Composite material containing COF, heat storage and release member, manufacturing method of the composite material, COF single crystal, and manufacturing method thereof

Abstract

The composite material of the present invention comprises: single crystals of covalent organic frameworks (COFs) having a major axis length greater than 120 μm or polycrystals of COFs composed of multiple such single crystals, and at least one heat storage compound, wherein the heat storage compound is a compound that generates heat or absorbs heat through adsorption or desorption, etc. on the COF single crystals. In addition, the heat storage and release member of the present invention comprises this composite material as a heat storage and heat dissipation material. Moreover, the major axis length of the COF single crystals of the present invention is greater than 120 μm, and the manufacturing method of the COF single crystals of the present invention is a method in which single crystals of COF are grown by crystallizing raw material compounds of COF through a solution containing an ionic liquid or an organic salt and a balance regulator.

Description

Technical Field

[0001] The present invention relates to a composite material containing a covalent organic framework (hereinafter simply referred to as "COF"), a heat storage / release member, and a method for manufacturing the composite material. In addition, the present invention also relates to a COF single crystal and a method for manufacturing the same. Background Art

[0002] There has been proposed a heat storage / dissipation system that utilizes reaction heat or latent heat. As an example, a system that utilizes the hydration reaction of magnesium oxide can be cited. In the heat storage mode of this system, magnesium hydroxide is heated by heat to obtain magnesium oxide and water. On the other hand, in the heat release mode, magnesium oxide is hydrated with water to output reaction heat (Patent Document 1).

[0003] As another example, a system that utilizes the solid-liquid phase change of sodium acetate trihydrate can be cited. Sodium acetate trihydrate has a melting point (freezing point) near 57.5 °C and can store heat in the form of heat of fusion and release heat in the form of heat of solidification (Patent Document 2).

[0004] On the other hand, in 2005, Professor Yaghi of the University of California, Berkeley, and others published a porous material called COF, which forms a network structure by covalently bonding light atoms such as hydrogen, boron, carbon, oxygen, and nitrogen. COF is a framework structure material formed by covalently bonding a variety of structural unit molecules (hereinafter also referred to as "raw material compounds") through polycondensation. The structural unit molecules include a "main body part (linker)" as the basic framework and a "hand part (linkage)" that becomes a bonding group for connecting the linkers to each other. COF has the following characteristics: it has a microscopic periodic order, its structure is clearly defined, it has a high specific surface area, and uniform pore diameters.

[0005] In addition, COF has the following various advantages: since it is composed only of light elements such as H, C, N, O, B, and Si, the environmental load is low; since it is formed by covalent bonds, it has high thermal and chemical stability, and by selecting linkers and linkages, the design of structural and functional performance can be carried out in a predictable manner, etc. COF determines whether it becomes a two-dimensional COF or a three-dimensional COF according to the number and direction of the linkages possessed by the structural unit molecules. The two-dimensional COF adopts a planar stacked structure, while the three-dimensional COF adopts a three-dimensional solid structure.

[0006] COF can freely design uniform pore diameters by appropriately selecting joints and connecting bonds. In addition, since COF is a network structure formed by covalent bonds, it is considered chemically more stable than a network structure formed by metal coordination bonds, namely a metal-organic framework (MOF), and is expected to be used as a gas storage, separation, catalyst, etc. (Patent Document 3).

[0007] As mentioned above, COF is expected to be used for various purposes, but there is not much attention paid to thermal conductivity. According to very few reports, for example, regarding the thermal conductivity of powders composed of fine single crystals of COF-300, which is one of the COFs, there are reports that the thermal conductivity is 0.038 to 0.048 w / mK, and the thermal conductivity is inversely proportional to the cross-sectional area of the pores possessed by COF (Non-Patent Document 1). The value of this thermal conductivity is at the same level as that of kapok, etc., and is one digit smaller than resins such as polypropylene, two digits smaller than soda glass, three digits smaller than SUS, and four digits smaller than aluminum. In other words, COF is considered to be a material with low thermal conductivity.

[0008] COF is a crystal that shows a peak in X-ray diffraction, but until recently, single crystals of more than tens of microns were not known, and only powders composed of fine single crystals were known. However, in recent years, it has been reported that a single crystal of about 60 to 100 μm was generated for COF-300 and the like by a manufacturing method using aniline as a balance regulator (Non-patent Document 2). The document states that it takes 30 to 40 days to make a single crystal of more than 100 μm.

[0009] In addition, in the manufacture of COFs formed by imino bonds of raw material compounds with amino groups as linking bonds and raw material compounds with formyl groups as linking bonds, it is necessary to use an acid catalyst to generate imino bonds between the raw material compounds. At this time, it was reported that in addition to the existing combination of organic solvents and acid catalysts, ionic liquids that have both solvents and acid catalysts were used to synthesize nanocrystals of COF (3D-IL-COF-1) similar to COF-300 at room temperature (non-patent document 3). The document records that tetrakis(4-formylphenyl)-methane (TFPM) and p-phenylenediamine (PDA) were used as raw material compounds, and [BMIm][NTf2] (BMIm = 1-butyl-3-methylimidazole, NTf2 = bis(tetrafluoromethylsulfonyl)imide) was used as ionic liquids. As a result, the crystallinity was improved compared to when no ionic liquid was used, but the crystal size was less than 1μm.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent document 1: Japanese Patent Application Laid-Open No. 6-213529;

[0013] Patent Document 2: Japanese Unexamined Patent Application Publication No. 2013-87276

[0014] Patent Document 3: Japanese Patent Application Laid-Open No. 2008-518054

[0015] Non-Patent Document

[0016] Non-Patent Document 1: S.K.S. Freitas et al., “Thermal Conductivity of Covalent Organic Frameworks as a Function of Their Pore Size”, J. Phys. Chem. C 2017, 121, 27247-27252

[0017] Non-Patent Document 2: Ma et al., “Single-crystal x-ray diffraction structures of covalent organic frameworks”, Science 361, 48-52 (2018)

[0018] Non-Patent Document 3: X. Guan et al., “Fast, Ambient Temperature and Pressure Ionothermal Synthesis of Three-Dimensional Covalent Organic Frameworks” J. Am. Chem. Soc. 140, 4494 (2018). Summary of the Invention

[0019] Technical Problem to be Solved by the Invention

[0020] In the existing heat storage and heat release systems, there is a problem of low heat storage and heat release rates. That is, the thermal conductivities of heat storage and heat release materials such as magnesium oxide and sodium acetate trihydrate are low. Therefore, it takes time for the generated heat and the absorbed heat to diffuse from the surface. On the other hand, so far, there has been no report on using COF as a heat storage and heat release material. As described above, it has been reported that COF, as a stable network structure, has a low thermal conductivity, so it has not been considered as a heat storage and heat release material so far.

