JP6722393B2 - Metal-organic structure, gas storage material using the same, and method for producing the same - Google Patents

Description

The present invention relates to a metal organic structure having a paddle wheel type binuclear complex as a basic skeleton, a gas storage material using the same, and a method for producing the same.

Metal-organic structures (MOFs) have large voids and surface areas inside crystals due to their structural characteristics, and have recently attracted attention as novel gas storage materials. Among them, HKUST-1 [Cu ₃ (benzene-1,3,5-tricarboxylate) ₂ , Cu ₃ (BTC) ₂ ] has trimesic acid (H ₃ RTC) coordinated to a binuclear cluster of Cu ²⁺ ions. It has a paddle wheel type three-dimensional skeleton structure and has large pores inside the crystal, and is known to exhibit a high methane storage amount (J. Am. Chem. Soc. , 2013, 135, 11887-11894 (Non-Patent Document 1)).

However, HKUST-1 has low moisture resistance and water resistance, and there is a problem that destruction of the crystal structure due to moisture, water vapor, and water occurs, and gas storage performance decreases (J. Mater. Chem. A, 2013, Volume 1, 11922-11932 (Non-Patent Document 2) and Adv. Funct. Mater., 2014, Volume 24, 3855-3865 (Non-Patent Document 3).

For this reason, J. Am. Chem. Soc. , 2014, Vol. 136, pp. 16978-16981 (Non-patent document 4), it is proposed to improve the moisture resistance and water resistance of HKUST-1 by surface-treating HKUST-1 with silicone.

Y. Peng et al. Am. Chem. Soc. , 2013, 135, 11887-11894. J. B. De Coste et al. Mater. Chem. A, 2013, Volume 1, 11922-11932. G. Majano et al., Adv. Funct. Mater. , 2014, Vol. 24, pp. 3855-3865 W. Zhang et al. Am. Chem. Soc. , 2014, Vol. 136, pp. 16978-16981

However, even if HKUST-1 is surface-treated with silicone, its moisture resistance and water resistance are not necessarily sufficient. For example, if it is exposed to an atmosphere containing water for a long time (for example, 10 days or more), HKUST-1 However, there was a problem that the gas storage performance of (especially, methane storage performance) was significantly reduced.

The present invention has been made in view of the above problems of the conventional art, and has a paddlewheel binuclear complex as a basic skeleton, and a metal organic structure excellent in water resistance (moisture resistance) and a method for manufacturing the same. The purpose is to provide.

As a result of earnest studies to achieve the above object, the present inventors have found that at least one selected from the group consisting of acetone and a compound derived from acetone is used as a paddlewheel binuclear complex that is three-dimensionally linked. It has been found that the water resistance (moisture resistance) of the paddle wheel type binuclear complex is improved by coordinating the organic ligands of some species, and the present invention has been completed.

That is, the metal-organic structure of the present invention comprises a divalent metal ion and a first organic ligand having three carboxyl groups in one molecule coordinated to the divalent metal ion. , A three-dimensionally linked paddlewheel binuclear complex, and a second organic ligand that is acetone,
The second organic ligand is coordinated to 30% to 100% of coordination unsaturated sites of the divalent metal ion in the paddle wheel binuclear complex. ..

In the metal organic structure of the present invention, the divalent metal ions include Cu ²⁺ , Zn ²⁺ , Ru ²⁺ , Rh ²⁺ , Mo ²⁺ , Cr ²⁺ , Ni ²⁺ , Mg ²⁺ , Fe ²⁺ , Pb ²⁺ , Sn ^2+. And at least one selected from the group consisting of Ca ^2+, and the first organic ligand is benzene-1,3,5-tricarboxylate, 4,4′,4″-benzene. Selected from the group consisting of -1,3,5-triyl-tribenzoate and 4,4',4"-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate. At least one of the above is preferable.

Further, the metal organic structure of the present invention preferably has a silicone coating layer on at least a part of its outer surface.

Furthermore, the gas storage material of the present invention is characterized by comprising such a metal organic structure of the present invention.

The method for producing a metal-organic structure of the present invention comprises a divalent metal ion and a first organic ligand coordinated to the divalent metal ion, and is three-dimensionally connected to a paddle. An adsorption step of adsorbing a second organic ligand, which is acetone , on the wheel-type binuclear complex,
The paddle-wheel binuclear complex in which the second organic ligand is adsorbed is heated under atmospheric pressure or under pressure in a temperature atmosphere of 100 to 300° C. A heating step of coordinating the second organic ligand with 30% to 100% of the coordination unsaturated sites of the divalent metal ion;
It is characterized by including.

In such a method for producing a metal organic structure of the present invention, the paddle wheel in which the second organic ligand is adsorbed on 30% to 100% of the coordination unsaturated sites of the divalent metal ion. It is preferred to heat the type binuclear complex.

Further, in the method for producing a metal organic structure of the present invention, the paddlewheel binuclear complex is caused to adsorb the second organic ligand and silicone, and the second organic ligand and silicone are adsorbed. The paddle wheel type binuclear complex is heated under atmospheric pressure or pressure under a temperature atmosphere of 100 to 300° C. to adjust the coordination of the divalent metal ion in the paddle wheel type binuclear complex. It is preferable that the second organic ligand is coordinated with 30% to 100% of the saturated sites and a silicone coating layer is formed on at least a part of the outer surface of the metal organic structure.

