JP2007277106A - Porous metal complex, method for producing the same, adsorbent, separating agent, gas adsorbent, and hydrogen adsorbent - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a porous metal complex having higher bulk density, higher hydrogen adsorption capacity, and better effective hydrogen adsorption capacity than a prior art compound. <P>SOLUTION: The porous metal complex 1 comprises a three dimensional porous backbone structure constituted of a metal complex comprised of a central metal 3 and an organic ligand 4 comprising a heterocyclic monocarboxylic acid having a heterocyclic backbone 4a and a carboxylate group 4b coordinating to the central metal 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a porous metal complex, a method for producing a porous metal complex, an adsorbent, a separating material, a gas adsorbent, and a hydrogen adsorbent.

  In recent years, development competition for solid polymer fuel cells to be installed in fuel cell vehicles has been actively developed. In order to put such fuel cell vehicles into practical use, development of an efficient hydrogen storage method using a hydrogen storage material that is low in cost, lightweight, and has a high hydrogen storage density is desired.

  Therefore, a hydrogen storage material using a porous organometallic complex having a skeleton structure in which a two-dimensional lattice structure composed of a metal ion and an organic ligand is three-dimensionally stacked as a unit motif has been proposed (Patent Document 1, It is attracting attention as a gas adsorbent such as methane, nitrogen and hydrogen. Among them, an organometallic complex using a carbocyclic skeleton monocarboxylic acid compound such as benzoic acid or toluic acid has a property that its structure changes flexibly according to an external environment such as pressure and temperature. Thus, it has been found that a metal complex having a flexible skeleton structure has a selective adsorption property and is suitable as a gas storage material (see Patent Document 3 and Non-Patent Document 1).

In addition, an organometallic complex using a nitrogen-containing heterocyclic skeleton such as tetrazine or triazine as an organic ligand has been found to be suitable as a hydrogen storage material because of its improved affinity with hydrogen (Patent Document) 4).
JP 2001-348361 A US Patent Application Publication No. 2003/0004364 JP 2003-342260 A JP-A-2005-93181 Mori Kazuaki, Omura Tetsuki, Sato Tomohiko, “Gas Occlusion of Carboxylic Acid Metal Complexes and Their Applications”, PETROTECH, “Japan Petroleum Institute”, 2003, Vol. 26, No. 2, p. 105-112

  However, an organometallic complex using a carbocyclic skeleton monocarboxylic acid compound has a high effective hydrogen storage capacity, but it cannot be said that the hydrogen storage capacity is sufficient, and improvement of the storage capacity is indispensable for practical use. In addition, metal complexes using heterocyclic skeleton carboxylic acids and bridging ligands as ligands have a solid skeleton and hydrogen storage capacity is improved compared to other materials, but hydrogen is a metal complex. Phenomenon remaining in the interior is seen, and the effective hydrogen storage capacity is not sufficient.

  The present invention has been made to solve the above problems, and a porous metal complex according to the present invention includes a central metal and a heterocyclic ring coordinated to the central metal and having a heterocyclic skeleton and a carboxylate group. It includes a three-dimensional porous skeleton structure of a metal complex including an organic ligand composed of a monocarboxylic acid.

  The method for producing a porous metal complex according to the present invention comprises a three-dimensional porous skeleton of a metal complex comprising a central metal and an organic ligand coordinated to the central metal and having a heterocyclic skeleton and a carboxylate group. A method for producing a porous metal complex having a structure, wherein a first solution in which a heterocyclic monocarboxylic acid is dissolved in a first solvent, and a second solution in which a salt of a central metal is dissolved in a second solvent, Are mixed and reacted.

  The adsorbent according to the present invention includes the porous metal complex according to the present invention.

  The separating material according to the present invention includes the porous metal complex according to the present invention.

  The gas adsorbent according to the present invention includes the porous metal complex according to the present invention.

  The hydrogen adsorbent according to the present invention includes the porous metal complex according to the present invention.

  According to the present invention, when an organic ligand having a heterocyclic skeleton is used, the affinity with hydrogen is increased, and since the structure changes according to the external environment, the structure has a flexible structure. A porous metal complex having an increased bulk density, a high hydrogen storage capacity, and a good effective hydrogen storage capacity can be obtained.