[0021] As described above, it has been reported that a COF, which is a stable network structure, has a low thermal conductivity. However, the present inventors have conceived that the above-reported low thermal conductivity is caused by point contacts and grain boundaries between particles due to the measurement sample being an aggregate of fine single crystals, i.e., a powder. If a structure without point contacts or grain boundaries in the direction of heat flow, such as a single single crystal, is formed, high thermal conductivity will be exhibited within the single crystal. However, the particle size (length of the major axis) of the single crystal of the COF known heretofore is less than 100 μm, and from the viewpoint of engineering applications, this size generally belongs to the microscale and becomes an obstacle to realizing the above concept.

[0022] An object of the present invention is to provide: a COF single crystal having excellent heat transport properties suitable for engineering applications and a larger particle size than before, and a method for producing the same. Another object of the present invention is to provide: a composite material having excellent heat storage and release characteristics using such a COF single crystal, a heat storage and release member containing the composite material, and a method for producing the composite material.

[0023] Means for Solving the Technical Problem

[0024] The inventors have found that when synthesizing a COF, by using a solution containing both a balance regulator and an ionic liquid, a COF single crystal larger than before can be produced. Moreover, the present inventors believe that by compounding the heat conduction path generated by the network structure of such a large COF single crystal with a heat storage and heat release compound, high thermal conductivity and high heat storage and heat release amounts can be achieved concurrently, thereby completing the present invention.

[0025] [1]: A composite material, comprising: a single crystal of a covalent organic framework (COF) having a major axis length greater than 120 μm or a polycrystal of a COF composed of a plurality of such single crystals; and at least one heat storage compound,

[0026] The heat storage compound is a compound that generates heat or absorbs heat through adsorption or desorption on the COF single crystal, or a phase change or chemical reaction occurring in the range of -20 to 200°C.

[0027] [2]: The composite material according to [1], wherein: the above adsorption or desorption, the above phase change, and the above chemical reaction are reversible.

[0028] [3]: The composite material according to [1], wherein: the above covalent organic framework (COF) has a framework structure composed of the following (a) and (b),

[0029] (a) is a linker selected from the following formulas (I) to (VII):

[0030]

[0031] (Here, X is a carbon atom or a silicon atom. The hydrogen bonded to the aromatic rings (benzene ring, benzimidazole ring, and pyrrole ring) in formulas (I) to (VII) can be substituted by an alkyl group, alkenyl group, alkynyl group, aryl group, oxy group, halogen atom, hydroxyl group, nitro group, sulfo group, ether group, mercapto group, ester group, carbonate group, carbonyl group, amide group, amino group, azide group, carbamate group, cyano group, hydroxyl group, carboxyl group, sulfonate group, sultone group.);

[0032] (b) is a bond selected from -B(-O-)2, -C=C-, -C-N-, -C=N-, -C-N=C-, -N-B-N- and connecting the above-mentioned connectors to each other.

[0033] [4]: The composite material according to [1], characterized in that: the above-mentioned covalent organic framework (COF) is at least one selected from COF-300, COF-303, LZU-79 and LZU-111.

[0034] [5]: The composite material according to [1], characterized in that: the molecular diameter of the above-mentioned heat storage compound is smaller than the pore diameter of the above-mentioned covalent organic framework.

[0035] [6]: The composite material according to [1], characterized in that: the above-mentioned heat storage compound is at least one selected from water, sodium sulfate decahydrate, sodium acetate trihydrate and potassium alum dodecahydrate.

[0036] [7]: A heat storage and release member, characterized in that: it contains the composite material according to any one of [1] to [6] as a heat storage and release material.

[0037] [8]: The heat storage and release member according to [7], characterized in that: it has a heat storage and release layer composed of the composite material according to any one of [1] to [6], and a heat dissipation layer that contacts the heat storage and release layer and dissipates the heat from the heat storage and release layer.

[0038] [9]: The heat storage and release member according to [8], characterized in that: the above-mentioned heat dissipation layer is made of metal.

[0039]

[10] : The heat storage and release member according to [9], characterized in that: the above-mentioned heat dissipation layer is made of aluminum.

[0040]

[11] : A method for manufacturing a composite material, which is a method for manufacturing the composite material according to any one of [1] to [6], characterized in that it has the following steps:

[0041] A single crystal manufacturing step, in which a single crystal of COF is grown by reacting a raw material compound (the above-mentioned structural unit molecule) of the covalent organic framework (COF) through a solution containing a "balance regulator" and an "ionic liquid or organic salt";

[0042] Composite step: adding the above heat storage compound to the above COF single crystal to form a composite material.

[0043]

[12] : A COF single crystal, which is a single crystal of covalent organic framework (COF), characterized in that:

[0044] The length of the long axis is greater than 120 μm.

[0045]

[13] : The COF single crystal according to

[12] , characterized in that: the thermal conductivity is 0.05 Wm －1 K －1 or more.

