Composite of cellulose and metal-organic framework, and method for producing same

Abstract

To provide a composite carrying a large amount of metal organic framework (MOF) which is barely eliminated and has sufficient hardness, and a production method for the same.SOLUTION: A composite includes cellulose and a metal organic framework, in which the amount of the metal organic framework carried after ultrasonic cleaning operation of the composite is 4-60 wt.%. There is also provided a production method for the composite.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a composite of cellulose and a metal-organic framework, and a method for producing the same. [Background technology]

[0002] Cellulose has the molecular formula (C6H 10 O5) n Cellulose is a natural polymer composed of many β-glucose molecules polymerized in a linear chain via glycosidic bonds. Unlike synthetic polymers derived from petroleum, it is naturally occurring and biodegradable, making it an environmentally friendly material. Furthermore, cellulose possesses various characteristics not found in synthetic polymers. These characteristics include (i) its relative chemical stability and low solubility in various solvents, (ii) its heat resistance, preventing decomposition and melting even at relatively high temperatures, (iii) its hydrophilic and lipophilic properties, (iv) its low emission of harmful substances upon combustion, (v) its ability to be molded into various shapes by dissolving in special solvents, (vi) its ability to be functionalized through chemical reactions utilizing its hydroxyl groups, (vii) its low toxicity to the human body, and (viii) its low interaction with proteins and other substances.

[0003] Furthermore, cellulose that has been dissolved and regenerated is called regenerated cellulose, and not only can it be molded into any shape, but it can also have a microporous void structure inside the structure. Taking advantage of these characteristics, natural cellulose and regenerated cellulose are used in a variety of forms and for a variety of purposes, including various fibers, nonwoven fabrics, packaging films, excipients, artificial kidneys, filters, and cell culture substrates. Furthermore, in recent years, cellulose nanofibers have been studied. Furthermore, in the wake of the microplastics issue, biodegradable cellulose has once again attracted attention as an old yet new material, and new uses are expected.

[0004] Meanwhile, in recent years, metal-organic frameworks (MOFs) have been actively studied, and they are expected to have new applications. MOFs are crystalline porous materials obtained by the self-assembly of metal ions and organic ligands. The nodal metal ions are bridged by organic ligands to form a framework structure. Examples of MOFs include HKUST-1, which consists of copper and trimesic acid; MOF-5, which consists of zinc and terephthalic acid; ZIF-8, which consists of zinc and 2-methylimidazole; MIL-53(Fe), which consists of iron and terephthalic acid; and MOF-74(Fe), which consists of iron and 2,5-dihydroxyterephthalic acid. There are countless types of MOFs, depending on the combination of metal ions and organic ligands. Furthermore, compounds composed only of metal ions and ligands with extremely simple structures (e.g., oxide ions, sulfide ions, fluoride ions, chloride ions, bromide ions, iodide ions, cyanide ions, cyanate ions, thiocyanide ions, etc.) and compounds without organic ligands coordinated to the metal ions in the framework structure are not included in MOFs. For example, Prussian blue (PB), which consists of iron and cyanide ions, is not included in MOFs. As another example, porous crystalline solids composed of polyoxometalates, which are anionic clusters composed of metal ions and oxide ions, and any cation (e.g., metal ions, macrocations, alkylammonium ions, etc.), without organic ligands coordinated to the metal ions, are not included in MOFs.

[0005] The pores of MOFs are uniform in size and arranged periodically, compared to silica gel, zeolite, and activated carbon, which are also known as porous materials. By selecting the metal ions and ligands, it is possible to control physical properties such as pore size and arrangement, specific surface area, and surface polarity. Recently, various applications of MOFs, such as gas storage (e.g., hydrogen storage) and gas separation (e.g., reducing carbon dioxide emissions), have been explored, taking advantage of the properties of their pores.

[0006] MOFs can be synthesized by mixing a solution containing dissolved metal ions with a solution containing dissolved ligands at room temperature and pressure, or by mixing them under high temperature and pressure, applying microwaves or ultrasound to the solution, or by mixing the raw materials in a solid state and applying mechanical impact using a ball mill or other similar method. In all cases, MOFs are obtained in the form of powder or crystalline particles, and after synthesis, they are washed and recovered using membrane filtration or centrifugation. However, powder or particle forms can present handling challenges depending on the application. To address this issue, a method has been proposed in which MOFs are supported on some kind of support to form a composite.

[0007] The following Patent Document 1 reports a method for obtaining a composite knit of cellulose and HKUST-1 by using a cotton knit as a support and supporting HKUST-1 powder using an acrylic ester resin as a binder.

[0008] Patent Document 2 below reports a method for obtaining a composite in which PB is fixed to the surface of cellulose by using cellulose fibers as a support and mixing a first liquid, a solution of potassium hexacyanoferrate (II) aqueous solution and cellulose fibers, with a second liquid, an aqueous solution of iron (III) chloride.

[0009] Patent Document 3 below reports a method for obtaining a composite of cellulose and PBA by using a regenerated cellulose nonwoven fabric as a support, impregnating it with a dispersion of a pre-synthesized Prussian blue analogue (PBA), and drying it.

