Method for producing molded article comprising metal organic framework

Abstract

To provide a molded article on which a metal-organic framework is firmly supported.SOLUTION: The production method disclosed herein includes a first preparation step (S10) of obtaining a first slurry by mixing a metal ion source and a fiber material containing a site crosslinkable with a metal ion contained in the metal ion source, a second preparation step (S20) of obtaining a second slurry in which a metal-organic framework containing the metal ion and the organic ligand contained in the organic ligand source is disposed around the fiber material by mixing the first slurry and an organic ligand source, and a shaping step (S30) of obtaining a shaped product in which the metal-organic framework is supported on a substrate composed of the fiber material by shaping the second slurry.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a molded body having a metal-organic framework. [Background technology]

[0002] In recent years, active research has been conducted on metal organic frameworks (MOFs) as materials for use in gas storage and separation, deodorization, air and water purification, and other applications. Metal organic frameworks have a lattice structure consisting of metal ions and organic ligands, and have extremely large specific surface areas and pore volumes. Furthermore, by changing the types of metal ions and organic ligands, as well as their synthesis conditions, a wide variety of structural designs are possible for metal organic frameworks. For this reason, they are expected to be used in a wide range of fields.

[0003] For example, Patent Document 1 discloses a sheet-like molded body including a substrate containing a fibrous material and a metal-organic framework (porous metal complex) supported on the substrate. Patent Document 1 describes the production of a sheet-like molded body by a wet papermaking method including the following steps: mixing the metal-organic framework, the fibrous material, and an organic binder in a solvent to prepare a slurry; making the slurry in a papermaking machine to mold a wet paper; and dehydrating and drying the wet paper. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-154302 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the investigations of the present inventors, a metal-organic framework has the problem that it is likely to fall off from the substrate unless it is firmly supported (fixed) on the substrate.

[0006] The present invention has been made in view of the above points, and a main object of the present invention is to provide a molded body in which a metal organic framework is firmly supported on a substrate containing a fibrous material. [Means for solving the problem]

[0007] The present invention provides a method for producing a molded article comprising a substrate containing a fibrous material and a metal-organic framework containing metal ions and an organic ligand and supported on the substrate. The method includes a first preparation step of mixing, in a solvent, a metal ion source and a fibrous material containing a moiety crosslinkable with the metal ions contained in the metal ion source to obtain a first slurry, a second preparation step of mixing the first slurry with an organic ligand source to obtain a second slurry in which a metal-organic framework containing the metal ions and the organic ligand contained in the organic ligand source is disposed around the fibrous material, and a molding step of molding the second slurry to obtain a molded article in which the metal-organic framework is supported on a substrate made of the fibrous material.

[0008] According to the present invention, the metal organic framework can be supported relatively more firmly on the fiber material compared to the method of producing a molded body by separately preparing the metal organic framework and the fiber material as in, for example, Patent Document 1. Therefore, the integrity of the substrate (fiber material) and the metal organic framework can be improved, and the metal organic framework can be prevented from falling off from the substrate. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a molded article in which the metal-organic framework is firmly supported on the substrate and is unlikely to fall off from the substrate. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a flowchart showing a method for producing a molded body according to one embodiment. [Figure 2] FIG. 2(A) is a schematic diagram of the first slurry after the first preparation step, and FIG. 2(B) is a schematic diagram of the second slurry after the second preparation step. [Figure 3]FIG. 3(A) is a perspective view of an adsorption filter according to one embodiment, and FIG. 3(B) is a front view of the adsorption filter according to one embodiment. [Figure 4] FIG. 4 shows photographs of the evaluation results for the comparative example and the example. [Figure 5] FIG. 5 is a graph showing the evaluation results for the comparative example and the example. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a molded body according to one embodiment of the present invention will be described with reference to the drawings. It should be noted that the embodiment described here is not intended to limit the present invention in any way. Furthermore, the same reference numerals are used to designate components and parts that perform the same function, and redundant explanations will be omitted or simplified as appropriate. Furthermore, in this specification, the expression "X to Y" (X and Y are arbitrary numerical values) indicating a range means not only X or greater but also Y or less, and also encompasses the meanings of "greater than X" and "smaller than Y."

[0012] <Method of manufacturing molded body> The manufacturing method disclosed herein is a method for manufacturing a molded article including a substrate (hereinafter sometimes simply referred to as "substrate") containing a fibrous material and a metal-organic framework supported on the substrate. The metal-organic framework essentially contains metal ions and organic ligands. The metal-organic framework is typically a porous metal complex having a highly regular lattice structure (a porous three-dimensional structure) composed of metal ions and organic ligands and having a plurality of pores capable of accommodating specific molecules. The metal-organic framework may be composed of metal ions and organic ligands, or may further contain other structural moieties, such as an inorganic structural moiety (inorganic chain). The metal-organic framework is preferably a fluorinated metal-organic framework containing elemental fluorine. In this specification, the term "metal-organic framework" is synonymous with a porous coordination polymer (PCP) or a porous metal complex.

