JP6477086B2 - Method for producing porous material - Google Patents

Description

  The present invention relates to a porous material containing Zr or Ti and a method for producing the same, and more particularly to a porous material comprising a metal organic structure formed by Zr atoms or Ti atoms and a polydentate ligand. The present invention also relates to an adsorbent made of such a porous material.

Metal organic structures (MOF: Metal Organic Frameworks) are porous structures having uniform pores and a very large specific surface area. In recent years, gas storage materials that store hydrocarbons (HC) and the like, carbon dioxide Applications are expected as a gas separation material that selectively adsorbs and removes CO ₂ from a mixed gas of (CO ₂ ) and HC, and a water separation material that selectively adsorbs and removes moisture from a humidified atmosphere.

As such a metal organic structure, for example, Patent Document 1 (International Publication No. 2009/133366) and Non-Patent Document 1 (H. Furukawa et al., J. Am. Chem. Soc. 2014, Vol. 136, Zr-based metal organic structures described in pages 4369 to 4381) are known. This Zr-based metal organic structure has attracted attention as a material that is chemically stable and excellent in compression resistance.

International Publication No. 2009/133366

H. Furukawa et al., J. MoI. Am. Chem. Soc. 2014, 136, 4369-4381

  However, as a result of studies by the present inventors, in the Zr-based metal organic structure synthesized by the method described in Non-Patent Document 1, the organic solvent used during the synthesis and the unreacted organic ligand remain in the pores. However, since this causes a defect in the crystal structure, the adsorbent does not necessarily have sufficient adsorption characteristics.

  The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to provide a porous material composed of a metal organic structure that can be used as an adsorbent having excellent adsorption characteristics, and a method for producing the same. To do.

  As a result of intensive studies to achieve the above object, the inventors of the present invention obtained a porous material having excellent adsorption characteristics by subjecting a metal organic structure obtained by a conventional method to heat treatment in a solvent. As a result, the present invention has been completed.

The method for producing a porous material of the present invention has an octahedral structure formed of at least one metal atom selected from the group consisting of Zr and Ti, and is derived from a linear dicarboxylic acid to the metal atom. A metal-organic structure having a basic skeleton coordinated with a multidentate ligand, wherein the ratio of X-ray diffraction peak intensity between the Miller index (111) plane and the Miller index (200) plane [(111) / (200)] is less than 2.3, or the X-ray diffraction peak intensity ratio [(600) / (200)] between the Miller index (600) plane and the Miller index (200) plane is 0.00. More than 60 are provided with an octahedral structure formed by at least one metal atom selected from the group consisting of Zr and Ti by performing heat treatment in a poor solvent for the metal organic structure. Directly to the metal atom It consists of a metal organic structure having a basic skeleton coordinated with a polydentate ligand derived from a chain dicarboxylic acid, and has a Miller index (111) plane and a Miller index (200) plane of the metal organic structure. X-ray diffraction peak intensity ratio [(111) / (200)] is 2.3 to 3.5, and X-rays of the mirror index (600) plane and the mirror index (200) plane of the metal organic structure A porous material having a diffraction peak intensity ratio [(600) / (200)] of 0.30 to 0.60 is obtained.

Examples of the linear dicarboxylic acid include at least one dicarboxylic acid selected from the group consisting of a linear saturated dicarboxylic acid having 2 to 6 carbon atoms and a linear unsaturated dicarboxylic acid having 4 to 8 carbon atoms. preferable. The heating temperature during the heat treatment is preferably 30 to 80 ° C. The poor solvent is preferably at least one selected from the group consisting of water, acetonitrile, hexane and ethanol .

  The reason why a porous material excellent in adsorption characteristics can be obtained by the present invention is not necessarily clear, but the present inventors speculate as follows. That is, in the metal organic structure obtained by the conventional method, the organic solvent used at the time of synthesis and the free organic ligand remain in the pores, which causes defects in the crystal structure. In the present invention, a metal organic structure having defects in such a crystal structure is subjected to heat treatment in a solvent, so that rearrangement and growth of crystal planes occur, and the structure of the metal organic structure is close to a single crystal structure. It is assumed that As a result, the metal organic structure after the heat treatment has a larger specific surface area than that of the metal organic structure not subjected to the heat treatment, and it is assumed that the adsorption characteristics are improved.

