Organometallic structure, method for producing same, gas-adsorbing material using same, and method for producing gas-adsorbing material

Abstract

The present invention relates to a method for producing an organometallic structure using a devitrification device provided with a reactant introduction zone, a devitrification zone, a circulation zone, and a recovery zone. Wherein, in the reactant introduction zone, an aqueous solution containing a metal ion and an aqueous solution containing an organic ligand capable of coordinating with the metal ion are simultaneously and continuously added from different nozzles provided in the flow path, and are immediately mixed using a mixing mechanism. In the devitrification zone, the metal ions are reacted with the organic ligands to grow crystals of the metal-organic structure while producing crystal nucleuses of the metal-organic structure. In the circulation zone, a slurry containing the crystals of the metal-organic structure is circulated to the reactant introduction step. In the recovery zone, a portion of the slurry is withdrawn continuously or every prescribed time.

Description

Organometallic structures, their manufacturing methods, gas adsorbent materials using them, and methods for manufacturing gas adsorbent materials. Technical Field

[0001] This invention relates to organometallic structures and methods for manufacturing the same. Furthermore, this invention also relates to gas adsorption materials using organometallic structures and methods for manufacturing the same. Background Technology

[0002] Metal-organic frameworks (MOFs), also known as porous coordination polymers (PCPs), are porous materials with highly regular lattice structures formed by metal ions and organic ligands. Utilizing the highly regular lattice structure of MOFs, applications are anticipated, such as in hydrogen and other gas storage materials, carbon dioxide concentration and separation materials, inhomogeneous catalysts, conductive materials, and magnetic materials.

[0003] MOFs can be synthesized, for example, by a solution method in which metal ions and organic ligands self-aggregate in a liquid (see, for example, Non-Patent Literature 1). In this case, the solution is kept in a closed container at a temperature higher than the evaporation temperature of the solvent, causing the solution to evaporate and its own pressure to increase. MOFs can be synthesized under high pressure, driven by the fact that the molecular volume of the MOF is smaller than that of the solute (this is called hydrothermal synthesis in the case of aqueous solvents and solvothermal synthesis in the case of organic solvents), or by continuously feeding a solution of metal ions dissolved in an organic solvent and water and a solution of organic ligands melted in an organic solvent into a stirred tank and stirring, or by mixing in a tubular microreactor.

[0004] Whether using hydrothermal or solvothermal synthesis, in batch reactions, the high concentrations of metal ions and organic ligand ions in the solution during the initial stages of MOF synthesis inevitably lead to a decrease in solute concentration as the reaction progresses. Maximum supersaturation is achieved initially when metal and organic ligand ions are mixed, so the crystal growth rate should reach maximum supersaturation. However, in reality, the supersaturation, which serves as the driving force, is consumed by the nucleation rate, resulting in the precipitation of numerous tiny crystals. Furthermore, as crystallization proceeds, the solute concentration decreases, and the supersaturation disappears, ultimately leading to almost no crystal growth. Consequently, the production rate of MOF per unit volume and per unit time becomes extremely low. This is also true in continuous reactions such as those using tubular microreactors, where back-mixing of the solution occurs, but the solute concentration in the reaction field changes from high to low.

[0005] In contrast, continuously stirring the reaction in a stirred tank is an excellent method for maintaining constant reaction conditions (e.g., solute concentration, temperature, or pH) once a steady state is reached. However, for MOF crystals, no method has yet been shown to control the nucleation rate and linear growth rate within a specified range. Crystallization apparatuses that continuously supply reactants to a stirred tank and continuously remove products are commonly used. In particular, in so-called MSMPR (Mixed Suspension Mixed Product Removal) crystallization apparatuses where the entire stirred tank reaches approximately the same concentration, the reaction liquid within the apparatus changes abruptly into MOF particles due to the simultaneous reaction of MOFs during addition, making it impossible to maintain a high degree of supersaturation. As a result, the obtained MOF crystals are those with a high particle size and low bulk density.

[0006] It should be noted that pH is usually an important parameter when using ionic reactants for crystallization. There are also reports of crystallization in buffer solutions to maintain a constant pH in MOFs. However, this increases the variety of ions in the reaction field, resulting in a more complex reaction field.

[0007] Furthermore, organic ligands refer to organic compounds containing two or more carbon atoms, typically four or more, with at least two carboxylic acid groups, and stable at room temperature, atmospheric pressure, and 50% relative humidity. Examples include fumaric acid, terephthalic acid, trimesic acid, triazole, and oxalic acid. To synthesize MOFs, the organic compound and metal salt need to be in an ionic state, with the metal coordinating with the carboxylic acid groups of the organic compound. To dissolve both ions simultaneously, organic solvents such as DMF (dimethylformamide), DEF (diethylformamide), and NMP (N-methyl-2-pyrrolidone) are commonly used. However, such organic solvents are more expensive than water. Moreover, without completely washing and separating the organic solvent from the manufactured MOF, it cannot be used in fields such as pharmaceuticals and food.

[0008] As another method, Patent Document 1 proposes a method for manufacturing MOFs in a short time by applying centrifugal and shear forces to a complex formed by mixing a metal ion donor, a multidentate ligand, and a solvent as raw materials. (Prior art literature, Patent literature)

[0009] Patent Document 1: U.S. Patent Application Publication No. 2022 / 0220129, Specification, Non-Patent Document

[0010] Non-Patent Document 1: "Basics of Materials Science", No. 7, "Basics of Porous Coordination Polymers (PCP) / Metal Organic Structures (MOF)", Semester, September 2012, website<URL:https: / / www.sigmaaldrich.com / JP / ja / campaigns / materials-science-basic> Summary of the Invention

[0011] In hydrothermal or solvothermal synthesis methods, as temperature increases, water or solvent evaporates, leading to increased pressure. In the absence of crystals, the solute concentration is high, but the pressure is low. Therefore, during the period without nucleation, supersaturation gradually increases. If a certain level of supersaturation is reached, nucleation occurs rapidly, resulting in a large number of small-diameter crystals. Subsequently, the pressure increases further, increasing supersaturation, but the solute concentration decreases, and the solute for crystal growth disappears, resulting in a large number of small-diameter crystals. MOFs composed solely of these small-diameter crystals have a low bulk density, reducing the amount of MOF per unit volume when filling the apparatus, thus reducing adsorption capacity. To address this problem, a known method involves maintaining supersaturation at high temperature and high pressure for an extended period, causing the melting of small particles and the growth of larger particles—the so-called Ostwaldripening phenomenon—to increase particle size. However, this method requires a long time, resulting in an industrial problem of drastically reduced production rate per unit time.

[0012] In the case of a tubular microreactor, although the crystals move within the device as a single unit with the reaction liquid, the phenomenon is the same as that of the intermittent hydrothermal synthesis and solvothermal methods. Due to the aforementioned phenomenon, the MOFs become small in size, and the adsorption capacity per unit volume is reduced.

[0013] When MOFs are used as adsorbents in the above-mentioned applications, high crystallinity and high particle packing density are important for improving performance in these applications.

[0014] Therefore, the objective of this invention is to provide a MOF and a method for manufacturing the same thereof that can eliminate the aforementioned disadvantages of the prior art, as well as a gas adsorption material using MOF and a method for manufacturing the same thereof.

[0015] MOFs can be manufactured using the methods described above, but those produced have small particle sizes and low bulk density, resulting in poor filling properties. Furthermore, porous materials often employ one-dimensional or multi-dimensional microporous structures. The longer the micropores, the faster the adsorption and desorption rates tend to be due to capillary effects. In other words, higher crystallinity leads to faster adsorption and desorption rates. Therefore, the required crystal structure for porous materials like MOFs is a wide particle size distribution, allowing small crystal particles to enter the spaces between crystal particles, resulting in higher bulk density, and high crystallinity with faster adsorption and desorption rates. Additionally, it is obvious that MOFs with fewer impurities exhibit more stable adsorption and desorption.

[0016] To meet these requirements, a method for growing MOFs with a wide particle size distribution, containing both large and small grains, and high crystallinity, can be employed. The inventors conducted in-depth research on the shape of the apparatus used to manufacture such MOFs and achieved this through repeated experiments. Furthermore, the inventors discovered a method for cleaning impurities using a small amount of solvent and in a short time, in large quantities. Additionally, they discovered an industrially useful gas adsorbent material obtained by granulating the resulting metal-organic structure, and a preferred method for manufacturing this gas adsorbent material.

[0017] The crystallization phenomenon of MOFs based on metathesis reactions in aqueous solutions is characterized by almost no heat of crystallization. The metathesis reaction referred to here means that when the metal of the MOF is designated as M, the organic ligand as O, and their respective counter ions as X and Y, the crystallization occurs as MX. l +O m Y n →MO m +X l Y n The compound obtained is a MOF (MO). m ) and compounds that counterionize ions (X) l Y n The reaction of MOF is a common double displacement reaction. A surprising feature of this reaction is the almost absence of heat of crystallization. Generally, in crystallization, the heat generated is corresponding to the heat of solution if the reactants change from a solution to a crystalline solid. As a possibility, assuming the phase transition of the counterion in the double displacement reaction is sodium sulfate, its dissolution and precipitation, and therefore above 33°C, might be endothermic. However, the concentration of MOF in the double displacement reaction is significantly diluted compared to the solubility of sodium sulfate, thus negating the possibility that a phase transition would not occur.