[0013] FIG. 1 is a flowchart showing a manufacturing method according to this embodiment. As shown in FIG. 1, the manufacturing method according to this embodiment includes a first preparation step (step S10), a second preparation step (step S20), and a molding step (step S30) in this order. The manufacturing method disclosed herein may further include other steps at any stage. As shown in FIG. 1, it is preferable to perform the first preparation step (step S10) through the molding step (step S30) continuously in-line (in-situ). This can improve productivity and work efficiency.

[0014] The first preparation step (S10) is a step of mixing a metal ion source and a fiber material in a solvent to obtain a first slurry. When the metal ion source is in a powder, sol, gel, or other form, it is preferably dissolved in the solvent in advance. The fiber material is preferably dispersed in the solvent in advance. Therefore, in this embodiment, this step includes an initial solution preparation step (step S11) of mixing the metal ion source with the solvent to prepare an initial solution, a first raw solution preparation step (step S12) of mixing the fiber material with the solvent to prepare a first raw solution, and a first slurry preparation step (step S13) of mixing the initial solution containing the metal ion source with the first raw solution containing the fiber material to obtain a first slurry. The order of the initial solution preparation step (step S11) and the first raw solution preparation step (step S12) is not particularly limited. Furthermore, this step may include other steps at any stage.

[0015] In the initial solution preparation step (step S11), an initial solution is prepared by mixing a metal ion source and a solvent. The order of addition is not particularly limited, but in this embodiment, as shown in FIG. 1, the metal ion source is first added to a reaction vessel, and then the solvent is added to the reaction vessel and mixed. For mixing, a conventionally known stirring and mixing device such as a magnetic stirrer, a planetary mixer, or a disperser can be used as appropriate. Mixing is preferably carried out until the initial solution becomes homogeneous. The temperature environment for this step is preferably 10°C or higher, more preferably 20°C or higher, from the viewpoint of increasing the solubility of the metal ion source, etc. On the other hand, from the viewpoint of suppressing the evaporation of the solvent, etc., the temperature is preferably 40°C or lower, more preferably 30°C or lower.

[0016] The metal ion source is a compound containing at least the metal ions that constitute the metal organic framework. As the metal ion source, one or more types of metal ion sources that have been known to be usable for this type of application can be appropriately used. The metal ion source is typically a metal salt. The metal ion source may contain a metal ion and an anion (preferably an anion containing fluorine) that constitutes the inorganic structural portion of the molded body.

[0017] The metal ions bond with organic ligands in the second preparation step (step S20) described below to form the lattice structure of the metal-organic framework. There are no particular limitations on the metal ions, and depending on, for example, the type of organic ligand used and the molecules to be captured by the molded body, one or more types of metal ions that have been known to be usable for this type of application can be used as appropriate. While not particularly limited, the metal ions are preferably ions of metals belonging to Groups 1 to 14 of the periodic table, such as alkali metals, alkaline earth metals, transition metals, noble metals, and rare earth metals. The metal ions are preferably ions of metals belonging to Periods 4 or 5 of the periodic table.

[0018] Suitable examples of metals (and typical ionic forms) that make up the metal ions include potassium (K + ), magnesium (Mg 2+ ), calcium (Ca 2+ ), strontium (Sr 2+ ), scandium (Sc 3+ ), yttrium (Y 3+ ), Titanium (Ti 4+ ), zirconium (Zr 4+ ), vanadium (V 2+ , V 3+ , V 4+ , V 5+ ), chromium (Cr 3+ , Cr 6+ ), tungsten (W 6+ ), molybdenum (Mo 3+ , Mo 6+ ), manganese (Mn 2+ ), iron (Fe 2+, Fe 3+ ), cobalt (Co 2+ , Co 3+ ), Nickel (Ni 2+ , Ni 3+ ), copper (Cu 2+ ), silver (Ag + ), zinc (Zn 2+ ), cadmium (Cd 2+ ), aluminum (Al 3+ ), Gallium (Ga 3+ ), indium (In 3+ ), tin (Sn 2+ Sn 4+ ) and the like. Among these, the metal ions preferably contain ions of transition metals with a valence of 2 to 4, and more preferably contain Cu ions. These metals tend to bond strongly to the fibrous material in the first slurry. In addition, because the complex formation rate is high, the lattice structure of the metal-organic framework can be favorably grown around the fibrous material in the second preparation step (step S20) described below.