  Specifically, the crystal structure of Zr or Ti is an octahedral structure (FIG. 1, M represents Zr or Ti atom), and a plurality of polydentate ligands coordinated to the Zr atom or Ti atom. These octahedral structures are combined to form a metal organic structure having a three-dimensional structure as shown in FIG. In the conventional method, since defects exist in the crystal structure (octahedral structure) of the metal organic structure, it is formed by the Miller index (111) plane formed by the side surface of the octahedral structure or the central section of the octahedral structure. As a result, the specific surface area of the metal organic structure becomes small, and it is assumed that sufficient adsorption characteristics could not be obtained.

  On the other hand, in the present invention, the (111) plane and the (200) plane are rearranged or grown by subjecting a metal organic structure having defects in such a crystal structure to heat treatment in a solvent. Therefore, it is assumed that the defects of the crystal structure are reduced and the structure of the metal organic structure becomes close to a single crystal structure. As the structure of the metal organic structure becomes close to a single crystal structure, the specific surface area increases, so the metal organic structure subjected to heat treatment is adsorbed compared to the metal organic structure not subjected to heat treatment. It is assumed that the characteristics are improved.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to obtain the porous material which consists of a metal organic structure which can be utilized as an adsorbent excellent in the adsorption characteristic.

It is a schematic diagram which shows the octahedral structure of the metal atom concerning this invention. It is a schematic diagram which shows the structure of the metal organic structure concerning this invention. 3 is a graph showing a powder X-ray diffraction pattern of the powdered metal organic structure after hydrothermal treatment obtained in Example 1. FIG. 2 is a graph showing nitrogen adsorption isotherms of a powdered metal organic structure after hydrothermal treatment obtained in Example 1 and a powdered metal organic structure not subjected to hydrothermal treatment of Comparative Example 1. FIG. 3 is a graph showing water vapor adsorption isotherms of the powdered metal organic structure after hydrothermal treatment obtained in Example 1 and the powdered metal organic structure not subjected to hydrothermal treatment of Comparative Example 1. FIG. It is a graph which shows the powder X-ray-diffraction pattern of the powdery metal organic structure which has not performed the hydrothermal treatment of the comparative example 1.

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

  First, the porous material of the present invention will be described. The porous material of the present invention has an octahedral structure formed of at least one metal atom selected from the group consisting of Zr and Ti, and a polydentate derived from a linear dicarboxylic acid on the metal atom. It consists of a metal organic structure having a basic skeleton coordinated with a ligand.

  There is no restriction | limiting in particular as linear dicarboxylic acid used for this invention, For example, C2-C6 linear saturated dicarboxylic acid, such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid; fumaric acid C4-8 linear unsaturated dicarboxylic acids such as maleic acid and muconic acid. These linear dicarboxylic acids may be used alone or in combination of two or more. Of these linear dicarboxylic acids, fumaric acid and succinic acid are preferred from the viewpoint of forming a stable basic skeleton.

  In the metal organic structure according to the present invention, as shown in FIG. 2, two oxygen atoms in one carboxyl group of the linear dicarboxylic acid are adjacent two metals in one octahedral structure. A plurality of octahedral structures are linearly coordinated by coordinating to each atom and by coordinating two oxygen atoms in the other carboxyl group to two adjacent metal atoms in different octahedral structures. A three-dimensional structure is formed which is bound by a polydentate ligand derived from a linear dicarboxylic acid.

The basic skeleton of such a metal organic structure has an octahedral structure formed by the metal atom, and the polydentate ligand derived from the linear dicarboxylic acid is coordinated to the metal atom. For example, the following formula (1) or (2):
Zr ₆ O ₄ (OH) ₄ (DCL) ₆ (1)
Ti ₆ O ₄ (OH) ₈ (DCL) ₄ (2)
(In the formula, DCL represents a polydentate ligand derived from a linear dicarboxylic acid)
The thing represented by these is preferable.

