the aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof from the viewpoint of reactivity and the like.

In the present invention, the polycarboxylic acid component may contain a polycarboxylic acid or a reactive derivative thereof (such as an acid halide, an ester, an amidation, or an acid anhydride) other than the aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof. Examples of such polycarboxylic acids include aromatic dibasic acids such as phthalic acid, isophthalic acid, terephthalic acid, 1,4-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, and 2,7-pyrene dicarboxylic acid; aliphatic dibasic acids such as oxalic acid, methylmalonic acid, maleic acid, fumaric acid, malic acid, tartaric acid, thiomalic acid, and diglycolic acid; alicyclic dibasic acids such as 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, dicyclohexanemethane-4,4'-dicarboxylic acid, and norbornanedicarboxylic acid; and polybasic acids such as hydrogenated trimellitic acid, pyromellitic acid, hydrogenated pyromellitic acid, and benzophenonetetracarboxylic acid. At least one selected from the group consisting of these can be used.
A polycarboxylic acid or a reactive derivative thereof other than the aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof is a monomer that constitutes a copolymerization unit, which is a structural unit represented by formula (6).

The content of the aromatic tricarboxylic acid compound represented by formula (4) or its reactive derivative in the polycarboxylic acid component is 10 to 100 mol %, preferably 50 to 100 mol %. If it is less than 10 mol %, the gas storage and release properties may be reduced.

<Other reaction components>
In the present invention, in addition to the polycarboxylic acid component and the polyamine component, (di)amino(di)carboxylic acid compounds (diaminocarboxylic acid compounds, diaminodicarboxylic acid compounds, aminodicarboxylic acid compounds), lactams, etc. can be used as other reaction components as necessary during the polyamide polymerization reaction. (Di)amino(di)carboxylic acid and lactam are monomers that constitute copolymerization units, which are structural units represented by formula (7).

As the (di)amino(di)carboxylic acid compound, for example, one or more compounds selected from the group consisting of 7-aminoheptanoic acid, 8-aminooctanoic acid, 9-aminononanoic acid, 10-aminocapric acid, 11-aminoundodecanoic acid, aminobenzoic acid, diaminobenzoic acid, aminoterephthalic acid, diaminoterephthalic acid, aminoisophthalic acid, diaminoisophthalic acid, and the like can be used.
As the lactam, for example, one or more species selected from the group consisting of ε-caprolactam, ω-enantholactam, ω-undecalactam, ω-laurolactam, α-pyrrolidone, α-piperidone, and the like can be used.

<Reaction ratio of each component>
In the present invention, the reaction molar ratio of the polyamine component containing the tris(aminoalkyl)amine compound represented by formula (3) and the polycarboxylic acid component containing the aromatic tricarboxylic acid compound represented by formula (4) or its reactive derivative is 0.8 to 1.7 moles, preferably 0.9 to 1.6 moles, more preferably 0.95 to 1.45 moles of the polycarboxylic acid component containing the aromatic tricarboxylic acid compound represented by formula (4) or its reactive derivative, per mole of the polyamine component containing the amino group-terminated polyoxyalkylene-added triol compound represented by formula (3). If the amount of the polycarboxylic acid component containing the aromatic tricarboxylic acid compound represented by formula (4) or its reactive derivative is more than 1.7 moles or less than 0.8 moles, the molecular weight of the gas storage and release compound is not sufficiently large, and the gas storage and release properties may be reduced.
The molar ratio of the compound represented by formula (3) to the compound represented by formula (4) is formula (3):formula (4)=1:1.6 to 1:0.8, preferably 1:1.5 to 1:0.9.
The amount of the "other reactive components" per mole of the polyamine component containing the amino-terminated polyoxyalkylene-added triol compound represented by formula (3) is in the range of 0 to 9 moles, preferably 0 to 2 moles.

[Polymerization method]
In the present invention, as a method for reacting at least a polyamine component containing a tris(aminoalkyl)amine compound represented by formula (3) with a polycarboxylic acid component containing an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof, a known polyamide polymerization reaction means can be used.
for example,
(i) a method of converting an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof into an aromatic tricarboxylic acid chloride and reacting the resulting acid chloride with a polyamine component containing a tris(aminoalkyl)amine compound represented by formula (3);
(ii) a method in which an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof is converted into a dicarboxylic acid diester, and the diester is reacted with a polyamine component containing a tris(aminoalkyl)amine compound represented by formula (3) in the presence of a metal catalyst;
(iii) a method in which an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof is converted into a dicarboxylic acid and reacted with a polyamine component containing a tris(aminoalkyl)amine compound represented by formula (3) in the presence of a carbodiimide catalyst;
etc.
In the present invention, it is preferable to use a method in which an aromatic tricarboxylic acid compound represented by formula (4) or a reactive derivative thereof is converted into a dicarboxylic acid chloride and reacted with a polyamine component containing a tris(aminoalkyl)amine compound represented by formula (3).