[0010] Patent Document 4 below reports a method for obtaining a composite of MOF-90 and cellulose by using oxidized cellulose nanofibers as a support, treating the nanofibers with an aqueous zinc nitrate solution to introduce zinc ions as counter ions for the carboxyl groups, washing the nanofibers, and then adding a DMF solution of 2-imidazolecarbaldehyde.

[0011] Patent Document 5 below reports a method for obtaining a composite of ZIF-8 and polyethersulfone by dispersing zinc oxide particles in a DMAc solution in which polyethersulfone is dissolved, applying the film with an applicator, and drying it by heating to prepare a film in which the zinc oxide particles are dispersed, and then adding a DMAc solution of 2-methylimidazole. [Prior art documents] [Patent documents]

[0012] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-88499 [Patent Document 2] Japanese Patent Application Publication No. 2019-49063 [Patent Document 3] Patent No. 6345774 [Patent Document 4] Patent No. 6566463 [Patent Document 5] Special Publication No. 2019-523701 Summary of the Invention [Problem to be solved by the invention]

[0013] When MOFs are used as a composite supported on a support, it is necessary that the MOFs are not easily detached and that the pores of the MOFs are not damaged. Furthermore, when MOFs are used for storage or separation, it is desirable that a large amount of MOF can be supported. Furthermore, although this depends on the method of use of the composite, a low strength of the composite makes it difficult to handle, so a support method that does not reduce the strength of the composite is desirable.

[0014] While a composite can be easily obtained using a binder, as in Patent Document 1, there is a possibility that the pores of the MOF may be blocked by the binder, preventing the original performance, or that the MOF may be detached due to the deterioration or dissolution of the binder. Patent Document 2 describes the high ash yield due to the resistance to PB detachment and the treatment in the presence of cavitation bubbles, but the examples do not include data on ash retention, nor does it describe any examples of treatment in the presence of cavitation bubbles. In the method of Patent Document 3, the MOF is simply physically adsorbed to the cellulose surface, making it prone to detachment. It is known that the introduction of carboxyl groups using TEMPO-oxidized cellulose, as described in Patent Document 4, proceeds selectively on the fiber surface, with no reaction occurring inside. Therefore, even with this method, there is a risk of MOF detachment because the MOF is supported on the fiber surface. Furthermore, because cellulose is oxidized, strength decreases, especially in water, potentially limiting its use. The method of Patent Document 5 allows MOFs to be supported inside the support, potentially reducing the risk of MOF detachment. However, as can be seen from the XRD pattern described in Patent Document 5, not all of the zinc reacts with 2-methylimidazole and is converted to MOF. This means that it is difficult to increase the amount of MOF supported using this method. Furthermore, this method is limited in the type of support, solvent, and fine particles that can be used as precursors, which limits the composites that can be produced.

[0015] As described above, the present inventors have found that the composites obtained by existing technologies have room for improvement in terms of various performance requirements for practical use. In view of the above-mentioned state of the art, the problem to be solved by the present invention is to provide a composite that has a high MOF loading, is resistant to detachment, and has sufficient strength, and further to provide a composite with various shapes required for the intended use. [Means for solving the problem]

[0016] To solve the above problems, the present inventors conducted extensive research and experiments, and unexpectedly discovered that by reacting cellulose with a ligand in a state where the cellulose forms a complex containing a metal ion, MOFs can be synthesized inside the cellulose structure, providing a composite with a high MOF loading and resistance to detachment. Furthermore, the present inventors discovered that this method allows the shape of the composite to be freely changed, enabling the provision of a composite shape suited to the application. Furthermore, they surprisingly discovered that the composite of the present invention has improved strength compared to cellulose alone.

[0017] That is, the present invention is as follows. [1] A composite comprising cellulose and a metal-organic framework, wherein the loading rate of the metal-organic framework after an ultrasonic cleaning operation of the composite is 4% by weight to 60% by weight. [2] The ultrasonic cleaning operation is performed using a dual frequency switching ultrasonic cleaner containing pure water in a cleaning tank, and the following operations are performed: (1) subjecting a glass container containing the complex and a solvent that does not dissolve or decompose the metal-organic framework to an ultrasonic cleaner for 5 minutes; (2) replacing the solvent in the glass container; The complex according to [1] above, wherein the above procedure is carried out three times in total. [3] The composite according to [1] or [2], wherein the cellulose is regenerated cellulose. [4] The composite according to any one of [1] to [3] above, which has the shape of a staple fiber, a filament, a woven fabric, a knitted fabric, a nonwoven fabric, a film, a porous membrane, a hollow fiber, a particle, or a fine particle. [5] The following steps: A step of preparing a cellulose solution in which cellulose is dissolved as a complex containing a metal ion; a step of forming a structure containing cellulose and a metal ion from the cellulose solution; and a step of contacting the obtained structure with an organic ligand solution to obtain a composite containing cellulose and a metal-organic framework; A method for producing the complex according to any one of [1] to [4] above, comprising: [6] The method according to [5] above, wherein the metal ion is any one of copper, zinc, calcium, cadmium, cobalt, nickel, iron, palladium, and magnesium, or any combination thereof. [Effects of the Invention]

[0018] According to the present invention, a composite can be obtained which has a large MOF loading, is resistant to desorption, is easy to handle, and has any shape, and can be used for various purposes such as storage materials, adsorption materials, separation materials, and sustained-release materials. [Brief explanation of the drawings]