[0018] The driving force behind crystallization is supersaturation. Supersaturation is mainly dependent on temperature and concentration; therefore, when heat is generated due to crystallization, the supersaturation at the crystal growth interface decreases. However, in the crystallization of MOFs, there is almost no heat of crystallization, so as long as the concentration is accurately controlled, the supersaturation can be accurately controlled. Next, in this invention, when the crystal growth rate of MOFs was measured, it was naturally proportional to the supersaturation. However, although coarse particles were obtained, the crystal growth rate was unexpectedly low. Furthermore, it was found that increasing the supersaturation increases the crystal growth rate. This phenomenon is commonly observed when the solubility of the product is low; it occurs before growth and without consuming supersaturation. However, in the case of porous materials, since water is contained within the pores, the apparent growth rate increases, which is not always the case. However, the inventors have discovered for the first time that, as a unique phenomenon in MOFs, which are porous materials, the nucleation rate is unexpectedly dominant in relation to the balance between nucleation rate and crystal growth rate, and a large crystal growth rate cannot be obtained unless there is a fairly large degree of supersaturation.

[0019] Therefore, in this invention, a novel apparatus for obtaining coarse crystals of MOFs is designed by utilizing the newly discovered relationship between the linear growth rate and nucleation rate of MOFs. Specifically, a reactant introduction zone and a crystallization zone are set up in a portion of the crystallization apparatus. In the reactant introduction zone, a solution containing metal ions and a solution containing organic ligands are rapidly introduced and mixed to obtain a large supersaturation. By allowing crystal particles contained in the suspension slurry to pass through and mix with this highly supersaturated solution, crystals are epitaxially grown on the surface of the crystal particles, producing crystals with large grain size, i.e., large particle diameter.

[0020] On the other hand, the stirring speed used for mixing in the reactant introduction zone is related to the nucleation rate to some extent. That is, when the stirring speed is increased to improve mixing, the nucleation rate increases, and there is a tendency for the number of MOF crystal particles with small particle sizes to increase. A method was designed to grow crystals in the crystallization zone in accordance with the growth rate of the MOF, or to attach the generated particles to the crystal surface, thereby reducing the number of nuclei by taking in excessive nuclei to the crystal surface and producing coarse MOF crystals.

[0021] It should be noted that, unlike the stirring blades in the reactant introduction zone, an impeller for conveying the reaction liquid can be mounted coaxially, utilizing a so-called multi-stage impeller. This allows for separate control of the stirring state and conveying speed in the reactant introduction zone. However, in this invention, experiments were conducted with a multi-stage impeller, and no significant effects were observed.

[0022] By making MOF into coarse crystals, the specific surface area of ​​the crystals is reduced, which reduces the amount of mother liquor adhering to the crystal surface, thereby making it easier to clean the crystals.

[0023] Furthermore, as a method for separating MOF crystals from the mother liquor, one example is the use of large centrifugal force. The inventors have recently discovered that, although the exact nature of this phenomenon is unclear, it is possible to reduce the amount of washing solution by improving the cleanliness of the crystals.

[0024] The present invention provides an organometallic structure comprising a crystal containing an organic ligand and a metal ion, wherein the organic ligand is a dianion of fumaric acid or a dianion of terephthalic acid, and the metal ion is an aluminum ion, a zinc ion or an iron (III) ion, and the tap density of the organometallic structure is above 0.3 g / mL and below 0.9 g / mL.

[0025] In addition, the present invention provides a gas adsorption material comprising a granulated mixture of the organometallic structure as a gas adsorption component and a phenolic resin as a shape-maintaining component.

[0026] In addition, the present invention provides a method for manufacturing a metal-organic structure, which uses a crystallization device having a reactant introduction zone, a crystallization zone, a circulation zone, and a recovery zone. In the reactant introduction zone, an aqueous solution containing metal ions and an aqueous solution containing organic ligands capable of coordinating with the metal ions are simultaneously and continuously added from different nozzles provided in the flow path, and the solutions are immediately mixed using a mixing mechanism. In the crystallization zone, the metal ions react with the organic ligands to grow crystals of the metal-organic structure and generate crystal nuclei of the metal-organic structure. In the circulation zone, the slurry containing the crystals of the metal-organic structure is circulated to the reactant introduction step. In the recovery zone, a portion of the slurry is continuously or periodically extracted.

[0027] Furthermore, the present invention provides a continuous cleaning method for organometallic structures, which is a continuous cleaning method for organometallic structures manufactured using the above-described method. The continuous cleaning method includes a cleaning step in which the organometallic structure is cleaned with a cleaning solution to remove counter anions used to dissolve the metal ions constituting the organometallic structure and counter cations used to dissolve the organic ligands. The cleaning step includes a first cleaning step, a solid-liquid separation step, and a second cleaning step. In the solid-liquid separation step, the liquid that has undergone the first cleaning step is separated into solid components and liquid components. In the second cleaning step, the solid components are further cleaned, and the liquid components are used as part of the cleaning solution in the first cleaning step.

[0028] Furthermore, the present invention provides a method for manufacturing a gas adsorbent material, comprising: a step of mixing the organometallic structure manufactured by the above method with a thermosetting phenolic resin to obtain a mixture; a step of adding water to the mixture and performing rolling granulation to obtain granules; a step of separating the granules grown to a predetermined particle size according to the particle size; and a step of feeding the granules with a particle size smaller than the predetermined particle size back into the granulation step, and heating the granules that have reached the predetermined particle size at a first temperature to remove the water, and further heating them to a second temperature to cure the thermosetting phenolic resin. Attached Figure Description

[0029] Figure 1 is a schematic diagram showing an apparatus suitable for implementing the manufacturing method of the present invention. Figure 2 is a schematic diagram showing an example of a reaction apparatus suitable for implementing the manufacturing method of the present invention. Figures 3(a) and (b) are optical microscope photographs of the crystals of the MOF of the present invention, respectively. Figure 4 is a graph showing the results of nitrogen adsorption-desorption tests on the spherical granules of Example 4. Figure 5 is a graph showing the results of carbon dioxide adsorption tests on the organometallic structure of Example 1 and the spherical granules of Example 4. Figure 6 is a schematic diagram showing a continuous cleaning apparatus suitable for implementing the manufacturing method of the present invention. Detailed Implementation

[0030] Hereinafter, the present invention will be described with reference to FIG1 based on its preferred embodiments. The present invention relates to a method for manufacturing an organometallic structure, i.e., a MOF, composed of crystals containing organic ligands and metal ions. The present invention is a continuous method for manufacturing MOFs. For this purpose, in the present manufacturing method, a crystallization apparatus having a reactant introduction zone A, a crystallization zone B, a circulation zone C, and a recovery zone D is preferably used. The manufacturing method using this crystallization apparatus is generally divided into the following steps (1) to (4). (1) Reactant introduction step In this step, in the reactant introduction zone A, an aqueous solution M containing metal ions and an aqueous solution L containing organic ligands capable of coordinating with the metal ions are simultaneously and continuously added from different nozzles provided in the flow path, and the mixture is immediately mixed using a mixing mechanism E. (2) Crystallization step In this step, in the crystallization zone B, the metal ions react with the organic ligands to grow crystals of the metal-organic structure, and crystal nuclei of the metal-organic structure are generated at the same time. (3) Crystal Circulation Process: In this process, in circulation zone C, the slurry containing the crystals of the metal-organic structure is circulated to the reactant introduction process. That is, the metal-organic structure obtained in the reaction is smoothly moved to the reactant introduction process, and the crystals and solution are circulated. (4) Crystal Recovery Process: In this process, in recovery zone D, a portion of the slurry is continuously or periodically extracted. It should be noted that, in this manufacturing method, additional processes may be performed as needed before process (1), between process (1) and process (2), between process (2) and process (3), between process (3) and process (4), and / or after process (4). By combining the processes shown here, despite the phenomenon of low growth rate and high nucleation rate of the MOF newly discovered by the inventors, it is possible to manufacture MOFs with large particle sizes, thereby achieving a wider particle size distribution of MOFs and thus increasing the bulk density of MOFs. Meanwhile, according to the present invention, a high degree of supersaturation can be easily achieved in the crystallization process, thus greatly increasing the production rate of MOFs per unit volume and per unit time, enabling the inexpensive manufacturing of MOFs. Each process will be described below.

[0031] [Reactant Introduction Step] Since MOFs are substances formed from metal ions and organic ligands, this step first prepares the metal ions and organic ligands that will serve as the raw materials for MOFs. The metal ions are prepared in an aqueous solution state. The organic ligands are also prepared in an aqueous solution state. One characteristic of this manufacturing method is that MOFs are manufactured in water, not in an organic solvent. Manufacturing MOFs in water offers advantages such as less complex manufacturing equipment, greater flexibility in manufacturing conditions, and less environmental impact.

[0032] As metal ions, appropriate metal ions can be used depending on the specific application of the target MOF. In applications such as gas storage and gas separation, metal ions such as aluminum, iron, copper, zinc, zirconium, chromium, and cobalt can be used. Among these, aluminum, iron, chromium, and cobalt ions are typically six-coordinated. Copper and zinc ions are typically four-coordinated. Depending on the solvent and pH, zinc ions sometimes form clusters with four zinc nuclei, constituting a six-valent, six-coordinated ion; this zinc tetranuclear cluster ion is a type of zinc ion. Zirconium ions are four-coordinated and eight-coordinated; similar to zinc ions, the four-coordinated nuclei sometimes form four clusters, resulting in a six-coordinated ion. From the perspective of easily obtaining MOFs with high gas storage and gas separation performance from the aforementioned metal ions, aluminum, iron, zinc tetranuclear clusters, and copper ions are preferred.

