JP5227992B2 - Organometallic complex and method for producing the same - Google Patents

Description

  The present invention relates to an organometallic complex that can function as a hydrogen storage material and a method for producing the same.

  As is well known, a fuel cell generates electricity by supplying a fuel gas such as hydrogen to the anode and an oxidant gas such as oxygen to the cathode. Therefore, for example, a fuel cell vehicle equipped with a fuel cell is equipped with a gas storage container filled with hydrogen. The fuel cell vehicle travels using the atmosphere as an oxidant gas and hydrogen supplied from the gas storage container as a reaction gas.

  As can be understood from this, the fuel cell vehicle can be run for a longer distance as the hydrogen storage capacity of the gas storage container increases. However, mounting an excessively large gas storage container increases the weight of the fuel cell vehicle, resulting in a problem that the load on the fuel cell increases. From this point of view, various attempts have been made to improve the hydrogen storage capacity while keeping the volume of the gas storage container small.

  As one of the techniques, attempts have been made to accommodate a substance capable of storing or adsorbing hydrogen (hereinafter referred to as a hydrogen storage material) including a hydrogen storage alloy in a container. Since this type of hydrogen storage material takes in hydrogen into its molecular structure, it is possible to accommodate more hydrogen than the volume of the container.

  An organic metal complex is known as a suitable example of such a hydrogen storage material. That is, a compound in which an organic substance is bonded to a metal nucleus.

  In the organometallic complex, organic substances are regularly bonded to the metal nucleus. For this reason, there are some in which pores having a relatively uniform diameter are formed in the molecular structure. The inner wall of the pore is a site that physically adsorbs hydrogen. Of course, the larger the hydrogen adsorption amount, the better.

For example, in Non-Patent Document 1, hydrogen adsorption of [Cu ₃ (benzene-1,3,5-tricarboxylate) ₂ (H ₂ O) ₃ ] _n (hereinafter also referred to as Cu-BTC) at various temperatures. Characteristics have been reported. That is, the pressure extrapolated value at 77 K is 3.6 wt%, the hydrogen pressure at room temperature (298 K) is 0.35% at 65 bar (6.5 MPa), and the hydrogen adsorption amount at room temperature is less than 0.4 wt%. There are few.

B. Panella, M. Hirscher, H. Putter, U. Muller, Advanced Functional Materials Vol.16 No.4 p520-524 Published March 2006

  However, for example, the operating environment temperature of a fuel cell vehicle is generally around room temperature. Therefore, in this case, it is preferable that the amount of adsorption / release of hydrogen of the organometallic complex as the hydrogen storage material is larger near the room temperature.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an organometallic complex having a relatively large amount of hydrogen adsorption / release near room temperature and a method for producing the same.

In order to achieve the above object, the organometallic complex according to the present invention is formed by bonding a plurality of repeating units of Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ to each other, and the composition formula thereof is It is represented by [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n .

  This organometallic complex has a relatively large amount of hydrogen storage in a temperature range near room temperature. That is, for example, by storing this organometallic complex in a container, a large amount of hydrogen gas can be stored in the container.

In this case, the unit cell of the organometallic complex contains 24 Cu atoms and 20 pyridine-3,5-dicarboxylates. This space group of unit cells is expressed as Cmc21 in the Herman Morgan notation. This means that the crystal system of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n belongs to orthorhombic crystals.

  Further, this organometallic complex has a plurality of Cu dimer units formed by bonding two Cu atoms. In the organometallic complex, there are many spaces surrounded by the plurality of Cu dimer units and the plurality of the pyridine-3,5-dicarboxylates. The opening diameter and the inner diameter of this space are less than several inches, that is, less than 10 inches, but hydrogen molecules can enter and advance within this range.

  In addition, in this case, Cu atoms, O atoms, and N atoms face the inside of the space. These function effectively as hydrogen molecule adsorption sites.

