JP2011178749A - Method for producing organometallic complex - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a high-purity organometallic complex having high crystallinity and storing/discharging a relatively large amount of hydrogen within a temperature range of about room temperature. <P>SOLUTION: The organometallic complex [Cu<SB>2</SB>(pyridine-3,5-dicarboxylate)<SB>2</SB>]<SB>n</SB>is preferably obtained through: a first step of dissolving a raw material component in a solvent so as to obtain a solution; a second step of adding acetic acid or formic acid to the solution; a third step of heating the solution at 50-140°C for 24-168 hr so as to obtain a reaction product; a fourth step of purifying the reaction product; and a fifth step of removing a guest molecule from the purified reaction product. In the fourth step, the reaction product is immersed in an immersion solution prepared by adding acetic acid to the solvent, and an ultrasonic wave is applied to the immersion solution. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  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 77K is 3.6 wt%, and at room temperature (298K), the hydrogen pressure is 0.35 wt% 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 a method for producing an organometallic complex having a relatively large amount of hydrogen adsorption / release near room temperature.

In order to achieve the above object, the present invention is formed by bonding a plurality of repeating units of Cu ₂ (pyridine-3,5-dicarboxylate) ₂ to each other, and the composition formula thereof is [Cu ₂ (pyridine). −3,5-dicarboxylate) ₂ ] a method for producing an organometallic complex represented by _n ,
A step of dissolving a copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid in a solvent to obtain a raw material solution;
Heating the raw material solution at 50 to 140 ° C. for 24 to 168 hours to obtain a reaction product of copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid;
The reaction product is immersed in a dipping solution prepared by adding acetic acid to a solvent, and further, ultrasonic waves are applied to the dipping solution to remove the impurity phase from the reaction product. Purifying the reaction product;
Removing guest molecules from the purified reaction product;
It is characterized by having.

The organometallic complex thus obtained has a hydrogen storage amount in the temperature range near room temperature as compared with [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n obtained in an air atmosphere. Is relatively large. Therefore, for example, by storing this organometallic complex in a container, a large amount of hydrogen gas can be stored in the container.

  The reason why the hydrogen storage amount of the organometallic complex is large is that, by applying ultrasonic waves, an impurity phase that does not contribute much to the storage / release of hydrogen gas is removed from the organometallic complex, in other words, This is probably because the crystalline organometallic complex has high purity.

Here, it is preferable to add acetic acid or formic acid to the raw material solution and then heat the solution. In this case, the crystallinity of the obtained [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is increased. In other words, [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n with high crystallinity can be easily obtained by performing the above heat treatment after adding acetic acid or formic acid.

  According to the present invention, since the impurity phase is removed (purified) from the reaction product by applying ultrasonic waves, a high purity and high crystallinity can be obtained. Such an organometallic complex has a relatively large hydrogen storage amount in a 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.

FIG. 3 is a stereographic diagram showing a structure in which two pyridine-3,5-dicarboxylates are bonded to Cu ₂ (pyridine-3,5-dicarboxylate) ₂ which is a repeating unit. It is a plane schematic diagram of pyridine-3,5-dicarboxylate. [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] is a three-dimensional schematic diagram showing a unit cell of _n . It is the plane schematic diagram which showed the plane formed by the a-axis and b-axis of the unit cell from the viewpoint from the c-axis direction. It is the plane schematic diagram which expanded further the principal part of the plane in FIG. FIG. 6 is a three-dimensional schematic diagram showing a three-dimensional structure formed by stacking the two-dimensional structures shown in FIGS. 4 and 5 with the viewpoint as the a-axis direction. It is a principal part enlarged view of FIG. It is the plane schematic diagram which showed the three-dimensional structure shown by FIG. 6 from the viewpoint from the c-axis direction. It is a principal part enlarged view of FIG. It is a scanning electron micrograph of the crystal | crystallization (after deguest process) of an Example. It is a scanning electron micrograph of the crystal of a comparative example (after deguest treatment). It is a graph showing the relationship between the ratio of the weight of the storage hydrogen with respect to the weight of each crystal | crystallization of an Example and a comparative example, and the hydrogen pressure in the sample cell of a positive displacement type hydrogen pressure-composition isotherm measurement apparatus. It is a graph showing the relationship between the ratio of the discharge | released hydrogen weight with respect to the weight of each crystal | crystallization of an Example and a comparative example, and the hydrogen pressure in the sample cell of a positive displacement type hydrogen pressure-composition isotherm measurement apparatus.