[0033] Aqueous solutions of metal ions are obtained, for example, by dissolving a water-soluble metal compound in water. Examples of water-soluble metal compounds include water-soluble salts, halides, and hydroxides. Specifically, when the metal ion is, for example, aluminum ions, aluminum sulfate and aluminum chloride can be used as water-soluble metal compounds. When the metal ion is, for example, iron ions, ferric chloride (II), ferric chloride (III), and ferric sulfate (II) can be used as water-soluble metal compounds. When the metal ion is, for example, copper ions, copper sulfate (II) and copper chloride (II) can be used as water-soluble metal compounds. When the metal ion is, for example, zinc ions, zinc sulfate can be used as a water-soluble metal compound. When the metal ion is, for example, cobalt ions, cobalt sulfate (II) and cobalt chloride (II) can be used as water-soluble metal compounds.

[0034] From the perspective of increasing the production rate per unit volume and per unit time, it is preferable that the concentration of metal ions in the aqueous solution of metal ions is 0.1 mol / L or more. From the viewpoint of making this advantage even more significant, the concentration of metal ions in the aqueous solution of metal ions is more preferably 0.15 mol / L or more, and even more preferably 0.3 mol / L or more. Furthermore, from the viewpoint of not having an extreme difference from the concentration of organic ligands, the concentration of metal ions in the aqueous solution of metal ions is preferably 1.8 mol / L or less. From the viewpoint of making this advantage even more significant, the concentration of metal ions in the aqueous solution of metal ions is more preferably 1.0 mol / L or less, and even more preferably 0.9 mol / L or less.

[0035] The pH of the aqueous solution of the metal ion is not particularly limited as long as it does not produce a precipitate containing the metal in the liquid. In the case where the pH of the aqueous solution of the organic ligand (described later) is alkaline, from the viewpoint of neutralizing the pH of the liquid containing the two aqueous solutions, it is preferable to set the pH of the aqueous solution of the metal ion to 4 or lower.

[0036] As for the organic ligands used in the production of MOFs with metal ions, there are no particular limitations on their types, as long as they can coordinate with the metal ion. Preferred organic ligands include nitrogen-donating ligands and oxygen-donating ligands. Examples of nitrogen-donating ligands include imidazole, 2,2'-bipyridine, 3,3'-bipyridine, 4,4'-bipyridine, 2,2'-bipyrazine, 2,2'-bipyrimidine, and 1,4-bis(4-pyridyl)benzene. These nitrogen-donating ligands can be used alone or in combination of two or more. On the other hand, examples of oxygen-donating ligands include anions of polybasic organic acids. Polybasic organic acids can be aliphatic or aromatic. Specifically, examples include dianions of dibasic organic acids such as oxalic acid, fumaric acid, terephthalic acid, phthalic acid, and isophthalic acid, and trianions of tribasic organic acids such as trimellitic acid. In aromatic polycyclic organic acids, the hydrogen atoms bonded to the aromatic ring can be replaced by various functional groups such as hydroxyl, amino, and nitro groups. These oxygen-donating ligands can be used alone or in combination of two or more.

[0037] The choice of organic ligands can be made according to the specific application of the MOF. From the perspective of easily obtaining MOFs with high bulk density, oxygen donor ligands are preferred, and dianions of dicarboxylic organic acids are particularly preferred.

[0038] From the perspective of maximizing the production rate per unit volume and per unit time, it is preferable that the concentration of the organic ligand in the aqueous solution of the organic ligand is 0.3 mol / L or more. From the viewpoint of making this advantage even more significant, the concentration of the organic ligand in the aqueous solution of the organic ligand is more preferably 0.5 mol / L or more, and even more preferably 0.6 mol / L or more. Furthermore, from the viewpoint of being below the saturation solubility of the organic ligand, the concentration of the organic ligand in the aqueous solution of the organic ligand is preferably 0.9 mol / L or less. From the viewpoint of making this advantage even more significant, the concentration of the organic ligand in the aqueous solution of the organic ligand is more preferably 0.85 mol / L or less, and even more preferably 0.8 mol / L or less.

[0039] Aqueous solutions containing organic ligands can be prepared, for example, by dissolving a polybasic organic acid in water or a salt of a polybasic organic acid in water. In cases where the solubility of a polybasic organic acid is low, it becomes readily soluble, for example, by adding the acid to water with a pH adjusted to above 9 using an alkaline substance such as sodium hydroxide (in this case, the aqueous solution becomes an aqueous solution of a salt of the polybasic acid).

[0040] Depending on the type of polybasic acid or its salt, a water-soluble organic solvent may also be included in the aqueous solution containing the organic ligand. The water-soluble organic solvent is formulated to improve the solubility of the polybasic acid or its salt. Examples of water-soluble organic solvents include monohydric alcohols such as ethanol, methanol, and isopropanol; diols such as ethylene glycol, diethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, butanediol, and hexanediol; mono- or diethers of these diols with lower alcohols such as methanol, ethanol, propanol, and butanol; esters of these diols with lower fatty acids; and polyols such as glycerol and sorbitol. These water-soluble organic solvents can be used alone or in combination of two or more.

[0041] From the perspective of easily obtaining MOFs with high bulk density, it is preferable to simultaneously add an aqueous solution containing metal ions and an aqueous solution containing organic ligands to the reaction vessel. Examples of methods for simultaneously adding the two aqueous solutions to the reaction vessel include: supplying the aqueous solution containing metal ions and the aqueous solution containing organic ligands separately to a reaction vessel having a bottom and walls connected thereto; or supplying the aqueous solution containing metal ions from one end of a tubular reaction vessel and the aqueous solution containing organic ligands from the other end, allowing the two aqueous solutions to meet in a convective manner within the reaction vessel. From the viewpoint of MOF productivity and ease of reaction control, the method of separately supplying the aqueous solution containing metal ions and the aqueous solution containing organic ligands to a reaction vessel having a bottom and walls connected thereto is preferred.

[0042] From the perspective of easily obtaining MOFs with high bulk density, it is preferable to continuously add an aqueous solution containing metal ions and an aqueous solution containing organic ligands to the reaction vessel. In this specification, "continuous addition" includes not only the case of adding the two aqueous solutions without interruption, but also the case of adding the two aqueous solutions intermittently to a degree that can be considered continuous addition. For example, the case of intermittently adding the two aqueous solutions at intervals of up to 600 seconds is included in "continuous addition".

[0043] Preferably, the aqueous solutions containing metal ions and organic ligands are added in such a way that the molar number of metal ions in the aqueous solution containing metal ions and the molar number of organic ligands in the aqueous solution containing organic ligands achieve an approximate stoichiometric ratio to the target MOF.

[0044] The combination of metal ions and organic ligands used to manufacture MOFs can be appropriately selected according to the specific application of the MOF. Preferred combinations include, for example, combinations of six-coordinate metal ions such as aluminum, iron, chromium, zinc tetranuclear clusters, and cobalt ions with bidentate ligands such as dibasic organic acids, and combinations of four-coordinate metal ions such as copper and zinc ions with tridentate ligands such as ternary organic acids.

[0045] Specific combinations of metal ions and organic ligands include, for example, combinations where the metal ion is aluminum ion and the organic ligand is a dianion of fumaric acid. When using this combination, it is preferable to add 0.9 mol or more and 1.1 mol or less of the dianion of fumaric acid relative to 1 mole of aluminum ion, more preferably 0.95 mol or more and 1.05 mol or less, and even more preferably 0.98 mol or more and 1.03 mol or less.

[0046] When the metal ion is aluminum ion and the organic ligand is a dianion of terephthalic acid, it is preferable to add 0.9 moles or more and 1.1 moles of dianion of terephthalic acid relative to 1 mole of aluminum ion, more preferably 0.95 moles or more and 1.05 moles or less, and even more preferably 0.98 moles or more and 1.03 moles or less.

[0047] When the metal ion is iron(III) ion and the organic ligand is a dianion of terephthalic acid, it is preferable to add 0.9 moles or more and 1.1 moles of dianion of terephthalic acid relative to 1 mole of iron(III) ion, more preferably 0.95 moles or more and 1.05 moles or less, and even more preferably 0.98 moles or more and 1.03 moles or less.

[0048] When the metal ion is zinc(II) ion and the organic ligand is a dianion of fumaric acid, it is preferable to add 0.9 moles or more and 1.1 moles of the dianion of fumaric acid relative to 4 moles of zinc(II) ion, more preferably 0.95 moles or more and 1.05 moles or less, and even more preferably 0.98 moles or more and 1.03 moles or less.

[0049] The introduction of aqueous solutions containing metal ions and aqueous solutions containing organic ligands into the reaction vessel is preferably carried out in a manner that maintains the pH of the reaction solution at a specific value. For example, in the case of manufacturing MOFs composed of aluminum fumarate crystals, it is preferable to maintain the pH of the reaction solution at 3 or higher and 6 or lower, more preferably at 3 or higher and 5 or lower, and even more preferably at 3 or higher and 4.5 or lower. Furthermore, in the case of manufacturing MOFs composed of zinc fumarate crystals, it is preferable to maintain the pH of the reaction solution at 5 or higher and 9 or lower, more preferably at 6 or higher and 9 or lower, and even more preferably at 6.5 or higher and 8.5 or lower. Furthermore, in the case of manufacturing MOFs composed of aluminum terephthalate crystals, it is preferable to maintain the pH of the reaction solution at 3 or higher and 7 or lower, more preferably at 3.5 or higher and 7 or lower, and even more preferably at 3.5 or higher and 6 or lower. In addition, when manufacturing MOF composed of ferric terephthalate (III) crystals, it is preferable to maintain the pH of the reaction solution at 3 or higher and 7 or lower, more preferably at 4.5 or higher and 6.5 or lower, and even more preferably at 5 or higher and 6 or lower.