[0019] The solvent is typically water, but may also be a mixed solvent mainly composed of water. The solvent other than water constituting the mixed solvent may be an organic solvent that is uniformly miscible with water, such as a lower alcohol such as methanol, ethanol, or propanol, or a lower ketone. Purified water such as ion-exchanged water, distilled water, ultrafiltered water, or reverse osmosis water can be suitably used as the water, from the viewpoint of preventing the incorporation of impurities.

[0020] The initial solution is a solution in which at least the metal ions of the metal ion source are dissolved in a solvent. For example, when the metal ion source is Cu(BF4)2 and the solvent is water, the initial solution contains Cu as the metal ions. 2+ and tetrafluoroborate ([BF4]) as the anion of the inorganic structural part. - ) is dissolved in water as a solvent. Although not particularly limited, the concentration of metal ions in the initial solution is preferably 0.1 to 1 mol / L, more preferably 0.1 to 0.5 mol / L, and even more preferably 0.1 to 0.12 mol / L.

[0021] In the first raw solution preparation step (step S12), a fiber material is mixed with a solvent to prepare a first raw solution. The first raw solution is typically a dispersion liquid in which the fiber material is dispersed in a solvent. For mixing, a conventional stirring and mixing device such as that described above can be used as appropriate. Mixing is preferably carried out until the first raw solution becomes homogeneous. The temperature environment for this step is preferably 10°C or higher, more preferably 20°C or higher. On the other hand, from the viewpoint of suppressing evaporation of the solvent, it is preferably 40°C or lower, more preferably 30°C or lower. As the solvent, one or more of the media exemplified as those usable for the initial liquid can be used as appropriate. The solvent may be the same as or different from the initial liquid. The solvent is typically water.

[0022] The fibrous material constitutes the substrate portion of the molded body. In the technology disclosed herein, at least a portion of the fibrous material has a site capable of crosslinking (bonding) with a metal ion. This allows the metal-organic framework to be firmly supported on the fibrous material (substrate). The site capable of crosslinking with a metal ion (hereinafter simply referred to as a "crosslinkable site") is typically a functional group. Suitable examples of the crosslinkable site include functional groups containing at least one of a hydroxyl group and a nitrogen atom, preferably functional groups having nucleophilicity, such as a hydroxy group (-OH), a carboxy group (-C(=O)OH), an amide group (-C(=O)NH), an amino group (-NH-, -NH2), and an amide bond (e.g., -C(=O)-NH-). Among these, amino groups and amide bonds, which are functional groups containing a nitrogen atom, are preferred. This facilitates strong bonding with the metal ions described above in the first slurry.

[0023] The fiber material may be composed solely of a fiber material having crosslinkable moieties (first fiber material), or may further contain a fiber material not having crosslinkable moieties (second fiber material) in addition to the first fiber material. From the viewpoint of achieving a high level of effectiveness of the technology disclosed herein, it is preferable that the fiber material be composed primarily of the first fiber material (a component accounting for 50% or more by mass; the same applies below). In particular, when the total of the first fiber material and the second fiber material is taken as 100% by mass, the proportion of the first fiber material is preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably substantially all of the first fiber material (95% by mass or more of the first fiber material).

[0024] The first fiber material is not particularly limited as long as it has crosslinkable moieties, and one or more materials known to be useful for this type of application can be used as appropriate. The first fiber material preferably contains organic fibers because it has many crosslinkable moieties. The first fiber material is preferably composed primarily of organic fibers. The first fiber material may be composed of organic fibers. The first organic fibers may be natural fibers or chemically synthesized chemical fibers (artificial fibers). Examples of natural fibers include plant fibers such as pulp fibers, animal fibers, and mineral fibers. Chemical fibers may be recycled fibers, semi-synthetic fibers, or synthetic fibers. Examples of chemical fibers include aramid fibers, cellulose fibers, polyester fibers, polyethylene fibers, polypropylene fibers, acrylic fibers, rayon fibers, polyamide fibers, polyimide fibers, and polylactic acid fibers. Among these, at least one of aramid fibers and cellulose fibers is preferred from the viewpoints of durability, versatility, and availability, and aramid fibers containing nitrogen atoms are more preferred from the viewpoint of achieving the effects of the technology disclosed herein at a higher level.

[0025] However, the first fiber material may be an inorganic fiber as long as it has a crosslinkable site. Examples of inorganic fibers include glass fiber, metal fiber, ceramic fiber, and carbon fiber.