  In the porous material of the present invention, the X-ray diffraction peak intensity ratio [(111) / (200)] between the mirror index (111) surface and the mirror index (200) surface of the metal organic structure is 2.3 to 2.3. 3.5. When the peak intensity ratio [(111) / (200)] is less than the lower limit, there is a defect in the crystal structure of the metal organic structure, the specific surface area is reduced, the adsorption characteristics are lowered, and the upper limit is exceeded. If it exceeds, crystallinity will improve, but it will be a condition where it is difficult to obtain crystals due to the growth of a specific crystal plane. Moreover, from the viewpoint that the crystal structure has few defects and the adsorption characteristics of the porous material are further improved, the peak intensity ratio [(111) / (200)] is preferably 2.4 to 3.0.

  The X-ray diffraction peak intensity ratio [(600) / (200)] between the mirror index (600) surface and the mirror index (200) surface of the metal organic structure is 0.30 to 0.60. When the peak intensity ratio [(600) / (200)] is less than the lower limit, the crystallinity is improved, but it becomes a condition that it is difficult to obtain crystals due to the growth of a specific crystal plane, and on the other hand, when the upper limit is exceeded. In addition, defects exist in the crystal structure of the metal organic structure, the specific surface area is reduced, and the adsorption characteristics are deteriorated. Moreover, from the viewpoint that the crystal structure has few defects and the adsorption characteristics of the porous material are further improved, the peak intensity ratio [(600) / (200)] is preferably 0.35 to 0.55.

In the porous material of the present invention, the pore volume of the metal organic structures, preferably ^{0.38~0.53cm 3 / g, 0.40~0.45cm 3 /} g is more preferable. The specific surface area of the metal organic structures, preferably ^{700~1200m 2 / g, 800~1100m 2 /} g is more preferable. These physical property values are obtained by the nitrogen adsorption method and the BET method.

  Next, the manufacturing method of the porous material of this invention is demonstrated. The method for producing a porous material of the present invention has an octahedral structure formed of at least one metal atom selected from the group consisting of Zr and Ti, and is derived from a linear dicarboxylic acid to the metal atom. A porous organic material according to the present invention is obtained by subjecting a metal organic structure having a basic skeleton coordinated with a multidentate ligand to heat treatment in a poor solvent for the metal organic structure. It is a method.

  By subjecting the metal organic structure to heat treatment in the poor solvent, crystal structure defects are reduced and the specific surface area of the metal organic structure is increased. Can be obtained. The decrease in defects in the crystal structure is due to the X-ray diffraction of the Miller index (111) plane and the Miller index (200) plane of the metal organic structure after the heat treatment as compared to the metal organic structure before the heat treatment. The peak intensity ratio [(111) / (200)] increases, and the X-ray diffraction peak intensity ratio [(600) / (200)] between the Miller index (600) plane and the Miller index (200) plane increases. It can be confirmed by decreasing.

  As heating temperature at the time of the said heat processing, 30-80 degreeC is preferable and 50-80 degreeC is more preferable. When the heating temperature is less than the lower limit, rearrangement or growth of the (111) plane or the (200) plane is difficult to occur, crystal structure defects do not decrease, and the specific surface area of the metal organic structure does not increase, It tends to be difficult to improve the adsorption characteristics of the porous material. On the other hand, when the heating temperature exceeds the upper limit, there is a possibility of hydrolysis, and the crystals tend to collapse.

  As the poor solvent used in the method for producing a porous material of the present invention, a solvent (a hardly soluble solvent) in which the metal organic structure used in the method for producing a porous material of the present invention is difficult to dissolve, preferably a solvent that does not dissolve Although it will not be restrict | limited especially if it is (insoluble solvent), For example, water, acetonitrile, hexane, and ethanol are mentioned. These poor solvents may be used alone or in combination of two or more. Of these poor solvents, water is preferable from the viewpoints of safety and workability.

  The metal organic structure used in the method for producing the porous material of the present invention may be prepared by a conventionally known method (for example, H. Furukawa et al., J. Am. Chem. Soc., 2014, Vol. 136, pages 4369 to 4381). (Method described in Non-Patent Document 1)). For example, a metal compound (metal salt, metal alkoxide, etc.) containing at least one metal atom selected from the group consisting of Zr and Ti, the linear dicarboxylic acid, and an organic solvent and acid as necessary. After mixing and heat-treating the obtained mixed liquid, a metal organic structure can be obtained by performing a washing process and a drying process.

