JP2014156434A - Functional metal-organic framework material containing novel composite particles - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a zeolite-like imidazolate framework material easily in a large scale without solvent, salt, etc., and also to provide a composite material containing novel composite particles containing a zeolite-like imidazolate structure, and a production method of the same and a method of using the same as a functional material.SOLUTION: Provided is a composite material containing composite particles containing polycrystal-type particles comprising metal oxide particles at a central part of the composite particles and a zeolite-like imidazolate structure at an outer shell part of the metal oxide particles. The metal in the metal oxide particles and the zeolite-like imidazolate structure is one selected from the group consisting of zinc and cobalt, and the imidazolate ligand is one derived from imidazole which may have a substituent, or a derivative thereof. Also provided are a production method of the same and a method of using the same as a functional material.

Description

  The present invention relates to a functional metal-organic framework material, and more particularly to a composite functional metal-organic framework material containing novel composite particles. Specifically, the present invention relates to a composite containing novel composite particles containing metal oxide particles and polycrystalline particles of a zeolite-like imidazolate structure, and a method for producing the same and a method for using it as a functional material.

  In recent years, composite particles having a multilayer (for example, core / shell type) structure have attracted attention as functional materials. Such a composite particle having a multilayer structure has, for example, a structure in which the central portion and the outer shell portion are different from each other, thereby improving the function of the original structure of either the central portion or the outer shell portion. In addition, it is possible to expect an effect such that a plurality of functions originally produced by both structures are simultaneously and compositely exhibited. However, the production of composite particles having such a multilayer structure requires chemical control of the structures of the central portion and the outer shell portion.

In addition, a material with a metal-organic framework (MOF) as a skeleton is a crystalline three-dimensional microporous material synthesized through coordination bonds and self-assembly of metal ions and organic bridging ligands. Yes, it is expected as a functional material. The MOF can be designed in a wide range of structures by combining organic bridging ligands and metal ion species, and has uniform micropores (˜0.4 nm) and high specific surface area (˜6000 m ² / g). For example, it is expected as a functional material such as gas storage, gas separation, heterogeneous catalyst, and device (see Patent Documents 1 to 3 and Non-Patent Document 1).

  As one of the MOFs, an imidazolate structure (Zeolitic Imidazolate Framework: ZIF) having a zeolite-like topology composed of zinc (Zn) or cobalt (Co) as a metal and imidazole as an organic bridging ligand is used as a skeleton. The material to be synthesized is synthesized (see Non-Patent Document 2). ZIF has a zeolite-like topology, but on the other hand, unlike zeolite, it is formed by template-free self-assembly, so there is no need for a structure-directing agent. In addition to aluminum (Al), Unlike zeolite with an inorganic skeleton consisting of silicon (Si) and oxygen (O), it has an imidazole organic ligand, so it has structural flexibility. In addition, zeolite can change the entire molecule by changing the Si / Al ratio and cation species. In contrast, ZIF can control the hydrophilicity or hydrophobicity of the entire molecule simply by modifying the functional group on imidazole. It is highly expected from the aspect.

  As an example of ZIF, ZIF-8 comprising zinc as a metal and 2-methylimidazolate ligand as an imidazolate ligand is known (see Non-Patent Document 2, Patent Documents 4 and 5 above), which is a batholite. (Basolite) (registered trademark) Z1200 (manufactured by Sigma-Aldrich) is commercially available. As a method for producing such ZIF-8, a solvothermal method, a solution method and a mechanochemical method using a metal salt such as zinc nitrate as a starting material are known, as in a general method for producing ZIF. Here, the solvothermal method (see Non-Patent Document 3, Patent Documents 4 and 5) requires the use of an organic solvent such as N, N-dimethylformamide or ethanol, and therefore depends on its volatility, flammability, and toxicity. There are safety problems and adverse environmental effects, and high temperature and high pressure conditions are required. In addition, in the case of the solution method, in addition to the above problems when an organic solvent is used, the reaction rate is low, so that the yield of the product is low, and when water is used as a solvent (see Non-Patent Documents 4 and 5). Since the solubility of imidazole is extremely low, a large excess of imidazole ligand is required, and in addition, it is necessary to wash away the unreacted imidazole ligand remaining after the reaction. In addition, unreacted zinc ions remain in the solvothermal method and the solution method, and impurities such as hydroxides are generated when the product is recovered and washed with water. Therefore, the pore volume of the material (this is the mass specific volume cc / g, so the specific gravity is large and the pore volume is reduced when a material without pores is mixed as an impurity) Therefore, cleaning with an organic solvent is indispensable.