[0026] Although not particularly limited, the average length of the fiber material is typically preferably 0.01 μm to 30 mm. The average diameter of the fiber material is typically preferably 1 nm to 0.1 mm. The aspect ratio of the fiber material (ratio of average length to average diameter (average length / average diameter)) is preferably approximately 10 or more, for example, 100 or more, 1000 or more. The average length and average diameter can be number average values ​​of multiple fiber materials obtained by measurements based on electron microscope observation.

[0027] In the first slurry preparation step (step S13), the initial liquid prepared in the initial liquid preparation step (step S11) and the first raw solution prepared in the first raw solution preparation step (step S12) are mixed to obtain a first slurry. In this embodiment, the first raw solution is added to a reaction vessel containing the initial liquid and mixed. In this step, from the viewpoint of sufficiently fixing the metal ions to the fiber material, it is preferable to stir the mixed liquid in the reaction vessel for a predetermined time. For stirring and mixing, a conventionally known stirring and mixing device such as those described above can be appropriately used. The temperature environment in this step is preferably the same as or higher than that in the initial liquid preparation step (step S11), for example, preferably 10°C or higher, and more preferably 20°C or higher. On the other hand, from the viewpoint of suppressing evaporation of the solvent, it is preferably 40°C or lower, more preferably 30°C or lower. It is preferable to stir and mix until the first slurry becomes homogeneous. The stirring and mixing time is not particularly limited because it may vary depending on, for example, the concentration of metal ions in the first slurry, but is preferably 10 minutes or more, more preferably 30 minutes, from the viewpoint of sufficiently fixing the metal ions to the fiber material, while from the viewpoints of productivity, working efficiency, etc., it is preferably 120 minutes or less, more preferably 60 minutes or less.

[0028] Fig. 2(A) is a schematic diagram of a first slurry. As shown in Fig. 2(A), the first slurry contains at least metal ions and a fibrous material. The fibrous material contains sites (crosslinkable sites) that can crosslink with the metal ions. Therefore, in the first slurry, the metal ions are captured by the crosslinkable sites of the fibrous material, and at least some of the metal ions are fixed (bonded) to the crosslinkable sites.

[0029] The second preparation step (step S20) is a step of mixing the first slurry prepared in the first preparation step (step S10) with an organic ligand source to obtain a second slurry. When the organic ligand source is in a powder, sol, gel, or other form, it is preferable to dissolve it in a solvent beforehand. Therefore, in this embodiment, this step includes a second raw material solution preparation step (step S21) of mixing the organic ligand source with a solvent to prepare a second raw material solution, and a second slurry preparation step (step S22) of mixing the first slurry containing metal ions and a fibrous material with the second raw material solution containing the organic ligand source to obtain a second slurry. Note that this step may further include other steps at any stage.

[0030] In the second raw solution preparation step (step S21), an organic ligand source and a solvent are mixed to prepare a second raw solution. A conventional stirring and mixing device such as that described above can be used as appropriate for mixing. Mixing is preferably carried out until the second raw solution becomes homogeneous. The temperature environment in this step is preferably 10°C or higher, more preferably 20°C or higher, from the viewpoint of increasing the solubility of the organic ligand source. On the other hand, from the viewpoint of suppressing solvent evaporation, it is preferably 40°C or lower, more preferably 30°C or lower. One or more of the media exemplified as those usable in the initial liquid can be used as the solvent, as appropriate. The solvent is preferably one that can dissolve the organic ligand source. The solvent is typically an organic solvent (e.g., a lower alcohol). The solvent may be the same as or different from the initial liquid or first raw solution of the first slurry. The solvent is preferably compatible with the first slurry to be mixed.

[0031] The organic ligand source contains at least an organic ligand that constitutes the metal organic framework. As the organic ligand source, one or more organic ligands that have been known to be usable for this type of application can be appropriately used.

[0032] The organic ligand is an organic compound that has two or more sites capable of forming a coordinate bond with a metal ion within its molecule and that forms a lattice structure of a metal-organic framework by bonding with the metal ion in the second slurry preparation step (step S22) described below. The organic ligand is not particularly limited, and depending on, for example, the type of metal ion and the molecule to be captured, one or more compounds known to be useful for this type of application, such as aromatic compounds, aliphatic compounds, alicyclic compounds, and heterocyclic compounds, can be appropriately used. Specific examples of organic ligands include pyridines, pyrazines, pyrimidines, triazines, pyrazoles, imidazoles, triazoles, tetrazoles, dicarboxylic acids, tricarboxylic acids, and derivatives thereof. Among these, basic compounds are preferred. Because metal ions are typically electron acceptors, the use of a basic compound, which is an electron donor, allows the lattice structure of the metal-organic framework to grow favorably in the second slurry preparation step.