By coordinating the paddlewheel binuclear complex with acetone or the like, the water resistance (moisture resistance) of the paddlewheel binuclear complex is improved and the gas storage performance (particularly, methane storage performance) is reduced by moisture. Although the reason for the suppression is not always clear, the present inventors speculate as follows. That is, the paddle wheel binuclear complex has a structure in which an organic ligand is coordinated with a divalent metal ion, and the divalent metal ion is not coordinated with the organic ligand. There is a vacant coordination site (coordination unsaturated site). Water in the air is easily coordinated to such a coordination unsaturated site, and the water coordinated to the coordination unsaturated site hydrolyzes the coordination bond between the divalent metal ion and the organic ligand. Since it is cleaved by, the crystal structure of the paddle wheel binuclear complex is destroyed. Therefore, it is speculated that the paddle wheel binuclear complex has a markedly lowered gas storage performance (in particular, methane storage performance) when exposed to an atmosphere containing water.

On the other hand, in the metal organic structure of the present invention, at least one selected from the group consisting of acetone and a compound derived from acetone in at least a part of the coordination unsaturated site of the divalent metal ion of the paddle wheel binuclear complex. The species' organic ligand is coordinated. In such a metal-organic structure, water molecules are less likely to coordinate even when exposed to an atmosphere containing water, and hydrolysis of the coordination bond between the divalent metal ion and the organic ligand is less likely to occur. Destruction of the crystal structure of the paddle wheel type binuclear complex is suppressed. As a result, it is presumed that in the gas storage material comprising the metal organic structure of the present invention, deterioration of gas storage performance (particularly, methane storage performance) due to water content is suppressed.

According to the present invention, it is possible to obtain a metal organic structure having a paddle wheel type binuclear complex as a basic skeleton and excellent in water resistance (moisture resistance).

It is a schematic diagram which shows an example of the basic skeleton of the paddle wheel binuclear complex used for this invention. It is a schematic diagram which shows an example of the basic skeleton of the metal organic structure of this invention. It is a graph which shows the X-ray-diffraction pattern of the metal organic structure obtained by the Example and the comparative example before a moisture resistance test. It is a graph which shows the X-ray-diffraction pattern of the metal organic structure obtained by the Example and the comparative example before a moisture resistance test. It is a graph which shows the X-ray-diffraction pattern after the humidity resistance test of the metal organic structure obtained in the Example and the comparative example. 3 is a scanning electron micrograph of the metal-organic structure obtained in Example 1. 3 is a scanning electron micrograph of the metal organic structure obtained in Example 2. 4 is a scanning electron micrograph of the metal organic structure obtained in Example 3. 5 is a scanning electron micrograph of the metal-organic structure obtained in Comparative Example 1. 5 is a scanning electron micrograph of the metal-organic structure obtained in Comparative Example 2. It is a graph which shows the thermogravimetric change of the metal organic structure obtained by the example and the comparative example. 7 is a graph showing the GC/MS analysis results of the metal organic structure obtained in Comparative Example 1. 7 is a graph showing the GC/MS analysis results of the metal organic structure obtained in Example 3. 9 is a graph showing a GC/MS analysis result of the metal organic structure obtained in Comparative Example 3. It is a graph which shows the amount of methane occlusion before and behind a moisture resistance test of the metal organic structure obtained by the example and the comparative example.

Hereinafter, the present invention will be described in detail with reference to its preferred embodiments.

First, the metal organic structure of the present invention will be described. The metal organic structure of the present invention has, as a basic skeleton, a paddle wheel binuclear complex composed of a divalent metal ion and a first organic ligand coordinated to the divalent metal ion. The paddle wheel binuclear complex has a three-dimensionally connected structure.

The divalent metal ion used in the present invention is not particularly limited as long as it can form a paddle wheel binuclear complex, and for example, Cu ²⁺ , Zn ²⁺ , Ru ²⁺ , Rh ²⁺ , Mo ²⁺ , Cr ^2+. , Ni ²⁺ , Mg ²⁺ , Fe ²⁺ , Pb ²⁺ , Sn ²⁺ , Ca ²⁺ , Cd ²⁺ , Sr ²⁺ , Ba ²⁺ , Hg ²⁺ , Co ²⁺ , Mn ^{2+ and the} like. These divalent metal ions may be used alone or in combination of two or more. Further, among such divalent metal ions, Cu ²⁺ is preferable from the viewpoint of easy synthesis and easy formation of a hexacoordination complex.

The first organic ligand used in the present invention is not particularly limited as long as it can form a paddle wheel binuclear complex, but has a structure in which the paddle wheel binuclear complex is three-dimensionally linked. From the viewpoint of forming a group, an organic ligand having three carboxyl groups in one molecule is preferable. Further, among the organic ligands having three carboxyl groups in one molecule, those further having a cyclic structure (such as an alicyclic ligand or an aromatic ring) from the viewpoint of improving the mechanical strength of the metal organic structure. Ligands and the like) are more preferable, and those further having an aromatic ring (aromatic ligands) are particularly preferable. Examples of aromatic ligands having three carboxyl groups in one molecule include benzene-1,3,5-tricarboxylate [BTC], 4,4′,4″-benzene-1,3,5- Triyl-tribenzoate [BTB], 4,4′,4″-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate [BBC], phenol tricarboxylate [PTC ], 4,4',4"-[Triazine-2,4,6-triyl-tris(benzene-4,1-diyl)]tribenzoate [TAPB], 3,4-di(4-carboxyphenyl)benzoic acid Acid, etc. These first organic ligands may be used alone or in combination of two or more. Benzene-1,3,5-tricarboxylate [BTC], 4,4′,4″-benzene-1, 3,5-triyl-tribenzoate [BTB], 4,4′,4″-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)]tribenzoate [BBC] are preferable, Benzene-1,3,5-tricarboxylate [BTC] is more preferred.