  According to the present invention, a porous metal complex having flexibility can be obtained inexpensively and easily.

  According to the present invention, since the porous metal complex according to the present invention is used, an inexpensive adsorbent, separation material, gas adsorbent and hydrogen adsorbent can be obtained efficiently.

  Hereinafter, a porous metal complex, a method for producing a porous metal complex, an adsorbent, a separation material, a gas adsorbent, and a hydrogen adsorbent according to embodiments of the present invention will be described.

  FIG. 1 is a schematic diagram showing a two-dimensional lattice structure (motif M) of the crystal structure of an example of the porous metal complex 1. FIG. 2 is a schematic diagram showing a three-dimensional structure of the porous metal complex 1. A porous metal complex 1 according to an embodiment of the present invention includes an organic ligand composed of a central metal 3 and a heterocyclic monocarboxylic acid coordinated to the central metal 3 and having a heterocyclic skeleton 4a and a carboxylate group 4b. 4 and a three-dimensional porous skeleton structure of a metal complex.

  The two-dimensional lattice structure of the porous metal complex 1 is a binuclear complex having two copper ions as a central metal 3, and four heterocyclic carboxylate ions around the central metal 3 as organic ligands 4. It is coordinated. Each heterocyclic carboxylate ion has a heterocyclic skeleton 4a and one carboxylate group 4b, and is coordinated to a copper ion which is the central metal 3 through two oxygen atoms of the carboxylate group 4b. A cross-shaped lattice element 2 is formed. Each lattice element 2 has a zero-dimensional structure integrated by relatively weak bonds such as π-π interaction and hydrogen bond. Then, a lattice-like two-dimensional structure is formed in which rings (voids) having the lattice element 2 placed in parallel on the grid and having the central metal 3 as four lattice points are condensed. This two-dimensional lattice structure is used as a unit motif M, that is, a basic repeating pattern, and the motif M is separated in parallel in the stacking direction shown in FIG. 2 by the bonding between the central metal 3 and the oxygen of the carboxylate group 4b. And a three-dimensional porous skeleton structure in which the lattice elements 2 are self-assembled three-dimensionally is formed. As a result, as shown in FIG. 2, in this structure, the voids 5 of the plurality of motifs M are aligned in a line, so that the porous metal complex 1 forms a plurality of one-dimensional channels along the arrows 6 in FIG. is doing.

  When the porous metal complex according to the embodiment of the present invention has a heterocyclic skeleton as the organic ligand, the affinity with hydrogen increases, and the structure changes depending on the external environment. Compared with the conventional one, the hydrogen storage capacity is high and the effective hydrogen storage capacity is good. Moreover, since this porous metal complex consists only of the organic ligand which consists of a metal atom and heterocyclic monocarboxylic acid, it can be manufactured simply and cheaply. Furthermore, the bond in the depth direction (stacking direction) is not bonded by a bridging ligand as in the prior art, but is self-assembled (accumulated) by the bond between the metal and oxygen in the carboxyl group. The density is improved.

  In this porous metal complex, a three-dimensional porous skeleton structure in which a motif M having a two-dimensional lattice structure is laminated is a skeleton portion that defines voids, and the pore diameter of each void is 0.3 to 2.0 [nm. ]. A gas or liquid molecule smaller than the pore diameter can be taken into the skeleton structure. In addition, since the organic ligand is bonded by a relatively weak bond, the bond is shifted according to an external environment such as pressure and heat, so that the skeleton structure forms a flexible structure having flexibility. Further, the skeleton structure changes flexibly according to the external environment such as heat or pressure. For this reason, the space | gap of this porous metal complex is deformable, and is excellent in the adsorption / desorption of gas.

The heterocyclic monocarboxylic acid has the following general formula (I)
HOOC-R (I)
It is preferable that a heterocyclic monocarboxylic acid represented by the formula (wherein R includes a heterocyclic ring) is included. In the above general formula (I), R preferably contains an element selected from an element group containing N, O, S, P, B, As, Si, Sb and Hg in the heterocyclic ring skeleton.

R represents the following general formulas (II) to (XXVII)

It is preferable that the substituent represented by any one of these is included. In the general formulas (II) to (XXVII), the carboxylate group may be bonded to any position of the ring, and the two oxygen atoms of the carboxylate group are coordinated to the central metal to form a two-dimensional lattice structure. Form. In addition, since different heterocyclic monocarboxylic acid organic ligands can be used, heterocyclic monocarboxylic acid metal complexes with changed affinity for hydrogen, pore shape, and diameter are cheaper and more expensive than before. Efficiently obtained.