[0033] The organic ligand is preferably an aromatic compound, more preferably an aromatic compound composed of the elements C, H, and N, and particularly preferably a heterocyclic aromatic compound containing one or two nitrogen atoms in the aromatic ring. For example, pyridines (pyridine and bipyridine) having a pyridine skeleton and pyrazines (e.g., pyrazine) having a pyrazine skeleton are preferred. A specific example is 4,4'-bipyridine. These compounds have a nitrogen atom with a lone electron pair that can donate to a metal ion, contributing to good compatibility and favorable growth of the metal-organic framework. Therefore, metal-organic frameworks synthesized using these organic ligands exhibit good adsorption properties.

[0034] The second raw material solution is a solution in which an organic ligand of the organic ligand source is dissolved in a solvent. For example, when the organic ligand is a pyridine (e.g., 4,4'-bipyridine) and the solvent is an alcohol (e.g., ethanol), the second raw material solution is a solution in which the pyridine as the organic ligand is dissolved in the alcohol as the solvent. The concentration of the organic ligand in the second raw material solution is not particularly limited because it may vary depending on, for example, the concentration of the metal ion in the first slurry, but is preferably 0.1 to 2 mol / L, more preferably 0.5 to 1.5 mol / L, and even more preferably 0.9 to 1 mol / L.

[0035] In the second slurry preparation step (step S22), the first slurry prepared in the first slurry preparation step (step S13) and the second raw solution prepared in the second raw solution preparation step (step S21) are mixed to obtain a second slurry. In this embodiment, a second raw solution containing an organic ligand source is added to a reaction vessel containing the first slurry and mixed. In this step, the mixed solution in the reaction vessel is preferably stirred for a predetermined period of time. For stirring and mixing, a conventionally known stirring and mixing device such as those described above can be used as appropriate. The temperature environment in this step is preferably the same as or higher than that in the first slurry preparation step (step S13), for example, preferably 10°C or higher, and more preferably 20°C or higher. On the other hand, from the viewpoint of suppressing solvent evaporation, a temperature of 40°C or lower is preferably 40°C or lower, and more preferably 30°C or lower. Stirring and mixing is preferably performed until the second slurry becomes homogeneous. The stirring and mixing time is not particularly limited as it may vary depending on, for example, the type of metal-organic framework to be produced, but is preferably 1 hour or higher, and more preferably 10 hours or higher. On the other hand, from the viewpoint of productivity and work efficiency, 48 hours or less is preferable, and 24 hours or less is more preferable.

[0036] The second slurry may further contain various additives known to be useful for this type of application, as long as they do not significantly impair the effects of the technology disclosed herein. One or more additives known to be useful for this type of application may be used as appropriate to improve various properties of the molded body, such as mechanical strength and durability. Specific examples of additives include inorganic additives such as inorganic fillers and inorganic binders, and organic additives such as antioxidants, dispersants, flocculants, preservatives, stabilizers, and colorants (pigments, dyes, etc.). The proportion of these additives is preferably 10% by mass or less, more preferably 5% by mass or less, 3% by mass or less, 2% by mass or less, or 1% by mass or less, based on 100% by mass of the entire second slurry.

[0037] The second slurry preferably does not contain an organic binder, such as that described in Patent Document 1. This makes it difficult for the structural change of the structurally flexible metal-organic framework to be inhibited, and the structural flexibility can be favorably maintained, allowing the performance of the compact (for example, adsorption performance when used as an adsorbent) to be maximized. In this specification, "does not contain" means that the proportion in the second slurry is approximately 1% by mass or less, preferably 0.1% by mass or less.

[0038] FIG. 2(B) is a schematic diagram of the second slurry. As described above, the first slurry contains a complex in which metal ions are fixed (bonded) to the crosslinkable sites of the fibrous material. The second raw material solution contains organic ligands. As shown in FIG. 2(B), the organic ligands bond with the metal ions to form a lattice structure of the metal organic framework. As a result, a metal organic framework containing the metal ions and the organic ligands is generated from the second slurry and disposed around the fibrous material. In this embodiment, the metal organic framework contains copper ions (Cu 2+ ) as an organic ligand, and tetrafluoroboric acid ([BF4] - ) and can be a compound represented by the formula: Cu(bpy)(BF4)2(H2O)2bpy; where bpy is 4,4'-bipyridine.

[0039] The forming step (step S30) is a step of forming the second slurry prepared in the second preparation step (step S20) to obtain a formed body in which the metal-organic framework is supported on a substrate made of a fibrous material. In this embodiment, this is a step of forming the second slurry into a sheet by a wet papermaking method. This forms a sheet-like formed body. The wet papermaking method can achieve a more uniform sheet-like formed body. This step can be performed, for example, using a conventionally known papermaking machine. In this embodiment, this step includes a papermaking step (step S31) and a drying step (step S32). Note that this step may further include other steps at any stage. For example, a washing step may be included before, during, or after the dehydration step (step S31).