[0019] [Figure 1] 1 shows X-ray diffraction data of the cellulose-HKUST-1 composite film obtained in Example 1. [Figure 2] 1 is an SEM photograph of the surface of the cellulose-HKUST-1 composite film obtained in Example 1. [Figure 3] 1 is a cross-sectional TEM photograph of the cellulose-HKUST-1 composite film obtained in Example 1. [Figure 4] 1 is an optical photograph of the cellulose-HKUST-1 conjugated long fiber nonwoven fabric obtained in Example 7. [Figure 5] 1 is a cross-sectional TEM photograph of the cellulose-MOF-2 composite film obtained in Example 12. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, embodiments of the present invention will be described in detail. One embodiment of the present invention is a composite containing cellulose and a metal organic framework, in which the loading rate of the metal organic framework after an ultrasonic cleaning operation of the composite is 4 wt % to 60 wt %.

[0021] The MOF of this embodiment is a porous material with a structure in which metal ions are crosslinked with each other via organic ligands. The pore size and chemical properties can be adjusted by changing the types of metal ions and organic ligands depending on the purpose. Known MOFs and future MOFs can be used. Examples of MOFs include HKUST-1, MOF-2, MOF-4, CPL-1, CPL-2, Cu-BTTri, ELM-11, MOF-505, PCN-6, MOF-5, MOF-74, MOF-177, ZIF-8, ZIF-zni, Zn-BTB, ZIF-67, MIL-100, MIL-53, MIL-89, UiO-66, and PCN-111. To support MOFs inside cellulose, HKUST-1, MOF-2, MOF-4, CPL-1, CPL-2, Cu-BTTri, ELM-11, MOF-505, PCN-6, MOF-5, MOF-74, MOF-177, ZIF-8, ZIF-Zn, Zn-BTB, ZIF-67, MIL-100, MIL-53, and MIL-89, which contain metal species used to dissolve cellulose, are preferred. The MOFs of this embodiment can be used alone or in combination of two or more.

[0022] Any metal species can be used as the metal species constituting the MOF of this embodiment, and examples thereof include lithium, beryllium, sodium, magnesium, aluminum, potassium, calcium, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, gallium, rubidium, strontium, yttrium, zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, and indium. Examples of metal species include rhenium, tin, cesium, barium, lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, hafnium, tantalum, tungsten, rhenium, osmium, iridium, platinum, gold, mercury, thallium, lead, bismuth, francium, radium, actinium, thorium, protactinium, and uranium. MOFs may contain one or more metal species. In particular, to support MOFs inside cellulose, it is preferable to contain metal species used to dissolve cellulose. Among these, copper, zinc, calcium, cadmium, cobalt, nickel, iron, palladium, and magnesium are more preferable due to the ease of cellulose dissolution. Furthermore, it is particularly preferable that the resulting cellulose contains copper with voids.

[0023] The organic ligands constituting the MOF of this embodiment may be any organic ligand capable of coordinating with metal ions to form a framework structure, and may be any known organic ligand or organic ligand that may be produced in the future. Examples of organic ligands include carboxylic acid-based ligands, ketone-based ligands, aldehyde-based ligands, ether-based ligands, amine-based ligands, imine-based ligands, amino acid-based ligands, nitrile-based ligands, phosphate-based ligands, phosphine-based ligands, sulfonic acid-based ligands, thiol-based ligands, sulfide-based ligands, fluoride-based ligands, chloride-based ligands, bromide-based ligands, and iodide-based ligands. The MOF may contain one or more organic ligands, which can be freely selected depending on the purpose. Furthermore, depending on the combination of metal ions and organic ligands, the framework of the metal-organic framework may be positively or negatively charged. To maintain electrical neutrality, anions or cations may be included within the MOF. MOFs do not include compounds composed only of metal ions and ligands with extremely simple structures (e.g., oxide ions, sulfide ions, fluoride ions, chloride ions, bromide ions, iodide ions, cyanide ions, cyanate ions, thiocyanide ions, etc.), or compounds that do not have organic ligands coordinated to the metal ions in the framework structure. For example, Prussian blue (PB), which consists of iron and cyanide ions, and porous crystalline solids composed of polyoxometalates, which are anionic clusters consisting of metal ions and oxide ions, and any cation (e.g., metal ions, macrocations, alkylammonium ions, etc.), which do not have organic ligands coordinated to the metal ions, are not included in MOFs.

[0024] Various celluloses can be used as the cellulose constituting the composite of this embodiment. Cellulose is both hydrophilic and lipophilic, and is insoluble in most common solvents. Therefore, various solvents can be used for adsorption separation of target substances from liquids, or as a catalyst for reaction control. Furthermore, cellulose has a certain degree of heat resistance and does not melt, making it usable over a wide temperature range. Furthermore, various solvents can be used to recover the target substance adsorbed by the MOF, and recovery can be performed in a certain thermal environment. Regenerated cellulose is preferred as the cellulose constituting the composite of this embodiment because it can be molded into any shape. Among these, regenerated cellulose obtained from cellulose solutions containing metal complex solvents such as cuprammonium, cadoxene, cooxene, nioxene, zincoxene, and EWNN is more preferred. These regenerated celluloses have a void structure, which allows for easy molecular access to the MOFs present within the composite, facilitating their use for storage, adsorption, separation, and sustained release. Cuprammonium regenerated cellulose is particularly preferred due to its ease of molding and the ability to control voids.