[0046]

[14] : The COF single crystal according to

[12] , characterized in that: the above covalent organic framework (COF) has a framework structure composed of the following (a) and (b),

[0047] (a) is a linker selected from the following formulas (I) to (VII):

[0048]

[0049] (Here, X is a carbon atom or a silicon atom. The hydrogen bonded to the aromatic rings (benzene ring, benzimidazole ring and pyrrole ring) in formulas (I) to (VII) can be substituted by alkyl, alkenyl, alkynyl, aryl, oxy, halogen atom, hydroxyl, nitro, sulfo, ether, mercapto, ester, carbonate, carbonyl, amide, amino, azide, carbamate, cyano, hydroxyl, carboxyl, sulfonate, sultone group.)

[0050] (b) is a bond selected from -B(-O-)2, -C = C-, -C-N-, -C = N-, -C-N = C-, -N-B-N- and connecting the above linkers to each other.

[0051]

[15] : The COF single crystal according to

[14] , characterized in that: the above bond is -C = N-.

[0052]

[16] : The COF single crystal according to

[12] , characterized in that: the COF single crystal is at least one selected from COF-300, COF-303, LZU-79 and LZU-111.

[0053]

[17] : A method for manufacturing a COF single crystal, which is a method for manufacturing a COF single crystal according to any one of

[12] to

[16] , characterized in that:

[0054] It has a single crystal manufacturing step, that is, the single crystal of COF grows by reacting the raw material compounds of covalent organic framework (COF) through a solution containing an ionic liquid or an organic salt and a balance regulator.

[0055]

[18] : The manufacturing method of the COF single crystal described in

[17] , characterized in that: the above raw material compound is an aldehyde having multiple formyl groups and an amine having multiple amino groups.

[0056]

[19] : The manufacturing method of the COF single crystal described in

[17] , characterized in that: the above balance regulator is an aldehyde having a single formyl group or an amine having a single amino group.

[0057]

[20] : The manufacturing method of the COF single crystal described in

[17] , characterized in that: the above ionic liquid or organic salt is one or more compounds selected from methyltrioctylammonium bis(trifluoromethanesulfonyl)imide, methyltrioctylammonium chloride, methyltributylphosphonium bis(trifluoromethanesulfonyl)imide, and methyltributylphosphonium iodide.

[0058]

[21] : The manufacturing method of the COF single crystal described in

[20] , characterized in that: the above ionic liquid or organic salt is methyltrioctylammonium bis(trifluoromethanesulfonyl)imide.

[0059]

[22] : The composite material described in [1], characterized in that: the thermal conductivity is 0.05 Wm －1 K －1 or more.

[0060] Advantages of the Invention

[0061] According to the present invention, a COF single crystal with a larger particle size than before and its manufacturing method can be provided. In addition, according to the present invention, by using such a COF single crystal, a composite material with excellent heat storage and release characteristics, a heat storage and release member containing the composite material, and a manufacturing method of the composite material can be provided. Description of the Drawings

[0062] Figure 1 is a schematic diagram of a COF single crystal (COF-300).

[0063] Figure 2 is a diagram showing the Lewis acidity of the cation and the Lewis basicity of the anion of the ionic liquid or organic salt.

[0064] Figure 3 is a schematic diagram of heat storage and release using the composite material.

[0065] Figure 4 is a schematic diagram showing an example of the heat storage and release member.

[0066] Figure 5 is a micrograph of the COF crystal produced in the example.

[0067] Figure 6 is a histogram showing the crystal size of the COF single crystal produced in the example.

[0068] ​​​​​​Figure 7 is a graph showing the results of adsorption and desorption of water molecules on a COF single crystal (COF-300) measured by thermogravimetric analysis and differential scanning calorimetry.

[0069] Figure 8 is a graph showing the results of measuring the specific heat of a COF single crystal (COF-300) by the three-point method using differential scanning calorimetry.

[0070] Figure 9 is a schematic diagram of a measurement cell used in temperature wave thermometry, a microscopic image of a COF single crystal (COF-300) sample for measurement, and a graph showing the results of measuring the thermal diffusivity of the sample by temperature wave thermometry. Detailed Embodiments

[0071] Hereinafter, the configuration of the embodiments of the present invention will be described. The present invention can be implemented with appropriate modifications within the scope of its gist.

[0072] 1. COF Single Crystal

[0073] Hereinafter, the COF single crystal of the present invention will be described. The COF single crystal of the present invention has a major axis (c-axis) length of 120 μm or more.

[0074] Here, the covalent organic framework (COF) has a framework structure composed of linkers and bonds connecting the above linkers to each other.

[0075] The linker is preferably an organic group containing one or more atomic groups selected from substituted or unsubstituted aromatic rings, substituted or unsubstituted heteroaromatic rings, substituted or unsubstituted non-aromatic rings, substituted or unsubstituted heterocyclic non-aromatic rings, and substituted or unsubstituted hydrocarbon groups.

[0076] More preferably, it has a framework structure composed of (a) and (b), where (a) is a linker selected from the following formulas (I) to (VII):

[0077]

[0078] (Here, X is a carbon atom or a silicon atom. The hydrogen bonded to the aromatic rings (benzene ring, benzimidazole ring, and pyrrole ring) in formulas (I) to (VII) can be substituted by an alkyl group, alkenyl group, alkynyl group, aryl group, oxy group, halogen atom, hydroxyl group, nitro group, sulfo group, ether group, thiol group, ester group, carbonate group, carbonyl group, amide group, amino group, azide group, carbamate group, cyano group, hydroxyl group, carboxyl group, sulfonate group, sultone group.)

[0079] ​​​(b) is a bond selected from -B(-O-)2, -C=C-, -C-N-, -C=N-, -C-N=C-, -N-B-N- and connecting the above joints to each other.

[0080] Among these, as the COF of the present invention, at least one selected from COF-300, COF-303, LZU-79 and LZU-111 is preferred.

