Method for producing a metal organic structure

Abstract

The purpose of the present invention is to produce a high-quality metal-organic structure in a short period of time. The method for producing a metal-organic structure according to the present invention comprises applying centrifugal force and shearing force simultaneously and continuously to a formulation containing a metal ion donor, a polydentate ligand, and a solvent.

Description

Method for producing metal-organic framework

[0001] The present invention relates to a method for producing a metal organic framework (MOF).

[0002] A group of materials called metal-organic frameworks (MOFs) have been attracting attention in fields such as gas storage and gas separation. Metal-organic frameworks are compounds with a structure in which metal atoms are cross-linked by organic ligands, and are typically porous. Porous metal-organic frameworks are also known as porous coordination polymers (PCPs).

[0003] Typically, liquid-phase synthesis methods such as solution synthesis, hydrothermal synthesis, microwave synthesis, and ultrasonic synthesis are used as methods for producing metal-organic frameworks. Solid-phase synthesis methods using a mortar, ball mill, or the like are also sometimes used. Recently, a method for synthesizing metal-organic frameworks using a twin-screw kneading device called an extruder has also been reported. In this method, a first reactant containing a specific metal ion donor and a second reactant containing a specific organic ligand are kneaded under pressure and shear force to synthesize a metal-organic framework (Patent Document 1).

[0004] U.S. Patent No. 9,815,222

[0005] However, the present inventors have found that when the above-mentioned methods are used, it may be difficult to synthesize a high-quality metal-organic framework in a short reaction time. That is, an object of the present invention is to provide a method for producing a high-quality metal-organic framework in a short time.

[0006] The present inventors have conducted extensive research to solve the above problems, and as a result have discovered a new method for applying a technique that has conventionally been used exclusively for dispersing and / or atomizing particles or droplets to substance synthesis.

[0007] The present invention includes, for example, the following aspects: [1] A method for producing a metal organic framework, comprising simultaneously and continuously applying centrifugal force and shear force to a mixture containing a metal ion donor, a multidentate ligand, and a solvent. [2] The production method according to [1], wherein the solvent is a poor solvent for at least one of the metal ion donor and the multidentate ligand. [3] The production method according to [1] or [2], wherein the amount of the solvent is within a range of 30 to 2000 wt % with respect to the total amount of the metal ion donor and the multidentate ligand. [4] The production method according to any of [1] to [3], wherein the production is carried out at a temperature below the normal boiling point of the solvent. [5] The production method according to any of [1] to [4], wherein the production is carried out while supplying at least one gas selected from the group consisting of dry air, argon, nitrogen, and oxygen into a reaction vessel. [6] The manufacturing method according to any one of [1] to [5], wherein the centrifugal force is generated by stirring the blend by rotating a rotor blade in a reaction vessel, and the shear force is generated by contact between the blend and the inner wall of the reaction vessel or by contact between particles constituting the blend due to the stirring. [7] The manufacturing method according to any one of [1] to [6], wherein the centrifugal force and shear force are applied to the blend by a thin film vortex mixing method. [8] The manufacturing method according to any one of [1] to [7], wherein the metal-organic framework is a porous coordination polymer.

[0008] According to the present invention, it is possible to produce a high-quality metal-organic framework in a short period of time.

[0009] Fig. 1 is a cross-sectional view schematically showing an example of a reaction apparatus used in a production method according to one embodiment of the present invention, and Fig. 2 is a cross-sectional view schematically showing an example of a reaction apparatus used in a production method according to another embodiment of the present invention.

[0010] A manufacturing method according to one embodiment of the present invention will be described below. When referring to the drawings, components that perform the same or similar functions are designated by the same reference numerals, and redundant explanations will be omitted.

[0011] A method for producing a metal organic framework according to one embodiment of the present invention comprises simultaneously and continuously applying centrifugal force and shear force to a mixture containing a metal ion donor, a multidentate ligand, and a solvent. This production method may comprise, for example, preparing a mixture containing the metal ion donor, the multidentate ligand, and a solvent, and mixing the mixture while simultaneously and continuously applying centrifugal force and shear force. Alternatively, this production may be carried out by sequentially adding the materials constituting the mixture.

[0012] There is no particular limitation on the type of metal-organic framework to be produced. A metal-organic framework having a desired structure can be produced by appropriately combining the type and coordination number of metal ions with the type and topology of multidentate ligands. The metal-organic framework may contain two or more types of metal elements, or may contain two or more types of multidentate ligands. The metal-organic framework may further contain a monodentate ligand. The metal-organic framework may be porous. That is, the metal-organic framework may be a porous coordination polymer.