[0025] The composite of this embodiment has a MOF loading rate (ratio) of 4% to 60% by weight after ultrasonic cleaning. If the MOF ratio is low, functions such as storage, adsorption, separation, and sustained release may be insufficient. If the ratio exceeds 60% by weight, the toughness of the composite decreases, and handling problems may occur depending on how it is used. From the perspective of performance, the ratio is preferably 10% by weight or more, more preferably 20% by weight or more, and even more preferably 30% by weight or more. From the perspective of handling, the ratio is preferably 50% by weight or less, and more preferably 40% by weight or less.

[0026] The ultrasonic cleaning operation uses a two-frequency ultrasonic cleaner with pure water in the cleaning tank. A glass container containing a solvent that does not dissolve or decompose the MOF and the complex is cleaned in the ultrasonic cleaner for 5 minutes, after which the solvent in the glass container is replaced with fresh solvent and the container is cleaned again. This operation is repeated a total of three times. The reason why ultrasonic cleaning was selected as the method for cleaning the complex in this embodiment is that it can easily clean complexes of various shapes. When performing ultrasonic cleaning, it is necessary to select a solvent that will not decompose the MOF. For example, DMF or ethanol can be used for ultrasonic cleaning of HKUST-1, which decomposes in the presence of water.

[0027] In the composite of this embodiment, it is preferable that a certain amount of MOF is present inside the cellulose. The MOF present inside the cellulose is not only less likely to be detached, but is also thought to contribute to improving the mechanical properties of the composite.

[0028] The form of the composite of this embodiment can be selected arbitrarily depending on the intended use. Examples include short fibers, long fibers, woven fabrics, knitted fabrics, nonwoven fabrics, films, porous membranes, hollow fibers, particles, and microparticles. These can be used alone or in combination. They can also be used in combination with other materials or incorporated into some kind of module. Furthermore, the size and shape of the voids can be selected arbitrarily depending on the intended use. For example, when performing gas separation, a dense structure can prevent non-selective gas permeation, and when performing adsorption separation, a sparse structure can increase the specific surface area and improve adsorption efficiency.

[0029] Another embodiment of the present invention is a method for producing a method for manufacturing a semiconductor device comprising the steps of: preparing a cellulose solution in which cellulose is dissolved as a complex containing a metal ion; A step of forming a structure containing cellulose and metal ions from the cellulose solution; and a step of contacting the obtained structure with an organic ligand solution to obtain a composite containing cellulose and a metal-organic framework; a method for producing the composite, comprising: The method for producing the composite of this embodiment is not particularly limited and any method can be used. However, a preferred method involves preparing a cellulose solution in which cellulose is dissolved as a complex containing a metal ion, producing a structure containing cellulose and a metal ion from the cellulose solution, and then contacting the structure with an organic ligand solution to synthesize an MOF within the cellulose structure. Because the metal ions have already formed a complex with cellulose, the structure obtained by molding from the cellulose solution has the metal ions immobilized within it. When the structure is contacted with an organic ligand solution, MOFs can be precipitated within the cellulose structure. Since one metal ion can coordinate to each glucose ring constituting cellulose, many metal ions can be immobilized within the structure, allowing for the loading of a large amount of MOF. For example, it has been reported that when a cuprammonium solution is used as a solvent, copper ions coordinate to the hydroxyl groups at C2 and C3. In this method, the structure formed from the cellulose solution can be treated with an organic ligand solution while it is still unclogged, allowing for simultaneous coagulation of the structure and synthesis of the MOF. Alternatively, the structure formed from the cellulose solution can be first coagulated in a poor solvent that does not disrupt the coordination between cellulose and metal ions, followed by treatment with an organic ligand solution to synthesize the MOF. If necessary, a subsequent treatment to disrupt the coordination between cellulose and metal ions may also be performed. Furthermore, when the composite of this embodiment is prepared by treating the cellulose with an organic ligand solution while it is still in a state where it has formed a complex containing metal ions, the mechanical properties are surprisingly improved compared to cellulose alone. While the exact mechanism is unknown, possible explanations include the MOF present within the cellulose structure serving as a reinforcing material, forming hydrogen bonds with cellulose and acting as a crosslinker, or the presence of the MOF during structure formation changing the crystalline structure of cellulose itself. The improved mechanical properties of the composite lead to advantages such as improved handling during practical use.

[0030] In the method of this embodiment, in terms of increasing the MOF loading amount, a method in which the structure obtained by molding from a cellulose solution is treated with an organic ligand solution while it is still in an uncoagulated state, thereby simultaneously coagulating the structure and synthesizing the MOF (or its intermediate) is preferred. On the other hand, in terms of being able to control the cellulose shape and voids, a method in which the structure is first coagulated in a poor solvent that does not break the bonds between cellulose and metal ions, and then treated with an organic ligand solution is preferred. The MOF loading rate can also be adjusted by changing conditions such as the concentration, temperature, and reaction time of the organic ligand solution. For example, when a cuprammonium solution is used as a cellulose solvent, the pH becomes alkaline due to the presence of ammonia, so precipitation may not occur depending on the type of MOF. Even in such cases, a method in which the structure is coagulated by deammoniation in a poor solvent that does not break the bonds between cellulose and metal ions, and then treated with an organic ligand solution is preferred. Depending on the type of MOF, treatment with an organic ligand solution alone may result in insufficient reaction or the formation of intermediates. In such cases, high pressure treatment, high temperature treatment, treatment with an acidic solution, treatment with an alkaline solution, ultrasonic treatment, microwave treatment, etc. may be carried out as necessary.