[0050] As mentioned above, this manufacturing method is continuous, which is advantageous from the perspective of easily maintaining a constant pH of the reaction solution. In contrast, in batch manufacturing methods, the pH of the reaction solution easily changes as the reaction proceeds, making it difficult to maintain the pH of the reaction solution at an optimal value from the start to the end of the reaction.

[0051] To ensure the pH of the reaction solution is within the preferred range described above, it is preferable to supply an alkaline compound such as sodium hydroxide to the reaction vessel simultaneously with the supply of metal ions and organic ligands. This can be achieved, for example, by containing an alkaline substance in the aqueous solution containing the organic ligands.

[0052] From the viewpoint of successfully obtaining the desired MOF by appropriately controlling the pH of the reaction solution, the molar ratio of the basic substance to the organic ligand supplied to the reaction vessel is preferably a specific value. For example, when the organic ligand is fumaric acid, the metal ion is aluminum ion, and the basic substance is sodium hydroxide, the molar ratio (basic substance / organic ligand) is preferably 2.5 or more and 4.5 or less, more preferably 2.6 or more and 4.4 or less, and even more preferably 2.7 or more and 3.8 or less. Furthermore, when the organic ligand is fumaric acid, the metal ion is zinc ion, and the basic substance is sodium hydroxide, the molar ratio (basic substance / organic ligand) is preferably 7 or more and 10 or less, more preferably 7.5 or more and 9.5 or less, and even more preferably 7.5 or more and 8.5 or less. Additionally, when the organic ligand is terephthalic acid, the metal ion is aluminum ion, and the basic substance is sodium hydroxide, the molar ratio (basic substance / organic ligand) is preferably 2.5 or more and 4 or less, more preferably 2.6 or more and 4 or less, and even more preferably 2.8 or more and 3.5 or less. Furthermore, when the organic ligand is terephthalic acid, the metal ion is iron(III) ion, and the basic substance is sodium hydroxide, the molar ratio (basic substance / organic ligand) is preferably 2 or more and 4 or less, more preferably 2.4 or more and 3.8 or less, and even more preferably 2.6 or more and 3.3 or less. It should be noted that the number of moles of the basic substance used to calculate the molar ratio (basic substance / organic ligand) also includes the number of moles of the basic substance required to neutralize the organic ligand.

[0053] Figure 2 schematically illustrates an example of a reaction apparatus suitable for this manufacturing method, but it is not limited to this example as long as it has the same four steps as the present invention. The reaction apparatus 10 shown in the figure is a crystallization apparatus of the type called a flow tube baffle (hereinafter also referred to as "DTB"). The reaction apparatus 10 includes a reaction vessel 13, which has a bottom 11 and a wall 12 connected to the bottom 11. A cylindrical flow tube 14 is disposed inside the reaction vessel 13. The flow tube 14 is disposed inside the reaction vessel 13 with its axial direction parallel to the depth direction of the reaction vessel 13. The cross-sectional shape of the flow tube 14 can be, for example, circular, elliptical, or polygonal. The flow tube 14 is open at both the upper and lower ends. The lower end 14a of the flow tube 14 is located at a predetermined distance from the bottom of the reaction vessel 13.

[0054] The reaction apparatus 10 includes a first supply pipe 15 for supplying an aqueous solution containing metal ions into the reaction vessel 13. Additionally, the reaction apparatus 10 includes a second supply pipe 16 for supplying an aqueous solution containing organic ligands into the reaction vessel 13. Both the first supply pipe 15 and the second supply pipe 16 are disposed inside the flow-through pipe 14. The lower ends 15a and 16 of both the first supply pipe 15 and the second supply pipe 16 are positioned above the lower end 14a of the flow-through pipe 14. The vicinity of the lower ends 15a and 16a of the first supply pipe 15 and the second supply pipe 16 corresponds to the aforementioned reactant introduction zone.

[0055] The reaction apparatus 10 is equipped with a liquid stirring mechanism. Examples of stirring mechanisms include stirring by rotating an impeller, stirring by circulating the liquid with a pump, and stirring by blowing in air bubbles. Figure 2 shows a stirring mechanism utilizing the rotation of an impeller 17. The impeller 17 is connected to the lower end of a drive shaft 18, and the upper end of the drive shaft 18 is connected to a drive source 19, such as an electric motor, located outside the reaction vessel 13. Driven by the drive source 19, the drive shaft 18 and the impeller 17 connected thereto rotate around the drive shaft, thereby generating downward or upward flow. The vicinity of the impeller 17 corresponds to the crystallization zone described above. In this case, from the viewpoint that coarse crystals can be easily obtained by increasing the number of cycles, the sum of the volumes of the reactant introduction zone and the crystallization zone of the reaction apparatus 10 is preferably 30% or less of the volume of the crystallization apparatus. From the viewpoint of making this advantage more significant, the sum of the volumes of the reactant introduction zone and the crystallization zone is preferably 10% or more and 30% or less of the volume of the crystallization device, more preferably 15% or more and 30% or less, and even more preferably 20% or more and 30% or less.

[0056] [Crystallization Process] In this process, the metal ions are reacted with the organic ligand by mixing the aqueous solution of the metal ions supplied to the reaction vessel to generate crystals of the target MOF. The reaction will be described with reference to Figure 2.

[0057] The reaction between the metal ions and the organic ligands in this process is preferably carried out in a manner that maintains the reaction product in a supersaturated state in the mixture of the two aqueous solutions. This results in a higher bulk density of the MOF as the reaction product. In this specification, "supersaturated state" refers to a state in which the concentration of the MOF as the reaction product in the reaction solution reaches a level higher than its saturation solubility.

[0058] In this manufacturing method, to achieve a supersaturated state in the MOF, a reaction apparatus 10 consisting of a DTB-type crystallization device as shown in Figure 2 is used. In Figure 2, in the reaction apparatus 10, an aqueous solution containing metal ions and an aqueous solution containing organic ligands are supplied to the flow tube 14 via a first supply tube 15 and a second supply tube 16 arranged within the flow tube 14. The two aqueous solutions mix to generate a reaction solution. At this time, by controlling the rotation direction of the impeller 17, the reaction solution within the flow tube 14 is made to flow downwards. The aforementioned supersaturation state easily occurs within the flow tube 14. It is particularly prone to occur between the lower ends 15a and 16a of the first and second supply tubes 15 and the impeller 17. The supersaturation state can occur locally or throughout the entire reaction solution.

[0059] When supplying the aqueous solution containing metal ions and the aqueous solution containing organic ligands into the reaction vessel 13, from the viewpoint of promoting the reaction, either or both of the two aqueous solutions can be supplied under heating. The heating temperature can be set to 40°C or higher, preferably 60°C or higher, and more preferably 70°C or higher. Alternatively, the heating temperature can be set to 95°C or lower, preferably 90°C or lower, and more preferably 85°C or lower.

[0060] Regardless of whether the aqueous solution containing metal ions and / or the aqueous solution containing organic ligands is heated, the reaction can be carried out in an open system, i.e., at atmospheric pressure. This is advantageous from the perspective of simplifying the reaction apparatus 10 and making the reaction easier to control. However, it is also acceptable to carry out this manufacturing method in a closed system, such as under autogenous pressure exceeding 1 atmosphere.

[0061] During the downward flow of the reaction solution through the flow tube 14, metal ions react with organic ligands to generate MOF crystal nuclei, and the crystals grow around these nuclei. The generated MOF crystals, along with the reaction solution, flow from the lower end 14a of the flow tube 14 towards the bottom 11 of the reaction vessel 13, colliding with the bottom 11, thereby changing the flow direction upward. The reaction solution containing MOF crystals flows upward along the outer surface of the flow tube 14, reaching the upper end 14b of the flow tube 14. The area generating this flow corresponds to the aforementioned circulation zone. The liquid circulating within the crystallization apparatus is an aqueous solution containing metal ions and an aqueous solution containing organic ligand ions, and further, a slurry in which the generated organometallic structures are suspended. These liquids are integrated and circulate within the crystallization apparatus. As described above, a downward flow occurs within the flow tube 14, therefore the reaction solution (containing MOF) reaching the upper end 14b of the flow tube 14 is introduced into the flow tube 14 and flows downward within it. As described above, an aqueous solution containing metal ions and an aqueous solution containing organic ligands are supplied in the flow tube 14 via the first supply tube 15 and the second supply tube 16. As a result, the MOF contained in the reaction solution reacts with the newly supplied metal ions and organic ligands, and the growth of MOF crystals and the aggregation of crystals together occur, and the particle size of MOF increases.

[0062] Thus, according to this manufacturing method, the reaction liquid circulates inside and outside the flow tube 14, thereby causing the formation of MOF nuclei and the growth of crystals to occur simultaneously and continuously. As a result, MOFs with a wide particle size distribution are generated, from large-diameter particles to small-diameter particles. In MOFs with a wide particle size distribution, small-diameter particles easily fill the spaces between large-diameter particles, resulting in a high bulk density. The degree of reaction liquid circulation can be controlled by the rotational speed of the impeller 17. Generally, the higher the rotational speed of the impeller 17, the higher the circulation speed of the reaction liquid. In addition, to ensure that the reaction liquid circulates along the vertical direction of the reaction vessel 13, it is preferable to adjust the volume of the reaction liquid so that the liquid level L is positioned higher than the upper end 14b of the flow tube 14.