[0081] Both COF-300 and COF-303 have a molecular structure in which the joints of formula (I) and formula (V) (X is carbon) are covalently bonded through -C=N- (a part of the imine bond). The difference between COF-300 and COF-303 is that for COF-300, the carbon (C) of the connecting bond is on the side of formula (I) and the nitrogen (N) is on the side of formula (V), while for COF-303, it is the opposite, the carbon (C) of the connecting bond is on the side of formula (V) and the nitrogen (N) is on the side of formula (I). LZU-79 has the following molecular structure: formula (V) (X is carbon) and formula (VII) are covalently bonded through -C=N-, the carbon (C) of the connecting bond is on the side of formula (VII) and the nitrogen (N) is on the side of formula (V). LZU-111 has the following molecular structure: formula (V) (X is carbon) and formula (V) (X is silicon) are covalently bonded through -C=N-, the carbon (C) of the connecting bond is on the side of formula (V) (X is silicon) and the nitrogen (N) is on the side of formula (V) (X is carbon). For details of the structures and the like of these compounds, reference can be made to Non-Patent Document 2.

[0082] Figure 1 A schematic diagram showing a COF single crystal (COF-300) is presented. The left side of this figure shows a three-dimensional view of the COF single crystal, and the right side shows a side view. The COF single crystal belongs to the tetragonal system. When observed with reference to three axes (a-axis, b-axis, c-axis), the top view (lower side view) seen from the c-axis direction has a "field" shape (a cross inside a quadrilateral), and the side views seen from the a-axis and b-axis directions have a hexagonal shape. The long axis in the present invention is the c-axis of the figure, and the length (dimension) of the COF single crystal of the present invention in the c-axis direction is 120 μm or more. The length of the long axis of the COF single crystal is preferably 150 μm or more, more preferably 200 μm or more, and particularly preferably 250 μm or more. The upper limit of the length of the long axis of the COF single crystal is, for example, 1 mm, and further exemplified as 10 mm, and can be a length of 10 mm or more.

[0083] The COF single crystal has pores between its network skeletons. In COF-300, the reported theoretical pore diameter is (F.J. Uribe-Romo et al., J. Am. Chem. Soc. 131, 4570 (2009)). When it is desired to increase the pore diameter, it can be easily increased by changing the linker, for example, changing terephthalaldehyde as the linker to 4,4’-diformylbiphenyl or 4,4”-diformyl-p-terphenyl, etc. The COF single crystal exhibits various properties by complexing with elements or compounds added in the pores. In addition, the frameworks of the COF single crystals penetrate each other like interlocking puzzle rings and have a very strong structure. Therefore, the COF single crystal has stable properties thermally, chemically, and physically.

[0084] The thermal conductivity of the COF single crystal is preferably 0.05 Wm －1 K －1 or more. Compared with the conventional aggregate of fine crystal powders with a size of 1 μm or less, the crystal size of the COF single crystal of the present invention is large, so it is regarded as a single material. Therefore, in the COF single crystal with a large crystal size, since the thermal resistance due to the point contact between the fine powder crystals is sharply reduced, the thermal conductivity is higher compared within the long-distance range (equal to its single crystal size). Therefore, the COF single crystal can be particularly preferably used as the heat storage and release material described later. The thermal conductivity of the COF single crystal is preferably 0.1 Wm －1 K －1 or more, more preferably 0.2 Wm －1 K －1 or more, further preferably 0.5 Wm － 1 K －1 or more, and most preferably 1 Wm －1 K －1 or more.

[0085] 2. Manufacturing method of COF single crystal

[0086] Hereinafter, the manufacturing method of the COF single crystal will be described. The manufacturing method of the COF single crystal has the following single crystal manufacturing steps: The single crystal of COF grows by reacting the raw material compound (structural unit molecule) of COF via a solution containing an ionic liquid or an organic salt and a balance regulator.

[0087] The covalent organic framework (COF) can be made using raw material compounds of various combinations of linking bonds and linkers as structural unit molecules. As the raw material compounds constituting the COF, there can be mentioned: aldehydes having a plurality of formyl groups in an aromatic ring (for example, a benzene ring and a pyrrole ring, the same applies hereinafter), and amines having a plurality of amino groups in an aromatic ring. These aldehydes and amines are condensed to form a covalent bond (imine bond), thereby forming a COF with a bond of -C=N-.

[0088] As raw material compounds for manufacturing COF, for example, in COF-300, tetrakis(4-aminophenyl)methane (TAM) and terephthalaldehyde (BDA) can be cited. Additionally, as raw material compounds, in COF-303, tetrakis(4-formylphenyl)methane (TFM) and phenylenediamine (PDA) can be cited, in LZU-79, TAM and 4,7-bis(4-formylbenzyl)-1H-benzimidazole (BFBZ) can be cited, and in LZU-111, TAM and tetrakis(4-formylphenyl)silane (TFS) can be cited.

[0089] The equilibrium regulator is a substance like a catalyst in a condensation reaction, which is not consumed itself and plays a role in enhancing the reversibility of the condensation reaction. As the equilibrium regulator, aromatic aldehydes having a single formyl group or aromatic amines having a single amino group can be cited. As specific examples of the equilibrium regulator, aniline, benzaldehyde, etc. can be cited. The equilibrium regulator is preferably used in an excess amount relative to the raw material compound. For example, relative to 1 mole of the total amount of the raw material compound, the equilibrium regulator is preferably 2 to 200 moles, more preferably 10 to 100 moles, and particularly preferably 20 to 80 moles.

[0090] The raw material compound or the equilibrium regulator is preferably used after being dissolved in an aqueous or non-aqueous solvent. As examples of such solvents, water, pentane, hexane, benzene, toluene, xylene, chlorobenzene, nitrobenzene, cyanobenzene, naphthalene, naphtha, methanol, ethanol, n-propanol, isopropanol, acetone, 1,2-dichloroethane, dichloromethane, chloroform, carbon tetrachloride, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, dimethylacetamide, diethylformamide, thiophene, pyridine, ethanolamine, triethylamine, ethylenediamine, diethyl ether, acetonitrile, dioxane, etc. can be cited.