  The metal organic structure synthesized in this way has an octahedral structure formed of at least one metal atom selected from the group consisting of Zr and Ti, and the metal atom has a linear dicarboxylic acid. Those having a basic skeleton coordinated by an acid-derived polydentate ligand, preferably those represented by the formula (1) or (2), may be subjected to washing treatment or drying treatment. Since the organic solvent used during the synthesis and the unreacted linear dicarboxylic acid remain in the pores, there is a defect in the crystal structure, usually with the Miller index (111) plane and the Miller index (200) The X-ray diffraction peak intensity ratio [(111) / (200)] of the surface is less than 2.3, or the X-ray diffraction peak intensity ratio of the surface with the Miller index (600) and the surface with the Miller index (200) [(600) / (200)] is 0.60 It has become excessive. In the method for producing a porous material of the present invention, it is preferable to subject the metal organic structure having a defect in the crystal structure to a heat treatment in the poor solvent, whereby the adsorption property of the porous material There is a tendency for the effect of the present invention to be improved to appear significantly.

  The metal compound is not particularly limited, and examples thereof include zirconium salts such as chlorinated zirconium oxide octahydrate, zirconium chloride and zirconium oxynitrate, and titanium alkoxides such as titanium isopropoxide. There is no restriction | limiting in particular as said organic solvent, For example, N, N'- dimethylformamide (DMF), N, N'-diethylformamide (DEF) etc. are mentioned. There is no restriction | limiting in particular as said acid, For example, formic acid, hydrochloric acid, an acetic acid etc. are mentioned.

  The heat treatment of the mixed solution is preferably performed in an atmosphere of an inert gas such as nitrogen or argon. The heating temperature is preferably 120 to 160 ° C., and the heating time is preferably 2 to 6 hours.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

(Synthesis Example 1)
H. Furukawa et al., J. MoI. Am. Chem. Soc. , 2014, Vol. 136, pages 4369 to 4381 (Non-Patent Document 1), a metal organic structure (MOF-801-P) was synthesized. That is, 1.6 g (5.0 mmol) of zirconium chloride octahydrate and 0.6 g (5.2 mmol) of fumaric acid were mixed in a mixed solvent of 20 ml of N, N′-dimethylformamide (DMF) and 7.0 ml of formic acid. Dissolved and heated at 130 ° C. for 6 hours under nitrogen atmosphere. The obtained white crystalline powder was filtered by suction, washed with DMF, further washed with acetone, and then dried under reduced pressure at room temperature for 3 hours. The basic skeleton was Zr ₆ O ₄ (OH) ₄ (fumarate) ₆ As a result, 2.0 g of a powdery metal organic structure (MOF-801-P) was obtained.

(Synthesis Example 2)
A powdered metal organic structure (MOF-801-P) 2 in which the basic skeleton is Zr ₆ O ₄ (OH) ₄ (fumarate) ₆ in the same manner as in Synthesis Example 1 except that the heating temperature is changed to 140 ° C. 0.1 g was obtained.

(Synthesis Example 3)
The amount of N, N′-dimethylformamide (DMF) is 100 ml and the amount of formic acid is 30. In the same manner as in Synthesis Example 1 except that the heating temperature was changed to 120 ° C., a powdery metal organic structure (MOF−) having a basic skeleton of Zr ₆ O ₄ (OH) ₄ (fumarate) ₆ was used. 801-P) 2.0 g was obtained.

Example 1
0.5 g of the powdery metal organic structure (MOF-801-P) obtained in Synthesis Example 1 and 20 g of water were placed in a sample bottle and sealed. This was allowed to stand in an oven at 80 ° C. for 4 days, and then suction filtered, and the filter cake was dried by heating overnight in a vacuum dryer at 80 ° C. to remove adsorbed moisture.