  On the other hand, the mechanochemical method is a method of mechanically mixing at room temperature and pressure without using a solvent, so it is possible to use reagents that are difficult to dissolve in a solvent, and a wide range of structural designs of products is possible. It becomes. In addition, since an organic solvent is not used and the only by-product generated in the reaction step is water, there are advantages such as less adverse effects on the environment and the human body and high cost performance. However, a complete mechanochemical method has not been achieved so far for the production of ZIF-8, and according to reported examples (see Non-Patent Documents 6 and 7), a small amount of organic solvent (for example, Dimethylformamide, ethanol, etc.) and the presence of ammonium salts (eg, ammonium nitrate, ammonium methylsulfate, ammonium sulfate) as auxiliaries, and without these reagents, zinc oxide as a metal source and imidazole ligand can react. It has not been suggested. Further, the production scale is several hundred milligram scale, and a method capable of being produced on a larger scale is desired.

Japanese Patent No. 5083762 JP-A-2005-255651 Patent No. 4994398 Special table 2009-528251 Special table 2012-530722

By Kitagawa Susumu, Basics of Materials Science, No. 7, published by Sigma-Aldrich O.M.Yaghi et al., Accounts of Chemical Research 43, 58 (2010) O.M.Yaghi et al., Proc. Natl. Acad. Sci. USA 103, 10186 (2006) Y. Pan et al., Chem. Comm. 47, 2071 (2011) S. Tanaka et al., Chem. Lett., 41, 1337 (2012) T. Friscic et al., Angew. Chem. Int. Ed. 49, 712 (2010) T. Friscic et al., Chem. Sci. 3, 2495 (2012)

  An object of the present invention is to obtain an imidazolate skeleton material having a zeolite-like topology easily without requiring a solvent such as an organic solvent and an ammonium salt, and without requiring high temperature and high pressure conditions. To do. It is another object of the present invention to provide a composite containing novel composite particles containing a zeolite-like imidazolate structure, and a method for producing the same and a method for using the same as a functional material.

  In order to achieve the above-mentioned object, the present inventors diligently studied a simple method for producing ZIF including ZIF-8 by mechanochemical method, and as a result, a metal oxide was used as a starting material and no solvent was used. It was found that the reaction proceeds on a large scale by a dry production method that is not. Compared with the solvothermal method and the solution method, the dry production method of the present invention has the advantage that the metal oxide is used as a raw material and the unreacted material remains as the metal oxide, and no impurities are generated by reaction with water. is there. In addition, unexpectedly, the product obtained by the production method was found to be a composite containing novel composite particles containing metal oxide particles and polycrystalline particles of zeolite-like imidazolate structure (ZIF). It was. Furthermore, it has been found that the composite containing the composite particles containing polycrystalline particles of the zeolite-like imidazolate structure (ZIF) has a function superior to that of the single crystal particles of ZIF alone. That is, the present invention is as follows.