[0091] Ionic liquids are molten salts at room temperature composed only of ions, with anions and cations forming pairs. Similarly to organic salts, anions and cations form pairs in organic salts, but they are solids at room temperature. In Non-Patent Document 3, ionic liquids have an acid catalyst effect of promoting the condensation (imine formation reaction) between starting compounds and are used simultaneously as a solvent and an acid catalyst to replace the organic solvents used previously. However, in order to obtain large-sized single crystals, crystal growth needs to be carried out from a homogeneous solution in which the starting molecules are completely dissolved. In the crystal production method of Non-Patent Document 3, since the solubility of the structural unit molecules (for example, the tetra(4-aminophenyl)methane molecules used in the present invention) in the ionic liquid is low, the undissolved structural and block molecules dispersed in the solution become the "basis" (= crystal nuclei) for crystal growth, and as a result, a large number of fine single crystals are generated. On the other hand, the present inventors expected the control effect of an ionic liquid different from that of Non-Patent Document 3 on the COF crystal growth rate (described later), and used it as an additive in an organic solvent rather than as a solvent to generate COF single crystals using a homogeneous solution. In the present invention, in order to obtain a larger crystal in a short time, about 9 times the catalytic amount of acetic acid (1.2 mmol of acetic acid) used in Non-Patent Document 2 was added while using the hydrogen bond between the anion constituting the ionic liquid and the functional group present on the surface of the growing crystal as a means of controlling crystal nucleation and growth. Starting from this unprecedented new concept, the following insights were obtained.

[0092] Specific examples of the ionic liquid or organic salt include: methyltrioctylammonium bis(trifluoromethanesulfonyl)imide, methyltrioctylammonium chloride, methyltributylphosphonium bis(trifluoromethanesulfonyl)imide, and methyltributylphosphonium iodide, etc. Relative to 1 mole of the total amount of the starting compounds, the ionic liquid or organic salt is preferably 0.1 to 100 moles, more preferably 0.5 to 10 moles, and particularly preferably 1 to 5 moles.

[0093] As the ionic liquid or organic salt, from the viewpoint of manufacturing a larger-sized COF single crystal, an ionic liquid or organic salt in which both the Lewis acidity of the cation and the Lewis basicity of the anion are weak is preferred. From this perspective, among the above specific examples, in particular, methyltrioctylammonium bis(trifluoromethanesulfonyl)imide ([N 8881 [NTf2]) is particularly preferred. The reasons are described below.

[0094] In COFs having imine bonds such as COF-300, an acid catalyst is required for the formation reaction of the imine bond. By adding an acid having Na +Ionic liquids having cations with strong Lewis acidity, such as those mentioned above, where the cation acts as a Lewis acid catalyst, significantly promote the COF formation reaction, generating a large number of crystal nuclei and consuming a large amount of raw material compounds. As a result, the number of raw material molecules available for use in the subsequent crystal growth stage is reduced, and it is impossible to grow into crystals with a sufficiently large size. Consequently, a large number of fine crystals are produced. From this perspective, if an ionic liquid or organic salt has a cation with weak Lewis acidity, it is beneficial for crystal growth.

[0095] On the other hand, as described above, hydrogen bonds are formed between the anion of the ionic liquid and the unreacted functional groups present on the surface of the COF single crystal. The stronger the Lewis basicity of the anion, the stronger the hydrogen bond, which hinders the COF formation reaction and slows down crystal nucleation and crystal growth. In the present invention, in order to suppress the formation of a large number of crystal nuclei, ionic liquids with different Lewis basicities are used, and the rate of crystal growth is suppressed. As a result, among the anions of the ionic liquids used in the present invention, [NTf2] with the weakest Lewis basicity － has the most suitable Lewis basicity strength, and the largest-sized COF crystals are obtained. This is also considered to be the case especially for organic salts dissolved in solvents.

[0096] Figure 2 is a graph showing the Lewis acidity of the cations and the Lewis basicity of the anions of the ionic liquids or organic salts listed in the above specific examples. As shown in this graph, methyltrioctylammonium bis(trifluoromethanesulfonyl)imide ([N 8881 [NTf2]) is a combination of methyltrioctylammonium ([N 8881 ) with the weakest Lewis acidity and bis(trifluoromethanesulfonyl)imide ([NTf2]) with the weakest Lewis basicity. Therefore, as also shown in the examples described later, when using methyltrioctylammonium bis(trifluoromethanesulfonyl)imide ([N 8881 [NTf2]), larger-sized COF single crystals can be obtained compared to the case of using other ionic liquids or organic salts.

[0097] Regarding the chemical properties (Lewis basicity) of basic solvents, as an index of the scale of the enthalpy that can form an adduct with a reference Lewis acid, there is the "donor number" (DN). On the other hand, for acidic solvents, as a parameter for evaluating their Lewis acidity, there is the "acceptor number" (AN). The Lewis acidity of the cation and the Lewis basicity of the anion of an ionic liquid can be quantitatively evaluated based on the acceptor number of the cation and the donor number of the anion, respectively.

[0098] The following shows the donor numbers of the anions of the ionic liquids used in the present invention (source: M. Holzweber et al., Chem. Eur. J. 19, 288 - 293 (2013)). Under the condition of using the same cation (1 - butyl - 3 - methylimidazolium: C4min + ), the donor numbers of the anions are in the order shown in this table. The smaller the donor number, the weaker the Lewis basicity.

[0099] [Table 1]

[0100] Cation Anion DN <![CDATA[C4mim + > <![CDATA[Cl - > 22.6 <![CDATA[C4mim + > <![CDATA[CH3COO - > 11.32 <![CDATA[C4mim + > I 7.59 <![CDATA[C4mim + > <![CDATA[NTf2 - > --3.44

[0101] In the ionic liquid used in the present invention, under the condition that the cation is C4min + , the donor number (DN) of the anion is preferably 0 or less, more preferably - 3.00 or less.