[0031] After the MOF is synthesized inside the cellulose of this embodiment, a washing treatment can be carried out as necessary. If unreacted metal ions or ligands remain in the complex, they can be dissolved and washed with a solvent that does not decompose the synthesized MOF.

[0032] The composite of this embodiment may be dried as needed, or may be used as is without drying, or may be used after solvent substitution. If the synthesized MOF is solvated and has low activity, drying or activation treatment may be necessary. Furthermore, if it is desired to maintain the cellulose voids, solvent substitution drying may be performed, or the composite may be used as is without drying. [Example]

[0033] First, the evaluation methods used in the following examples and comparative examples will be described. As an example, the evaluation method when the MOF is HKUST-1 is described, but the solvent and container used for washing may be selected in consideration of the solubility of the metal ions and ligands forming the MOF and the stability of the MOF.

[0034] <Measurement of the loading rate of MOF in the composite> The composite is dried under reduced pressure and vacuum at 105°C for one day and night, and the absolute dry weight of the composite is measured. Subsequently, 10 wt% sulfuric acid and the composite are placed in a sealable container and immersed for 1 hour to decompose the MOF supported on the composite. The remaining cellulose structure is recovered and washed with pure water. This washing process with 10 wt% sulfuric acid and pure water is repeated once more. The obtained cellulose structure is dried under reduced pressure and vacuum at 105°C for 1 hour, and the absolute dry weight of the cellulose structure is measured. The loading rate of MOF in the composite is calculated from the measured absolute dry weight of the composite and the absolute dry weight of the cellulose structure using the following formula: Loading rate of MOF in the composite (%) = { (Absolute dry weight of the composite - Absolute dry weight of the cellulose structure) ÷ Absolute dry weight of the composite} × 100 It is calculated by.

[0035] <Washing operation of the composite> An ultrasonic cleaner manufactured by AS ONE (ASU-6D, dual-frequency switching type) is used as the ultrasonic cleaner, and pure water is placed in the cleaning tank. Furthermore, ethanol and the composite are placed in a sealable glass container and washed with the ultrasonic cleaner for 5 minutes. After washing for 5 minutes, the ethanol in the container is replaced, and a series of ultrasonic cleaning operations are performed a total of 3 times.

[0036] <Measurement of the loading rate of MOF in the composite after ultrasonic cleaning when MOF cannot be decomposed> When the MOF cannot be decomposed, a solvent that dissolves cellulose such as NMMO but does not decompose the MOF is used to dissolve the cellulose, isolate the MOF, measure the absolute dry weight, and from the measured absolute dry weight of the composite and the absolute dry weight of the MOF, the loading rate of MOF in the composite is calculated using the following formula: Loading rate of MOF in the composite (%) = { (Absolute dry weight of the MOF) ÷ Absolute dry weight of the composite} × 100 It is calculated by.

[0037] <Calculation of the desorption rate of MOF before and after washing> The desorption rate of the MOF before and after the washing operation was calculated from the loading rate of the complex before and after the washing operation using the following formula: MOF desorption rate (%) = {(loading rate before washing - loading rate after washing) ÷ loading rate before washing} × 100 It is calculated as follows.

[0038] <Example 1: Preparation of cellulose-HKUST-1 composite film> Cotton linters were dissolved in cuprammonium solution using a known method to prepare a cellulose cuprammonium solution containing 10 wt% cellulose, 7 wt% ammonia, and 3.6 wt% copper. A 300 μm thick film was cast onto an 8 cm square glass substrate using an applicator. The glass substrate was then immersed in 50 ml of pure water in a 10 cm square stainless steel container with a lid, heated to 40°C, for 10 minutes to allow for coagulation. The glass substrate was then immersed in 50 ml of DMF in a 10 cm square stainless steel container with a lid, heated to 40°C, for 10 minutes to allow for DMF substitution. The glass substrate was then immersed in 50 ml of a 5.0 wt% DMF solution in a 10 cm square stainless steel container with a lid, heated to 40°C, for 30 minutes to allow for reaction of the copper ions complexed with the hydroxyl groups of the cellulose with the trimesic acid. After the reaction, the film was peeled from the glass substrate and placed in a 10 cm square stainless steel container with a lid with 50 ml of ethanol. The film was rinsed with tweezers to remove HKUST-1 from the surface, and then left to stand in ethanol for 5 minutes to remove unreacted trimesic acid. This series of washing procedures was repeated until the coloration due to HKUST-1 detachment in the ethanol was no longer observed. The resulting washed film was sandwiched between a 5 cm square stainless steel mold and dried under reduced pressure at 50 °C for 1 day while minimizing drying shrinkage. The resulting film had the characteristic blue color of HKUST-1. Analysis using an X-ray diffraction analyzer (Rigaku Mini Flex II) confirmed both cellulose and HKUST-1 peaks, as shown in Figure 1. These results confirmed the formation of a cellulose-HKUST-1 composite film.