[1] A composite comprising composite particles containing metal oxide particles in the center of the composite particles and polycrystalline particles of a zeolite-like imidazolate structure in the outer shell of the metal oxide particles,
The metal in the metal oxide particles and the zeolite-like imidazolate structure is a metal selected from the group consisting of zinc and cobalt,
The imidazolate ligand is an imidazolate ligand derived from imidazole which may have a substituent or a derivative thereof, wherein the substituent includes a C _1-6 alkyl group, a halogen group and a nitro group. 1 to 3 substituents selected from the group consisting of groups, or adjacent substituents at positions 4 and 5 on the imidazolate ligand may be combined to have a substituent. The complex, which may form a condensed 5- or 6-membered aromatic carbocyclic ring or aromatic heterocyclic ring.
[2] The composite according to [1], wherein the metal is zinc and the zeolite-like imidazolate structure is ZIF-8.
[3] The abundance ratio of the metal oxide particles in the composite particles and the total number of polycrystalline particles of the zeolite-like imidazolate structure is 9: 1 to 2: 8 in molar ratio. ] Or the complex according to any one of [2].
[4] The composite according to any one of [1] to [3], wherein the composite is a composite composed of composite particles and metal oxide particles.
[5] The method for producing a composite according to any one of [1] to [4], comprising the following steps;
1) a step of blending and mixing a metal oxide and imidazole or a derivative thereof in a molar ratio of 1: 0.1 to 1: 5.0; and 2) i) a step of grinding and mixing the reaction mixture; or ,
ii) A step of heating and standing the reaction mixture.
[6] The production method according to [5], wherein the metal oxide is zinc oxide, and the imidazole or a derivative thereof is 2-methylimidazole.
[7] An adsorbent containing the complex according to any one of [1] to [4].
[8] The adsorbent according to [7] for a gas, a dye, or an organic solvent.
[9] Use of the composite according to any one of [1] to [4] for gas storage, gas separation, a gas sensor device, or a heterogeneous reaction catalyst.

  According to the present invention, there is provided a composite comprising composite particles containing metal oxide particles in the center of the composite particles, and polycrystalline particles of a zeolite-like imidazolate structure (ZIF) in the outer shell of the metal oxide particles. As compared with the case of conventional single crystal particles of ZIF alone, an excellent function (for example, adsorption ability) can be achieved.

It is drawing which shows the schematic diagram of the structure of ZIF-8. 1 is a drawing showing a powder X-ray diffraction spectrum of a complex product before washing in Example 1. It is drawing which shows the comparison of the change of the diffraction peak intensity of the zinc oxide in Example 1, 2-methylimidazole, and ZIF-8. 1 is a drawing showing a powder X-ray diffraction spectrum of a complex product after washing in Example 1. It is drawing which shows the thermogravimetric (TG) analysis chart of a composite product. It is drawing which shows the relationship between manufacturing time and the ZIF-8 presence rate in a composite_body | complex. 2 is a powder X-ray diffraction spectrum of the composite product of Example 2. 4 is a powder X-ray diffraction spectrum of the composite product of Example 3. It is drawing which shows the time-dependent change of the image of the scanning electron micrograph of a composite product when zinc oxide and 2-methylimidazole (Hmim) are made to react. For comparison, an image of an electron micrograph of a ZIF-8 single crystal prepared by a solution method (water) is also shown. It is drawing which shows the image of the scanning electron micrograph before and behind reaction of the zinc oxide of a different particle diameter (-5 micrometers). It is drawing which shows the powder X-ray-diffraction spectrum of a product when using a zinc oxide of a different particle diameter (-5 micrometers). It is a diagram showing changes over time when examining the adsorption capacity for nitrogen gas complex to form a zinc oxide and a 2-methylimidazole at a certain time reaction (N _2). For comparison, the measurement results for the ZIF-8 single crystal are also shown. It is drawing which shows the spectrum of the ultraviolet visible spectrophotometer (UV) which shows the adsorption capacity with respect to the rhodamine B of a composite_body | complex.

The present invention is described in further detail below.
(Definition)
The definitions of terms used in the present specification and claims are shown below. Unless otherwise indicated, the first definition given for a group or term herein applies to the group or term herein individually or as part of another group.