The paddle wheel binuclear complex used in the present invention is composed of the two divalent metal ions and the four first organic ligands coordinated with the two divalent metal ions. The metal organic structure has a structure in which such paddle wheel binuclear complexes are three-dimensionally connected. Examples of such a three-dimensionally connected paddle wheel binuclear complex include HKUST-1 [Cu ₃ (BTC) ₂ ], MOF-143 [Cu ₃ (BTB) ₂ ], MOF-399 [Cu ₃ (BBC) ₂ ], MOF-388 [Cu ₃ (TAPB) ₂ ], and the like. These paddle wheel binuclear complexes may be used alone or in combination of two or more. Among such paddle wheel binuclear complexes, HKUST-1 [Cu ₂ (BTC) ₄ ] is preferable from the viewpoint of gas storage performance (particularly, methane storage performance).

The structure of such a paddle wheel type binuclear complex will be described by taking HKUST-1 as an example. FIG. 1 is a schematic diagram showing the basic skeleton of HKUST-1. As shown in FIG. 1, the paddle wheel binuclear complex, which is the basic skeleton of HKUST-1, has a structure in which four BTCs are coordinated to two Cu ²⁺ . More specifically, two oxygen atoms of one carboxyl group in each BTC are coordinated with two Cu ²⁺ to form a paddlewheel binuclear complex that is a basic skeleton of HKUST-1. ing. Then, three carboxyl groups in one BTC molecule are coordinated to Cu ²⁺ , which respectively constitute different basic skeletons, whereby a structure in which the paddle wheel type dinuclear complex is three-dimensionally linked (paddle A structure in which a wheel-type binuclear complex is three-dimensionally crosslinked) is formed. In the structure in which the paddle wheel type binuclear complex is three-dimensionally linked, as shown in FIG. 1, Cu ²⁺ (divalent metal ion) has a coordination unsaturated site 1. In the present invention, “coordinative unsaturated site” means that the first organic ligand is coordinated among the coordination sites of the divalent metal ion forming the paddle wheel type binuclear complex. Not mean a vacant coordination site.

The metal-organic structure of the present invention is such that at least a part of the coordination unsaturated site of the divalent metal ion in such a three-dimensionally connected paddle wheel type binuclear complex is derived from acetone and acetone. At least one second organic ligand selected from the group consisting of compounds is coordinated. FIG. 2 is a schematic diagram showing a basic skeleton of a metal organic structure in which acetone is coordinated as a second organic ligand 2 at a coordination unsaturated site of Cu ²⁺ in HKUST-1. Examples of the acetone-derived compound include acetic acid and carbon dioxide. These second organic ligands may be used alone or in combination of two or more. Among these second organic ligands, acetone is preferable from the viewpoint of operability that it is hard to volatilize at room temperature and has a low boiling point.

In the metal-organic structure of the present invention, such a second organic ligand is coordinated with 30 to 100% of the coordination unsaturated sites of the divalent metal ion in the paddlewheel binuclear complex. There is. When the ratio of the coordinatively unsaturated sites coordinated by the second organic ligand is less than the lower limit, the water resistance (moisture resistance) of the metal organic structure is lowered and the metal organic structure was exposed to an atmosphere containing water. In this case, the gas storage performance (particularly, methane storage performance) is significantly reduced. Further, from the viewpoint that the water resistance (moisture resistance) of the metal organic structure is improved, the proportion of coordination unsaturated sites coordinated by the second organic ligand is preferably 35 to 100%, 50 to 100% is more preferable.

Further, in the metal organic structure of the present invention, it is preferable that a silicone coating layer is formed on at least a part of the outer surface thereof. Thereby, the water resistance (moisture resistance) of the metal organic structure is further improved, and the structural destruction due to water is suppressed. The polysiloxane for forming such a silicone coating layer is not particularly limited, but examples thereof include methylhydrogenpolysiloxane, dimethylpolysiloxane, methylphenylpolysiloxane, cyclic dimethylpolysiloxane, and diaminepolysiloxane. These polysiloxanes may be used alone or in combination of two or more. Of these polysiloxanes, methylhydrogenpolysiloxane and dimethylpolysiloxane are preferable, and methylhydrogenpolysiloxane is more preferable, from the viewpoint of stability of the crystal surface.

Next, a method for producing the metal organic structure of the present invention will be described. The method for producing a metal-organic structure of the present invention comprises an adsorption step of adsorbing a second organic ligand to a paddle wheel type binuclear complex that is three-dimensionally connected, and the second organic ligand is adsorbed. The paddle wheel type binuclear complex is heated at atmospheric pressure or under pressure to generate a second organic compound on at least a part of the coordination unsaturated site of the divalent metal ion in the paddle wheel type binuclear complex. And a heating step for coordinating a ligand.