  The central metal preferably includes a metal selected from a metal group including a divalent to tetravalent metal, and particularly preferably includes a divalent metal. More preferably, the central metal includes a metal selected from the group of metals including Cu, Zn, Mo, Ru, Ni, Cr and Rh. The central metal is preferably obtained from a metal salt selected from the group of metal salts including nitrates, sulfates, acetates, carbonates and formates. In this case, the metal salt is dissociated in the solvent and the metal that becomes the central metal is easily ionized, so that the reaction with the heterocyclic monocarboxylic acid is promoted during the production of the porous metal complex.

  The porous metal complex having such a structure is produced as follows. A method for producing a porous metal complex according to an embodiment of the present invention includes a three-dimensional metal complex comprising a central metal and an organic ligand coordinated to the central metal and having a heterocyclic skeleton and a carboxylate group. A method for producing a porous metal complex containing a porous skeleton structure, comprising: a first solution in which a heterocyclic monocarboxylic acid is dissolved in a first solvent; and a salt in which a central metal salt is dissolved in a second solvent. It mixes with the solution of 2 and makes it react, It is characterized by the above-mentioned. In this production method, since the porous metal complex consists only of a metal atom and an organic ligand composed of a heterocyclic monocarboxylic acid, it can be produced simply and inexpensively.

  Any one of dissolution, mixing, and reaction preferably includes irradiating the first or second solution with ultrasonic waves. In this case, since the reaction between the heterocyclic monocarboxylic acid and the salt of the central metal is promoted, the reaction time can be reduced, the reaction temperature can be reduced, and the reaction yield can be increased.

  One of the first and second solvents is selected from the solvent group comprising N, N′-dimethylformamide, N, N′-diethylformamide, water, alcohols, tetrahydrofuran, benzene, toluene, hexane, acetone and acetonitrile. It is preferable to contain a solvent. As the alcohol, for example, methanol, ethanol, propanol or the like can be used. These solvents dissolve the heterocyclic monocarboxylic acid and the metal salt of the central metal, but do not dissolve the target metal complex, so that the target product can be obtained efficiently. In particular, one of the first and second solvents preferably includes a solvent selected from the group of solvents including N, N′-dimethylformamide, N, N′-diethylformamide, water, and alcohols. Further, the first and second solvents may be the same solvent.

  As described above, when the porous metal complex according to the embodiment of the present invention has a heterocyclic skeleton as the organic ligand, the affinity with hydrogen increases, and the structure depends on the external environment. Changes, the bulk density is increased, and a porous metal complex having a higher hydrogen storage capacity and a better effective hydrogen storage capacity than the conventional one can be obtained. Moreover, according to the method for producing a porous metal complex according to the embodiment of the present invention, a porous metal complex having flexibility can be obtained inexpensively and easily. In addition, when an adsorbent, a separation material, a gas adsorbent and a hydrogen adsorbent are produced using the porous metal complex according to the embodiment of the present invention, the target product can be obtained more efficiently and at a lower cost than in the past. .

  Hereinafter, the porous metal complex according to the embodiment of the present invention will be described more specifically with reference to Examples 1 to 4 and Comparative Examples 1 to 2, but the scope of the present invention is limited to these. is not.

1. Sample Preparation Example 1 Synthesis of Copper Picolinate Picolinic acid was used as the heterocyclic monocarboxylic acid. A solution prepared by dissolving 4.92 [g] picolinic acid in water and a solution prepared by dissolving 1.82 [g] copper acetate monohydrate in water were mixed and stirred overnight. The reaction solution was filtered, and the filtrate was allowed to stand at normal temperature and pressure. The precipitate was collected by filtration and dried to obtain the desired product.

Example 2 Synthesis of Copper Pyrazineate Using a pyrazine acid 4.96 [g] as a heterocyclic monocarboxylic acid, the same treatment as in Example 1 was carried out as Example 2.