  The formation mechanism of the composite of the present invention is considered to be composite by a grinding / condensation process. Specifically, first, a reaction with imidazole occurs on the outer surface portion of the metal oxide particles, and a ZIF crystal is generated. Then, the composite particles of metal oxide to which these ZIF crystals are attached are condensed, and aggregates (aggregates) of the composite particles are once generated. These aggregates are then ground into smaller composite particle aggregates. At the same time, the reaction with imidazole proceeds in many places on the outer surface of the metal oxide particles, and the particle diameter of the metal oxide particles gradually decreases, with the result that the metal oxide particles are in the center (core) and the outer shell. Composite particles having ZIF crystal particles in the part are formed. These composite particles condense with each other to form a composite as an aggregate (aggregate). Further, when the composites condense to form an aggregate (aggregate), an unreacted metal oxide may be taken in to form the composite.

  The term “composite particle” refers to a particle having metal oxide particles in the central part (so-called core part) and crystals of a zeolite imidazolate structure aggregated in the outer shell part (so-called shell part) of the metal oxide particles. Means a composite particle containing metal oxide particles and polycrystalline particles of a zeolite-like imidazolate structure having a structure in which a large number of particles are coated.

  The term “composite” means an aggregate (aggregate) in which composite particles are condensed. The composite may include unreacted metal oxide particles. The composite has a porous structure. The abundance ratio of the composite particles to the metal oxide particles in the composite is about 100: 0 to about 5:95 in a molar ratio, such as about 95: 5 to about 20:80, for example about 90:10 to about 50:50, typically about 80:20. These abundance ratios can be measured and calculated from peak intensities at the time of thermogravimetric analysis (TG) and powder X-ray diffraction spectrum (XRD) measurement.

  The term “metal oxide particles” means zinc (II) oxide (ZnO) or cobalt (II) oxide (CoO) particles, with zinc oxide particles being preferred. Metal oxide particles having various particle sizes can be purchased commercially or can be prepared using manufacturing methods known in the art.

The term “zeolite-like imidazolate structure (sometimes abbreviated as“ ZIF ”” herein) means a structure having a zeolite-like topology in which a metal and an imidazolate ligand interact. To do. Particularly preferred is ZIF-8 (sometimes referred to herein as “Zn (mim) ₂ ”), wherein the metal is zinc and the imidazolate ligand is a 2-methylimidazolate ligand. . A schematic diagram of the structure of ZIF-8 is shown in FIG. In the composite particles of the present invention, when 2-methylimidazolate is replaced with an imidazolate derived from imidazole or a derivative thereof which may have the following substituent as the imidazolate ligand, a zeolite-like imidazole formed The rate structure may have a structure similar to ZIF-8.

  The term “polycrystalline particles” means a state in which a large number of particles in which crystals of a zeolite imidazolate structure are aggregated exist. A polycrystal is composed of small single crystals, which means that there is a grain boundary (meaning an interface existing between two or more small crystals in a polycrystal) between adjacent single crystals. . In the composite of the present invention, the grain boundary between single crystals is larger than the pores inside the single crystals. Therefore, for example, general ZIF-8 shows a low adsorption amount with respect to rhodamine B, whereas the complex of the present invention can show a high adsorption amount.

  The term “imidazolate ligand” means a ligand derived from imidazole that can coordinate with a metal at the position of the nitrogen atom from which the hydrogen is eliminated from the NH group at position 1 on the imidazole and the nitrogen atom at position 3 To do.

The term “optionally substituted imidazole or derivative thereof” means unsubstituted imidazole, or at least one or more of the 2, 4, or 5 positions on imidazole (preferably monosubstituted at the 2 position) ) Selected from the group consisting of an alkyl group having ₁ to 6 carbon atoms (C _1-6 ) (for example, 1 to 3 carbon atoms (C _1-3 )), a halogen group, and a nitro group. A fused cyclic 5- or 6-membered fragrance optionally having 1 to 3 substituents, or adjacent substituents at positions 4 and 5 on the imidazole taken together Means imidazole which may form an aromatic carbocyclic ring or an aromatic heterocyclic ring. Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, neobutyl, t-butyl, n-pentyl, n-hexyl, and the like. N-propyl and isopropyl are more preferable, methyl and ethyl are more preferable, and methyl is particularly preferable. Examples of the halogen group include fluoro, chloro, bromo and iodo, and chloro is preferred.