[0102] In the formation reaction of COF, it is preferable to use an acid catalyst other than the cations of ionic liquids or organic salts in combination. Examples of such acid catalysts include acetic acid, hydrochloric acid, etc. Relative to 1 mole of the total amount of raw material compounds, the acid catalyst is preferably 2 - 200 moles, more preferably 10 - 150 moles, and particularly preferably 50 - 100 moles.

[0103] The COF formation reaction can be carried out under appropriately preferred conditions. As the temperature of the COF formation reaction, for example, it can be carried out at 10 - 60 °C, preferably 20 - 50 °C, and more preferably at room temperature (about 25 °C). The growth of COF single crystals with a size exceeding 120 μm is probably completed within 1 - 30 days and can be completed within 10 days according to the conditions (7 days in the following examples). Obtaining large - sized COF single crystals in such a short period compared to the technology described in Non - Patent Document 2 is also an effect of the manufacturing method of the present invention.

[0104] 3. Composite materials using COF single crystals

[0105] Hereinafter, the composite materials using COF single crystals will be described. The composite material of the present invention includes: single crystals of covalent organic frameworks (COF) with a major axis length greater than 120 μm or polycrystals of COF composed of a plurality of such single crystals, and at least one heat - storage compound.

[0106] The single crystals of COF can be the COF single crystals described above. The polycrystals of COF are composed of a plurality of COF single crystals. (a) Near room temperature, the single crystals of COF preferably have a higher thermal conductivity than the heat - storage compound in the bulk state. Here, the thermal conductivity in the bulk state refers to the thermal conductivity in the state where there is only the heat - storage compound, rather than the thermal conductivity of the heat - storage compound in the state of being compounded with COF single crystals.

[0107] The heat storage compound refers to: (1) a compound that generates or absorbs heat through adsorption or desorption on the single crystal of COF, or (2) a compound that generates or absorbs heat through a phase change or chemical reaction occurring within the range of -20 to 200°C. If these adsorption, desorption, phase change, and chemical reactions are reversible, the composite material can be repeatedly used as the heat storage and release component described below, so it is preferred.

[0108] The heat storage compound of (1) can be adsorbed on the surface or inside (pores) of the COF single crystal, and heat is stored in the form of adsorption enthalpy. On the other hand, it can be desorbed from the COF single crystal, and the stored enthalpy is released in the form of heat. Examples of such heat storage compounds include water.

[0109] The heat storage compound of (2) is a compound that absorbs and releases heat through the latent heat of its own phase change or a chemical reaction. Among these, materials that undergo a phase change are generally referred to as PCM (Phase Change Material). The heat storage compound of (2) in the present invention is a compound that generates or absorbs heat through a phase change or chemical reaction occurring within the range of -20 to 200°C. Examples of such heat storage compounds include sodium sulfate decahydrate, sodium acetate trihydrate, and potassium alum dodecahydrate. In addition, these heat storage compounds can be used not only singly but also in combination of two or more.

[0110] The molecular diameter of the heat storage compound is preferably smaller than the pore diameter of COF. Thus, the heat storage compound can be introduced into the pores of COF for heat storage and release. However, it is not limited to this. Even if the molecular diameter of the heat storage compound is larger than the pore diameter of COF, heat absorption and generation can be carried out using the heat storage compound on the surface of the COF single crystal, etc.

[0111] Figure 3 The schematic diagram showing heat storage and release using the composite material of the present invention is shown. During heat storage, the heat storage compound (water in this figure) introduced into COF comes into contact with high-temperature air and is desorbed from COF, so the enthalpy increases, and air and moisture are discharged. On the other hand, during heat release, water in the air and moisture is adsorbed on COF, so the enthalpy decreases and heat is generated, and dry high-temperature air is released.

[0112] From the viewpoint of enabling rapid heat exchange, the thermal conductivity of this composite material is preferably 0.05 Wm －1 K －1 or more. More preferably, it is 0.1 Wm －1 K －1 or more, further preferably 0.2 Wm －1 K －1 or more, further preferably 0.5 Wm －1 K －1 or more, and most preferably 1 Wm－1 K －1 Above. Near room temperature, the composite material preferably has a higher thermal conductivity than the bulk state of the heat storage compound that constitutes the composite material.

[0113] 4. Method for manufacturing a composite material

[0114] The method for manufacturing the composite material of the present invention is as follows: The single crystal manufacturing step described in the above-described method for manufacturing a COF single crystal is carried out, and then a compounding step is carried out, that is, a heat storage compound is added to the obtained COF single crystal to form a composite material. Since the single crystal manufacturing step has been described above, a detailed description thereof is omitted here. In the compounding step, a heat storage compound is added to the COF single crystal to produce a composite material. As the method for adding the heat storage compound to the COF single crystal, there is no particular limitation, and it can be carried out under appropriate conditions (for example, 10 to 50 ° C, 1 to 100 hours, etc.) according to the types of the COF single crystal and the heat storage compound. For example, the following methods can be cited: Under the temperature condition where the heat storage compound is liquefied, the COF single crystal is immersed in the molten heat storage compound so that the heat storage compound molecules penetrate into the pores of the COF. More specifically, for example, in the case of sodium acetate trihydrate, compounding is carried out by melting it at 57.5 ° C or higher and bringing it into contact with the COF single crystal.

[0115] 5. Heat storage and release member

[0116] The composite material of the present invention can be suitably used as a heat storage and release material in a heat storage and release member. The heat storage and release member of the present invention has: a heat storage and release layer composed of a composite material; and a heat dissipation layer that is in contact with the heat storage and release layer (including the case of a welding layer composed of a "low melting point metal material" described later) and dissipates heat from the heat storage and release layer. As the heat dissipation layer, a metal having a high thermal conductivity, etc., is preferably used, and aluminum is particularly suitable.