[0063] From the viewpoint of successfully obtaining MOFs with a wide particle size distribution, in this process, it is preferable to adjust the nucleation rate of MOFs generated by the reaction of metal ions with organic ligands. From this viewpoint, the preferred nucleation rate of MOF crystals is 1 × 10⁻⁶. 5 pcs / (h·m) 3 ) or more, preferably 5×10 5 pcs / (h·m) 3 (above) , further preferably 1×10 6 pcs / (h·m) 3 The nucleation rate of MOF crystals is preferably 1 × 10⁻⁶. 16 pcs / (h·m) 3), More preferably, it is 5×10 15 pieces / (h·m 3 ), Further preferably, it is 1×10 14 pieces / (h·m 3 ). For example, by adjusting the rotation speed of the impeller 17, the diameter of the flow pipe 14, and the concentration and supply rate of the aqueous solution containing metal ions and the aqueous solution containing organic ligands, etc., the nucleation rate of the MOF crystals can be controlled.

[0064] The nucleation rate of the MOF crystals is measured by the following method. In a continuous crystallization device, it is known that if a steady state is achieved, the production rate P / ρcV′, the nucleation rate Fv′, the linear growth rate (dl / dθ) av , particle size and the particle size distribution m and the crystal suspension density (1-ε i ) satisfy the following relational expressions (Nippon Kagaku Kogyo Gijutsu Hokoku Creative, 1, No.5(2004) Website <URL:https: / / www.nippon-chem.co.jp / dcms_media / other / cre2004-2.pdf). In the following formula, V′ represents the device volume, ρ c represents the crystal density, k a represents the crystal surface shape factor, k v represents the crystal volume shape factor. m represents the gradient of the particle size distribution line of the point distribution in the Rosin-Rammler diagram, represents the particle size characteristic number when the product crystals are point-distributed in the Rosin-Rammler diagram.

[0065] [Mathematical formula 1]

[0066] Here, since there are 6 variables and 2 equations, the degree of freedom is 4. Therefore, if four of these variables can be measured actually, the remaining two variables can be calculated. The production rate P / ρcV′ can be measured actually based on the mass of the crystals obtained from the crystallization device. The particle size l and the particle size distribution m can be measured actually by observing the crystals with a microscope or by a particle size distribution measuring device. Regarding the suspension density (1-ε i ), the slurry in the crystallization device can be sampled, and the ratio of the volume of the slurry to the volume of the crystals can be measured actually. As a result, the nucleation rate and the linear growth rate can be measured equivalently to the measured values by these two formulas.

[0067] In this process, from the viewpoint of successfully obtaining MOFs with a wide particle size distribution, it is advantageous to control, or instead control, the linear growth rate of the MOF crystals, in addition to controlling the nucleation rate of the MOF crystals. From this viewpoint, the linear growth rate of the MOF crystals is preferably 1 μm / h or more, more preferably 10 μm / h or more, and even more preferably 80 μm / h or more. Furthermore, the linear growth rate of the MOF crystals is preferably 200 μm / h or less, more preferably 150 μm / h or less, and even more preferably 100 μm / h or less. For example, the linear growth rate of the MOF crystals can be controlled by adjusting the rotational speed of the impeller 17, the diameter of the flow tube 14, and the concentration and supply rate of the aqueous solution containing metal ions and the aqueous solution containing organic ligands.

[0068] The linear growth rate of MOF crystals can be determined using the same method as the determination of nucleation rate described above.

[0069] [Crystal Recovery Process] In this process, MOF crystals precipitated in the reaction solution are removed from the reaction vessel 13. The crystals are removed via an outlet pipe 20 provided in the reaction apparatus 10. One end of the outlet pipe 20 is located inside the reaction vessel 13, and the other end is located outside the reaction vessel 13. Although not shown, a pump and / or on / off valve for removing the reaction solution may be attached to the outlet pipe 20. The area where crystals are removed using the outlet pipe 20 corresponds to the recovery area described above. The MOF crystals contained in the reaction solution are extracted from the reaction vessel 13 along with the reaction solution through the outlet pipe 20. It is preferable to continuously or periodically extract the reaction solution containing MOF crystals. When extracting the reaction solution periodically, the extraction interval may be constant or variable. In either case, the extraction interval depends on the volume of the reaction vessel 13 and the production rate of MOF, but from the viewpoint of maintaining a constant volume of the crystallization apparatus, it is generally preferable to set it to 0.5 minutes or more and 10 minutes or less. From the viewpoint of making this advantage more significant, the interval for extracting the reaction solution is more preferably 1 minute or more and 5 minutes or less, and even more preferably 1 minute or more and 2 minutes or less.

[0070] The amount of reaction solution extracted is preferably controlled in a manner that stabilizes the MOF formation reaction within the reaction vessel 13. Specifically, it is preferable to extract the reaction solution in a manner that balances the amount of MOF generated within the reaction vessel 13 with the amount of MOF extracted from the outlet pipe 20.

[0071] To manufacture MOFs with large crystal sizes, it is advantageous to increase the number of times the crystals pass through the reaction solution introduction zone and the crystallization zone. The number of passes through the zone X [times / min] represents the discharge flow rate Q [m³] of the impeller 17. 3 / min] divided by the sum of the volumes of the reaction solution introduction zone A and the crystallization zone B, V[m3 The value obtained is X = Q / V (Equation 3). Each time the crystal passes through, it grows by a linear growth amount G [μm] corresponding to the supersaturation and residence time within the region. Multiplying this by the number of passes X yields the grain size L. total [μm / min]. L total =G×X (Equation 4) Particle size L total The particle size is proportional to the number of passes; therefore, the longer the overall residence time of the crystallization apparatus, the larger the particle size. However, nucleation also occurs during crystal growth, thus widening the crystal size distribution. The overall average crystal size of the apparatus is not necessarily related to the overall residence time. In summary, the longer the overall residence time of the apparatus, the easier it is to obtain coarse crystals, and therefore, the longer the overall residence time of the apparatus, the wider the particle size distribution.

[0072] Thus, from the viewpoint of successfully obtaining MOFs with a wide particle size distribution, controlling the residence time of the reaction solution during extraction is also advantageous. From this viewpoint, it is preferable to extract MOF crystals from the reaction vessel 13 with a residence time of at least 3 minutes in the crystallization apparatus, including the reactant introduction zone, crystallization zone, circulation zone, and recovery zone; particularly preferably, with a residence time of at least 5 minutes, especially at least 10 minutes. Similarly, from the same viewpoint, it is preferable to extract MOF crystals from the reaction vessel 13 with a residence time of 30 minutes or less; particularly preferably, with a residence time of 25 minutes or less, especially at least 20 minutes. In the MOF reaction, the overall residence time of the apparatus is determined by dividing the sum of the flow rates of the metal component and the organic ligand component in the complex decomposition reaction by the overall volume of the apparatus.

[0073] [Cleaning Process] The MOF crystals extracted from reaction vessel 13 are subjected to a cleaning process as needed. The cleaning process primarily involves washing with water. For example, the reaction solution containing MOF crystals can be extracted from reaction vessel 13 and filtered to separate it from water using a Buchner funnel or similar method, thereby obtaining a cake-like MOF crystal. This crystal is then further washed with water to remove impurities. Alternatively, the MOF crystals can be cleaned by washing. Another method may be a cleaning method using a hydrocyclone separator.

[0074] In particular, it is advantageous to reduce the amount of cleaning solution by applying the following continuous cleaning method to the organometallic structure manufactured by the above method. This continuous cleaning method includes a cleaning step of cleaning the organometallic structure with a cleaning solution to remove counter anions used to dissolve the metal ions constituting the organometallic structure and counter cations used to dissolve the organic ligands. Examples of the cleaning solution include water and mixtures of water and water-soluble organic solvents. Examples of water-soluble organic solvents include water-soluble lower aliphatic alcohols. Preferably, aliphatic monohydric alcohols with 1 or more but less than 4 carbon atoms are used; specifically, methanol, ethanol, and isopropanol are examples.

[0075] The aforementioned cleaning process preferably includes a first cleaning process, a solid-liquid separation process, and a second cleaning process. In these processes, it is preferable to separate the liquid from the first cleaning process into solid and liquid components in the solid-liquid separation process, further clean the solid components in the second cleaning process, and use the liquid components as part of the cleaning solution in the first cleaning process. Thus, as described above, the amount of cleaning solution can be reduced. In particular, by repeatedly performing the cleaning process and the solid-liquid separation process, and using the liquid components obtained in the solid-liquid separation process as part of the cleaning solution in the previous stage of the cleaning process, the amount of cleaning solution can be further reduced. There are no particular limitations on the method for separating the solid and liquid components in the solid-liquid separation process. For example, using centrifugal force for solid-liquid separation can effectively separate the solid and liquid components.