  The powder X-ray diffraction (PXRD) pattern of the powdered metal organic structure subjected to the hydrothermal treatment in this manner was converted into an X-ray by using a powder X-ray diffractometer ("Ultima IV" manufactured by Rigaku Corporation). Measured as a source. The result is shown in FIG. In the obtained PXRD pattern, the peak position and peak intensity of each surface of the Miller index (111), the Miller index (200), and the Miller index (600) are obtained. Further, the surface of the Miller index (111) and the Miller index (200 ) Plane X-ray diffraction peak intensity ratio [(111) / (200)] and Miller index (600) plane and Miller index (200) plane X-ray diffraction peak intensity ratio [(600) / (200) ] Was calculated. These results are shown in Table 1.

  Furthermore, the nitrogen adsorption isotherm of the powdered metal organic structure after the hydrothermal treatment was measured at a temperature of 77 K using a nitrogen gas adsorption amount measuring device (“AUTOSORB-1” manufactured by Cantachrome). The result is shown in FIG. Further, the water vapor adsorption isotherm of the powdered metal organic structure after hydrothermal treatment was measured at a temperature of 25 ° C. using a vapor adsorption amount measuring device (“BELSORP-18” manufactured by Nippon Bell Co., Ltd.). The result is shown in FIG.

(Comparative Example 1)
Powder X-ray diffraction (PXRD) of the powdery metal organic structure (MOF-801-P) obtained in Synthesis Example 1, that is, the powdery metal organic structure (MOF-801-P) not subjected to hydrothermal treatment ) The pattern was measured as in Example 1. The result is shown in FIG. In the obtained PXRD pattern, the peak position and peak intensity of each surface of the Miller index (111), the Miller index (200), and the Miller index (600) are obtained. Further, the surface of the Miller index (111) and the Miller index (200 ) Plane X-ray diffraction peak intensity ratio [(111) / (200)] and Miller index (600) plane and Miller index (200) plane X-ray diffraction peak intensity ratio [(600) / (200) ] Was calculated. These results are shown in Table 1.

  Further, the nitrogen adsorption isotherm and water vapor adsorption isotherm of the powdered metal organic structure (MOF-801-P) not subjected to hydrothermal treatment were measured in the same manner as in Example 1. The results are shown in FIGS.

  As is clear from the results shown in Table 1, the powdered metal organic structure (Example 1) after hydrothermal treatment was a powdered metal organic structure (MOF-801-P) (Comparative Example 1) before hydrothermal treatment. ), The PXRD peak intensity ratio of the Miller index (111) plane to the Miller index (200) plane is increased, and the PXRD peak intensity ratio of the Miller index (600) plane to the Miller index (200) plane is increased. Diminished. These results show that the hydrothermal treatment causes rearrangement and growth of the (111) crystal plane and the (200) crystal plane, and the crystal structure of the powdered metal organic structure is close to a single crystal structure. It was.

  Further, as is apparent from the results shown in FIG. 4, the powdered metal organic structure (Example 1) after hydrothermal treatment is a powdered metal organic structure (MOF-801-P) (comparative) before hydrothermal treatment. Compared with Example 1), it was found that the nitrogen adsorption amount increased and the specific surface area of the powdered metal organic structure increased by the hydrothermal treatment. This is considered to be due to the fact that the crystal structure of the powdery metal organic structure is close to a single crystal structure.

Further, as is apparent from the results shown in FIG. 5, the powdered metal organic structure (Example 1) after hydrothermal treatment is a powdered metal organic structure (MOF-801-P) (comparative) before hydrothermal treatment. Compared to Example 1), it was found that the amount of water vapor adsorption increased, and the adsorption performance of the powdered metal organic structure was improved by the hydrothermal treatment. This is considered due to an increase in the specific surface area of the powdery metal organic structure. Moreover, in the vicinity of relative pressure P / P ₀ = 0.1, the water vapor adsorption amount of the powdered metal organic structure after hydrothermal treatment (Example 1) is the same as that of the powdered metal organic structure (MOF-801) before hydrothermal treatment. -P) Compared with the water vapor adsorption amount of (Comparative Example 1), it increased rapidly. From this, it was found that the pores of the powdered metal organic structure were made uniform by the hydrothermal treatment.