In the method for producing a metal organic structure of the present invention, first, a paddle wheel binuclear complex having a second organic ligand adsorbed thereon is prepared (adsorption step). The method of adsorbing the second organic ligand to the paddle wheel binuclear complex is not particularly limited, and for example, a paddle wheel binuclear complex and a second organic ligand are mixed and, if necessary, A method of removing an extra second organic ligand can be adopted. As a method of removing the extra second organic ligand, a method of evaporating the second organic ligand under atmospheric pressure or under pressure and under a temperature atmosphere of 70° C. or lower is preferable. On the other hand, in the reduced pressure treatment, the second organic ligand adsorbed on the paddle wheel binuclear complex is desorbed, and the proportion of coordination unsaturated sites adsorbed by the second organic ligand decreases (for example, , Less than 30%), which is not preferable.

The mixing ratio of the paddle wheel binuclear complex and the second organic ligand is not particularly limited, but the second organic ligand is 29 to 800 with respect to 100 parts by mass of the paddle wheel binuclear complex. It is preferable to mix by mass, when the mixing ratio of the second organic ligand is less than the lower limit, it may not be possible to coordinate a sufficient amount of the second organic ligand. If the upper limit is exceeded, it may be necessary to remove a large amount of extra second organic ligand.

Next, the paddle wheel type binuclear complex in which the second organic ligand is adsorbed is heated (heating step). As a result, the second organic ligand is coordinated to at least a part of the coordination unsaturated site of the divalent metal ion in the paddle wheel type binuclear complex. The heating method is not particularly limited as long as it is a method of heating/heating under atmospheric pressure or under pressure. On the other hand, when the temperature is raised and heated under reduced pressure, the second organic ligand adsorbed on the paddle wheel binuclear complex is desorbed, and the coordination unsaturated site adsorbed by the second organic ligand It is not preferable because the ratio becomes small (for example, less than 30%).

In the method for producing a metal organic structure of the present invention, the heating temperature is 100 to 300°C. If the heating temperature is lower than the lower limit, slightly remaining water molecules cannot be removed. On the other hand, if the heating temperature is higher than the upper limit, the metal organic structure is thermally decomposed. The heating time is not particularly limited, but is preferably 3 to 12 hours.

In addition, in the method for producing a metal organic structure of the present invention, it is preferable that 30% to 100% (preferably 35 to 100%, more preferably 50 to 100%) of the coordination unsaturated sites of the divalent metal ion. It is preferable to heat the paddle wheel type binuclear complex in which the two organic ligands are adsorbed. Thereby, 30% to 100% (preferably 35 to 100%, more preferably 50 to 100%) of the coordination unsaturated sites of the divalent metal ion in the paddle wheel type binuclear complex is subjected to the second organic coordination. The ligand can be coordinated, and a metal organic structure excellent in water resistance (moisture resistance) can be obtained. On the other hand, when the proportion of the coordinatively unsaturated sites adsorbed by the second organic ligand is less than 30%, the second organic ligand is coordinated to 30% or more of the coordinatively unsaturated sites. In some cases, a metal organic structure having excellent water resistance (moisture resistance) cannot be obtained.

Further, in the method for producing a metal organic structure of the present invention, it is preferable to form a silicone coating layer on at least a part of the outer surface of the metal organic structure. Thereby, a metal organic structure having excellent water resistance (moisture resistance) can be obtained.

As a method of forming the silicone coating layer, first, in the adsorption step, the paddlewheel binuclear complex is caused to adsorb the second organic ligand and silicone. The method of adsorbing the second organic ligand and the silicone to the paddle wheel binuclear complex is not particularly limited, and for example, the paddle wheel binuclear complex and the second organic ligand may be mixed to obtain According to the above, the excess second organic ligand is removed, and after adsorbing the second organic ligand to the paddle wheel type binuclear complex, silicone is mixed to make the second organic ligand Method of adsorbing silicone to adsorbed paddle wheel type binuclear complex; mixing paddle wheel type binuclear complex and silicone to adsorb silicone to paddle wheel type binuclear complex, and then adsorbing second organic ligand A method of mixing, removing excess second organic ligand as needed, and adsorbing the second organic ligand to the paddlewheel binuclear complex adsorbed by silicone; paddlewheel binuclear complex And a second organic ligand and silicone are mixed, and if necessary, an extra second organic ligand is removed to form a paddle wheel type binuclear complex with the second organic ligand and silicone. It is possible to adopt a method of simultaneously adsorbing

The mixing ratio of the paddle wheel binuclear complex and the silicone is not particularly limited, but 0.5 to 5 parts by mass of silicone is preferably mixed with 100 parts by mass of the paddle wheel binuclear complex. If the mixing ratio is less than the lower limit, the silicone coating layer may not be sufficiently formed, while if it exceeds the upper limit, the gas storage performance (particularly, methane storage performance) may be significantly reduced.

Next, the paddle wheel type binuclear complex in which such a second organic ligand and silicone are adsorbed is heated under the same conditions as above. As a result, the second organic ligand is coordinated with at least a part of the coordination unsaturated site of the divalent metal ion in the paddle wheel type binuclear complex, and at least a part of the outer surface of the silicone coating layer. Is formed, and a metal organic structure having further excellent water resistance (moisture resistance) can be obtained.

Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Example 1)
As paddle wheel type binuclear complexes linked _{three-dimensionally, HKUST-1 ([Cu 3} (BTC) 2], Aldrich "BasoliteC300") was used. In the above formula, BTC represents benzene-1,3,5-tricarboxylate. 2.0 g of this HKUST-1 was weighed, put into a flask, and vacuum dried for 60 minutes. To the dried HKUST-1, 20 ml of acetone (super dehydration) was added, and further 100 μl of methyl hydrogen polysiloxane (“KF-9901” manufactured by Shin-Etsu Chemical Co., Ltd.) was added. The obtained mixture was stirred under a nitrogen gas flow for 10 minutes to adsorb acetone and silicone to HKUST-1 and then heated in an oil bath at 37°C to evaporate excess acetone. Then, the flask containing HKUST-1 in which acetone and silicone were adsorbed was placed in an oven preheated to 150° C. and heated under atmospheric pressure for 12 hours. After heating, the obtained powder was quickly transferred from the flask to a sample bottle, deaerated at room temperature for 3 hours, and then stored under a nitrogen atmosphere.

(Example 2)
Acetone and silicone adsorbed HKUST-in the same manner as in Example 1 except that 20 μl of dimethylpolysiloxane (“KF-96-30CS” manufactured by Shin-Etsu Chemical Co., Ltd.) was used instead of methylhydrogenpolysiloxane. Preparation 1 and heat treatment were performed, the obtained powder was degassed in the same manner as in Example 1, and then stored in a nitrogen atmosphere.

(Example 3)
Acetone-adsorbed HKUST-1 was prepared and heat-treated in the same manner as in Example 1 except that methylhydrogenpolysiloxane was not added, and the obtained powder was degassed in the same manner as in Example 1. Then, it was stored under a nitrogen atmosphere.

(Comparative Example 1)
The purchased HKUST-1 was used as it was.

(Comparative example 2)
Preparation and heat treatment of HKUST-1 adsorbed with hexane and silicone were performed in the same manner as in Example 1 except that 20 ml of hexane was added instead of acetone, and the obtained powder was degassed in the same manner as in Example 1. After that, it was stored under a nitrogen atmosphere.

(Comparative example 3)
Acetone adsorbed HKUST-1 was prepared in the same manner as in Example 3. The flask containing HKUST-1 adsorbed with acetone was heated under reduced pressure at 50° C. for 10 minutes, then at 100° C. for 10 minutes, then at 120° C. for 1 hour, then at 130° C. for 2 hours. After heating, it was placed in an oven preheated to 150° C. and heated under atmospheric pressure for 12 hours. After completion of heating, the obtained powder was degassed in the same manner as in Example 1 and then stored under a nitrogen atmosphere.

<Moisture resistance test>
At room temperature, each powder sample obtained in Examples and Comparative Examples was stored for a predetermined time in a desiccator whose relative humidity was adjusted to 75% RH by a saturated salt method using a saturated aqueous solution of NaCl, and exposed to an atmosphere containing water. Let

<Powder X-ray diffraction (PXRD) measurement>
The X-ray diffraction patterns of the powder sample before and after the moisture resistance test were measured using a powder X-ray diffractometer (“Ultima IV” manufactured by Rigaku Corporation). Specifically, the powder sample is pressed against a grooved glass plate, and X-ray source: CuKα ray (λ=1.5418Å, 40 kV, 40 mA), in air, 10 deg. It was measured under the condition of /min. The results are shown in FIGS. 3A to 3C. 3A and 3B are graphs showing X-ray diffraction patterns of powder samples before the moisture resistance test, and FIG. 3C shows a moisture resistance test (Example 1 for 12 days, Example 2 and Comparative Examples 1 and 2 for 13 days). , Example 3 is a graph showing an X-ray diffraction pattern of the powder sample after 14 days). 3A to 3C show powder X-ray diffraction patterns obtained by calculation for HKUST-1 (FIG. 1), and FIG. 3B shows HKUST in which acetone is coordinated to the coordination unsaturated site of Cu. The powder X-ray diffraction pattern obtained by calculation for -1 (FIG. 2) is also shown.

As shown in FIG. 3A, in each of the powder samples obtained in Examples 1 to 3 and Comparative Examples 1 to 2, the peak position in the powder X-ray diffraction pattern was the powder X-ray calculated by HKUST-1. It coincided with the peak position in the diffraction pattern, and was confirmed to be a metal organic structure (MOF) having a HKUST-1 structure as a basic skeleton.

Further, as shown in FIG. 3A, in the powder X-ray diffraction patterns of the metal organic structures obtained in Examples 1 to 3, the powder obtained by calculation for HKUST-1 was around 2θ=5.8°. There were peaks not seen in the X-ray diffraction pattern. This peak near 2θ=5.8° is found in the powder X-ray diffraction pattern obtained by calculation for HKUST-1 in which acetone is coordinated to the coordination unsaturated site of Cu, as shown in FIG. 3B. It is confirmed that, in the metal organic structures obtained in Examples 1 to 3, acetone is coordinated to the coordination unsaturated site of Cu of HKUST-1.