[0076] [MOFs obtained by this manufacturing method] MOFs obtained by this manufacturing method typically have the general formula ML x A y The compositional formula is shown above. In the above general formula, M represents a metal ion, L represents an organic ligand, and A represents an anion other than the organic ligand represented by L. Details of M and L are as described above. The combination of M and L can be appropriately selected according to the specific application of the MOF. For example, a dianion of fumaric acid or terephthalic acid can be selected as M, and aluminum ions, zinc ions, or iron(III) ions can be selected as L. In the above general formula, the anion represented by A is selected from hydroxide ions, sulfate ions, chloride ions, and oxide ions (O). 2- One or more of the following.

[0077] In the above general formula, x represents the number of moles of organic ligand L per mole of metal ion M1. For example, when M is an aluminum ion or an iron(III) ion and L is a dianion of fumaric acid or a dianion of terephthalic acid, x is preferably 0.85 or more and 1.15 or less, more preferably 0.88 or more and 1.12 or less, and even more preferably 0.9 or more and 1.1 or less. Furthermore, when M is a zinc ion and L is a dianion of terephthalic acid, x is preferably 0.6 or more and 0.9 or less, more preferably 0.65 or more and 0.85 or less, and even more preferably 0.7 or more and 0.8 or less. Additionally, when M is a zinc ion and L is a dianion of fumaric acid, x is preferably 0.20 or more and 0.30 or less, more preferably 0.22 or more and 0.28 or less, even more preferably 0.23 or more and 0.27 or less, and particularly preferably 0.24 or more and 0.26 or less.

[0078] In the above general formula, y represents the number of moles of anion A per mole of metal ion M. For example, when M is aluminum ion, L is a dianion of fumaric acid or terephthalic acid, and A is hydroxide ion, y is preferably 0.7 or more and 1.2 or less, more preferably 0.8 or more and 1.2 or less, and even more preferably 0.9 or more and 1.1 or less. Furthermore, when M is iron(III) ion, L is a dianion of fumaric acid or terephthalic acid, and A is hydroxide ion, y is preferably 0.8 or more and 1.2 or less, more preferably 0.88 or more and 1.12 or less, and even more preferably 0.9 or more and 1.1 or less. Furthermore, when M is a zinc ion, L is a dianion of terephthalic acid, and A is an oxide ion, if x is set to 3 / 4, then y is preferably 0.20 or more and 0.30 or less, more preferably 0.22 or more and 0.28 or less, even more preferably 0.23 or more and 0.27 or less, and particularly preferably 0.24 or more and 0.26 or less. Additionally, when M is a zinc ion, L is a dianion of fumaric acid, and A is a hydroxide ion and an oxide ion, the MOF has the composition ZnL... x (OH) y1 O y2 (Where L represents the dianion of fumaric acid). In this case, if x is set to 1 / 4, then y1 is preferably 0.8 or more and 1.2 or less, more preferably 0.88 or more and 1.15 or less, and even more preferably 0.9 or more and 1.1 or less. Furthermore, y2 is preferably 0.20 or more and 0.30 or less, more preferably 0.22 or more and 0.28 or less, even more preferably 0.23 or more and 0.27 or less, and particularly preferably 0.24 or more and 0.26 or less.

[0079] According to this manufacturing method, MOFs with a wide particle size distribution ranging from large to small particle size and high crystallinity can be easily obtained. The wide particle size distribution of MOFs obtained by this manufacturing method can be confirmed not only by measurement using a particle size distribution measuring device but also by tap density. When evaluating the particle size distribution of MOFs by tap density, a higher tap density indicates a wider particle size distribution. Tap density refers to the mass per unit volume of a sample when the volume change disappears after the naturally falling powder is filled into a container and subjected to vibration. It can be measured according to JIS K 5101-12-2:2004. Specifically, tap density can be measured, for example, using a DUALAUTOTAP (manufactured by Yuasa Ionics). The preferred tap density of MOFs measured by this method is 0.3 g / cm³. 3 Above and 0.9g / cm 3 The following is more preferably 0.4 g / cm³. 3 Above and 0.9g / cm 3 The following is a further preferred value: 0.5 g / cm³ 3 Above and 0.8g / cm 3 The following is a further preferred value: 0.6 g / cm³ 3 Above and 0.7g / cm 3 Therefore, the MOF obtained by this manufacturing method has a high tap density, and thus, when used as an adsorbent for, for example, carbon dioxide, the amount of carbon dioxide adsorbed per unit volume of the adsorbent is high.

[0080] The MOF obtained by this manufacturing method has a wide particle size distribution and a large average particle size. Specifically, the average particle size of the MOF obtained by this manufacturing method is preferably 10 μm or more and 150 μm or less, more preferably 20 μm or more and 100 μm or less, and even more preferably 30 μm or more and 100 μm or less. The average particle size of the MOF is determined by the following method. As in this invention, when the number of particles of MOF with a particle size of 1 μm or more is dominant, the particle size distribution can be determined by image analysis using a Keyence optical microscope VHX-7000. Furthermore, it can also be measured using a Horiba Manufacturing Co., Ltd. laser scattering particle size distribution measuring device LA-960. Since the evaluation criteria are different, it is impossible to compare the absolute values ​​of the particle size, but the particle size can be evaluated without problems using the average particle size measured by the same method. In any case, in addition to the so-called average particle size (region diameter), if the Risin-Rammler particle size characteristic number L is determined in advance... The slope m is useful for calculating the nucleation rate and the linear growth rate.

[0081] Furthermore, the MOF obtained by this manufacturing method also possesses the characteristic of having a large average particle size but a large BET specific surface area. Specifically, the BET specific surface area of ​​the MOF obtained by this manufacturing method is preferably 740 m². 2 / g or more and 1200m 2 / g or less, preferably 800m 2 / g or more and 1150m 2 / g or less, more preferably 900m 2 / g or more and 1150m 2 The BET specific surface area of ​​MOFs was determined by the following method: 10-20 mg of sample was introduced into the testing container and kept at 573 K for 1 hour under vacuum to remove adsorbed substances such as water. After creating a vacuum of 77 K inside the testing container, nitrogen gas was slowly introduced into the container, causing the nitrogen to be adsorbed onto the MOF. The amount of nitrogen adsorbed onto the MOF was measured, followed by depressurization of the container to measure the amount of nitrogen desorbed. This study investigated the relationship between nitrogen adsorption and desorption and pressure changes, and thus determined the BET specific surface area.

[0082] Furthermore, the MOFs obtained by this manufacturing method exhibit high crystallinity. Specifically, the crystallinity of the MOFs obtained by this manufacturing method shows high values ​​such as 100% or more, particularly 150% or more, and especially 200% or more. The crystallinity of the MOFs is determined by the following method: The MOFs are analyzed by powder X-ray diffraction, and the height of the highest peak, i.e., the first peak, appearing around 2θ = 10° is determined. For commercially available MOFs manufactured by Sigma-Aldrich (CAS No.: 1370461-06-5), the ratio of the height of the same peak can be calculated, and the crystallinity is determined by setting the reference height as 100%. In addition, due to the high crystallinity, even after repeated water adsorption and desorption, the MOFs obtained by this manufacturing method show little change in the angle of the diffraction peaks observed by XRD, and at the same time, the change in the height of the diffraction peaks is also small.

[0083] [Gas Adsorbent Material] The MOF obtained by this manufacturing method is suitable for use as a gas adsorbent material, for example. Therefore, the present invention provides the use of the MOF obtained by this manufacturing method as a gas adsorbent material. In particular, the present invention provides the use of an organometallic structure composed of aluminum fumarate crystals with a tap density of 0.3 g / mL or more and 0.9 g / mL or less as a gas adsorbent material.

[0084] Gas adsorbent materials are, for example, granules composed of a mixture of MOF (Metal-Oxide-Foil) as a gas adsorption component and phenolic resin as a shape-maintaining component. Preferably, the gas adsorbent material comprises: a step A of mixing MOF with thermosetting phenolic resin to obtain a mixture; a step B of adding water to the mixture and performing rolling granulation to obtain granules; a step C of separating the granules grown to a predetermined particle size according to particle size; and a step D of feeding the granules that are smaller than the predetermined particle size back into the granulation step, and heating the granules that have reached the predetermined particle size at a first temperature to remove the water, and further heating them to a second temperature to cure the thermosetting phenolic resin.

[0085] There are no particular restrictions on the type of thermosetting phenolic resin used in step A; any thermosetting phenolic resin known to date can be used. If water is added in step B, it acts as a coagulant, causing the granules to grow in a snowball-like fashion during rolling granulation, thus achieving highly efficient granulation. From this perspective, it is preferable to add water after micronization. To micronize the water, a mist-generating device such as a sprayer can be used, for example. In step C, a sieving operation can be performed, for example, to separate the granules according to their particle size. The first temperature used in step D can be any temperature sufficient to remove the water contained in the granules; for example, it can be set to 80°C or higher and 130°C or lower. The second temperature used to cure the thermosetting phenolic resin is higher than the first temperature, and depending on the type of thermosetting phenolic resin, it can typically be set to 130°C or higher and 200°C or lower.

[0086] To ensure the gas adsorbent material obtained in this way possesses sufficient strength for practical use, its compressive strength is preferably 20 N or more, more preferably 30 N or more, and even more preferably 50 N or more. Similarly, the rotational strength of the gas adsorbent material when evaluated using a rolling device is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. The compressive strength of the gas adsorbent material is determined according to the Japan Powder Industry Association Standard G001, Method for Determination of Compressive Strength of Granulated Materials (=JIS Z 8841:1993). The rotational strength of the gas adsorbent material is determined according to the Japan Powder Industry Association Standard G002, Method for Determination of Rotational Strength of Granulated Materials (=JIS Z 8841:1993).