(Example 2)
Implementation was performed except that the powdery metal organic structure (MOF-801-P) obtained in Synthesis Example 2 was used in place of the powdery metal organic structure (MOF-801-P) obtained in Synthesis Example 1. Hydrothermal treatment was performed in the same manner as in Example 1, and suction filtration was performed. Then, the filter cake was dried to remove adsorbed moisture.

  In the same manner as in Example 1, the powder X-ray diffraction (PXRD) pattern of the powdered metal organic structure after hydrothermal treatment was measured, and the X-rays of the Miller index (111) plane and the Miller index (200) plane were measured. The diffraction peak intensity ratio [(111) / (200)] and the X-ray diffraction peak intensity ratio [(600) / (200)] between the Miller index (600) plane and the Miller index (200) plane were determined. The results are shown in Table 2.

(Example 3)
Example except that the powdery metal organic structure (MOF-801-P) obtained in Synthesis Example 3 was used instead of the powdery metal organic structure (MOF-801-P) obtained in Synthesis Example 1. Hydrothermal treatment was performed in the same manner as in No. 1, and after suction filtration, the filter cake was dried to remove adsorbed moisture.

  In the same manner as in Example 1, the powder X-ray diffraction (PXRD) pattern of the powdered metal organic structure after hydrothermal treatment was measured, and the X-rays of the Miller index (111) plane and the Miller index (200) plane were measured. The diffraction peak intensity ratio [(111) / (200)] and the X-ray diffraction peak intensity ratio [(600) / (200)] between the Miller index (600) plane and the Miller index (200) plane were determined. The results are shown in Table 2.

  As apparent from the results shown in Table 2, even when the hydrothermal treatment conditions are the same, as the synthesis temperature of the raw material powdery metal organic structure (MOF-801-P) decreases, the Miller index (200) increases. It was found that the PXRD peak intensity ratio of the surface with the Miller index (111) relative to the surface increased, and the PXRD peak intensity ratio of the surface with the Miller index (600) relative to the surface with the Miller index (200) decreased.

  As described above, according to the present invention, it is possible to obtain a porous material composed of a metal organic structure that can be used as an adsorbent having excellent adsorption characteristics.

  Therefore, since the porous material of the present invention is excellent in water vapor adsorption characteristics, it is useful as an adsorbent used in an adsorption heat pump or the like.

Claims (4)

It has an octahedral structure formed of at least one metal atom selected from the group consisting of Zr and Ti, and a polydentate ligand derived from a linear dicarboxylic acid is coordinated to the metal atom. A metal-organic structure having a basic skeleton, wherein an X-ray diffraction peak intensity ratio [(111) / (200)] between a Miller index (111) plane and a Miller index (200) plane is less than 2.3. The metal organic structure has a certain ratio, or the X-ray diffraction peak intensity ratio [(600) / (200)] between the Miller index (600) plane and the Miller index (200) plane exceeds 0.60. It has an octahedral structure formed by at least one metal atom selected from the group consisting of Zr and Ti , and is subjected to heat treatment in a poor solvent for the body, and the metal atom has a linear dicarboxylic acid Derived polydentate ligand Of the X-ray diffraction peak intensity ratio [(111) / of the Miller index (111) plane and the Miller index (200) plane of the metal organic structure. (200)] is 2.3 to 3.5, and the X-ray diffraction peak intensity ratio [(600) / (200) of the Miller index (600) surface and the Miller index (200) surface of the metal-organic structure. )] Is obtained from 0.30 to 0.60 . A method for producing a porous material, comprising: The linear dicarboxylic acid is at least one dicarboxylic acid selected from the group consisting of a linear saturated dicarboxylic acid having 2 to 6 carbon atoms and a linear unsaturated dicarboxylic acid having 4 to 8 carbon atoms. The manufacturing method of the porous material of Claim 1 characterized by the above-mentioned. The method for producing a porous material according to claim 2 , wherein the heating temperature during the heat treatment is 30 to 80 ° C. The method for producing a porous material according to claim 2 or 3 , wherein the poor solvent is at least one selected from the group consisting of water, acetonitrile, hexane and ethanol.