In addition, the adjacent substituents at the 4- and 5-positions on the imidazole together form a condensed cyclic 5- or 6-membered aromatic carbocycle or aromatic heterocycle which may have a substituent. It may be. Examples of fused cyclic 5- or 6-membered aromatic carbocycles include benzo groups. The fused cyclic 5- or 6-membered aromatic heterocycle means a fused 5- or 6-membered aromatic heterocycle containing at least one atom selected from oxygen, nitrogen or sulfur atoms as a hetero atom. Examples of the 5-membered aromatic heterocycle include a furo group, a thiopheno group, a pyrrolo group, an imidazolo group, a pyrazolo group, an isoxazolo group, and a tetrazolo group. Examples of the 6-membered aromatic heterocycle include a pyrido group, a pyrazino group, Group, pyrimidino group, pyridazino group and the like. A typical example of imidazole or a derivative thereof is shown in the following formula.
The most preferred specific example includes 2-methylimidazole (sometimes abbreviated as “Hmim” in the present specification), and the ligand derived therefrom is 2-methylimidazolate (in the present specification, Which may be abbreviated as “mim”), which is a ligand that constitutes “ZIF-8” described above. Imidazole and its various derivatives can be purchased commercially or synthesized using methods known in the art.

In the composite particles of the present invention, the outer surface portion of the metal oxide particles may be entirely covered with the polycrystalline particles of the zeolite-like imidazolate structure, or a part thereof may be covered. The degree of such coating is adjusted by adjusting the compounding ratio of the metal oxide particles and imidazole or its derivative to be blended at the time of producing the composite particles, or by modifying the reaction conditions (for example, the reaction time) at the time of producing the composite, It can be changed by controlling. The abundance ratio of the metal oxide particles in the composite particles of the present invention and the total number of polycrystalline particles of the zeolite-like imidazolate structure is a molar ratio, for example, about 99: 1 to about 1:99, preferably Of about 9: 1 to about 2: 8, typically about 3: 1. For example, as the compounding ratio of imidazole or a derivative thereof is increased in molar ratio with respect to the metal oxide particles, the abundance ratio of the metal oxide in the resulting composite particles decreases, and when imidazole is reacted in a large excess amount All metal oxide particles can be converted into composite particles.
These abundance ratios can be measured and calculated from the peak intensity at the time of thermogravimetric analysis and powder X-ray diffraction spectrum measurement.

  The average particle diameter of the metal oxide particles is, for example, about 5 nm to about 5 μm, preferably about 1 μm or less, for example, about 10 nm to about 1 μm, more preferably about 20 nm to about 100 nm, and the zeolite-like imidazo The average particle size of one of the polycrystalline particles of the rate structure is, for example, about 10 nm to about 50 nm, preferably about 20 nm to about 30 nm, and the average particle size of the composite particles is, for example, about 50 nm to about 50 nm. 500 nm, preferably from about 50 nm to about 300 nm. The size of the single crystal constituting the polycrystal can be estimated by, for example, analyzing the result of XRD using a method well known in the art, for example, Scherrer's equation. These average particle diameters are confirmed by analyzing the image of a scanning electron microscope and calculating the yield from thermogravimetric analysis. In the formation of the composite particles of the present invention, when a certain ratio of metal oxide particles and imidazole are reacted, the larger the average particle size of the metal oxide particles, the smaller the surface area of the metal oxide particles per mole relative to imidazole. Therefore, the possibility that the reaction between the metal oxide and imidazole proceeds is reduced.

(Manufacturing)
A method for producing the composite of the present invention will be described below.
The composite of the present invention can be produced using a dry production method as a mechanochemical method. Such a dry production method is a method for producing a reaction reagent as a raw material by mechanically mixing it without using any reaction solvent.