  Preferred embodiments of the method for producing an organometallic complex according to the present invention will be described below in detail with reference to the accompanying drawings.

First, the organometallic complex that is the final product will be described. The organometallic complex obtained by the present embodiment has Cu ₂ (pyridine-3,5-dicarboxylate) ₂ as a repeating unit, and the composition formula thereof is [Cu ₂ (pyridine-3,5-dicarboxylate) _2. ] It is represented by _n .

Here, FIG. 1 shows a structure in which two pyridine-3,5-dicarboxylates are bonded to Cu ₂ (pyridine-3,5-dicarboxylate) ₂ which is a repeating unit. In this structure, a portion surrounded by a broken line corresponds to a repeating unit. For convenience of explanation, all conjugated bonds such as in the pyridine ring are omitted, and the same applies to the following.

  First, the structure of pyridine-3,5-dicarboxylate will be described with reference to FIG. As understood from FIG. 2, 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. Hydrogen is bonded to the 2-position, 4-position and 6-position.

  The repeating unit will be described. As shown in a portion surrounded by a broken line in FIG. 1, a dimer unit is formed by two Cu atoms. Two pyridine-3,5-dicarboxylates are bonded to the two Cu atoms constituting the dimer unit.

  That is, pyridine-3,5-dicarboxylate has two carboxylates, in which an O atom in one carboxylate is bonded to one Cu atom and another in the carboxylate. Are bonded to the remaining one Cu atom. With respect to the dimer unit in this repeating unit, one pyridine-3,5-dicarboxylate in another repeating unit and one pyridine-3,5-dicarboxylate in another repeating unit By similarly bonding, the structure of FIG. 1 is formed.

In other words, the structure of FIG. 1 is formed by coordination of four pyridine-3,5-dicarboxylates to the 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”.

The remaining one carboxylate constituting the pyridine-3,5-dicarboxylate forms a similar coordination bond to another dimer unit (not shown), thereby providing another Cu ₂ (COO). Configures a _4- paddle wheel structure. Further, Cu ₂ (COO) ₄ paddle on one Cu in dimer units constituting the wheel structure, another Cu ₂ (COO) ₄ N in pyridine-3,5-dicarboxylate constituting the paddle wheel structure Some form coordinate bonds with atoms. As a result, the unit cell shown in FIG. 3 is formed. Note that arrows a, b, and c in FIG. 3 indicate the a-axis, b-axis, and c-axis in the unit cell.

This unit cell contains 12 Cu atoms and 12 pyridine-3,5-dicarboxylates. That is, the composition ratio of Cu and pyridine-3,5-dicarboxylate is 1: 1. Of course, the dimer unit and the four carboxylates constitute a Cu ₂ (COO) ₄ paddle wheel structure as described above.

The space group of the unit cell expressed by the Herman Morgan notation is P6 ₃ mc. That is, the crystal system of this unit cell belongs to hexagonal crystal. The intersection angle between the a-axis and the b-axis is 120 °, the intersection angle between the b-axis and the c-axis, and the intersection angle between the c-axis and the a-axis are both 90 °. Furthermore, the lengths of the a axis and the b axis measured by instrumental analysis are 18.71 to 19.41 mm, and the length of the c axis is 13.40 to 13.62 mm.

  Here, a plane formed by the a-axis and the b-axis is shown in FIG. The center of the dimer unit is located on a straight line parallel to the a axis, on a straight line parallel to the b axis, and on a straight line parallel to the bisector of the intersection angle between the a axis and the b axis. is doing.