Further, the present invention is formed by bonding a plurality of repeating units Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ to each other, and the composition formula thereof is [Cu ₂₄ (pyridine-3,5-dicarboxylate). Rat) ₂₀ ] a method for producing an organometallic complex represented by _n ,
A step of obtaining a solution by dissolving copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate or copper acetate anhydride, and pyridine-3,5-dicarboxylic acid in a solvent;
Adding nitric acid to the solution;
By heating the solution at 50 to 140 ° C. for 24 to 168 hours, copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate or copper acetate anhydride, pyridine-3,5-dicarboxylic acid, Obtaining a reaction product of
Removing guest molecules from the reaction product;
It is characterized by having.

Through such a process, the above-described organometallic complex, that is, [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n having a large hydrogen storage amount in the temperature range near room temperature is easily obtained. be able to.

  The organometallic complex according to the present invention has a relatively large hydrogen storage amount in the temperature range near room temperature. For this reason, by accommodating the organometallic complex in a container, a large amount of hydrogen gas can be accommodated in the container. Accordingly, it is possible to prolong the time during which hydrogen can be supplied and, for example, the operation duration time of the fuel cell.

  Thereby, for example, the frequency of hydrogen replenishment when driving the fuel cell vehicle can be reduced. In other words, the driving distance of the fuel cell vehicle can be increased.

  Moreover, according to the manufacturing method of the organometallic complex which concerns on this invention, an above-described organometallic complex can be obtained easily.

It is a plane schematic diagram of pyridine-3,5-dicarboxylate. [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] is a three-dimensional schematic diagram showing a part of a unit cell of _n . [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] is a schematic plan view showing a part of the planar structure of _n . It is a three-dimensional schematic diagram showing a structure in which four pyridine-3,5-dicarboxylates are bonded to one Cu dimer unit. FIG. 4 is a schematic plan view showing a part of the unit cell with the viewpoint as the a-axis direction. FIG. 5 is a schematic plan view showing a difference in molecular structure between an odd layer and an even layer included in the unit cell with a viewpoint as a b-axis direction. It is a plane schematic diagram which shows the difference of the molecular structure of the odd-numbered layer and even-numbered layer contained in the said unit cell by making a viewpoint into a c-axis direction. FIG. 5 is a schematic plan view showing that the odd-numbered layer and the even-numbered layer included in the unit cell are cross-linked with the viewpoint as the a-axis direction. FIG. 5 is a schematic plan view showing that the odd-numbered layer and the even-numbered layer included in the unit cell are cross-linked with the viewpoint as the a-axis direction. FIG. 4 is a schematic perspective view showing that the odd-numbered layer and the even-numbered layer included in the unit cell are cross-linked with the viewpoint as the a-axis direction. It is an inverted microscope picture of the crystal before the deguest treatment. It is a scanning electron micrograph of the crystal after deguest processing. These are an X-ray diffraction theoretical pattern of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n and an actual measurement pattern obtained by performing X-ray diffraction measurement on the crystal after deguest treatment. It is a graph showing the relationship between the ratio of the storage hydrogen weight with respect to the weight of a crystal | crystallization, and the hydrogen pressure in the sample cell of a volume type hydrogen pressure-composition isotherm diagram measuring apparatus.

  Hereinafter, preferred embodiments of the organometallic complex and the method for producing the same according to the present invention will be described in detail with reference to the accompanying drawings.

The organometallic complex according to the present embodiment has Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ as a repeating unit, and the composition formula thereof is [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ]. It is represented by _n .

  First, the structure of pyridine-3,5-dicarboxylate will be described with reference to FIG. As can be seen from FIG. 1, pyridine-3,5-dicarboxylate is formed by bonding a carboxylate group (—COO) to each of the 3-position and 5-position of the pyridine ring. A hydrogen atom (H) is bonded to the 2-position, 4-position and 6-position of the pyridine ring, and a nitrogen atom (N) is present at the 1-position.

  Actually, the pyridine ring includes a conjugated bond, but all the conjugated bonds are omitted in FIG. The same applies to the subsequent drawings.

[Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n represents a part of the unit cell, and as shown in FIG. 2, pyridine-3,5-dicarboxylate having the structure as described above Is formed by sterically bonding via Cu. Here, arrow a, arrow b, and arrow c in FIG. 2 mean the a-axis, b-axis, and c-axis in the unit cell, respectively, and the same applies to the subsequent drawings. In FIG. 2, only the (010) plane and the (001) plane in the three-dimensional structure are representatively shown for easy understanding, and the illustration of each atom is omitted.

  A similar planar structure is formed on both sides so that the structure shown on the (010) plane in FIG. 2 is compared with the structure shown on the (001) plane. This planar structure will be described with reference to FIG. 3 showing the (001) plane.

The part enclosed with the dashed-dotted line of FIG.2 and FIG.3 has shown the Cu dimer unit formed by two Cu atoms. As understood from FIG. 3, [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n is a dimer unit of Cu and pyridine-3,5-dicarboxylate in the direction of arrow b (b-axis). ) And the mononuclear Cu, which will be described later, and pyridine-3,5-dicarboxylate are alternately arranged along the direction of arrow a (a-axis).

  First, the planar structure along the b-axis direction will be described. As described above, pyridine-3,5-dicarboxylate has two carboxylate groups. Two O atoms of one carboxylate group in this bond to each of two Cu atoms in the Cu dimer unit. On the other hand, the two O atoms of the remaining one carboxylate group are bonded to each of two Cu atoms in a Cu dimer unit different from the above.

  A separate carboxylate group of pyridine-3,5-dicarboxylate is bonded to the Cu dimer unit and the other Cu dimer unit.

  That is, one pyridine-3,5-dicarboxylate is bonded to another two pyridine-3,5-dicarboxylates via a carboxylate group bonded to the Cu dimer unit.

  Next, a planar structure along the a-axis direction will be described. As can be seen from FIG. 3, in the two pyridine-3,5-dicarboxylates adjacent via the Cu dimer unit, the 3-positions, the 5-positions, or the 3-position and the 5-position Opposite. Therefore, in these two pyridine-3,5-dicarboxylates, the 1-position Ns face each other in opposite directions.

  One Cu (mononuclear Cu) is bonded to N. The mononuclear Cu is further bonded to N of another pyridine-3,5-dicarboxylate. That is, one pyridine-3,5-dicarboxylate is separated from the other two pyridine-3,5-dicarboxylates linked via the carboxylate group and the Cu dimer unit, separately from N and single. It binds to another pyridine-3,5-dicarboxylate via the core Cu.

  Eventually, six pyridine-3,5-dicarboxylates are bonded via four Cu dimer units and two mononuclear Cus to form a ring as shown in FIG. The Inside the annular body, a hole-shaped space, in other words, a cavity is formed.

  The remaining (010) plane has the same structure as that shown in FIG. 3, and therefore illustration and detailed description thereof are omitted.

  As can be seen from FIG. 2, the planar structure of the (010) plane and the planar structure of the (001) plane that are orthogonal to each other are bonded only through the Cu dimer unit. Eventually, as shown in FIG. 4, four pyridine-3,5-dicarboxylates are sterically coordinated to one Cu dimer unit.

The four pyridine-3,5-dicarboxylates are about 90 ° apart from each other about the Cu—Cu bond axis in the dimer unit. In the following, such a configuration of coordination bond is also referred to as “Cu ₂ (COO) ₄ paddle wheel structure”.

In FIG. 3, the (010) plane and the (001) plane are representatively shown as planes orthogonal to each other. For example, the (010) plane has a Cu structure in the (010) plane. The other surface (not shown) is orthogonal to the location where the dimer unit exists. In other words, all the Cu dimer units form a Cu ₂ (COO) ₄ paddle wheel structure as shown in FIG.

  That is, a plurality of surfaces including the same planar structure as that included in the (001) plane are stacked on the (010) plane. Similarly, a plurality of surfaces including the same planar structure as that included in the (010) plane are stacked on the (001) plane.