[0087] The present invention has been described above based on preferred embodiments, but the present invention is not limited to the above embodiments. For example, in the above embodiments, the reaction liquid in the flow tube 14 is given a downward flow by the rotation of the impeller 17 to cause the reaction, but it is also possible to give the reaction liquid in the flow tube 14 an upward flow instead to cause the reaction. Examples

[0088] The present invention will now be described in more detail through embodiments. However, the scope of the present invention is not limited to these embodiments.

[0089] [Example 1] In this example, a MOF composed of aluminum fumarate was continuously manufactured using the reaction apparatus 10 shown in Figure 2. Aluminum sulfate was dissolved in water to obtain an aqueous solution of aluminum sulfate with a pH of 3.1 and a concentration of 0.8 mol / L. Separately, fumaric acid and three molar amounts of sodium hydroxide were dissolved in water to obtain an aqueous solution of fumaric acid with a pH of 14.1 and a concentration of 0.75 mol / L. The aqueous solutions of aluminum sulfate and fumaric acid were simultaneously and continuously supplied to a 3.3 L reaction vessel 13. The supply rate of the aqueous solution of aluminum sulfate was 0.07 L / min. The supply rate of the aqueous solution of fumaric acid was 0.15 L / min. The liquid temperatures of both the aqueous solutions of aluminum sulfate and fumaric acid were set to 80 °C. The pH of the reaction solution was 3.6, which remained essentially constant. The reaction between aluminum ions and fumarate ions was controlled by the rotational speed of the impeller 17. The nucleation rate and linear growth rate measured by the above method are shown in Table 1 below. The MOF generated in reaction vessel 13 is continuously extracted from the reaction vessel 13 through outlet pipe 20 along with the reaction liquid. At this time, the extraction rate of MOF is adjusted to be equal to the amount of MOF generated in reaction vessel 13. The residence time of the reaction liquid, determined by the above method, is shown in Table 2 below. Other conditions are shown in Table 2. Furthermore, the tap density, average particle size, BET specific surface area, and crystallinity of the obtained MOF are determined by the above method. These results are shown in Table 2 below. Optical microscope photographs of the obtained MOF crystals are shown in Figures 3(a) and (b). The crystals are translucent, with slightly uneven surfaces on small-diameter crystals. The overall shape is an ellipsoid with rounded edges, but it is approximated as spherical when calculating the volume shape factor and surface area shape factor using the above method. Regarding the production rate P / ρcV', the mass of the MOF crystals obtained from the crystallization device is measured and calculated from the crystal density and the volume of the crystallization device. Particle size l and particle size distribution m were determined by observing the crystals under a microscope or by measuring the particle size distribution using a particle size distribution measuring device. Regarding the suspension density (1-ε) iThe slurry in the crystallization apparatus was sampled, and the volume ratio of slurry to crystals was measured. The nucleation rate and linear growth rate were calculated using Equations 1 and 2, and are shown in Table 1. Table 1 records the experimental results with varying conditions. Experiments 1-3 represent the results with a reaction vessel volume of 3.3 L and various changes in residence time; Experiments 4-9 represent the results with a reaction vessel volume of 10 L and various changes in residence time. In Experiments 8 and 9, the concentrations of fumaric acid and aluminum sulfate were varied. The sum of the volumes of the reactant introduction zone and the crystallization zone in Experiments 1-3 was 18% of the volume of the crystallization apparatus. Furthermore, the sum of the volumes of the reactant introduction zone and the crystallization zone in Experiments 4-9 was 25% of the volume of the crystallization apparatus. Table 2 summarizes the results of Table 1. The values ​​in Table 2 are averages from Experiments 1-9.

[0090] [Example 2] In this example, a MOF composed of aluminum terephthalate was continuously manufactured using the reaction apparatus 10 shown in FIG. 2. Aluminum sulfate was dissolved in water to obtain an aqueous solution of aluminum sulfate with a pH of 3.1 and a concentration of 0.8 mol / L. Terephthalic acid and sodium hydroxide were dissolved in water to obtain an aqueous solution of terephthalic acid with a pH of 14.2 and a concentration of 0.75 mol / L. The aqueous solutions of aluminum sulfate and terephthalic acid were simultaneously and continuously supplied to a 10 L reaction vessel 13. The supply rate of the aluminum sulfate aqueous solution was 0.21 L / min. The supply rate of the fumaric acid aqueous solution was 0.45 L / min. The liquid temperatures of both the aluminum sulfate and terephthalic acid aqueous solutions were set to 80 °C. The pH of the reaction solution was 5.8, which remained essentially constant. The reaction between aluminum ions and terephthalate ions was controlled by the rotational speed of the impeller 17. The nucleation rate and linear growth rate measured by the above method are shown in Table 1 below. The MOF generated in the reaction vessel 13 is continuously extracted from the reaction liquid through the outlet pipe 20 and out of the reaction vessel 13. During this process, the amount of MOF extracted is balanced with the amount of MOF generated in the reaction vessel 13, and fine adjustments are made to maintain a constant liquid level in the crystallization apparatus. The residence time of the reaction liquid, measured by the above method, is shown in Table 2 below. The tap density, average particle size, BET specific surface area, and crystallinity of the MOF obtained by the above method are also shown in Table 2 below. In this embodiment, the sum of the volumes of the reactant introduction zone and the crystallization zone is 25% of the volume of the crystallization apparatus.

[0091] [Example 3] In this example, a MOF composed of zinc fumarate was continuously manufactured using the reaction apparatus 10 shown in Figure 2. Zinc sulfate was dissolved in water to obtain a zinc chloride aqueous solution with a pH of 4.1 and a concentration of 0.4 mol / L. Additionally, fumaric acid and 8 moles of sodium hydroxide were dissolved in water to obtain a fumaric acid aqueous solution with a pH of 12.6 and a concentration of 0.1 mol / L. The zinc chloride aqueous solution and the fumaric acid aqueous solution were simultaneously and continuously supplied to a 10 L reaction vessel 13. The supply rate of the zinc chloride aqueous solution was 0.3 L / min. The supply rate of the fumaric acid aqueous solution was 0.3 L / min. The liquid temperatures of both the zinc chloride and fumaric acid aqueous solutions were set to 80 °C. The pH of the reaction solution was 7.5, which remained essentially constant. The reaction between zinc ions and fumarate ions was controlled by the rotational speed of the impeller 17. The nucleation rate and linear growth rate measured by the above method are shown in Table 2 below. The MOF generated in the reaction vessel 13 is continuously extracted from the reaction vessel 13 through the outlet pipe 20 along with the reaction liquid. At this time, the extraction rate of MOF is adjusted to be equal to the amount of MOF generated in the reaction vessel 13. The residence time of the reaction liquid, measured by the above method, is shown in Table 2 below. The tap density, average particle size, BET specific surface area, and crystallinity of the MOF obtained by the above method are measured. These results are shown in Table 2 below. In this embodiment, the sum of the volumes of the reactant introduction zone and the crystallization zone is 25% of the volume of the crystallization device.

[0092] [Reference Example 1] In this reference example, MOF composed of aluminum fumarate was produced in an intermittent manner. Aluminum sulfate was dissolved in water to obtain an aqueous solution of aluminum sulfate with a pH of 3 and a concentration of 0.32 mol / L. Separately, fumaric acid and sodium hydroxide were dissolved in water to obtain an aqueous solution of fumaric acid with a pH of 14 and a concentration of 0.63 mol / L. 1 L of the aluminum sulfate aqueous solution was added to a 3.3 L reaction vessel and stirred with a stirring blade. 1.1 L of the fumaric acid aqueous solution was added over 1 hour. The temperature of both the aluminum sulfate and fumaric acid aqueous solutions was set to 80 °C. After the addition was complete, the reaction solution was further stirred with an impeller to generate MOF. The reaction time was set to 1 hour. The pH of the reaction solution was 3 at the beginning of the reaction and 3.6 at the end of the reaction. The tap density, average particle size, BET specific surface area, and crystallinity of the obtained MOF were measured using the above method. These results are shown in Table 2 below.

[0093]

[0094]

[0095] As shown in Tables 1 and 2, the MOFs obtained in each example have high tap density, large average particle size, high BET specific surface area, and high crystallinity. Additionally, a MOF with high tap density was also obtained in Reference Example 1 using a batch reaction, but the residence time of the reaction solution was long, requiring a long synthesis time for the MOF.

[0096] [Example 4] An experiment was conducted to granulate the MOF obtained in Example 1 to prepare a gas adsorbent material. A mixture was prepared by mixing an MOF composed of aluminum fumarate and a thermosetting phenolic resin (Bellpearl S890 manufactured by Air Water-Performance Chemicals). The addition rate of the thermosetting phenolic resin in the mixture is shown in Table 3. Next, the mixture was placed in a 70 cm diameter granulator for mixing, and a small amount of water was added to the mixture using a spray gun for slow granulation. The granules were sieved, and granules reaching the specified particle size were removed; granules with a smaller particle size were returned to the mixture. Granules with a diameter of 3 mm were heated at a first temperature to remove water, and further heated to a second temperature to cure the thermosetting phenolic resin. The compressive strength and rotational strength of the obtained spherical granules were measured according to Japanese Industrial Standards JIS Z 8841:1993 and JIS Z 8841:1993. The results are shown in Table 3. In addition, based on the gas adsorption method, the nitrogen adsorption-desorption capacity of the obtained spherical granules at 77 K and the carbon dioxide adsorption capacity at 20 °C were determined. The nitrogen adsorption-desorption capacity was determined using a BELSOAP MAX instrument manufactured by BEL Corporation of Japan. The carbon dioxide adsorption capacity at 20 °C was determined using an iSORB instrument manufactured by Anton Paar. These results are shown in Figures 4 and 5. Furthermore, for comparison, Figure 5 also shows the carbon dioxide adsorption capacity of the MOF prepared in Example 1.