Example 3 Synthesis of rhodium picolinate Instead of copper acetate monohydrate, rhodium acetate dimer dihydrate was used, and picolinic acid 2.46 [g], rhodium acetate 2.39 [g], and ethyl acetate were used. The mixture was mixed in an autoclave and heated overnight. After cooling, the precipitate was collected by centrifugation and vacuum dried to obtain the desired product.

Example 4 Synthesis of Copper Thiophenecarboxylate Example 4 was prepared by subjecting 2-thiophenecarboxylic acid 5.68 [g] as a heterocyclic carboxylic acid to the same treatment as in Example 1.

Comparative Example 1 Synthesis of copper tetrazine dicarboxylate-triethylenediamine 1,2,4,5-tetrazine-3,6-dicarboxylic was used as the heterocyclic carboxylic acid. First, tetrazine dicarboxylic acid 0.58 [g] and copper sulfate pentahydrate 0.85 [g] were dissolved in absolute ethanol, and the reaction solution was heated and stirred at room temperature to 40 [° C.] for several [days]. An anhydrous toluene solution of triethylenediamine 0.19 [g] was added to the obtained reaction mixture, and the mixture was heated and stirred at 120 [° C.] for 3 [hour] using an autoclave. The obtained precipitate was filtered, washed with methanol, and dried under reduced pressure at 100 [° C.] to obtain the desired product.

Comparative Example 2 Synthesis of copper p-toluate p-toluic acid was used as a monocarboxylic acid. p-Toluic acid 5.44 [g] and copper acetate monohydrate 1.82 [g] were dissolved in ethyl acetate and stirred overnight. The reaction solution was filtered, and the filtrate was allowed to stand at normal temperature and pressure. The precipitate was collected by filtration and dried to obtain the desired product.

2. Measurement of effective hydrogen storage capacity
For the samples obtained in Examples 1 to 4 and Comparative Examples 1 to 2, the effective hydrogen storage capacity was measured and the hydrogen adsorption performance was evaluated. The measurement method followed the hydrogen storage / release measurement test of JIS H7201. After weighing the sample and placing it in a pressure-resistant sample tube for measurement and evacuating it at 200 [° C.] for 3 [hours] to release the gas remaining in the sample tube and obtaining the origin where hydrogen is not occluded Measurements were made. The measurement temperature was 25 [° C.]. Thereafter, the pressure was reduced to atmospheric pressure, and the amount of hydrogen released was confirmed.

3. Confirmation of crystal structure To confirm the crystal structure of the synthesized sample, an X-ray diffractometer (MXP 18VAHF) manufactured by Max Science was used, and measurement was performed at a voltage of 40 [kV], a current of 300 [mA], and an X-ray wavelength of CuKα. .

4). Confirmation of composition The composition of the synthesized sample was confirmed by elemental analysis. The method described in JPI-5S-65-2004 was used for confirmation of carbon, hydrogen, and nitrogen, and inductively coupled plasma emission spectroscopy was used for confirmation of metal elements.

Table 1 shows the effective hydrogen storage capacity of the samples obtained in Examples 1 to 4, Comparative Example 1 and Comparative Example 2. Table 1 also shows the measurement pressures of the examples and comparative examples.

  In Comparative Example 1, tetrazine dicarboxylate copper is used as a unit motif, and the copper contained in the unit motif and the copper contained in the other unit motif are bonded with triethylenediamine as a bridging ligand to form a three-dimensional porosity. A sex skeleton structure was formed. For this reason, the sample obtained in Comparative Example 1 has a firm skeleton structure. On the other hand, in Examples 1 to 4, each unit motif is not bonded by a bridging ligand, but is self-assembled by bonding between the central metal and oxygen in the carboxyl group. Improved and the hydrogen storage capacity increased. In Comparative Example 2, an organic ligand having no heterocyclic skeleton was used. On the other hand, in Examples 1 to 4, since the organic ligand having a heterocyclic skeleton was used, the affinity with hydrogen was increased, and the hydrogen storage capacity was higher than that of Comparative Example 2 and effective. A porous metal complex having a good hydrogen storage capacity was obtained. In Examples 1 to 4, the reaction was completed in a shorter time than Comparative Example 1, and in Examples 1, 3, and 4, the reaction proceeded without heating. On the other hand, in Comparative Example 1, in order to coordinate triethylenediamine serving as a bridging ligand to copper ions as the central metal, it was necessary to increase the temperature and pressure by an autoclave, and the reaction time was long. .