[0013] Specific examples of metal-organic frameworks include those described in the following documents: Document 1: Yabing He et al., Methane Storage in Metal-Organic Frameworks, Chem Soc Rev, 2014 Document 2: Jarad A. Mason et al., Evaluating metal-organic frameworks for natural gas storage, Chem. Sci., 2014, 5, 32-51 Document 3: International Publication No. 2019 / 026872

[0014] As described above, the compound used as the raw material for the metal-organic framework contains a metal ion donor, a multidentate ligand, and a solvent. Any substances can be used as the metal ion donor and the multidentate ligand as long as they are suitable as a combination for synthesizing a metal-organic framework.

[0015] Examples of the metal element constituting the metal ion donor include any element belonging to alkali metals (Group 1), alkaline earth metals (Group 2), and transition metals (Groups 3 to 12). The metal element is typically selected from the group consisting of magnesium, calcium, iron, aluminum, zinc, copper, nickel, cobalt, zirconium, and chromium. The metal ion donor may contain multiple metal elements. Alternatively, multiple metal ion donors containing different metal elements may be used in combination.

[0016] Typically, a metal salt is used as the metal ion donor. The metal ion donor may be an organic salt or an inorganic salt. The metal ion donor is typically selected from the group consisting of hydroxide salts, carbonate salts, acetate salts, sulfate salts, nitrate salts, and chloride salts. Multiple metal ion donors containing the same metal element may be used in combination.

[0017] The polydentate ligand is typically an organic polydentate ligand, and is selected from the group consisting of, for example, a carboxylate anion, an amine compound, a sulfonate anion, a phosphate anion, and a heterocyclic compound. Examples of the carboxylate anion include a dicarboxylic acid or tricarboxylic acid anion. Specific examples include anions of citric acid, malic acid, terephthalic acid, isophthalic acid, trimesylic acid, and derivatives thereof. Examples of the heterocyclic compound include bipyridine, imidazole, adenine, and derivatives thereof.

[0018] The type of solvent contained in the formulation is not particularly limited, and solvents commonly used in the synthesis of metal-organic frameworks can be used. However, it is preferable that the solvent be a poor solvent for at least one of the metal ion donor and the multidentate ligand. When such a configuration is adopted, the formulation does not become a complete solution, but rather becomes a semi-solid state with solids remaining, typically a slurry. This allows the formulation to be more effectively subjected to the centrifugal force and shear force described below. Here, a solvent being a "poor solvent" for a certain target refers to a solvent whose solubility in the target in the solvent is 1 g / 50 mL (= 20 g / L) or less at 25°C and atmospheric pressure. Examples of usable solvents include water, alcohols such as methanol and ethanol, carboxylic acids such as formic acid and acetic acid, amides such as N,N-dimethylformamide (DMF) and N,N-diethylformamide (DEF), and esters such as ethyl acetate. A mixture of multiple solvents may also be used.

[0019] The amount of the solvent is, for example, in the range of 30 to 2000% by weight, and preferably in the range of 100 to 1000% by weight, based on the total amount of the metal ion donor and the multidentate ligand. By adopting such a configuration, for example, it is possible to improve the production efficiency of the metal organic framework.

[0020] The above-mentioned formulation may further contain an additional substance such as a reaction accelerator. The reaction accelerator is, for example, a basic substance or an acidic substance, and is typically a basic substance. Examples of basic substances include diethylamine, triethylamine, 2,6-lutidine, pyridine, imidazole, potassium hydroxide, and sodium hydroxide. Examples of acidic substances include formic acid, acetic acid, trifluoroacetic acid, sulfuric acid, nitric acid, hydrochloric acid, and phosphoric acid. As the additional substance, multiple reaction accelerators may be used in combination. As the additional substance, a reaction inhibitor may be added.

[0021] The above-mentioned compound is mixed while simultaneously and continuously applying centrifugal force and shear force, which enables the production of a metal-organic framework in a short time with high quality.

[0022] As the term "structure" suggests, metal-organic frameworks are somewhat fragile compared to ordinary organometallic compounds. Therefore, it is difficult to produce high-quality metal-organic frameworks without devising a manufacturing method. For example, in the case of solid-phase synthesis using a ball mill or the like, extremely strong forces are applied intermittently to the raw materials. Therefore, there is considerable variation in the quality of the resulting metal-organic frameworks. Furthermore, in synthesis methods using an extruder, extremely strong shear forces are applied locally under high pressure, so similar problems are likely to occur.