The reaction formula of the present invention is shown below.
(Reaction formula)
As shown in the above formula, a metal oxide (abbreviated as “MO”) (1 equivalent) and imidazole (z molar equivalent with respect to the metal oxide) are reacted to form a composite (“M (min) ₂ / MO ") is generated. The only by-product generated in the reaction process is water.

The operation of the manufacturing method consists of the following steps.
1) First, a metal oxide and imidazole or a derivative thereof are blended and mixed in a suitable reaction vessel. At this time, the molar ratio of the metal oxide and the imidazole or a derivative thereof is about 1: 0.1 to about 1: 5.0, and about 1: 0.1 to about 1: 2.0. A ratio of about 1: 0.5 is preferred, and a ratio of about 1: 0.5 is more preferred.

2) i) Next, after mixing the reaction mixture, the reaction mixture is ground and mixed. Specifically, it is carried out in a suitable reaction vessel in accordance with a generally known pulverization and mixing operation. An example of the reaction vessel is a ball mill. The rotation speed is about 50 to about 200 rpm, and a preferred example is about 100 rpm. In addition, the reaction mixture may be heated at a high temperature (for example, about 50 ° C. to about 200 ° C.) during the reaction, and the reaction time can be shortened by these operations. The reaction time may vary depending on the reaction conditions such as the rotation speed or reaction temperature, but is preferably about 1 hour to about 240 hours, more preferably about 3 hours to about 120 hours.

  Alternatively, in place of the above pulverization / mixing operation i), the reaction mixture after blending may be heated and allowed to stand for an appropriate time. The heating time is preferably about 50 ° C to about 200 ° C, more preferably about 100 ° C. An example of a reaction vessel that can be used in this case is a Teflon vessel. Further, during the reaction, the reaction mixture may be heated and left under pressure (for example, about 2 to 50 atm) in a pressure vessel (for example, a commercially available stainless steel pressure vessel). Can be shortened. The reaction time may vary depending on the reaction conditions such as the reaction temperature or pressure, but is preferably about 1 hour to about 72 hours, more preferably about 12 hours to about 48 hours.

  As the step 2), the operation of pulverizing and mixing is preferable from various viewpoints such as yield and reaction time.

  The conversion rate from the metal oxide as the raw material to the complex as the product (which means the yield of the product) can be measured by thermogravimetric analysis.

(use)
Next, a method for using the composite of the present invention obtained by the above production method as a functional material will be described.

1. Improvement of functions originally possessed by ZIF crystal particles First, since the composite of the present invention contains ZIF crystal particles as its constituent elements, it can provide the functions inherent to ZIF itself. For example, when ZIF-8 crystal particles are included, the function inherent to ZIF-8 itself (for example, as an adsorbent for various substrates) can be provided. Examples of substrates include gases (eg, nitrogen gas, hydrogen, carbon monoxide, carbon dioxide, helium, argon), dyes (eg, basic dyes such as rhodamine B, auramine, malachite green, methylene blue)), peptides, proteins And organic solvents (for example, lower alcohols such as methanol and ethanol; polyhydric alcohols such as polyethylene glycol).

2. Creation of composite function of metal oxide particle function and ZIF crystal particle function Next, the composite of the present invention includes metal oxide particles and ZIF crystal particles as its constituent elements. In addition to the functions originally possessed, it can be expected that the metal oxide particles themselves exhibit the functions originally possessed in a composite manner. For example, zinc oxide as a metal oxide is known to function as a photocatalyst (for example, H. Zhang et al., J. Mater. Chem. 19, 5089 (2009); HAD Maria et al., Energy Environ Sci. 2, 1231 (2009); K. Rajeshwar et al., J. Photochem. Photobiol. C: PHOTOCHEM. REV. 9, 171 (2008)), the complex of the present invention contains the above ZIF-8. It can be expected that the function as a photocatalyst can be simultaneously and compositely exhibited in addition to the function inherent in itself.