  From the results of Examples 1 to 4, Comparative Example 1 and Comparative Example 2, the porous metal complex according to the embodiment of the present invention has an increased bulk density and hydrogen as compared to the conventional porous metal complex. As a result, a porous metal complex having a higher hydrogen storage capacity and a better effective hydrogen storage capacity was obtained.

  Although the present embodiment has been described above, it should not be understood that the description and the drawings, which form part of the disclosure of the above embodiment, limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

It is a schematic diagram which shows the two-dimensional structure of a porous metal complex. It is a schematic diagram which shows the three-dimensional structure of a porous metal complex.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Porous metal complex 2 Lattice element 3 Central metal 4 Organic ligand 4a Heterocyclic skeleton 4b Carboxylate group M Two-dimensional lattice structure

Claims (20)

  It includes a three-dimensional porous skeleton structure of a metal complex comprising a central metal and an organic ligand composed of a heterocyclic monocarboxylic acid having a heterocyclic skeleton and a carboxylate group coordinated to the central metal. Porous metal complex.   2. The porous metal complex according to claim 1, wherein the three-dimensional porous skeleton is formed by accumulation due to a bond between the central metal and oxygen in the carboxylate group. The heterocyclic monocarboxylic acid has the following general formula (I)
HOOC-R (I)
The porous metal complex according to claim 1 or 2, wherein the heterocyclic monocarboxylic acid represented by (wherein R includes a heterocyclic ring) is included.   4. The porosity according to claim 3, wherein R includes an element selected from an element group including N, O, S, P, B, As, Si, Sb, and Hg in the heterocyclic skeleton. Metal complex. R represents the following general formulas (II) to (XXVII)

5. The porous metal complex according to claim 3, comprising a substituent represented by any one of the following: 5.   The porous metal complex according to any one of claims 1 to 5, wherein the central metal includes a metal selected from a metal group including a divalent to tetravalent metal.   The porous metal complex according to claim 6, wherein the central metal includes a divalent metal.   The porous metal complex according to claim 7, wherein the central metal includes a metal selected from a metal group including Cu, Zn, Mo, Ru, Ni, Cr, and Rh.   9. The center metal according to any one of claims 1 to 8, wherein the central metal is obtained from a metal salt selected from a group of metal salts including nitrate, sulfate, acetate, carbonate and formate. The porous metal complex described.   The porous metal complex according to any one of claims 1 to 9, wherein the porous metal complex has a gas or a liquid taken into the three-dimensional porous skeleton structure.   The porous metal complex according to any one of claims 1 to 10, wherein the three-dimensional porous skeleton structure is flexible.   12. The three-dimensional porous skeleton structure includes a skeleton portion that defines a void, and the void can be deformed by deforming the skeleton portion from the outside by heat or pressure. Porous metal complex. A method for producing a porous metal complex comprising a three-dimensional porous skeleton structure of a metal complex comprising a central metal and an organic ligand coordinated to the central metal and having a heterocyclic skeleton and a carboxylate group, ,
Including mixing and reacting a first solution in which a heterocyclic monocarboxylic acid is dissolved in a first solvent and a second solution in which the salt of the central metal is dissolved in a second solvent. A method for producing a porous metal complex.   The method for producing a porous metal complex according to claim 13, wherein any one of the dissolution, mixing, and reaction includes irradiating the first or second solution with ultrasonic waves. .   One of the first and second solvents is selected from the solvent group comprising N, N′-dimethylformamide, N, N′-diethylformamide, water, alcohols, tetrahydrofuran, benzene, toluene, hexane, acetone and acetonitrile. The method for producing a porous metal complex according to claim 13 or 14, comprising a solvent that has been prepared.   The one of the first and second solvents includes a solvent selected from the group of solvents including N, N'-dimethylformamide, N, N'-diethylformamide, water, and alcohols. 15. A method for producing a porous metal complex according to 15.   An adsorbent comprising the porous metal complex according to any one of claims 1 to 12.   A separation material comprising the porous metal complex according to any one of claims 1 to 12.   A gas adsorbent comprising the porous metal complex according to any one of claims 1 to 12.   A hydrogen adsorbent comprising the porous metal complex according to any one of claims 1 to 12.

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