  Among them, two dimer units located on a straight line parallel to the b-axis and adjacent to each other are bonded through a coordinate bond of pyridine-3,5-dicarboxylate. In addition, two pyridine-3,5-dicarboxylates located across the dimer unit are orthogonal to the plane formed by the a-axis and the b-axis, and b is the center of the dimer unit. Opposing each other across a plane including a straight line parallel to the axis. That is, they are located in regions opposite to each other with the plane as a boundary.

  Two pyridine-3,5-dicarboxylates adjacent to each other further face each other across a plane parallel to the plane formed by the a-axis and the b-axis, as shown in FIG. That is, they are located in regions opposite to each other with the plane as a boundary.

  These pyridine-3,5-dicarboxylates are coordinately bonded to the dimer unit so that the N atoms in the pyridine ring are located farthest from each other. Specifically, the N atom in the pyridine ring constituting one pyridine-3,5-dicarboxylate is the lowest end in the c-axis direction, and the remaining one pyridine-3,5-dicarboxylate is The N atom in the constituting pyridine ring is the uppermost end in the c-axis direction.

  As described above, a linear structure in which dimer units and pyridine-3,5-dicarboxylate are alternately bonded is formed in a direction parallel to the b-axis.

  A structure similar to the above is also formed in the a-axis. That is, two dimer units located on a straight line parallel to the a axis and adjacent to each other are bonded via a coordination bond of pyridine-3,5-dicarboxylate, and the dimer unit and A linear structure in which pyridine-3,5-dicarboxylate is alternately bonded is formed.

  In addition, two dimer units located on a straight line parallel to the bisector of the intersection angle between the a axis and the b axis are also arranged with pyridine-3,5-dicarboxylate as described above. They are linked via a coordinate bond. Further, in a direction parallel to the bisector, a linear structure in which dimer units and pyridine-3,5-dicarboxylate are alternately bonded is formed.

As shown in FIG. 4, the Cu ₂ (COO) ₄ paddle wheel structure has a position X, b axis where the linear structure extending parallel to the b axis and the linear structure parallel to the a axis intersect. A position Y where the linear structure extending in parallel with the linear structure and the linear structure extending in parallel with the bisector of the intersection angle between the a axis and the b axis intersect, and in parallel with the a axis The linear structure that extends and the linear structure that extends parallel to the bisector of the intersection angle between the a-axis and the b-axis are located only at three positions Z. That is, the linear structure parallel to the a-axis, the linear structure extending parallel to the b-axis, and the linear structure extending parallel to the bisector of the intersection angle between the a-axis and the b-axis The structure does not intersect at the same position.

  In the linear structure extending parallel to the b-axis, the position X and the position Y exist alternately. In the linear structure extending parallel to the a axis, the position X and the position Z are alternately present, and the linear structure extending parallel to the bisector of the intersection angle between the a axis and the b axis. Then, the position Z and the position Y exist alternately.

Eventually, in this organometallic complex, the linear structure extending in parallel to the b axis in the plane direction parallel to the plane formed by the a axis and the b axis, and the above extending in parallel to the a axis. The linear structure and the linear structure extending in parallel with the bisector of the intersection angle between the a axis and the b axis form a two-dimensional network structure by the Cu ₂ (COO) ₄ paddle wheel structure. ing.

  As shown in FIG. 6 with the a-axis direction as a viewpoint, this organometallic complex forms a three-dimensional structure by laminating the above-described two-dimensional structure along the c-axis direction. FIG. 6 shows a configuration in which the first layer, the second layer, the third layer, and the fourth layer are stacked in this order from below.

  As shown in FIG. 7, which is an enlarged view of the main part of FIG. N atoms in the ring are bonded by forming a coordinate bond with Cu atoms adjacent to the first layer side in the dimer unit existing in the second layer. In the dimer unit existing in the first layer, Cu atoms adjacent to the second layer side, and in the pyridine ring of pyridine-3,5-dicarboxylate present in the second layer and adjacent to the first layer side No bond is formed with the N atom.