[0039] <Example 2: Preparation of cellulose-HKUST-1 composite film> A cellulose-HKUST-1 composite film was prepared in the same manner as in Example 1, except that the coagulation liquid used was a 50 wt % aqueous acetone solution instead of pure water.

[0040] <Example 3: Preparation of cellulose-HKUST-1 composite film> A cellulose-HKUST-1 composite film was prepared in the same manner as in Example 1, except that the coagulation liquid used was a 2 wt % aqueous solution of caustic soda instead of pure water, and after coagulation, the film was immersed in 50 ml of pure water for 5 minutes to replace the pure water, and this procedure was repeated three times before DMF replacement.

[0041] <Preparation of regenerated cellulose film> A regenerated cellulose film was prepared in the same manner as in Example 1, except that a 10 wt % aqueous sulfuric acid solution was used instead of a DMF solution with a trimesic acid concentration of 5.0 wt %.

[0042] <Comparative Example 1: Preparation of cellulose-HKUST-1 composite film by post-processing> A cellulose-HKUST-1 composite film was prepared with reference to Patent Document 2. 50 ml of a 50 vol% ethanol solution containing 5.0 wt% trimesic acid and a regenerated cellulose film were placed in a sealable glass container, mixed, and allowed to stand for 10 minutes. Next, 50 ml of a 50 vol% ethanol solution containing 3.7 wt% copper (II) nitrate trihydrate was added, the container was closed, and the mixture was heated to 105°C and reacted for 60 minutes. The resulting film was washed with ethanol as in Example 1, sandwiched between an 8 cm square stainless steel mold, and vacuum-dried at 50°C for one day and night while suppressing drying shrinkage, yielding a dried film. The resulting film had the characteristic blue color of HKUST-1.

[0043] <Comparative Example 2: Preparation of cellulose-HKUST-1 composite film by post-processing> With reference to Patent Document 3, trimesic acid and copper (II) nitrate trihydrate were first reacted to synthesize HKUST-1 particles, which were then dispersed in DMF and applied to a regenerated cellulose film, followed by drying, to obtain a dried film in the same manner as in Comparative Example 1. The obtained film had the blue color characteristic of HKUST-1.

[0044] <Evaluation of physical properties of cellulose-HKUST-1 composite film> The HKUST-1 loading rate was measured using a portion of the cellulose-HKUST-1 composite films obtained in Examples 1 to 3 and Comparative Examples 1 and 2. A washing operation was then performed, and the HKUST-1 loading rate after washing was measured, and the HKUST-1 desorption rate before and after the washing operation was calculated. The results are shown in Tables 1 and 2 below.

[0045] [Table 1]

[0046] [Table 2]

[0047] As is clear from Table 1, the composites obtained in Examples 1 to 3 had high MOF loading rates and were less susceptible to MOF detachment during washing. On the other hand, as is clear from Table 2, the composites obtained by methods other than the present embodiment had low MOF loading rates before washing and were more susceptible to detachment during washing. The surface and cross section of the film obtained in Example 1 were then observed using SEM and TEM, respectively. Figures 2 and 3 show the respective photographs. The composite obtained in Example 1 was less susceptible to detachment because the MOF was also loaded internally, whereas the composite obtained in the comparative example was more susceptible to MOF detachment. Furthermore, when each film and a regenerated cellulose film not carrying MOF were pulled to check handling, the films obtained in Comparative Examples 1 and 2 broke with the same force as the regenerated cellulose film. In contrast, the films obtained in Examples 1 to 3 were less susceptible to breaking than the regenerated cellulose film.

[0048] <Example 4: Preparation of cellulose-HKUST-1 composite long fibers> A cellulose cuprammonium solution was subjected to tension spinning in pure water using a conventional method to obtain gel-like long fibers containing cellulose and copper. Next, 50 mL of DMF was placed in a 10 cm square stainless steel container with a lid and heated to 40°C. 2.5 g of long fibers were immersed for 10 minutes to perform DMF exchange. Next, 50 mL of a 5.0 wt% DMF solution of trimesic acid was placed in a 10 cm square stainless steel container with a lid and heated to 40°C. The DMF-exchanged long fibers were immersed for 30 minutes in 50 mL of a DMF solution containing 5.0 wt% trimesic acid, allowing the copper ions complexed with the hydroxyl groups of the cellulose to react with the trimesic acid. After the reaction, the long fibers were removed and placed in a 10 cm square stainless steel container with a lid and shaken to wash off the HKUST-1 adhering to the surface. They were then allowed to stand in ethanol for 5 minutes to wash off any unreacted trimesic acid. This series of washing procedures was repeated until the coloration due to HKUST-1 detachment into the ethanol was no longer observed. The washed long fibers were wound around a 5 cm square stainless steel mold and dried under reduced pressure at 50°C for one day and night while suppressing drying shrinkage, yielding dried long fibers. The obtained long fibers had the characteristic blue color of HKUST-1.