In addition, as shown in FIG. 3C, the metal organic structures obtained in Examples 1 and 2 also showed a powder X-ray diffraction pattern obtained by calculation for HKUST-1 in the powder X-ray diffraction pattern after the moisture resistance test. Since the peak was observed at the peak position in, it was found that the HKUST-1 structure was maintained even after the moisture resistance test and that the water resistance (moisture resistance) was excellent. Further, in the powder X-ray diffraction pattern after the humidity resistance test, the metal organic structure obtained in Example 3 has a lower peak intensity than that before the humidity resistance test, but the powder obtained by calculation for HKUST-1 Since a peak was observed at the peak position in the X-ray diffraction pattern, it was found that the HKUST-1 structure remained even after the humidity resistance test and that it had water resistance (moisture resistance).

On the other hand, as shown in FIG. 3C, the metal-organic structure (HKUST-1) obtained in Comparative Example 1 had powder X-rays calculated by HKUST-1 in the powder X-ray diffraction pattern after the moisture resistance test. No peak was found at the peak position in the diffraction pattern, indicating that the HKUST-1 structure was destroyed by the water content in the air. In addition, the metal organic structure obtained in Comparative Example 2 has a greatly reduced peak intensity in the powder X-ray diffraction pattern after the humidity resistance test as compared with that before the humidity resistance test, and the HKUST-1 structure due to the moisture in the air. Found that most of the
<SEM observation>
The powder sample (metal organic structure) before and after the moisture resistance test was observed using a scanning electron microscope (“(SU3500”, manufactured by Hitachi High-Technologies Corporation). Specifically, the powder sample was fixed to a carbon tape. Then, after conducting a Pt vapor deposition conductive treatment (30 seconds), SEM observation was performed at an acceleration voltage of 5 kV (high vacuum mode), and the results are shown in FIGS. 4A to 4C and 5A to 5B.

As shown in FIG. 4A, in the metal organic structure obtained in Example 1, no significant change was observed in the crystal appearance shape before and after the humidity resistance test. Further, as shown in FIG. 4B, in the metal organic structure obtained in Example 2, voids were observed on the crystal surface before the humidity resistance test, but there was a large change in the appearance of the crystal before and after the humidity resistance test. I couldn't see it. Further, as shown in FIG. 4C, in the metal-organic structure obtained in Example 3, voids were observed on the crystal surface before the moisture resistance test, and the voids were slightly increased by the water content in the air. No collapse was seen.

On the other hand, as shown in FIG. 5A, in the metal organic structure obtained in Comparative Example 1, the crystal shape was largely collapsed by the moisture in the air, and the shape before the moisture resistance test was not retained. Further, as shown in FIG. 5B, in the metal organic structure obtained in Comparative Example 2, no collapse of the crystal shape due to moisture in the air was observed, but voids were observed on the crystal surface before the moisture resistance test. The water content in the air significantly increased the number of voids.

As described above, in the results of PXRD measurement and SEM observation, comparing Example 3 and Comparative Example 1, by coordinating acetone to HKUST-1, the water resistance (moisture resistance) of the metal organic structure is improved, It was found that the destruction of the HKUST-1 structure due to water in the air can be suppressed. Further, comparing Comparative Example 2 with Comparative Example 1, even if a silicone coating layer was formed on the outer surface of HKUST-1, destruction of the HKUST-1 structure due to moisture in the air was hardly suppressed. Comparing Examples 1 and 2 with Comparative Example 2, by forming a silicone coating layer on the outer surface of HKUST-1 and coordinating acetone to the coordinatively unsaturated sites, HKUST-1 due to moisture in the air was used. It was found that the destruction of the structure can be sufficiently suppressed.

<Thermogravimetric measurement (TG)>
The thermogravimetric changes of the powder samples (metal organic structures) obtained in the Examples and Comparative Examples were measured using a thermogravimetric measuring device (“ThermoPlusTG8120” manufactured by Rigaku Corporation). Specifically, 5 mg of the powder sample was weighed in a platinum pan, and the weight change was measured when the temperature was raised from room temperature to 800° C. at a heating rate of 10° C./min under nitrogen gas flow. The result is shown in FIG.

<Thermal desorption-gas chromatograph/mass spectrometry (TD-GC/MS)>
Conducted using a thermal decomposition furnace ("PY-2020D" manufactured by Frontier Laboratories Ltd.) and a gas chromatograph-mass spectrometer (GC/MS analyzer, "Agilent 6890 GC/5973 MSD" manufactured by Agilent Technologies). The powder samples (metal organic structure) obtained in Examples and Comparative Examples were analyzed by GC/MS. Specifically, 0.5 mg of the powder sample was placed in a pyrolysis furnace, and heated from 40° C. to 500° C. at a heating rate of 10° C./min under helium gas flow, and the gas generated at this time was heated. , GC/MS analyzer was used for detection. The results are shown in FIGS. 7A to 7C.