[0117] Figure 4 is a schematic diagram showing an example of a heat storage and release member, Figure 4 (a) shows an example using the large-particle-size COF single crystal of the present invention, Figure 4(b) of the figure shows an example envisioned in the case of using existing COF fine powder. As shown in (a) of the figure, within a COF single crystal, a heat conduction path (pathway) is formed through the framework structure of the COF, which transfers heat from the surface of the COF single crystal through the interior to another surface. Additionally, since the major axis length of the COF single crystal of the present invention is as high as 120 μm or more, the length of the heat conduction path is also long. On the other hand, as shown in (b) of the figure, if using COF fine powder or small single crystals as in the past, in order to fabricate a long heat conduction path, it is necessary to stack multiple small particles. In this case, point contacts are formed between the particles, and it is difficult to achieve large-area contact. Additionally, in the case where the particles are not single crystals, grain boundaries also exist within the particles. Therefore, the heat conduction efficiency of the COF single crystal with a large crystal size like the present invention is superior to the example envisioned in the case of using existing COF fine powder, and it is more preferable as a heat storage and release member.

[0118] As a method for laminating a heat storage and release layer and a heat dissipation layer composed of a composite material, the following methods can be cited: growing a COF single crystal directly on the material constituting the heat dissipation layer, and then adding a heat storage compound to the COF single crystal to form a composite material; welding the COF single crystal to the material constituting the heat dissipation layer using a low-melting-point metal material, such as indium, and then adding a heat storage compound to the COF single crystal to form a composite material; or, after adding a heat storage compound to the COF single crystal to form a composite material, welding it to the material constituting the heat dissipation layer.

[0119] If a metal member with a heat sink is used as the heat dissipation layer, the heat storage and release member can be used as a radiator. As applications of the heat storage and release member, the following can be cited: automobiles, computers, household televisions, OA equipment, mobile phones, smart phones, lighting, air conditioners, power devices, etc.

[0120] Examples

[0121] Hereinafter, the present invention will be specifically described based on examples, but these examples do not limit the purpose of the present invention. Additionally, the present invention is not limited by these examples.

[0122] 1. Example 1: Synthesis of COF-300 single crystal

[0123] 1-1: Preparation of solution and crystal growth

[0124] First, weigh 3.35 mg (0.025 mmol; regarded as 1 equivalent) of solid powder of terephthalaldehyde (hereinafter denoted as BDA) and place it in a 6 mL glass vial. Next, measure 0.25 mL of dioxane and 0.03 mL of aniline (both are liquids) and add them to the vial. Then, perform ultrasonic dispersion for 10 minutes to dissolve BDA and prepare solution A.

[0125] Then, 4.76 mg (0.0125 mmol, 0.5 equivalent) of solid powder of tetra(4-aminophenyl)methane (hereinafter referred to as TAM) was weighed and put into another glass vial with a capacity of 6 mL. Then, 0.25 mL of dioxane was weighed and put into this vial.

[0126] Next, ultrasonic dispersion was carried out for 10 minutes to dissolve TAM and form solution B. The molecular structure of the raw material is shown below.

[0127]

[0128] Then, 0.16 mL (2.8 mmol) of acetic acid and the additive (one of Nos. #1 to #11) shown in the following table were weighed and put into another glass vial with a capacity of 6 mL to form solution C. #1 is an additive used in the existing COF synthesis (comparative example).

[0129] [Table 2]

[0130] Number Name Type State at room temperature Usage amount #1 Ultra-pure water Ultra-pure water Liquid 2.2 mmol #2 <![CDATA[[EIM][NTf2]]]> Ionic liquid Liquid 0.07 mmol #3 <![CDATA[[C2mim][NTf2]]]> Ionic liquid Liquid 0.07 mmol #4 <![CDATA[[C6mim][NTf2]]]> Ionic liquid Liquid 0.07 mmol #5 <![CDATA[[C 10 mim][NTf2]]]> Ionic liquid Liquid 0.07 mmol #6 <![CDATA[[C2mim][Acetate]]]> Ionic liquid Liquid 0.07 mmol #7 <![CDATA[[P 4441 [NTf2]]]> Ionic liquid Liquid 0.07 mmol #8 <![CDATA[[N 8881 [NTf2]]]> Ionic liquid Liquid 0.07 mmol #9 <![CDATA[[P 4441 [I]]]> Organic salt Solid 0.07 mmol #10 <![CDATA[[N 8881 [C1]]]> Organic salt Solid 0.07 mmol #11 <![CDATA[[Na][NTf2]]]> Organic salt Solid 0.07 mmol

[0131] The molecular structures of the additives (ionic liquids and organic salts) are shown below.

[0132]

[0133] After that, solution A and solution C were mixed in a glass vial with a capacity of 2 mL, and ultrasonic dispersion was carried out for about 5 minutes. Then, solution B was slowly added to this vial, and it was left standing in the dark for 7 days. Crystals appeared on the bottom surface and the inner peripheral wall surface of this vial from the second day, and the growth almost stopped on the seventh day. After that, the crystals were taken out according to the following steps and washed and dried.

[0134] 1 - 2: Washing and drying of the obtained single crystal

[0135] After the above crystal growth, a single crystal group of grown COF-300 was obtained by suction using a pipette as a transfer tool. They were washed successively with dioxane, acetone, and toluene. In the final toluene wash, the single crystal group was separated with filter paper. The single crystal group together with the filter paper was put into a ring-shaped electric furnace, and while passing dry nitrogen, it was dried at 95 °C for 8 hours. The summary of the results is shown in the following table. In addition, the micrograph of the obtained crystal is shown in Figure 5 .