[0049] <Example 5: Preparation of cellulose-HKUST-1 composite knitted fabric> The continuous fibers obtained in Example 4 were tubular knitted on a tubular knitting machine to obtain a cellulose-HKUST-1 composite knitted fabric.

[0050] <Example 6: Preparation of cellulose-HKUST-1 composite hollow fiber> A cellulose-HKUST-1 composite hollow fiber was prepared in the same manner as in Example 4, except that a conventionally known double concentric spinneret was used, and a cellulose cuprammonium solution was used as the outer liquid and a 2 wt % caustic soda solution as the inner liquid. The spinning was performed by discharging the spinning material into a bath of 2 wt % caustic soda solution, and 2.5 g of the resulting hollow fiber was immersed in 50 ml of pure water for 5 minutes, followed by replacement with pure water, three times.

[0051] <Example 7: Preparation of cellulose-HKUST-1 composite long fiber nonwoven fabric> A cellulose-HKUST-1 composite continuous fiber nonwoven fabric as shown in FIG. 4 was prepared in the same manner as in Example 4, except that a cellulose cuprammonium solution was subjected to wet spunbond spinning using a conventional method.

[0052] <Example 8: Preparation of cellulose-HKUST-1 composite particles> The cellulose cuprammonium solution was diluted to a viscosity of 60 mPa·s and spray-dried using a conventional method to prepare particles containing cellulose and copper. Next, 50 ml of a 5.0 wt% DMF solution of trimesic acid was placed in a 10 cm square stainless steel container with a lid and heated to 40°C. 0.5 g of particles were immersed for 30 minutes, allowing the copper ions complexed with the hydroxyl groups of the cellulose to react with the trimesic acid. After the reaction, the particles were collected by centrifugation, placed in a centrifuge tube with 50 ml of ethanol, and shaken to wash off the HKUST-1 adhering to the surface. The particles were then left in ethanol for 5 minutes to wash off any unreacted trimesic acid. This washing procedure was repeated until the color due to HKUST-1 detachment disappeared. The washed particles were collected by centrifugation and dried under reduced pressure at 50°C for 1 day, resulting in dried particles. The resulting particles had the characteristic blue color of HKUST-1.

[0053] <Example 9: Preparation of cellulose-HKUST-1 composite microparticles> Cellulose-HKUST-1 composite microparticles were prepared in the same manner as in Example 8, except that the cellulose cuprammonium solution was diluted to adjust the cellulose concentration to 0.37 wt %, the cellulose cuprammonium solution was poured into a 27 wt % acetone aqueous solution to coagulate, and 2.5 g of particles recovered by centrifugation after coagulation were immersed in 50 mL of DMF heated to 40°C for 10 minutes to replace the DMF.

[0054] <Comparative Example 3: Preparation of cellulose-HKUST-1 composite continuous fiber by post-processing> Using regenerated cellulose long fibers obtained from a cellulose cuprammonium solution, cellulose-HKUST-1 conjugated long fibers were prepared in the same manner as in Comparative Example 1. The HKUST-1 loading rate of the obtained conjugated long fibers was 8.1 wt %, and the HKUST-1 loading rate after ultrasonic cleaning was 2.6 wt %.

[0055] <Evaluation of physical properties of cellulose-HKUST-1 complexes with different shapes> The composites obtained in Examples 4 to 9 and Comparative Example 3 all had the blue color characteristic of HKUST-1. Furthermore, the physical properties were evaluated in the same manner as for the composite film. The results are shown in Table 3 below.

[0056] [Table 3]

[0057] As is clear from Table 3, the composite obtained by the method of this embodiment could be prepared in any shape.

[0058] <Evaluation of ammonia gas adsorption performance of cellulose-HKUST-1 composite long fibers> The cellulose-HKUST-1 composite long fibers obtained in Example 4 were packed into a commercially available glass calcium tube, and both ends were sealed with absorbent cotton. A 0.5 wt. % ammonia aqueous solution was placed in a commercially available glass beaker, and the calcium tube packed with the cellulose-HKUST-1 composite long fibers was connected to it. Similarly, a calcium tube packed with the cellulose-HKUST-1 composite long fibers obtained in Comparative Example 3 was also prepared. The ammonia gas concentration was measured in the open end of the calcium tube using a commercially available gas sampler and ammonia gas detector tube. When the calcium tube was not packed with the cellulose-HKUST-1 composite long fibers, the ammonia concentration was 140 ppm. When the calcium tube was packed with the composite long fibers obtained in Example 4, the ammonia concentration was below the detection limit (10 ppm or less), and when the composite long fibers obtained in Comparative Example 3 were packed, the ammonia concentration was 20 ppm. These results demonstrate that the composite of the present invention not only exhibits the performance due to the high MOF loading rate, but is also easy to handle and can be configured to suit a variety of applications.

[0059] <Example 10: Preparation of cellulose-HKUST-1 composite film> A cellulose-HKUST-1 composite film was prepared in the same manner as in Example 1, except that the composition of the cellulose cuprammonium solution was changed to a cellulose concentration of 10 wt %, an ammonia concentration of 8 wt %, and a copper concentration of 4.3 wt %.

[0060] <Example 11: Preparation of cellulose-HKUST-1 composite film> A cellulose-HKUST-1 composite film was prepared in the same manner as in Example 1, except that the cellulose cuprammonium solution used in Example 10 was used and air-dried instead of coagulating with pure water.