[0040] In the dewatering step (step S31), the solvent contained in the second slurry is roughly removed, and the solid content in the second slurry is made into a sheet (molded). In one example, a papermaking machine is used to first make paper by filtration and perform primary dewatering. The papermaking and filtration conditions may be the same as conventional. In the drying step (S32), the solvent is further removed from the wet paper obtained in the dewatering step (step S31). It is preferable to perform solvent removal in multiple stages. For example, dewatering by pressing may be performed, followed by drying. The pressing and drying methods and conditions are not particularly limited and may be the same as conventional. The drying temperature is preferably determined taking into account the boiling point of the solvent contained in the second slurry. For example, if the solvent contains water and alcohol, a temperature of 50°C or higher is preferable, and 70°C or higher is more preferable.

[0041] By removing the solvent in this step, a molded article can be obtained in which a metal-organic framework is supported on a substrate containing a fiber material. In the molded article produced in this embodiment, the metal-organic framework is firmly fixed to the substrate via the crosslinkable moieties of the fiber material. By being provided with the metal-organic framework, the molded article of this embodiment has the function of selectively capturing desired components from, for example, a fluid composition or the environment, and can be suitably used as an adsorbent, occlusion material, separation material, etc. The molded article of this embodiment can be suitably used, for example, in a gas adsorption device or gas separation device that adsorbs and separates specific gas components from a mixed gas.

[0042] The sheet-like molded article obtained above can be further molded into various shapes such as corrugated, honeycomb, slit, pleated, roll, etc., and used for various applications. By processing the sheet-like molded article into the above shapes, the contact area per unit volume with the object to be separated (for example, gas) can be increased, and the performance of the molded article can be further improved.

[0043] FIG. 3(A) is a perspective view of the adsorption filter 100, and FIG. 3(B) is a front view of the adsorption filter 100. The adsorption filter 100 is configured to include the sheet-like molded article obtained above. As shown in FIG. 3(A), the adsorption filter 100 has a cylindrical outer shape in this embodiment. However, the outer shape of the adsorption filter 100 is not limited to a cylindrical shape and can have various shapes in other embodiments. As shown in FIG. 3(B), the adsorption filter 100 includes a molded article 10 obtained by molding the above-mentioned sheet-like molded article into a corrugated (wave-shaped) or pleated shape. The adsorption filter 100 can be used, for example, to purify exhaust gases emitted from engines of motorcycles, generators, etc.

[0044] In the manufacturing method disclosed herein, first, in a first preparation step, a first slurry containing metal ions and a fibrous material containing crosslinkable moieties is prepared. As a result, the metal ions are fixed (bonded) to the crosslinkable moieties, for example, as shown in FIG. 2(A). Next, in a second preparation step, an organic ligand is added, causing a lattice structure of the metal-organic framework to grow around the fibrous material, for example, as shown in FIG. 2(B). This allows the metal-organic framework to be more firmly supported on the fibrous material (substrate). This improves the integrity between the fibrous material and the metal-organic framework, and prevents the metal-organic framework from falling off the fibrous material (substrate). Furthermore, since the metal-organic framework can be more firmly supported on the substrate, it is possible to eliminate the use of an organic binder or reduce the amount of organic binder used.

[0045] In this embodiment, a sheet-like compact is formed in the molding process. This allows for a thinner and lighter compact than, for example, a pellet-like compact or an extrusion-molded compact, and also ensures a larger surface area. Furthermore, since the sheet can be easily molded into various shapes, the range of applications and shapes can be expanded.

[0046] In this embodiment, the steps from the first preparation step to the molding step are carried out in-line. For example, in the second preparation step, the organic ligand source is added to the first slurry and mixed. This reduces the labor and improves productivity and work efficiency compared to, for example, a case where the first slurry is shipped out of the production line or transported to a separate facility.

[0047] In the present embodiment, in the forming step, the second slurry is formed into a sheet by a wet papermaking method, which not only improves productivity and work efficiency but also makes it possible to realize a more uniform sheet-like formed body.

[0048] In this embodiment, in the first preparation step, a fiber material having a functional group containing at least one of a hydroxyl group and a nitrogen atom as a site crosslinkable with the metal ion is used. For example, at least one of aramid fiber and cellulose fiber is used as the fiber material. This makes it easier for the metal ions of the metal-organic framework to bond strongly to the fiber material (substrate), and the metal-organic framework can be more firmly supported on the substrate.