[0023] Therefore, the present inventors wondered whether the above problems could be solved by simultaneously and continuously applying centrifugal force and shear force to the above-mentioned blend. Such a technique has conventionally been used exclusively for the purpose of dispersing and / or atomizing particles or droplets, and has not been used for substance synthesis. However, the present inventors discovered that by applying the above-mentioned technique to the production of a metal-organic framework, a metal-organic framework can be produced with high quality in a short time.

[0024] Examples of methods for simultaneously and continuously applying centrifugal force and shear force to the blend include the following: First, the blend is introduced into a reaction vessel. Next, the rotary blades provided in the reaction vessel are rotated to stir the blend at high speed. This rotation applies centrifugal force to the blend. This centrifugal force then presses the blend against the inner wall of the reaction vessel. Such contact between the blend and the inner wall of the reaction vessel applies shear force to the blend. In this way, both centrifugal force and shear force are simultaneously and continuously applied to the blend. In this state, the metal ion donor and the multidentate ligand in the blend react to obtain a metal organic framework. Note that the shear force can also be generated by mutual contact between particles constituting the blend.

[0025] When using the above method, it is preferable that the rotation axis of the rotating blades is parallel to the direction of gravity, since in this case, the centrifugal force and shear force applied to the blend by the rotation are less uneven than when, for example, the rotation axis is perpendicular to the direction of gravity.

[0026] One example of the above technique is the thin film vortex mixing method developed by Primix Corporation. In this method, a thin film vortex high-speed mixer is used to simultaneously and continuously apply centrifugal force and shear force to the introduced material. In conventional use cases, this results in the dispersion and / or atomization of particles or droplets. Specific device configurations are disclosed, for example, in Japanese Patent Publication No. 2007-125454.

[0027] 1 is a cross-sectional view schematically illustrating an example of a reaction apparatus used in a production method according to one embodiment of the present invention. The reaction apparatus 100 shown in FIG. 1 is a batch-type production apparatus.

[0028] The reactor 100 includes a reaction vessel 102. The reaction vessel 102 is, for example, cylindrical. The reaction vessel 102 typically includes an outer layer 104 for temperature control. The outer layer 104 is configured to allow a liquid such as water to be injected into it. This makes it possible to control the temperature inside the reaction vessel 102, particularly the temperature of the inner wall IW, which will be described later.

[0029] The reaction apparatus 100 includes a rotating impeller 106A and a rotating shaft 106B connected thereto inside the reaction vessel 102. The rotating impeller 106A can be rotated by the rotation R of the rotating shaft 106B. The rotating impeller 106A is, for example, a cylindrical wheel having a small gap with the inner wall IW of the reaction vessel 102. This wheel is typically provided with a large number of holes for allowing the compound F to pass through.

[0030] A dam 108 is provided above the reactor 100. This prevents reactants from leaking out of the reactor 100.

[0031] In the production method using the reaction apparatus 100, first, the composition F is introduced into the reaction vessel 102. Next, the composition F is stirred by rotating the rotary blades 106A via the rotary shaft 106B. The centrifugal force applied to the composition F causes the composition F to be pressed against the inner wall IW while rotating. As a result, not only the centrifugal force but also a steady shear force is applied to the composition F. In this way, the composition F is mixed while centrifugal force and shear force are applied simultaneously and continuously. After the reaction is completed, the reaction product is recovered to obtain the desired metal organic framework.

[0032] 2 is a cross-sectional view schematically showing an example of a reaction apparatus used in a production method according to another embodiment of the present invention. The reaction apparatus 200 shown in FIG. 2 is a continuous production apparatus.

[0033] The reaction apparatus 200 includes a reaction tank 202. The reaction tank 202 is provided with two outer layers for temperature control. Specifically, in addition to an outer layer 204A having a configuration similar to that of the outer layer 104, an additional outer layer 204B is provided in the upper part of the reaction tank 202. This makes it possible to control the reaction temperature also in the upper part of the reaction tank 202.

[0034] The reaction apparatus 200 includes a rotating impeller 206A and a rotating shaft 206B connected thereto inside a reaction tank 202. The configurations of the rotating impeller 206A and the rotating shaft 206B are similar to those described for the rotating impeller 106A and the rotating shaft 106B, respectively.

[0035] A dam 208 is provided above the reactor 200. The dam 208 is smaller in size than the dam 108. This allows at least a portion of the reaction product to be sent to the upper part of the reactor 200.

[0036] The reactor 200 is equipped with an inlet 210A and an outlet 210B. The inlet 210A is provided at the bottom of the reactor 200, through which the formulation F can be continuously injected. The outlet 210B is provided at the top of the reactor 200, through which at least a portion of the reaction product can be discharged to the outside of the system.