  The second layer and the third layer are also present in the second layer and the N atom in the pyridine ring of pyridine-3,5-dicarboxylate adjacent to the third layer side is present in the dimer unit in the third layer. Bonding is formed by forming a coordinate bond with Cu atoms adjacent to the second layer side.

  The bond between the third layer and the fourth layer is the same as the bond between the first layer and the second layer. That is, the coordinate bond position of N atoms formed between the third layer and the fourth layer with respect to Cu atoms is the coordinate bond position of N atoms formed between the first layer and the second layer with respect to Cu atoms. Matches the position of.

  When a further layer is laminated on the fourth layer, the bond between the fourth layer and the fifth layer is the same as the bond between the second layer and the third layer. As can be understood from this, the laminated structure along the c-axis direction is obtained by sequentially repeating the coupling mode of the first layer and the second layer.

  FIG. 8 is a plan view of the laminated structure showing the viewpoint as the c-axis direction. As shown in FIG. 8, this organometallic complex has a plurality of cavities (spaces) in which atoms are not closely packed in a plane formed by the a-axis and the b-axis. 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. 9 which is an enlarged view of FIG. 8, 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.

  When the X-ray diffraction measurement is performed for the organometallic complex having the above structure with the diffraction angle 2θ in the range of 5 ° to 20 °, 5.2 ° to 5.5 °, 8.33 ° to 8.63 °. 9.17 ° to 9.47 °, 10.55 ° to 10.95 °, 12.41 ° to 12.81 °, 13.03 ° to 13.33 °, 14.10 ° to 14.44 ° , 15.56-15.76, 15.93 ° -16.43 °, 16.85 ° -17.25 °, 17.23 ° -17.73 °, 18.49 ° -18.99 °, 19 A peak appears at a position of .27 ° to 19.77 °.

In this organometallic complex ([Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n ), the hydrogen storage amount increases as the impurity phase content decreases. Next, a method for producing an organometallic complex according to the present embodiment, which is capable of obtaining an organometallic complex having a high purity and a large hydrogen storage amount, will be described.

  In the method for producing an organometallic complex according to the present embodiment, a first step of obtaining a raw material solution in which raw material components are dissolved, a second step of adding a crystallinity improving component to the solution, and heating the solution Then, a third step of obtaining a reaction product of the raw material components, a fourth step of purifying the reaction product, and a fifth step of removing guest molecules from the purified reaction product are performed. .

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

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

  The solvent may be any solvent as long as it can dissolve both copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid. Dimethylformamide, diethylformamide, dimethylsulfoxide, ethanol, methanol Etc. can be mentioned as a suitable example. In particular, dimethylformamide is most preferable because an organometallic complex having high crystallinity can be obtained.

  The addition ratio of copper acetate monohydrate or copper acetate anhydride 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 acetate monohydrate or copper acetate anhydride smaller than the addition ratio of pyridine-3,5-dicarboxylic acid. This is because an organometallic complex having high crystallinity can be obtained.

  Next, in the second step, a crystallinity improving component for improving the crystallinity of the organometallic complex is added to the raw material solution in which such raw material components are dissolved. The crystallinity improving component is specifically acetic acid or formic acid.

  It is sufficient to set the ratio of addition to the solvent to 0.0001 to 0.5 mol% in the case of acetic acid and 0.0001 to 0.1 mol% in the case of formic acid. In addition, the more preferable addition rate of acetic acid is 0.001-0.1 mol%, and the more preferable addition rate of formic acid is 0.001-0.05 mol%. Even in such a very small amount, the crystallinity of the organometallic complex as the final product is remarkably improved.

  Next, after this raw material solution is stored in a sealed container, the sealed container is sealed. And in a 3rd process, the said raw material 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 of copper acetate monohydrate or copper acetate anhydride with 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, copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid react with each other, and the crystallinity is high [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ]. _n generates. In addition, although a heating method is not specifically limited, A sand bath is mentioned as a suitable specific example.