[0136] [Table 3]

[0137] Number Summary of results #1 Fine crystals (method of "Prior art 1") #2 A small amount of fine crystals #3 A small amount of fine crystals #4 A small amount of fine crystals #5 A small amount of fine crystals #6 Almost no crystals precipitate. #7 The crystal size is about 2 times that of "Prior art 1" #8 The crystal size is about 4 times that of "Prior art 1" #9 The crystal size is about 1.5 times that of "Prior art 1" #10 The crystal size is about 1.5 times that of "Prior art 1" #11 A large amount of fine crystals

[0138] It can be seen from this result that the result of additive #8 is the best. For additive #8, 80 crystals were counted and a histogram of the crystal size distribution was made. Figure 6A histogram is shown. The upper part of the figure shows the results of the length of the a-axis (short axis), and the lower part shows the results of the length of the c-axis (long axis). It can be seen from the results that the lengths of the a-axis all exceed 60 μm, and the lengths of the c-axis all exceed 120 μm. The largest is that the length of the c-axis is almost 200 μm.

[0139] 2. Measurement of the heat of water vapor adsorption of COF-300 single crystals

[0140] The heat of water vapor adsorption of the COF-300 single crystal obtained by the above additive #8 was measured. Using a differential scanning calorimetry device (Shimadzu Corporation, DSC-60), a water vapor adsorption saturated sample was used, and the COF-300 single crystal was placed in a measurement cell, and thermogravimetric analysis (TG) and differential scanning calorimetry analysis (DSC) were performed under a dry nitrogen environment and a heating rate of 5 °C / min. In addition, in this measurement, water vapor corresponds to the "heat storage compound" of the present invention, and a sample saturated with water vapor adsorption (water vapor saturated COF-300 single crystal) corresponds to the "composite material" of the present application. The results are shown in Figure 7 . Desorption of water vapor was carried out in the first week of heating, and confirmation of the end of desorption of water vapor in the first week was carried out in the second week of heating.

[0141] Based on these results, by dividing the measured heat of adsorption by the weight of the adsorbed water, the heat of water vapor adsorption of the COF-300 single crystal was found to be Δh = 2345.5 kJ / kg (H2O). This is almost equal to the enthalpy of evaporation of water at room temperature. This implies that the interaction between H2O molecules and the framework of COF-300 is strong, and it is considered that the interaction with H2O molecules is of the same degree. In the present invention, as described below, by increasing the size of the single crystal, the thermal conductivity can reach several times that of the powder, so it can become a heat storage and heat dissipation system with improved heat storage and heat dissipation rates.

[0142] 3. Specific heat measurement of COF-300 single crystals

[0143] For the COF-300 single crystal obtained by the above additive #8, a differential scanning calorimetry device (PerkinElmer, DSC 8000) was used, and the specific heat was measured by the three-point method using DSC. A dry COF-300 sample was used in this measurement. The specific heat was measured by the three-point method at intervals of 5 °C between 10 and 55 °C. The measurement error was corrected by the difference between the measured value of sapphire attached to the above differential scanning calorimetry device and the literature value. The results are shown in Figure 8 . According to this result, the specific heat CP of the COF-300 single crystal is 1.19 kJkg －1 K －1 .

[0144] 4. Measurement of the thermal diffusivity of COF-300 single crystals

[0145] For the COF-300 single crystal obtained by the above additive #8, the thermal diffusivity was measured by temperature wave thermal analysis. Temperature wave thermal analysis is a method of measuring the phase lag of an alternating current temperature in the thickness direction of a specimen, and the thermal diffusivity is obtained from the change in the phase lag of the temperature wave measured by changing the frequency. The measurement was carried out in the atmosphere, and the water vapor adsorption state of the single crystal specimen was not clear. Figure 9 The outline and results of this measurement are shown. The outline of the measurement cell is as shown in the "Schematic diagram of the measurement cell" in the figure. As shown in this figure, the crystal specimen was placed on the ITO film formed on the surface of the glass substrate, and the temperature wave was detected using electrodes. The heating direction of the crystal was the lateral direction of the crystal (a-axis direction). As a result, the thermal diffusivity of the COF-300 single crystal was α = 1.33×10 －7 m 2 s －1 。

[0146] 5. Thermal conductivity of COF-300 single crystal

[0147] Next, using the specific heat and thermal diffusivity values measured previously, the thermal conductivity of the COF-300 single crystal was calculated. The thermal conductivity λ of the single crystal sample was calculated by the following formula.

[0148] λ = α·C P ·ρ (formula)

[0149] (Here, α: thermal diffusivity, C P : specific heat, ρ: density)

[0150] Here, the density of the single crystal sample was calculated using the crystal structure data of the COF-300 single crystal in Non-Patent Document 2 through the Material Studio software. As a result, the density ρ of the COF-300 single crystal was 0.735 [g / cm 3 , and the unit cell volume was

[0151] From the above results, it can be seen that: the thermal conductivity λ of the COF-300 single crystal = 0.116 Wm －1 K －1 。 Compared with the literature values of the thermal conductivity of the above COF-300 powder, which are 0.038 - 0.048 W / mK, it is more than twice as high. It can be confirmed that the idea that a higher thermal conductivity can be achieved by making a single crystal is correct. Based on the measurement results of the COF single crystal, it is considered that if a composite material containing a heat storage compound in the pores of the COF single crystal is made to eliminate the pores inside the COF, the thermal conductivity can be further increased.

Claims

1. A method for manufacturing a COF single crystal, characterized in that, The COF single crystal is a covalent organic framework (COF) single crystal with the length of the long axis greater than 120 μ m, and The manufacturing method has a single crystal manufacturing step, that is, a single crystal of COF is grown by reacting an aldehyde having a plurality of formyl groups on an aromatic ring with an amine having a plurality of amino groups on an aromatic ring via a solution containing an ionic liquid or an organic salt and a balance regulator. Among them, the ionic liquid or the organic salt is one or more compounds selected from methyltrioctylammonium bis(trifluoromethanesulfonyl)imide, methyltrioctylammonium chloride, methyltributylphosphonium bis(trifluoromethanesulfonyl)imide, and methyltributylphosphonium iodide; the balance regulator is an aldehyde having a single formyl group or an amine having a single amino group.

2. The manufacturing method of the COF single crystal according to claim 1, characterized in that: The ionic liquid or the organic salt is methyltrioctylammonium bis(trifluoromethanesulfonyl)imide.

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