  The composite of the present invention can be used as a functional material for various applications based on the above functions. For example, gas storage and gas separation for gas (eg, nitrogen, hydrogen, carbon monoxide, carbon dioxide, helium, argon); catalyst (eg, heterogeneous catalyst (hydrogenation reaction catalyst, photocatalyst, Kunefener gel condensation) Reaction catalysts)); and devices (eg gas sensor devices, solid electrolytes for fuel cells).

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Zinc oxide (0.02 μm and −5 μm) was purchased from Wako Pure Chemical Industries, Ltd. 2-Methylimidazole was purchased from Sigma-Aldrich. Rhodamine B was purchased from Wako Pure Chemical Industries.
Characterization of the product of the complex was performed by analysis of various spectroscopic analyses. Specifically, the time course of the reaction is measured by measuring the powder X-ray diffraction spectrum of the reaction mixture and analyzing with an electron microscope, and the conversion rate from metal oxide to composite particles (so-called composite yield). Was performed by thermogravimetric analysis and powder X-ray diffraction spectrum.

Manufacture of composite (grinding and mixing)
8.1 g (about 100 mmol) in a 300 ml ceramic pot mill vessel (93% Al ₂ O ₃ , 5% SiO ₂ ) filled with 100 YTZ balls (φ10 mm, 95% ZrO ₂ + HfO ₂ , 5% Y ₂ O ₃ ) ) Zinc oxide (0.02 μm) and 16.4 g (about 200 mmol) of 2-methylimidazole were added and rotated and ground and mixed at 100 rpm with a desktop pot mill stand (UBM-2, Masuda Rika Kogyo Co., Ltd.). The mixing time was 3 hours to 240 hours. After pulverization and mixing, the product was taken out from the ceramic pot mill container, dispersed in 50 ml of water and washed twice to remove unreacted 2-methylimidazole. When manufactured in 3 hours, 6 hours, 24 hours, 120 hours, and 240 hours, about 13 g, about 15 g, about 17 g, about 19 g, and about 20 g of the composite were obtained, respectively.

Powder X-ray diffraction (XRD) measurement: X-ray diffraction (XRD) measurement of the obtained composite was performed using a commercially available X-ray diffraction apparatus (manufactured by Rigaku Corporation, trade name: MiniFlex600. FIG. It is a XRD pattern of the composite_body | complex (before washing | cleaning) obtained in Example 1. Fig. 3 shows the comparison of the change of the diffraction peak intensity of zinc oxide, 2-methylimidazole, and ZIF-8. Since the diffraction peak intensity of imidazole decreases and the diffraction peak intensity of ZIF-8 increases, the reaction between zinc oxide and 2-methylimidazole can be confirmed, and Fig. 4 shows the XRD of the complex after washing. Based on the diffraction pattern, the composite can be identified as a composite of composite particles of ZIF-8 and ZnO, and the size of the single crystal (crystallite) can be determined from the broadening of the diffraction peak. Evaluation and calculation by the formula of cherrer (Sheller) When produced in 48 hours, the average particle diameter (crystallite diameter) of zinc oxide in the composite particles is about 12 nm, and the average particle diameter (crystallite diameter) of ZIF-8 Was calculated to be about 25 nm.
D = Kλ / βcos θ (where D: crystallite size, λ: measured X-ray wavelength (= 0.15418 nm, β: broadening of diffraction line by crystallite size (radian unit)), θ: diffraction line Bragg angle, K: Scherrer constant (= 0.94)))

Thermogravimetric analysis: Thermogravimetric (TG) analysis of the obtained composite was performed using a commercially available thermogravimetric analyzer (manufactured by Shimadzu Corporation, trade name: DTG-60H). FIG. 5 is a TG chart of the composite obtained in Example 1. As a comparative example, TG analysis was performed using a ZIF-8 single crystal prepared by a solution method (water). ZIF-8 is thermally decomposed in air at 400-450 ° C. to produce zinc oxide having a mass of about 35% of ZIF-8. Based on the TG chart of the composite obtained at each reaction time, the abundance ratio of ZIF-8 polycrystalline particles and zinc oxide particles in each composite could be quantified. FIG. 6 shows the relationship between the production time and the proportion of ZIF-8 polycrystalline particles in the composite based on the results of FIG.