[0061] <Evaluation of physical properties of cellulose-HKUST-1 composite film> The physical properties of the cellulose-HKUST-1 composite films obtained in Examples 10 and 11 were evaluated, and the results are shown in Table 4 below.

[0062] [Table 4]

[0063] As is clear from Table 4, in the methods of Examples 10 and 11, the amount of MOF supported could be controlled by adjusting the amount of metal ions and the coagulation method.

[0064] <Example 12: Preparation of cellulose-MOF-2 composite film> A cellulose-MOF-2 composite film was obtained in the same manner as in Example 1, except that the solution to be reacted after coagulation was a DMF solution with a terephthalic acid concentration of 4.0 wt%. The obtained film was light blue, and analysis using an X-ray analyzer confirmed peaks for both cellulose and MOF-2. A cross-sectional TEM image of the cellulose-MOF-2 composite film is shown in Figure 5.

[0065] <Example 13: Preparation of cellulose-MOF-5 composite film> A cellulose-MOF-5 composite film was obtained in the same manner as in Example 1, except that a zincoxene solution was used to dissolve the cotton linters, the cellulose concentration was 7 wt%, the zinc concentration was 4.5 wt%, and the ethylenediamine concentration was 13.5 wt%, and the solution to be reacted after coagulation was a DMF solution with a terephthalic acid concentration of 4.0 wt%. The obtained film was white, and when analyzed using an X-ray analyzer, peaks for both cellulose and MOF-5 were confirmed.

[0066] <Example 14: Preparation of cellulose-ZIF-8 composite film> A cellulose-ZIF-8 composite film was obtained in the same manner as in Example 18, except that the solution to be reacted after coagulation was a 50 vol% aqueous ethanol solution with a 2.1% 2-methylimidazole concentration. The obtained film was white, and when analyzed using an X-ray analyzer, peaks of both cellulose and ZIF-8 were confirmed.

[0067] <Example 15: Preparation of cellulose-MIL-53(Fe) composite film> A cellulose-MIL-53(Fe) composite film was obtained in the same manner as in Example 1, except that EWNN was used as the solution for dissolving cotton linters, the cellulose concentration was 4.0 wt%, the iron concentration was 1.5 wt%, the tartaric acid concentration was 12.9 wt%, and the sodium hydroxide concentration was 18.7 wt%, the solution was washed with pure water three times after coagulation, and then DMF substitution was performed, and the solution to be reacted after coagulation was a DMF solution with a terephthalic acid concentration of 4.0 wt%. The obtained film was yellow, and when analyzed using an X-ray analyzer, peaks for both cellulose and MIL-53(Fe) were confirmed.

[0068] <Performance evaluation of cellulose-various MOF composite films> The physical properties of the composite films obtained in Examples 12 to 15 were evaluated, and the results are shown in Table 5 below.

[0069] [Table 5]

[0070] As is clear from Table 5, the methods of Examples 12 to 15 allowed for the combination of various metal ions and ligands. [Industrial Applicability]

[0071] The composite of the present invention can be used for gas storage such as hydrogen storage, gas separation for the purpose of suppressing carbon dioxide emissions, etc., filters that remove chemical impurities from gases and liquids, additives that serve as reaction fields for polymer synthesis, etc., catalysts that control reactions, adsorption separation that separates target substances from gases and liquids, recovery of valuable materials from liquids, dialysis membranes that remove waste products from blood, sustained-release agents that sustainably release substances trapped in pores, interior materials for buildings and automobiles that have deodorizing, humidity-regulating, and antibacterial properties, scaffolding materials for the crystalline sponge method, ion-conductive materials, electrodes and separators for secondary batteries, electrochromic materials, etc.

Claims

1. A composite comprising regenerated cellulose and a metal organic framework, wherein the loading rate of the metal organic framework after an ultrasonic cleaning operation of the composite is 4% by weight to 60% by weight.

2. The ultrasonic cleaning operation is performed using a dual frequency switching ultrasonic cleaner containing pure water in a cleaning tank, and the following operations are performed: (1) subjecting a glass container containing the composite and a solvent that does not dissolve or decompose the metal-organic framework to an ultrasonic cleaner for 5 minutes; (2) replacing the solvent in the glass container; The complex according to claim 1, wherein the above procedure is carried out three times in total.

3. 3. The composite according to claim 1 or 2, which has the shape of any one of short fibers, long fibers, woven fabrics, knitted fabrics, nonwoven fabrics, films, porous membranes, hollow fibers, particles, and microparticles.

4. The following steps: preparing a cellulose solution in which cellulose is dissolved as a complex containing a metal ion; A step of forming a structure containing cellulose and metal ions from the cellulose solution; and a step of contacting the obtained structure with an organic ligand solution to obtain a composite containing cellulose and the metal-organic framework; The method for producing a composite comprising cellulose and a metal organic framework, wherein the loading rate of the metal organic framework after an ultrasonic cleaning operation is 4 wt % to 60 wt %, comprising:

5. 5. The method of claim 4, wherein the metal ions are copper, zinc, calcium, cadmium, cobalt, nickel, iron, palladium, magnesium, or any combination thereof.

Images