The gas storage/release compound of the present invention has a mesh-like structure because it contains a structural unit represented by formula (1) and a structural unit represented by formula (2). It is speculated that this mesh-like structure acts like a wall that holds hydrogen molecules, thereby exerting the function of storing and releasing gas, for example, hydrogen molecules (hydrogen gas), but the present invention is not limited by this speculation in any way.

[Gas storage and release material]
The gas storage and release material of the present invention contains one or more kinds of the gas storage and release compounds in an amount of 1 to 100% by mass, preferably 10 to 100% by mass, and more preferably 50 to 100% by mass. If the content of the gas storage and release compounds is less than 1% by mass, the gas storage properties may not be fully exhibited.
Examples of components other than the gas storage/release compound having structural units represented by formulas (1) and (2) that may be contained in the gas storage/release material of the present invention include resins, fillers, various additives, etc.

The resin is not particularly limited, but examples thereof include polyolefin resin, polyester resin, acrylic resin, polyamide resin, urethane resin, etc. The filler is not particularly limited, but examples thereof include silica, talc, clay, calcium carbonate, barium sulfate, titanium oxide, glass flake, carbon fiber, glass fiber, metal fiber, organic fiber, organic nanofiber, inorganic nanofiber, metal nanofiber, etc. The various additives are not particularly limited, but examples thereof include colorants such as organic pigments, inorganic pigments, and dyes, adsorbents such as zeolite and activated carbon, plasticizers, antibacterial agents, conductive materials, etc.

The gas storage and release material may have any shape, such as particles, fibers, films, nonwoven fabrics, woven fabrics, porous bodies, molded bodies, and the like.
In the case of particles, the average particle diameter can be arbitrarily adjusted within the range of, for example, 0.1 μm to 20 mm. The average particle diameter of the gas storage/release material in the present invention is the volume-based cumulative particle diameter _D50 value at a cumulative volume of 50% by volume as measured by a laser diffraction/scattering particle size distribution measurement method.
In the case of fibers, the length can be adjusted to any value within the ranges of 1 mm to 3 m, the diameter 0.1 mm to 5 mm, and the denier number 0.5d to 20d.
In the case of a film, the thickness can be adjusted to any value within the range of, for example, 2 μm to 5 mm. The width and length of the film can be any size. In the case of a nonwoven fabric or woven fabric, the basis weight can be adjusted to any value within the range of, for example, 5 g/m ² to 200 g/m ² .
In the case of a porous body, the apparent density can be adjusted to within the range of 0.1 g/m ³ to 1.2 g/m ³ and the porosity can be adjusted to within the range of 5 to 80 vol %.
In the case of a molded article, any molding means such as extrusion molding or injection molding may be used to prepare a molded article of any shape.
The gas storage/release material of the present invention is preferably in the form of particles, porous bodies, nonwoven fabrics, films or fibers from the standpoints of ease of production, adjustment of the area in contact with gases such as hydrogen, and improved handling.

[Gas]
The gas (gas) stored and released by the gas storage and release compound or gas storage and release material of the present invention is not particularly limited. For example, one or more types selected from the group consisting of hydrogen, carbon dioxide, nitrogen, rare gases (helium, neon, argon, krypton, radon), hydrocarbon gases (methane, ethane, propane, butane, acetylene, etc.), oxygen, halogen gases (fluorine, chlorine), etc. are included. Preferably, one or more types selected from the group consisting of hydrogen, nitrogen, argon, methane, ethane, propane, and acetylene are selected, and more preferably, hydrogen.

[Method of storing and releasing gas]
The method for storing (associating) and releasing (desorbing) a gas (gas) in the gas storage/release compound or gas storage/release material of the present invention can use a known method for storing and releasing hydrogen in a gas storage/release compound or gas storage/release material, particularly a hydrogen storage material.
For example, the method may include one or more means selected from the group consisting of pressurization, depressurization, temperature increase (heating), temperature decrease (cooling), application of electric potential, and irradiation with energy waves such as ultraviolet rays and infrared rays.

The storage means is preferably a method including one or more means selected from the group consisting of pressurization, depressurization, temperature increase (heating), temperature decrease (cooling), application of electric potential, and irradiation with ultraviolet light, and more preferably a method including one or more means selected from the group consisting of pressurization, depressurization, temperature increase (heating), and temperature decrease (cooling). In the present invention, a method including pressurization means is particularly preferably used.
The releasing means is preferably a method including one or more means selected from the group consisting of decompression, pressurization, temperature increase (heating), temperature decrease (cooling), application of electric potential, and irradiation with ultraviolet light, and more preferably a method including one or more means selected from the group consisting of decompression, pressurization, temperature increase (heating), and temperature decrease (cooling). In the present invention, a method including a decompression means is particularly preferably used.