[0037] In the production method using the reaction apparatus 200, first, the composition F is introduced into the reaction vessel 202 through the inlet 210A. Next, the composition F is stirred by rotating the rotary blades 206A via the rotary shaft 206B. The centrifugal force applied to the composition F causes the composition F to be pressed against the inner wall IW while rotating. As a result, not only the centrifugal force but also a steady shear force is applied to the composition F. In this way, the composition F is mixed while centrifugal force and shear force are simultaneously and continuously applied. The reaction product obtained by this mixing is discharged from the outlet 210B as the reaction progresses. The desired metal organic framework is obtained by recovering the discharged reaction product.

[0038] Specific examples of devices that enable the above-mentioned manufacturing method include FILMICS (PRIMIX Corporation), APEX DISPERSER ZERO (Hiroshima Metal & Machinery Chemtech Company), and HIGH SHEAR MIXER (SILVERSON). Any other device that can simultaneously and continuously apply both centrifugal force and shear force to the blend may also be used.

[0039] The above production is preferably carried out while controlling the reaction temperature. In this case, the above mixing is preferably carried out at a temperature below the normal boiling point of the solvent. The above mixing is carried out at a temperature of, for example, 80°C or lower, preferably 60°C or lower. In this way, it is possible to produce the metal organic framework while an appropriate amount of the solvent remains in the blend.

[0040] The above production can also be carried out while supplying at least one gas selected from the group consisting of dry air, argon, nitrogen, and oxygen into the reaction vessel. That is, in the production method according to one aspect of the present invention, the reaction can be carried out in a closed system. For example, by carrying out the above production in an inert gas atmosphere such as dry air, argon, or nitrogen, it becomes possible to produce with high precision a metal-organic framework that is sensitive to moisture. Alternatively, by carrying out the above production in an oxygen atmosphere, it becomes possible to produce with high precision a metal-organic framework that is advantageously synthesized in an oxygen-excess atmosphere.

[0041] Furthermore, the above production can be carried out by mixing the blend at a linear speed of, for example, 1 to 100 m / s, preferably 10 to 50 m / s. If the linear speed is too low, it may not be possible to apply a shear force to the blend continuously. If the linear speed is too low, the centrifugal force and shear force applied to the blend may become excessive.

[0042] Examples 1 to 38: Centrifugal shear synthesis A metal ion donor, a multidentate ligand, a solvent, and optionally a reaction accelerator shown in Table 1 were added to a thin film rotary high-speed mixer (Filmix 56-L model; manufactured by Primix Corporation). Next, high-speed stirring was carried out under the reaction conditions shown in Table 1. As a result, a metal organic framework was obtained.

[0043] Comparative Examples A1 to A9: Solvothermal synthesis A metal ion donor, a multidentate ligand, a solvent, and optionally a reaction accelerator shown in Table 2 were added to a 100 mL high-pressure reaction vessel (HU-100, manufactured by San-ai Scientific Co., Ltd.). Next, solvothermal synthesis was carried out under the reaction conditions shown in Table 2 using a constant temperature oven (OFP-300V; manufactured by AS ONE Corporation).

[0044] Comparative Examples B1 to B10: Ball Mill Synthesis A metal ion donor, a polydentate ligand, a solvent, and optionally a reaction accelerator shown in Table 3 were added to a 125 mL milling jar. Stainless steel milling balls with a diameter of 5 mm were added to the jar, and ball mill synthesis was carried out under the reaction conditions shown in Table 3 using a high-energy ball mill (Emax; manufactured by Retsch).

[0045] Comparative Examples C1 to C7: Twin-screw kneading synthesis The metal ion donor and multidentate ligand shown in Table 4 were placed in a polyethylene bag and thoroughly mixed. Thereafter, the mixture was transferred to a stainless steel container, and the solvent shown in Table 4 was added thereto, followed by further stirring and mixing. This was added to a twin-screw kneader (Process 11; manufactured by Thermo Fisher Scientific), and twin-screw kneading synthesis was carried out under the reaction conditions shown in Table 4.

[0046] Evaluation The samples obtained by each of the above methods were dried under reduced pressure at room temperature for 24 hours using a vacuum desiccator (MVD-300; manufactured by AS ONE Corporation). The dried samples were subjected to XRD measurement using an X-ray diffractometer (MiniFlex; manufactured by Rigaku Corporation). Furthermore, at least some of the samples were heated and vacuum dried at 140°C for 4 hours using a gas adsorption pretreatment device (BELPREP-vacIII; manufactured by Microtrac-Bell), and then the BET specific surface area (N ２ ;77K) was measured.