As shown in FIG. 6, in the metal organic structure obtained in Comparative Example 1, a gradual weight loss was observed between room temperature and 150° C., and a weight loss was observed between 150° C. and 300° C. Little was seen, with a large weight loss between 300 and 370°C. In comparison with the GC/MS analysis results shown in FIG. 7A, the weight loss between room temperature and 100° C. is due to water (m/z=18) and the weight between 100° C. and 150° C. The decrease was found to be due to methanol (m/z=31). It is assumed that methanol was contained in the purchased HKUST-1. Further, in the GC/MS analysis result shown in FIG. 7A, carbon dioxide (m/z=44), benzene (m/z=78) and the like were detected at 300° C. or higher. It was found that the weight loss between 370° C. was caused by the thermal decomposition of BTC (benzene-1,3,5-tricarboxylate) which is a ligand constituting HKUST-1.

On the other hand, as shown in FIG. 6, in the metal organic structure obtained in Example 3, a gradual weight loss was observed between room temperature and 300° C., and a large weight reduction was observed between 300° C. and 370° C. A weight loss was seen. By comparison with the GC/MS analysis results shown in FIG. 7B, the weight loss between room temperature and 100° C. and the weight loss between 300° C. and 370° C. were the same as in Comparative Example 1, respectively (m/z= 18) and the thermal decomposition of BTC. On the other hand, as shown in FIG. 7B, in the metal organic structure obtained in Example 3, methanol was not detected. This is presumably because in Example 3, HKUST-1 adsorbed with acetone was heated at 150° C., and at this time, methanol contained in HKUST-1 was volatilized. On the other hand, in the metal organic structure obtained in Example 3, in the GC/MS analysis result shown in FIG. 7B, acetone (m/z=58) and acetic acid (m/z) were measured between 100° C. and 300° C. =60) and carbon dioxide (m/z=44) were detected. Here, it is considered that acetic acid and carbon dioxide were generated by decomposing HKUST-1 adsorbed with acetone at 150°C. Therefore, considering that the weight loss (100% by mass) between 100° C. and 300° C. in FIG. 6 is attributed to acetone, the molar ratio of acetone to Cu atom in HKUST-1 is acetone/Cu= It was calculated to be 0.36. From this result, in the metal organic structure obtained in Example 3, 36% of the coordination unsaturated sites of Cu ²⁺ are coordinated with acetone and a compound derived from acetone (acetic acid, carbon dioxide). I understood.

On the other hand, as shown in FIG. 6, in the metal-organic structure obtained in Comparative Example 3, a large weight reduction was observed between room temperature and 100° C., and a slight weight reduction was observed between 100° C. and 300° C. A weight loss was seen, with a large weight loss between 300 and 370°C. When compared with the GC/MS analysis results shown in FIG. 7C, the weight loss between room temperature and 100° C. and the weight loss between 300° C. and 370° C. were the same as in Comparative Example 1, respectively (m/z= 18) and the thermal decomposition of BTC. On the other hand, as shown in FIG. 7C, methanol was not detected in the metal organic structure obtained in Comparative Example 3. This is because, in Comparative Example 3, HKUST-1 having adsorbed acetone was heated under reduced pressure and then heated at 150° C., and it is speculated that the methanol contained in HKUST-1 was volatilized at this time. It On the other hand, in the metal organic structure obtained in Comparative Example 3, in the GC/MS analysis result shown in FIG. 7C, acetone (m/z=58) and acetic acid (m/z) were measured between 100° C. and 300° C. =60) and carbon dioxide (m/z=44) were detected. It is considered that acetic acid and carbon dioxide were generated by decomposing HKUST-1 adsorbed with acetone when heating under reduced pressure and heating at 150°C. Therefore, considering that the weight loss (100% by mass) between 100° C. and 300° C. in FIG. 6 is attributed to acetone, the molar ratio of acetone to Cu atom in HKUST-1 is acetone/Cu= It was calculated as 0.08. From these results, in the metal organic structure obtained in Comparative Example 3, 8% of the coordination unsaturated sites of Cu ²⁺ are coordinated with acetone and a compound derived from acetone (acetic acid, carbon dioxide). I understood.

From the above results, by heating HKUST-1 with adsorbed acetone under atmospheric pressure in a temperature atmosphere of 100 to 300° C., 30% or more of the coordination unsaturated sites of Cu ^{2+ in} HKUST-1 can be obtained. It was confirmed that acetone and a compound derived from acetone coordinate.

On the other hand, when HKUST-1 with adsorbed acetone is heated under reduced pressure and then heated under atmospheric pressure in a temperature atmosphere of 100 to 300° C., the coordination amount of acetone and the compound derived from acetone is It turned out to decrease. This is because acetone was desorbed by heating under reduced pressure, and the amount of adsorbed acetone when heated in an atmosphere at a temperature of 100 to 300° C. under atmospheric pressure was reduced (less than 30% of coordination unsaturated sites of Cu ²⁺ ). Inferred.