[Uses of gas storage and release compounds or gas storage and release materials]
The gas storage/release compound or gas storage/release material of the present invention can safely store a gas (gas) at room temperature (25° C.±20° C.) under atmospheric pressure for a long period of time, and can release the stored gas (gas) by a simple means. The gas storage/release compound or gas storage/release material of the present invention is useful as a hydrogen storage material, since it can safely store hydrogen at room temperature (25° C.±20° C.) under atmospheric pressure for a long period of time, and can release the stored hydrogen by a simple means.
Furthermore, even under low pressure conditions below atmospheric pressure where hydrogen storage alloys do not exhibit hydrogen storage/release characteristics, the alloys have excellent hydrogen storage/release characteristics, and from this point of view, they are also useful as hydrogen storage materials.
Furthermore, since it has excellent moldability, it can be easily processed into any shape, and since it is lightweight, it can be easily transported and stored.

For example, electricity generated at a wind power plant is used to produce hydrogen in a water electrolysis hydrogen production device, and the hydrogen is stored in the gas storage/release compound or gas storage/release material of the present invention housed in an on-board container. The container housing the gas storage/release compound or gas storage/release material with stored hydrogen is loaded onto a vehicle and transported to a hot spring facility having a hydrogen storage material tank and a pure hydrogen fuel cell as equipment, and hydrogen is transferred from the gas storage/release compound or gas storage/release material to these facilities.
The electricity and hot water generated by the fuel cell will be used in the hot spring facility, and "heat cascade utilization" will be implemented during hydrogen transport, with heat generated on the hydrogen storage side being used to heat the hydrogen release side. In addition, the heat required to release hydrogen from the hydrogen storage material tank can be provided by utilizing low-temperature exhaust heat from the building, improving energy efficiency.

The present invention will be described in more detail below with reference to examples. Note that the present invention is not limited in any way by these examples.

[Example]
Synthesis of Gas Storage and Release Compounds
2.0 g (0.0075 mol) of 1,3,5-benzenetricarbonyl trichloride, 1.1 g (0.0075 mol) of tris(2-aminoethyl)amine, and 4 ml of N,N-dimethylformamide were added to a 200 ml round-bottom flask, and the reaction system was stirred for 2 hours using a magnetic stirrer at a reaction temperature of 25°C. 10 ml of methanol was added to the reaction solution to cause precipitation, and the resulting precipitate was filtered using a glass filter G3 to obtain a polymer powder. The resulting polymer powder was vacuum-dried at 80°C for 3 hours to obtain the target gas storage/release compound.

<Structural analysis> (FT-IR)
The gas storage/release compound thus obtained was subjected to FT-IR measurement by a single reflection ATR method using a Fourier transform infrared spectrophotometer FT/IR-6800 manufactured by JASCO Corp. The results are as follows.
C=O: 1723, 1786 (cm ^-1 )
CH ₂ : 1495, 2932, 2963 (cm ⁻¹ )
NH: 1746, 1788 (cm ^-1 )
C-O-C: 1642, 1689 (cm ^-1 )
Phenyl ring: 3086 (cm ⁻¹ )

(Weight average molecular weight)
For the obtained gas storage/release compound, a HPLC column Shim-pack GPC-805 manufactured by Shimadzu GLC was attached to a gel permeation chromatography device manufactured by Shimadzu Corporation, the gas storage/release compound dissolved in N,N'-dimethylformamide solvent was injected, and the column retention time was measured. From the obtained column retention time, the molecular weight in terms of polystyrene was calculated by comparison with a calibration curve prepared in advance by measuring polystyrene whose molecular weight was known.
The gel permeation chromatography device manufactured by Shimadzu Corporation had the following configuration:
・System: Nexera GPC system ・System controller: CBM-40
・Liquid delivery unit LC40D
・Online degassing unit DGU-403
・Autosampler SIL-40C
・Column oven CTO-40C
・Detector: RID-20ABLK, LabSolutions GPC software, LC workstation PC, LabSolutions LC Single LC

(Structural analysis results)
From the results of the FT-IR and weight average molecular weight measurements, it was confirmed that the gas storage/release compound according to the example had at least the following two types of structural units (8) and (9), and was a network polyamide compound having a weight average molecular weight of 146,000 in which these structural units were bonded in a network shape through amide bonds.