  However, as shown in FIGS. 6 and 7, the positions of pyridine-3,5-dicarboxylate do not match between adjacent surfaces. More specifically, when the surface to be laminated is expressed as one layer, two layers, three layers,..., N layers, the positions of pyridine-3,5-dicarboxylate match in odd layers and even layers.

  Furthermore, as shown in FIG. 8 and FIG. 9, the planar structure included in the even layer and the odd layer are formed on both the plurality of surfaces orthogonal to the (010) plane and the plurality of surfaces orthogonal to the (001) plane. The contained planar structure is bonded via pyridine-3,5-dicarboxylate. Hereinafter, this pyridine-3,5-dicarboxylate is referred to as a crosslinked PDC.

  First, from a plurality of planes orthogonal to the (010) plane, mononuclear Cu existing in odd layers (1 layer, 3 layers) and in even layers (2 layers, 4 layers) in the plane. As shown in FIG. 8, the mononuclear Cu is bonded via two Os in the carboxylate group of the crosslinked PDC.

  As can be seen from FIG. 8, N of the cross-linked PDC that joins the first and second layers faces in the opposite direction to N of the cross-linked PDC that joins the second and third layers. Similarly, N of the cross-linked PDC that joins the two and three layers faces in the opposite direction to N of the cross-linked PDC that joins the three and four layers. Therefore, N of the cross-linked PDC that joins the first and second layers and the N of the cross-linked PDC that joins the third and fourth layers face in the same direction.

  All mononuclear Cu contained in a plurality of planes orthogonal to the (010) plane is bonded to the crosslinked PDC in this way. In this structure, the plane of the pyridine ring of the crosslinked PDC is parallel to the (100) plane.

  In addition, the odd-numbered mononuclear Cu bonds to O atoms close to the negative direction (downward in FIG. 8) in the b-axis direction among the two O atoms of the carboxylate group of the crosslinked PDC. On the other hand, the mononuclear Cu in the even layer is bonded to O atoms close to the positive direction (upward in FIG. 8) in the b-axis direction.

  As a result, the chain structure formed by the mononuclear Cu and the crosslinked PDC in the planar structure is orthogonal to a plurality of planar structures orthogonal to the (010) plane. Hereinafter, this chain structure is referred to as structure B. The structure B is located in a direction parallel to the c axis.

  In a plurality of planes orthogonal to the (001) plane, as shown in FIGS. 9 and 10, the mononuclear Cu existing in each plane is the pyridine ring constituting the crosslinked PDC contained in the structure B. It binds to N located at the 1-position.

  The cross-linked PDC existing in the structure B is the same as the cross-linked PDC that joins the planar structure included in the odd layers in the plurality of planes orthogonal to the (010) plane and the planar structure included in the even layers. is there. In other words, the cross-linked PDC existing in the structure B is included in the mononuclear Cu in the planar structure included in the odd layers in the plurality of planes orthogonal to the (010) plane and in the even layers by the carboxylate group. The mononuclear Cu in the planar structure is bonded to each other, and the mononuclear Cu in the plurality of planar structures orthogonal to the (001) plane is bonded to each other by the pyridine ring.

  As shown in FIG. 9, the crosslinked PDC molecule existing in the structure B that bonds one layer and two layers in a plurality of planes orthogonal to the (001) plane has 1 of the pyridine ring with respect to the b-axis direction. There are those in which the N-position is oriented in the positive direction and those oriented in the negative direction.

  Among these, N atoms oriented in the negative direction are bonded to mononuclear Cu in the planar structure of one layer. On the other hand, N atoms oriented in the positive direction are bonded to mononuclear Cu in the two-layer planar structure. In other words, a structure in which a chain structure B is sandwiched between one layer and two layers of a planar structure orthogonal to the (001) plane is formed.

  The relationship between the second and third layers and the structure B is the same. That is, in the structure B sandwiched between two and three layers, N atoms directed in the negative direction are bonded to mononuclear Cu in the two layers, and N atoms directed in the positive direction are in the three layers. Bonded with mononuclear Cu.