[0047] The presence or absence of crystalline peaks in XRD measurement and the BET specific surface area S ＢＥＴ The quality of the obtained metal organic framework was evaluated based on the size of the particle. The results are shown in Tables 1 to 4.

[0048] The following abbreviations are used in Tables 1 to 4: BTC: 1,3,5-benzenetricarboxylic acid (trimesic acid), pBDC: terephthalic acid, iBDC: isophthalic acid, INA: 4-pyridinecarboxylic acid, Mim: 2-methylimidazole, ADC: acetylenedicarboxylic acid, DOT: dihydroxyterephthalic acid, Fumalate: fumaric acid, BTC3Na: 1,3,5-benzenetricarboxylic acid trisodium. Ethanol (EtOH) with a purity of 99.5% or higher was used.

[0049]

[0050]

[0051]

[0052]

[0053] A comparison of Table 1 with Table 2 shows that by using the production method according to the present invention, a metal organic framework of higher quality can be synthesized while significantly shortening the reaction time compared to the case where the solvothermal method is used. Furthermore, a comparison of Table 1 with Tables 3 and 4 shows that by using the production method according to the present invention, a metal organic framework of higher quality can be synthesized in approximately the same reaction time compared to the case where the ball mill method and the twin-screw kneading method are used.

[0054] Furthermore, comparing, for example, Examples 1 to 4 in Table 1, it can be seen that the specific surface area of ​​the resulting metal-organic framework changes by controlling the amount of solvent. This result suggests that by controlling the viscosity of the blend through adjustment of the amount of solvent, it is possible to optimize the centrifugal force and shear force applied to the blend.

[0055] Furthermore, when comparing, for example, Examples 1, 5 and 6, or Examples 8 and 9 in Table 1, it can be seen that a metal organic framework of higher quality can be synthesized by carrying out the reaction at a temperature not higher than the normal boiling point of the solvent (78.4°C in the case of ethanol; 64.7°C in the case of methanol), preferably not higher than 60°C.

[0056] Furthermore, comparing, for example, Examples 20 to 23 in Table 1, it can be seen that a metal-organic framework of higher quality can be synthesized in some cases by carrying out the reaction under a dry air, nitrogen, or argon atmosphere. Similarly, comparing, for example, Examples 24 and 25, it can be seen that a metal-organic framework of higher quality can be synthesized in some cases by carrying out the reaction under a nitrogen atmosphere. Furthermore, comparing, for example, Examples 36 and 37 in Table 1, it can be seen that a metal-organic framework of higher quality can be synthesized in some cases by carrying out the reaction under an oxygen atmosphere. In this way, by carrying out the reaction in a closed system as necessary, it becomes possible to synthesize a wider range of metal-organic frameworks.

[0057] 100... reactor, 102... reactor vessel, 104... outer layer, 106A... rotor blades, 106B... rotor shaft, 108... dam, 200... reactor, 202... reactor vessel, 204A... outer layer, 204B... outer layer, 206A... rotor blades, 206B... rotor shaft, 208... dam, 210A... inlet, 210B... outlet, F... blend, IW... inner wall, R... rotor

Claims

1. A method for producing a metal organic framework, comprising simultaneously and continuously applying centrifugal force and shear force to a mixture containing a metal ion donor, a multidentate ligand, and a solvent.

2. The method according to claim 1, wherein the solvent is a poor solvent for at least one of the metal ion donor and the multidentate ligand.

3. The method according to claim 1 or 2, wherein the amount of the solvent is in the range of 30 to 2000% by weight based on the total amount of the metal ion donor and the multidentate ligand.

4. The process according to any one of claims 1 to 3, which is carried out at a temperature below the normal boiling point of the solvent.

5. The manufacturing method according to any one of claims 1 to 4, wherein the manufacturing method is carried out while supplying at least one gas selected from the group consisting of dry air, argon, nitrogen, and oxygen into the reaction vessel.

6. A manufacturing method according to any one of claims 1 to 5, wherein the centrifugal force is generated by stirring the compound by rotating a rotor blade in a reaction vessel, and the shear force is generated by the compound coming into contact with the inner wall of the reaction vessel or by particles constituting the compound coming into contact with each other as a result of the stirring.

7. A method according to any one of claims 1 to 6, wherein the centrifugal and shear forces are applied to the blend by thin film gyration mixing.

8. The method according to any one of claims 1 to 7, wherein the metal-organic framework is a porous coordination polymer.

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