<Evaluation of hydrogen storage and release capacity>
The hydrogen storage and release capacity was evaluated by filling a SUS sample tube with the test powder and observing the PCT curve at 25°C using a PCT characteristic evaluation device (PCT-4SDWIN, manufactured by Suzuki Shokan Co., Ltd.). The PCT characteristic measurement device is a device that measures the characteristics (P: pressure, C: storage amount (absorption amount), T: temperature) when a substance absorbs and releases hydrogen, and is also called a Sieverts device.
The relationship between pressure and the amount of hydrogen stored (Adsorption: mass%) and the amount of hydrogen released (Desorption: mass%) of the gas storage and release compound according to the embodiment is as shown in Figure 1. Note that the amount of hydrogen stored (absorption) or released is expressed as mass% relative to the mass of the gas storage and release compound.

<Scanning electron microscope observation>
The obtained powder of the gas storage/release compound was dried in a vacuum at 40° C. for 1 hour, and then an observation sample was prepared by a dispersion method. The surface of the gas storage/release compound was observed using a FE-SEM (field emission scanning electron microscope). The results are shown in FIG.
From FIG. 1, it can be seen that there are many pores of about 10 nm to 50 nm on the surface of the polymer particle, and it can be inferred that gas molecules are adsorbed inside the polymer chains through these pores.
The conditions for the scanning electron microscope observation are as follows.
・Field emission scanning electron microscope Zeiss Merlin
・Applying voltage 0.8kV

[Comparative Example]
2.0 g of graphene oxide powder (manufactured by Aldrich, product number (796034)) was placed in a vial and stored in a vacuum dryer (manufactured by AS ONE, ETTAS AVO-200V) at 120°C for 24 hours to be vacuum dried. The hydrogen storage and release capacity of this powder was evaluated in the same manner as in Example 1. The results are also shown in Figure 1. As a result, the gas storage compound of Example 1 (gas storage and release material containing it) showed a higher hydrogen storage and release capacity.

The present inventors speculate as follows about the reason why the gas storage and release properties of the gas storage and release compounds of the Examples are high.
Graphene oxide is a carbon compound formed by stacking layers of six-membered rings consisting of carbon-carbon bonds that are spread out two-dimensionally. The distance between each layer is in the range of 0.5 to 2.0 nm, and it is capable of capturing hydrogen molecules by applying a pressure of 10 MPa or more.
On the other hand, the gas storage and release compound of the present invention is a polymer in which aromatic rings having π electron clouds are arranged in a network shape, and hydrogen molecules can easily enter the inside of the polymer structure. It is presumed that hydrogen molecules are polarized to δ+ and δ- by π electrons, and that this makes it possible to easily capture hydrogen molecules inside the polymer structure (between aromatic rings) due to the interaction between the π electron clouds even under a pressure of about 1 MPa. However, the present invention is not limited to this presumption.

These results demonstrate that the gas storage and release compound of the present invention and the gas storage and release material containing it have a larger mass percentage of hydrogen storage (absorption) and release relative to the mass of the gas storage and release compound than the graphene oxide of the comparative example, and thus have a higher hydrogen storage and release capacity.
From this, it was confirmed that the gas storing and releasing compound of the present invention and the gas storing and releasing material containing the same are useful as materials capable of storing and releasing gas, particularly hydrogen.

Claims (6)

A gas storage and release material comprising a gas storage and release compound having a structural unit represented by formula (1) and a structural unit represented by formula (2).
(In formula (1), R ¹ to R ³ are each independently a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms. In formula (2), R ⁴ is a trivalent aromatic hydrocarbon group. Formulas (1) and (2) are bonded by an amide bond, and structural units of the same formula are not directly bonded.) The gas storage and release material according to claim 1 , wherein the gas storage and release compound has a network structure. A method for producing a gas storage and release material , comprising reacting at least a tris(aminoalkyl)amine compound represented by formula (3) with an aromatic tricarboxylic acid represented by formula (4).
(In formula (3), R ¹ to R ³ are each independently a divalent aliphatic hydrocarbon group having 2 to 8 carbon atoms. In formula (4), R ⁴ is a trivalent aromatic hydrocarbon group, and X, Y, and Z are each independently OH, halogen, OR ⁵ (R ⁵ is an alkyl group having 1 to 6 carbon atoms, and when there are multiple R 5 s, they may be the same or different), or NHR ⁶ (R ⁶ is an alkyl group having 1 to 6 carbon atoms, and when there are multiple R 6 s, they may be the same or different).) 3. The gas storage and release material according to claim 1 , wherein the gas is at least one selected from the group consisting of hydrogen, carbon dioxide, nitrogen, a rare gas, and a hydrocarbon gas. The gas storage and/or release material according to any one of claims 1, 2 and 4, wherein the gas is stored and/or released by a method including one or more means selected from the group consisting of pressurization, depressurization, temperature increase, temperature decrease, application of electric potential and irradiation with energy waves. 6. The gas storage and release material according to claim 1 , which is in the form of particles, fibers, a film, a nonwoven fabric, a woven fabric, a porous body, or a molded body.