  Then, for mononuclear Cu coupled to N facing the positive direction of the b-axis (upward in FIG. 9), O is coupled to a position that is point-symmetric with respect to N. Similarly, O couple | bonds with the position which becomes point-symmetric with respect to N also about the mononuclear Cu couple | bonded with N which faces the negative direction (downward in FIG. 9) of b-axis.

From the above, [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n is a Cu layer extending in the c-axis direction from a plurality of surfaces (layers) stacked in the b-axis direction. -It can be said that crosslinked PDC has a crosslinked structure.

The unit cell of the organometallic complex thus configured contains 24 Cu atoms and 20 pyridine-3,5-dicarboxylates. Further, in this case, the space group of the unit cell expressed by the Herman Morgan notation is Cmc21. This means that the crystal system of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n belongs to orthorhombic crystals. The intersection angle between the a axis and the b axis, the intersection angle between the b axis and the c axis, and the intersection angle between the c axis and the a axis are all 90 °.

  Note that the lengths of the a-axis, b-axis, and c-axis measured by instrumental analysis are 23.2 to 23.8 mm, 18.7 to 19.3 mm, and 18.4 to 19.0 mm, respectively.

  As shown in FIG. 3, the organometallic complex having such a structure has a plurality of surfaces (layers) orthogonal to the (001) plane and a plurality of surfaces (layers) orthogonal to the (010) plane, There is a cavity (space) in which atoms are not closely packed. This cavity has a hole shape with an opening diameter and an inner diameter of several mm, and as can be easily understood from FIG. 3, Cu atoms, O atoms, and N atoms are exposed on the inner surface.

  A cavity (a hole-shaped space) having an opening diameter and an inner diameter of several mm is a size sufficient for hydrogen molecules to enter or exude. Moreover, Cu atoms, O atoms, and N atoms exposed on the inner surface of the cavity effectively function as hydrogen molecule adsorption sites. For this reason, this organometallic complex corresponds to the surrounding hydrogen atmosphere being pressurized or depressurized, and can store or release a large amount of hydrogen even in a temperature range near room temperature.

  This organometallic complex exhibits high adsorption energy. For this reason, hydrogen molecules are adsorbed particularly at two locations of the Cu dimer unit and the mononuclear Cu. In some cases, the adsorbed hydrogen molecules may form part of the crystal structure.

Next, a method for producing this organometallic complex, that is, [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n will be described. In the present embodiment, a first step of obtaining a solution in which raw material components are dissolved, a second step of adding nitric acid to the solution, and heating the solution to obtain a reaction product of the raw material components. A third step and a fourth step of removing guest molecules from the reaction product are performed.

  First, in the first step, the raw material components are dissolved in a solvent.

  As raw material components, copper salt and pyridine-3,5-dicarboxylic acid are selected. The copper salt is specifically copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate, or copper acetate anhydride.

  The solvent should be capable of dissolving both copper salt (copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate or copper acetate anhydride) and pyridine-3,5-dicarboxylic acid. Suitable examples include dimethylformamide, diethylformamide, dimethyl sulfoxide, ethanol, methanol, and the like. In particular, dimethylformamide is most preferable because an organometallic complex having high crystallinity can be obtained.

  The addition ratio of the copper salt to the solvent is preferably set to 0.01 to 1.0 mol%, and more preferably set to 0.1 to 0.5 mol%. On the other hand, the addition ratio of pyridine-3,5-dicarboxylic acid to the solvent is preferably set to 0.01 to 3.0 mol%, and more preferably set to 0.2 to 1.0 mol%.

  In addition, it is more preferable to make the addition ratio of copper salt small compared with the addition ratio of pyridine-3,5-dicarboxylic acid. This is because an organometallic complex having high crystallinity can be obtained.

  Next, nitric acid is added to the solution in which the raw material components are dissolved in the second step. The ratio of nitric acid is preferably 0.0001 to 0.5 mol% and more preferably 0.001 to 0.1 mol% with respect to the solvent.