[0097] As shown in Figure 4, the nitrogen adsorption-desorption curves of the spherical granules in Example 4 show typical Type IV characteristics according to the IUPAC classification. Figure 5 shows the CO2 adsorption capacity of the MOF of Example 1 and the spherical granules of Example 4 at 20°C. These MOFs and spherical granules exhibit high adsorption capacities from 0 bar to 2 bar, and also high adsorption capacities in the pressure range above 2 bar. Such isothermal adsorption characteristics make them particularly suitable materials for PSA (Pressure Swing Adsorption Separator) and also suitable for TSA (Temperature Swing Adsorption Separator). Furthermore, the characteristic that the adsorption capacity increases above 6 bar suggests that they can also be used as CO2 storage materials. In addition, as shown in Figure 5, the CO2 adsorption capacity of the spherical granules in Example 4 is reduced by about 5% compared to the CO2 adsorption capacity of the MOF in Example 1, and the reduction is to the same extent as the amount of thermosetting phenolic resin added when manufacturing the spherical granules in Example 4.

[0098] [Example 5] The addition rate of thermosetting phenolic resin in Example 4 was set as shown in Table 3. Otherwise, spherical granules were obtained in the same manner as in Example 4. The obtained spherical granules were subjected to the same measurements as in Example 4. The results are shown in Table 3.

[0099] [Examples 6 and 7] The addition rate of thermosetting phenolic resin in Example 4 was set as shown in Table 3. Additionally, the particle diameter was set as shown in the table. Otherwise, spherical granules were obtained in the same manner as in Example 4. The obtained spherical granules were subjected to the same measurements as in Example 4. The results are shown in Table 3.

[0100] [Comparative Example 2] Granulated bodies were manufactured by extrusion molding. Specifically, in MOF composed of aluminum fumarate (tap density: 0.33 g / cm³), granules were produced. 3 A small amount of kaolin and carbon powder as a lubricant were added to the mixture (with an average particle size of 10.2 μm), and the mixture was extruded through a hole with a diameter of about 3 mm and cut into granules with a length of 3-4 mm to produce granules. The obtained granules were subjected to the same measurements as in Example 4. The results are shown in Table 3.

[0101]

[0102] As shown in Table 3, the granules obtained in each embodiment have practically sufficient strength.

[0103] [Example 8] Using the continuous cleaning apparatus shown in FIG6, counterions (sodium sulfate) in MOF crystals extracted from reaction vessel 13 shown in FIG2 were washed with water. In the first cleaning step 41, a slurry containing MOF crystals extracted from reaction vessel 13 and cleaning water from the second cleaning step were added and stirred. Then, the slurry from the first cleaning step was pumped to hydrocyclone 31 via pump 30, and a slurry containing large-diameter particles and mother liquor was pumped to the second cleaning step 42. In the second cleaning step 42, cleaning water (pure water) was added and stirred. The slurry was pumped to hydrocyclone 34 via pump 33, and the large-diameter particles and mother liquor were removed as products. The particles and mother liquor were then recycled to the second washing step 42. The obtained MOF crystals were placed in pure water, and the conductivity of the liquid was measured to determine the amount of impurities. A conductivity of 20 mS / m or less was used as a reference. As a result, the required amount of cleaning solution was 500 kg, which is 50% of the amount of water used for cleaning by filtration or rinsing, achieving the same cleaning effect.

[0104] [Comparative Example 3] The counterion of MOF crystals extracted from reaction vessel 13 shown in Figure 2, here sodium sulfate, was washed using a washing process. 200 kg of pure water was added to 25 kg of slurry containing MOF crystals, and the mixture was stirred and then allowed to stand for approximately 2 hours. The crystals settled, separating into a crystal layer and a clear mother liquor. Only the clear mother liquor was removed using a pump, and another 200 kg of pure water was added and stirred. The impurity level of the crystals was determined by measuring conductivity. This process was repeated until a specified impurity level was reached, specifically, until the conductivity reached 20 mS / m or less. This process was repeated 5 times until the conductivity reached 20 mS / m or less. Therefore, the amount of pure water used for washing was 1000 kg. Industrial Applicability

[0105] According to the present invention, MOFs with high crystallinity and high bulk density can be easily manufactured.

Claims

1. An organometallic structure comprising a crystal containing an organic ligand and metal ions, wherein, The organic ligand is a dianion of fumaric acid or a dianion of terephthalic acid, the metal ion is an aluminum ion, a zinc ion or an iron (III) ion, and the tap density of the organometallic structure is above 0.3 g / mL and below 0.9 g / mL.

2. The organometallic structure according to claim 1, wherein, The crystal is aluminum fumarate.

3. A gas adsorbent material comprising a granulated mixture of an organometallic structure as a gas adsorption component and a phenolic resin as a shape-maintaining component.

4. The gas adsorption material according to claim 3, wherein the compressive strength is 20 N or more, and the rotational strength when evaluated using a rolling device is 3% or less.

5. A method for manufacturing a metal-organic structure, comprising a method for manufacturing an organometallic structure using a crystallization device having a reactant introduction zone, a crystallization zone, a circulation zone, and a recovery zone, wherein, In the reactant introduction zone, an aqueous solution containing metal ions and an aqueous solution containing organic ligands capable of coordinating with the metal ions are simultaneously and continuously added from different nozzles provided in the flow path. They are immediately mixed using a mixing mechanism. In the crystallization zone, the metal ions react with the organic ligands to grow crystals of the metal-organic structure and generate crystal nuclei of the metal-organic structure. In the circulation zone, the slurry containing the crystals of the metal-organic structure is circulated to the reactant introduction process. In the recovery zone, a portion of the slurry is continuously or periodically extracted.

6. The manufacturing method according to claim 5, wherein, With the nucleation rate of the crystal being 1×10⁻⁶, 5 pcs / (h·m) 3 ) or more and 1×10 16 pcs / (h·m) 3 The two aqueous solutions are added in the following manner.

7. The manufacturing method according to claim 5 or 6, wherein, The two aqueous solutions are added at a linear growth rate of 1 μm / h or higher and 200 μm / h or lower than that of the crystal.

8. The manufacturing method according to claim 5 or 6, wherein, The crystals are extracted from the crystallization device in such a manner that the residence time of the crystallization device, including the entire reactant introduction zone, the crystallization zone, the circulation zone, and the recovery zone, is more than 3 minutes and less than 30 minutes.

9. The manufacturing method according to claim 5 or 6, wherein, The crystallization device is a flow-through baffle type crystallization device.

10. The manufacturing method according to claim 9, wherein, In the flow tube baffle type crystallization device, the sum of the volumes of the reactant introduction zone and the crystallization zone is less than 30% of the volume of the crystallization device.

11. The manufacturing method according to claim 5 or 6, wherein, The metal ion is an aluminum ion, and the organic ligand is a dianion of fumaric acid. More than 0.9 moles and less than 1.1 moles of the dianion of fumaric acid are added relative to 1 mole of the aluminum ion.

12. The manufacturing method according to claim 5 or 6, wherein, The metal ion is an aluminum ion, and the organic ligand is a dianion of terephthalic acid. Relative to 1 mole of the aluminum ion, 0.9 moles and 1.1 moles of the dianion of terephthalic acid are added.

13. The manufacturing method according to claim 5 or 6, wherein, The metal ion is an iron (III) ion, the organic ligand is a dianion of terephthalic acid, and 0.9 moles and 1.1 moles of the dianion of terephthalic acid are added relative to 1 mole of the iron (III) ion.

14. The manufacturing method according to claim 5 or 6, wherein, The metal ion is zinc(II) ion, the organic ligand is a dianion of fumaric acid, and 0.9 moles and 1.1 moles of the dianion of fumaric acid are added relative to 4 moles of the zinc(II) ion.

15. A continuous cleaning method for an organometallic structure, wherein the organometallic structure is manufactured using the method of claim 5, wherein... The continuous cleaning method includes a cleaning step in which the organometallic structure is cleaned with a cleaning solution to remove counter anions for dissolving the metal ions constituting the organometallic structure and counter cations for dissolving the organic ligands. The cleaning step includes a first cleaning step, a solid-liquid separation step, and a second cleaning step. In the solid-liquid separation step, the liquid that has passed through the first cleaning step is separated into solid components and liquid components. In the second cleaning step, the solid components are further cleaned, and the liquid components are used as part of the cleaning solution in the first cleaning step.

16. The continuous cleaning method according to claim 15, wherein, In the solid-liquid separation process, centrifugal force is used for solid-liquid separation.

17. A method for manufacturing a gas adsorbent material, comprising: a step of mixing the organometallic structure manufactured by the method of claim 5 with a thermosetting phenolic resin to obtain a mixture; a step of adding water to the mixture and performing rolling granulation to obtain granules; a step of separating the granules grown to a predetermined particle size according to the particle size; and a step of feeding the granules with a particle size smaller than the predetermined particle size back to the granulation step, and heating the granules that have reached the predetermined particle size at a first temperature to remove the water, and further heating them to a second temperature to cure the thermosetting phenolic resin.

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