<Methane storage amount measurement>
The methane storage amount of the powder sample (metal organic structure) before and after the moisture resistance test was measured using an automatic methane storage amount measuring device (manufactured by Toyota Central Research Institute Co., Ltd.). Specifically, after filling about 0.2 g of the powder sample into a measuring cell of an automatic methane storage amount measuring device, as a pretreatment, at room temperature, the inside of the measuring cell is heated from atmospheric pressure to 3 kPa for 5 minutes. Then, the pressure was reduced from 3 kPa to 1 kPa over 7 minutes, and further from 1 kPa to 0.6 kPa over 20 minutes. Next, nitrogen gas was filled for 3 minutes until the inside of the measurement cell reached 95 kPa. Then, the temperature of the measurement cell was raised from room temperature to 150° C. over 30 minutes while maintaining the state (95 kPa) filled with nitrogen gas. Then, the inside of the measuring cell was depressurized from 95 kPa to 0 kPa over 60 minutes while heating at 150° C., and the cell was kept at 0 kPa for 3 hours. After that, the heating was terminated, and when the temperature in the measurement cell became 30° C. or lower, the valve of the measurement cell was closed to complete the pretreatment. The methane storage amount of the powder sample thus pretreated was measured under the conditions of room temperature and methane supply pressure: 0 to 1 MPa. Table 1 shows the ratio of methane storage amount to the metal organic structure (unit: mass %). In addition, based on the obtained results, the results obtained by normalizing the methane storage amount of the metal organic structure after the humidity resistance test based on the methane storage amount of the metal organic structure before the humidity resistance test are shown in FIG.

As shown in FIG. 8, in the metal organic structure obtained in Comparative Example 1, it was found that the gas storage performance (methane storage performance) almost disappeared after the humidity resistance test for 13 days. In addition, in the metal organic structure obtained in Comparative Example 2, after 13 days of humidity resistance test, the methane storage amount decreased to 30% before the humidity resistance test, and only the silicone coating, the gas storage performance by moisture. It was difficult to suppress a decrease in (especially methane storage performance).

On the other hand, in the metal organic structures of the present invention obtained in Examples 1 to 3, even after the humidity resistance test for 12 to 14 days, the methane storage amount of 55% to 80% before the humidity resistance test is retained, It was found that the decrease in gas storage performance (particularly, methane storage performance) due to moisture was suppressed.

From the above results, it is possible to improve the water resistance (moisture resistance) of the paddle wheel binuclear complex by coordinating the paddle wheel binuclear complex with acetone or by additionally using a silicone coating. It has been found that a gas storage material can be obtained in which a decrease in gas storage performance (particularly, methane storage performance) is sufficiently suppressed.

As described above, according to the present invention, it is possible to improve the water resistance (moisture resistance) of a metal organic structure having a paddle wheel binuclear complex as a basic skeleton.

Therefore, the metal organic structure of the present invention has excellent water resistance (moisture resistance), and has excellent gas storage performance (especially methane) even when exposed to an atmosphere containing water for a long time (for example, 10 days or more). Therefore, it is useful as a gas storage material, particularly as a gas storage material in an atmosphere containing water.

1: Coordination unsaturated site 2: Second organic ligand

Claims (8)

A three-dimensionally connected paddle wheel composed of a divalent metal ion and a first organic ligand having three carboxyl groups in one molecule coordinated with the divalent metal ion. Type binuclear complex, and a second organic ligand that is acetone,
The metal organic structure, wherein the second organic ligand is coordinated with 30% to 100% of the coordination unsaturated sites of the divalent metal ion in the paddle wheel binuclear complex. body. The divalent metal ion is selected from the group consisting of Cu ²⁺ , Zn ²⁺ , Ru ²⁺ , Rh ²⁺ , Mo ²⁺ , Cr ²⁺ , Ni ²⁺ , Mg ²⁺ , Fe ²⁺ , Pb ²⁺ , Sn ²⁺ and Ca ^2+. It is at least 1 sort(s), The metal organic structure of Claim 1 characterized by the above-mentioned. The first organic ligand is benzene-1,3,5-tricarboxylate, 4,4′,4″-benzene-1,3,5-triyl-tribenzoate, and 4,4′,4. It is at least 1 sort(s) selected from the group which consists of "-[benzene-1,3,5-triyl-tris(benzene-4,1-diyl)] tribenzoate, The claim 1 or 2 characterized by the above-mentioned. Metal organic structure. The metal organic structure according to any one of claims 1 to 3, wherein a silicone coating layer is provided on at least a part of the outer surface. A gas storage material comprising the metal organic structure according to any one of claims 1 to 4. Bivalent coordinated to the metal ion and the divalent metal ion consists of a first organic ligand has a three dimensionally connected to have a paddle wheel type binuclear complex, second acetone An adsorption step of adsorbing the organic ligand of
The paddle-wheel binuclear complex in which the second organic ligand is adsorbed is heated under atmospheric pressure or under pressure in a temperature atmosphere of 100 to 300° C. A heating step of coordinating the second organic ligand with 30% to 100% of the coordination unsaturated sites of the divalent metal ion;
A method for producing a metal organic structure, comprising: In the heating step, the paddle wheel type binuclear complex in which the second organic ligand is adsorbed on 30% to 100% of the coordination unsaturated sites of the divalent metal ion is heated. The method for producing a metal-organic structure according to claim 6, wherein In the adsorption step, the paddlewheel binuclear complex is adsorbed with the second organic ligand and silicone,
In the heating step, the paddlewheel binuclear complex in which the second organic ligand and the silicone are adsorbed is heated under atmospheric pressure or under pressure at a temperature atmosphere of 100 to 300° C., and The second organic ligand is coordinated to 30% to 100% of the coordination unsaturated sites of the divalent metal ion in the paddle wheel type binuclear complex, and the outer surface of the metal organic structure is Forming a silicone coating layer on at least a part,
The method for producing a metal organic structure according to claim 6 or 7, characterized in that.