At this point, the reaction product [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n contains some impurity phases. This impurity phase is composed of Cu and pyridine-3,5-dicarboxylate in the same manner as [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n , but has a crystal structure. This is an amorphous phase with little hydrogen storage. That is, when [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n containing an impurity phase is used as a hydrogen storage material, the hydrogen storage amount per unit volume or unit weight is reduced. In order to avoid this, this impurity phase is removed in the fourth step which is the next step.

  First, acetic acid is added to a solvent to prepare a dipping solution. A solvent that can dissolve acetic acid or that does not cause phase separation with acetic acid may be selected as the solvent. Preferable examples of this type of solvent include dimethylformamide, diethylformamide, dimethyl sulfoxide, ethanol, methanol and the like, as with the solvent of the raw material solution.

  Moreover, the ratio of a solvent and acetic acid should just be 1: 20-20: 1 by volume ratio. It is more preferable to set it as 4: 6-6: 4. When the solvent is dimethylformamide, the ratio is particularly preferably 5: 5.

The reaction product obtained in the third step, that is, [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n containing some impurities is immersed in this dipping solution. Thereafter, ultrasonic waves are applied to the dipping solution.

When ultrasonic waves are applied for an excessively long time, dissociation of Cu and pyridine-3,5-dicarboxylate in crystalline [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is caused, yield. There is a concern that will decrease. In order to avoid this, it is preferable to shorten the application time of the ultrasonic wave as much as possible.

Specifically, when the output of the ultrasonic wave is 100 to 200 W, the application time is set to 30 to 90 seconds for 0.05 g of [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n . It is enough. Of course, when the amount of [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is larger than this, the application time may be lengthened.

  Acetic acid in the dipping solution is converted into acetate ions having a carboxylate by ionization. O contained in the carboxylate can be bonded to Cu.

Here, the bonding force between Cu and pyridine-3,5-dicarboxylate in the impurity phase which is an amorphous phase is Cu in crystalline [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n . It is smaller than the binding force between pyridine-3,5-dicarboxylate. For this reason, there is a high possibility that Cu in the impurity phase dissociates from pyridine-3,5-dicarboxylate and binds to O contained in the carboxylate of acetate ion. Alternatively, it is presumed that the binding force between Cu and pyridine-3,5-dicarboxylate is reduced even without dissociation.

This dissociation or decrease in binding force is more likely to proceed as ultrasonic waves, in other words, vibration energy is applied. As a result of this phenomenon, the impurity phase is dissolved or dispersed in the immersion solution. That is, [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n with the impurity phase removed and the purity improved can be obtained.

After performing the above purification operations, for example, [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is separated from the immersion solution by filtration. Thus, leading to high crystallinity [Cu ₂ (pyridine-3,5-dicarboxylate) _{2] n} can be obtained with high purity.

The obtained [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n 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 fifth step to remove guest molecules.

The deguest process for the solvent molecules is performed as follows. That is, first, a crystal of [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is taken out from the sealed container, and the surface thereof is washed with a solvent as described above. Thereby, unreacted raw material components, that is, copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid are dissolved in the washing solvent and removed from the crystal surface.

Next, the crystals of [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _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, [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n and dehydrated chloroform are separated by filtration, and [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is It accommodates in the container which can implement a heat | fever decompression process, and this container is sealed.

  Next, heat treatment is performed on the organometallic complex under reduced pressure. The pressure at this time 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 ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n crystals are obtained.

When the obtained [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n is exposed to the atmosphere, there is a concern that moisture in the atmosphere is adsorbed and deactivated. In order to avoid this, it is preferable to store under an inert gas atmosphere such as argon.

In the above-described embodiment, acetic acid or formic acid is added to the solution in which the raw material components are dissolved, but without adding them (that is, without performing the second step), You may make it implement 3 processes and a 5th process. Even in this case, Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n can be obtained.

  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.