[0049] In this embodiment, in the first preparation step, a metal ion source containing at least one of K, Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Cr, W, Mo, Mn, Fe, Co, Ni, Cu, Ag, Zn, Cd, Al, Ga, In, and Sn is used as the metal ions. For example, a metal ion source containing ions of transition metals with a valence of 2 to 4 is used as the metal ions. For example, a metal ion source containing Cu ions is used. These metals tend to bond strongly to the fibrous material in the first slurry. Furthermore, due to their high complex formation rate, the lattice structure of the metal-organic framework can be favorably grown in the second preparation step.

[0050] In this embodiment, in the second preparation step, an organic ligand source containing a basic compound is used as the organic ligand. Because metal ions are typically electron acceptors, by using a basic compound that is an electron donor, the lattice structure of the metal-organic framework can be favorably grown in the second slurry preparation step.

[0051] In this embodiment, the second preparation step uses an organic ligand source containing 4,4'-bipyridine as the organic ligand. Compounds containing a nitrogen atom, such as 4,4'-bipyridine, have a lone pair of electrons that can be donated to metal ions, contributing to good compatibility and favorable growth of the metal-organic framework. Therefore, the metal-organic framework synthesized using these organic ligands exhibits good adsorption properties.

[0052] In this embodiment, in the second preparation step, the second slurry does not contain an organic binder. This makes it difficult for the structural change of the structurally flexible metal-organic framework to be inhibited, and the structural flexibility can be favorably maintained, allowing the performance of the compact (e.g., adsorption performance when used as an adsorbent) to be maximized. Furthermore, since the surface of the metal-organic framework is not covered with the organic binder, the contact area between the target of separation (e.g., gas) and the metal-organic framework can be increased, allowing the performance of the compact (e.g., adsorption performance when used as an adsorbent) to be better exhibited.

[0053] In this embodiment, in the forming step, the sheet-like compact is further formed into a corrugated, honeycomb, slit, pleated, or roll shape, which increases the contact area per unit volume with the target of separation (e.g., gas), thereby enabling the compact to exhibit better performance.

[0054] Examples of the present invention will be described below, but it is not intended that the present invention be limited to those shown in these examples.

[0055] Comparative Example In this comparative example, a metal-organic framework was first synthesized and then mixed with a fiber material to produce a molded body. Specifically, 5.04 g of an aqueous solution of Cu(BF4)2 as a metal ion source was added to a reaction vessel, followed by 73.82 g of purified water and stirring and mixing for 10 minutes. Next, 2.99 g of 4,4'-bipyridine as an organic ligand source was added to a separate vessel, followed by 19.15 g of ethanol as a solvent and stirring and mixing for 10 minutes. Next, an organic ligand source prepared in a separate vessel was added to the reaction vessel containing the metal ion source, followed by stirring and mixing for 60 minutes to obtain a mixed solution. This allowed the metal-organic framework to be precipitated and generated from the mixed solution in advance.

[0056] Next, 1.4 g of aramid fiber as a fiber material and 500 g of water were added to a separate container and stirred and mixed for 5 minutes to prepare a slurry. This slurry was then added to a reaction vessel containing the metal-organic framework and stirred and mixed for 24 hours. The resulting slurry was then sheeted using a wet papermaking method. Specifically, the slurry after stirring and mixing for 24 hours was first suction filtered and made into a sheet (molded), then dehydrated using a press and further dried on a hot plate at 80°C for 30 minutes. This resulted in a sheet-like molded product.

[0057] <Example> In the example, as shown in Figure 1, a metal ion source and a fiber material were first mixed, and then an organic ligand source was added to produce a molded body. Specifically, 5.04 g of an aqueous solution of Cu(BF4)2 as a metal ion source was first added to a reaction vessel, and 73.82 g of purified water was added thereto and stirred and mixed for 10 minutes. This prepared an initial solution. Next, 1.4 g of aramid fiber as a fiber material and 500 g of water were added to a separate container and stirred and mixed for 5 minutes to prepare a first raw material solution. Next, the first raw material solution prepared in a separate container was added to the reaction vessel containing the metal ion source and stirred and mixed for 60 minutes to obtain a first slurry (first preparation step). This allowed the metal ions to be fixed (bonded) to the crosslinkable sites of the fiber material.

[0058] Next, 2.99 g of 4,4'-bipyridine as an organic ligand source was added to a separate container, and 19.15 g of ethanol as a solvent was added thereto and stirred and mixed for 10 minutes to prepare a second raw material solution. Next, the second raw material solution prepared in a separate container was added to the reaction vessel containing the first slurry, and stirred and mixed for 24 hours to obtain a second slurry (second preparation step). As a result, a metal-organic framework was precipitated and generated around the fibrous material. The obtained slurry was then sheeted by a wet papermaking method as in the comparative example to obtain a sheet-like molded product (molding step).