  Next, after this solution is contained in a sealed container, the sealed container is sealed. And in a 3rd process, the said solution is heated at 50-140 degreeC for 24 to 168 hours with this airtight container. If it is less than 50 ° C. or less than 24 hours, the reaction between the copper salt and pyridine-3,5-dicarboxylic acid does not proceed so much and the yield of the reaction product is also reduced. Even if heating is performed at a temperature exceeding 140 ° C. for more than 168 hours, the reaction rate and yield are saturated, which is uneconomical. More preferable heating conditions in the third step are 70 to 90 ° C. and 60 to 120 hours.

By this heating, the copper salt reacts with pyridine-3,5-dicarboxylic acid to produce [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n having high crystallinity. In addition, although a heating method is not specifically limited, A sand bath is mentioned as a suitable specific example.

[Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n , which is a reaction product, contains solvent molecules, moisture, and the like as guest molecules in the above-described cavities (pore-shaped spaces). Therefore, a deguest process is performed in the fourth step to remove guest molecules.

The deguest process for the solvent molecules is performed as follows. That is, first, the crystal surface of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n is washed with a solvent as described above. Thereby, unreacted raw material components, that is, copper salt (copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate or copper acetate anhydride), and pyridine-3,5-dicarboxylic acid are contained in the washing solvent. And is removed from the crystal surface.

Thereafter, the crystals of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n are immersed in dehydrated chloroform. As a result, solvent molecules present in the cavity and the like are replaced with dehydrated chloroform molecules.

  After one night has passed, the dehydrated chloroform is replaced with a new one, and further, the dehydrated chloroform is replaced and left to stand for one week. As a result, almost all of the solvent molecules are replaced with dehydrated chloroform. In addition, although replacement | exchange of dehydrated chloroform should just be performed 1 to 10 times in one week, the said substitution will become more reliable, so that there are many times. Therefore, it is preferable to exchange at least 5 times.

  Thus, after performing the deguest process of a solvent molecule, the deguest process of a water | moisture content and dehydrated chloroform is performed. Specifically, after separating the organometallic complex and dehydrated chloroform by filtration, the organometallic complex is subjected to heat treatment under reduced pressure.

  At this time, the pressure is preferably a high vacuum of 0.013 Pa or less. Such a high vacuum environment can be obtained by using, for example, a turbo molecular pump.

  Moreover, a suitable heating temperature is 40-300 degreeC, and a more suitable heating temperature is 80-200 degreeC. When raising the temperature, it is preferable that the rate of temperature rise is moderate at about 1 ° C./min.

By continuing this reduced-pressure heat treatment for 1 to 7 days, moisture and dehydrated chloroform are removed, and high-purity [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n crystals are obtained.

Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _{n, which} has been subjected to the deguest treatment, tends to deactivate by adsorbing moisture when left in the atmosphere. For this reason, it is preferable to store in an inert gas atmosphere such as argon.

  Hereinafter, the present invention will be described in detail with reference to examples, but it is needless to say that the present invention is not limited to the examples.

  In 9.91 ml of dimethylformamide, 151 mg of copper nitrate 2.5 hydrate was first added and dissolved, and then 109 mg of pyridine-3,5-dicarboxylic acid was added to the solution and dissolved. It was. Furthermore, 0.09 ml of nitric acid was then added and stirred thoroughly.

This solution was sealed in a vial having a volume of 20 ml, and the vial was placed in a sand bath and kept at 70 ° C. for 90 hours. This produced crystals of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n .

  Next, 0.05 g of this was weighed and washed with 50 ml of dehydrated dimethylformamide. Further, the washed crystal was immersed in dehydrated chloroform and allowed to stand in this state. After one night, dehydrated chloroform was replaced with a new one. Thereafter, the dehydrated chloroform was replaced with a new one once every 24 hours. The exchange was performed 7 times.