  First, 56.7 mg of copper acetate monohydrate was first added and dissolved in 9.89 ml of dimethylformamide, and then 65.3 mg of pyridine-3,5-dicarboxylic acid was added to the solution. And dissolved to obtain a raw material solution. Further, 0.11 ml of acetic acid was added to the raw material solution and sufficiently stirred.

After the raw material solution was sealed in a vial with a volume of 20 ml, the vial was embedded in a sand bath and held at 70 ° C. for 90 hours. This produced [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n crystals.

The above operation was performed 30 times to obtain a total of about 1 g of [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n crystals.

0.05 g of [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n thus obtained was weighed and mixed with 10 ml of dehydrated dimethylformamide and 10 ml of dehydrated acetic acid (for immersion). Solution). Furthermore, an ultrasonic wave with an output of 100 W was applied to the dipping solution for 60 seconds. Then, it filtered immediately and isolate | separated the solid phase from the solution for immersion.

  The resulting solid phase was washed with 50 ml of dehydrated dimethylformamide in order to perform a deguest treatment. Further, the washed crystal was immersed in 50 ml of 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.

  After 7 days, filtration was performed to separate dehydrated chloroform and crystals, and the solid phase (crystals) was 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. This is an example.

FIG. 10 is a scanning photomicrograph of the recovered crystals of the example. From FIG. 10, the surface of the obtained [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n crystal is very clean, in other words, the impurity phase is greatly removed. Is recognized.

For comparison, [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n was obtained in the same manner as above except that no ultrasonic wave was applied (purification was not performed). This is a comparative example.

  A scanning photomicrograph of the comparative crystal is shown in FIG. In contrast to FIG. 10, it can be seen that there are many impurity phases on the crystal surface.

  Furthermore, 0.344 g of the crystals of the example were 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 8.9 Mpa and pressurized. The hydrogen storage amount 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 0.008 Mpa. The hydrogen release amount was calculated from the hydrogen release equilibrium pressure at each hydrogen pressure in the middle.

  On the other hand, the hydrogen storage amount and the hydrogen release amount were similarly calculated for the crystals of the comparative example.

  The relationship between each of the hydrogen storage amount and the hydrogen release amount and the hydrogen pressure is shown as a graph in each of FIGS. In these graphs, the horizontal axis indicates the percentage of the stored hydrogen weight with respect to the weight of the crystal as a percentage, and the vertical axis indicates the hydrogen pressure in the sample cell. FIG. 12 shows the hydrogen storage amount of each crystal of the example and the comparative example, and FIG. 11 shows the hydrogen release amount of each crystal of the example and the comparative example.

  From FIG. 12 and FIG. 13, it is clear that the crystal of the example from which the impurity phase is removed has a larger hydrogen storage amount and hydrogen release amount near room temperature.

  When the hydrogen pressure was 8.9 MPa, the hydrogen storage amount of the crystal of the example was 0.54 wt%, and the hydrogen storage amount of the crystal of the comparative example was 0.49 wt%.

Claims (2)

A plurality of repeating units, Cu ₂ (pyridine-3,5-dicarboxylate) ₂ , are bonded to each other, and the composition formula is [Cu ₂ (pyridine-3,5-dicarboxylate) ₂ ] _n A method for producing an organometallic complex represented by:
A step of dissolving a copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid in a solvent to obtain a raw material solution;
Heating the raw material solution at 50 to 140 ° C. for 24 to 168 hours to obtain a reaction product of copper acetate monohydrate or copper acetate anhydride and pyridine-3,5-dicarboxylic acid;
The reaction product is immersed in a dipping solution prepared by adding acetic acid to a solvent, and further, ultrasonic waves are applied to the dipping solution to remove the impurity phase from the reaction product. Purifying the reaction product;
Removing guest molecules from the purified reaction product;
The manufacturing method of the organometallic complex characterized by having.   The method for producing an organometallic complex according to claim 1, wherein the heating is performed after adding acetic acid or formic acid to the raw material solution.

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