[0059] <Evaluation of Durability> The molded bodies of the Comparative Example and the Example were evaluated for the fixability (resistance to falling off) of the metal-organic framework to the substrate by the following procedure. That is, first, the weight of the molded body was measured using an electronic balance to obtain the weight before the test. Next, the molded bodies of the Comparative Example and the Example were separately placed in beakers containing 50 ml of ethanol, and these beakers were placed in the bath of an ultrasonic cleaner. Note that a Bransonic tabletop ultrasonic cleaner (model: Bransonic (trademark) CPX5800-J, ultrasonic output: 160 W, oscillation frequency: 40 kHz) was used as the ultrasonic cleaner. Then, after 10 minutes of ultrasonic treatment, the beaker was removed.

[0060] Figure 4 shows photographs of the evaluation results for the Comparative Example and the Example. As shown in Figure 4, in the beaker of the Comparative Example, the ethanol solution became very cloudy after ultrasonic treatment, and it was observed that the metal-organic framework had fallen off the substrate. On the other hand, in the beaker of the Example, the turbidity was relatively small even after ultrasonic treatment, and it was observed that the metal-organic framework had firmly adhered to the substrate.

[0061] The molded body was then removed from the beaker and placed on filter paper on a hot plate for approximately 20 minutes to dry. The weight of the dried molded body was then measured using an electronic balance to obtain the post-test weight. The results are shown in Table 1 and Figure 5.

[0062] [Table 1]

[0063] In Table 1 and Fig. 5, the change in weight before and after the test is considered to represent the amount of metal organic framework that fell off from the molded body. As shown in Table 1 and Fig. 5, in the Examples, the change in weight was relatively small compared to the Comparative Examples, and the amount of metal organic framework that fell off was small. This suggests that the metal organic framework was relatively firmly supported (fixed) on the substrate. These results demonstrate the significance of the technology disclosed herein.

[0064] Although the preferred embodiments of the present invention have been described above, the above-described embodiments are merely examples, and the present invention can be embodied in various other forms. [Explanation of symbols]

[0065] 10 Molded body 100 Adsorption Filter S10 1st preparation step S20 2nd preparation process S30 Molding process

Claims

1. A method for producing a molded article comprising: a substrate containing a fibrous material; and a metal organic framework supported on the substrate, the metal organic framework comprising a metal ion and an organic ligand, the method comprising: a first preparation step of mixing a metal ion source and a fibrous material containing a site capable of crosslinking with the metal ions contained in the metal ion source in a solvent to obtain a first slurry; a second preparation step of mixing the first slurry with an organic ligand source to obtain a second slurry in which a metal-organic framework including the metal ions and the organic ligands contained in the organic ligand source is disposed around the fibrous material; a molding step of molding the second slurry to obtain a molded body in which the metal organic framework is supported on a substrate made of the fibrous material; A method for producing a molded body, comprising:

2. In the molding step, a sheet-like molded body is molded. The method of claim 1.

3. The steps from the first preparation step to the molding step are carried out in-line. The method according to claim 1 or 2.

4. In the second preparation step, the organic ligand source is added to the first slurry and mixed. The method of claim 3.

5. In the forming step, the second slurry is formed into a sheet by a wet papermaking method. The method of claim 3.

6. In the first preparation step, a fiber material having a functional group containing at least one of a hydroxyl group and a nitrogen atom as a site capable of crosslinking with the metal ion is used. The method according to claim 1 or 2.

7. In the first preparation step, at least one of aramid fibers and cellulose fibers is used as the fiber material. The method of claim 6.

8. In the first preparation step, a metal ion source containing at least one of K, Mg, Ca, Sr, Sc, Y, Ti, Zr, V, Cr, W, Mo, Mn, Fe, Co, Ni, Cu, Ag, Zn, Cd, Al, Ga, In, and Sn is used as the metal ion. The method according to claim 1 or 2.

9. In the first preparation step, a metal ion source containing ions of a transition metal having a valence of 2 to 4 is used as the metal ions. The method according to claim 1 or 2.

10. In the first preparation step, a metal ion source containing Cu ions is used. The method according to claim 1 or 2.

11. In the second preparation step, an organic ligand source containing a basic compound is used as the organic ligand. The method according to claim 1 or 2.

12. In the second preparation step, an organic ligand source containing 4,4′-bipyridine is used as the organic ligand. The method according to claim 1 or 2.

13. In the second preparation step, the second slurry does not contain an organic binder. The method according to claim 1 or 2.

14. In the forming step, the sheet-like formed body is further formed into a corrugated shape, a honeycomb shape, a slit shape, a pleated shape, or a roll shape. The method of claim 2.

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