  After one week, filtration was performed to separate dehydrated chloroform and crystals, and the crystals were sealed in a container capable of vacuum heat treatment. The inside of this container was made into a high vacuum of 0.013 Pa or less by a turbo molecular pump. Meanwhile, the container was heated to 120 ° C. with a mantle heater and held for 2 days.

  Finally, the container was disassembled in a glove box in an argon atmosphere, and crystals were collected.

  Inverted micrographs of the crystals before the deguest treatment and scanning electron micrographs of the crystals after the treatment are shown in FIGS. 11 and 12, respectively. As shown in FIGS. 11 and 12, the shape of the crystal is approximately approximated to a rectangular parallelepiped shape.

  In addition, the crystal structure was determined by irradiating the crystal with a monochromatic X-ray beam having a constant wavelength and measuring the direction and intensity of X-ray diffracted in various directions. As a result, it was determined that the planar structure shown in FIG. 3 was laminated and the planar structures were orthogonal to each other. In this determination, RAXIS-RAPID manufactured by Rigaku Corporation was used and the measurement data was analyzed by a computer.

Further, X-ray diffraction measurement was performed on the crystal after the deguest treatment. The actual measurement pattern obtained as a result is shown in the upper part of FIG. The lower part of FIG. 13 is the theoretical pattern of [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n. By comparing these theoretical pattern and the actual measurement pattern, the two are almost the same. I understand. This result supports that the crystal after the deguest treatment has a three-dimensional structure in which the planar structures shown in FIG. 3 are stacked and the planar structures are orthogonal to each other.

  Furthermore, 0.102 g of the crystal after the deguest treatment was accommodated in a sample cell of a volumetric hydrogen pressure-composition isotherm measurement apparatus, and the temperature of the measurement system was set to 25 ° C. Subsequently, hydrogen gas was introduced into the sample cell stepwise until the pressure reached 8.31 MPa, and pressurization was performed. The amount of hydrogen stored was calculated from the hydrogen storage equilibrium pressure at each hydrogen pressure in the middle.

  Then, pressure reduction was performed by discharging in steps until the hydrogen pressure in the sample cell reached 0.006 MPa. The hydrogen release amount was calculated from the hydrogen release equilibrium pressure at each hydrogen pressure in the middle.

  The obtained results are shown as a graph in FIG. The horizontal axis of this graph represents the ratio of the weight of stored hydrogen with respect to the weight of the crystal as a percentage, and the vertical axis represents the hydrogen pressure in the sample cell.

FIG. 14 shows that the amount of hydrogen stored and released from [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n varies depending on the hydrogen pressure. When the hydrogen pressure is 8.3 MPa, the hydrogen storage amount is 0.468 wt%. This numerical value exceeds 0.35% of the hydrogen adsorption amount of Cu-BTC described in Non-Patent Document 1 when the hydrogen pressure at room temperature is 6.5 MPa.

From this, it is clear that [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n is a substance capable of storing a larger amount of hydrogen near room temperature.

Claims (3)

A plurality of repeating units, Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ , are bonded to each other, and the composition formula is [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n . An organometallic complex characterized by being represented.   The complex according to claim 1, wherein the unit cell contains 24 Cu atoms and 20 pyridine-3,5-dicarboxylates and is represented by Hermann-Morgan notation. An organometallic complex, wherein the group is Cmc21. A plurality of repeating units, Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ , are bonded to each other, and the composition formula is [Cu ₂₄ (pyridine-3,5-dicarboxylate) ₂₀ ] _n . A method for producing an organometallic complex represented by:
A step of obtaining a solution by dissolving copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate or copper acetate anhydride, and pyridine-3,5-dicarboxylic acid in a solvent;
Adding nitric acid to the solution;
By heating the solution at 50 to 140 ° C. for 24 to 168 hours, copper nitrate hydrate, copper nitrate anhydride, copper acetate monohydrate or copper acetate anhydride, pyridine-3,5-dicarboxylic acid, Obtaining a reaction product of
Removing guest molecules from the reaction product;
The manufacturing method of the organometallic complex characterized by having.

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