Manufacture of composite (grinding and mixing)
8.1 g (about 100 mmol) in a 300 ml ceramic pot mill vessel (93% Al ₂ O ₃ , 5% SiO ₂ ) filled with 100 YTZ balls (φ10 mm, 95% ZrO ₂ + HfO ₂ , 5% Y ₂ O ₃ ) ) Zinc oxide (0.02 μm) and 4.1 g (about 50 mmol) of 2-methylimidazole were added, and the mixture was rotated and ground and mixed at 100 rpm with a desktop pot mill mount (Masuda Rika Kogyo Co., Ltd. UBM-2). After pulverization and mixing, the composite was taken out from the ceramic pot mill container, and X-ray diffraction (XRD) measurement was performed in the same manner as in Example 1. FIG. 7 is an XRD pattern of the composite obtained in Example 2. Since all 2-methylimidazole reacted and was consumed, no diffraction peak was observed. Therefore, the washing process for removing 2-methylimidazole could be omitted.

Manufacture of composite (heated still)
0.81 g (about 10 mmol) of zinc oxide (0.02 μm) and 0.41 g (about 5 mmol) of 2-methylimidazole were placed in a 50 ml Teflon container and sealed. The sealed Teflon container was heated and allowed to stand at 100 ° C. for 48 hours, then cooled to room temperature, and the product was taken out from the Teflon container to obtain about 1.1 g of a composite. In the same manner as in Example 1, X-ray diffraction (XRD) measurement was performed. FIG. 8 is an XRD pattern of the composite obtained in Example 3. Since all 2-methylimidazole reacted and was consumed, no diffraction peak was observed. Therefore, the washing process for removing 2-methylimidazole could be omitted.

Electron microscope observation of the complex Scanning electron microscope observation: Commercially available scanning electron microscope apparatus (manufactured by Hitachi High-Tech, trade name: S-5000, acceleration voltage 2 kV, particle size 0.02 μm (20 nm) The composite obtained in Example 1 using zinc oxide was observed with an electron microscope, and the measurement results are shown in Fig. 9. As a comparative example, the electron of ZIF-8 single crystal prepared by the solution method (water) An image of a micrograph (Shunsuke Tanaka et al., Chem. Lett. 41, 1377, 2012) is also shown.

Effect of Zinc Oxide Particle Size on Complex Formation In the same manner as in Example 3, 50 ml of 0.81 g (about 10 mmol) of zinc oxide (-5 μm) and 0.41 g (about 5 mmol) of 2-methylimidazole were used. And sealed in a Teflon container. The sealed Teflon container was heated and allowed to stand at 100 ° C. for 48 hours, then cooled to room temperature, and the product was taken out from the Teflon container. In the same manner as in Example 4, the product after the reaction was observed with a scanning electron microscope. The electron microscope images before and after the reaction are shown in FIG. From the observation results, it was found that the raw material zinc oxide particles were observed and composite particles were not formed.
Further, in the same manner as in Example 1, X-ray diffraction (XRD) measurement was performed. FIG. 11 is an XRD pattern of the product obtained after the reaction obtained using −5 μm zinc oxide. The diffraction peak of the raw material 2-methylimidazole was confirmed, and when the particle diameter of zinc oxide was large, it was confirmed that the reaction between zinc oxide and 2-methylimidazole did not proceed.

Measurement of adsorption capacity of complex to nitrogen gas (N ₂ ) Measurement of nitrogen adsorption amount: The nitrogen adsorption amount was measured using a commercially available adsorption measuring device (BELSORP-max, manufactured by Nippon Bell Co., Ltd.). The measurement was performed in a state where the obtained composite was put into a sample tube and the sample tube was immersed in liquid nitrogen (77K). The measurement results are shown in FIG. FIG. 12 shows the adsorption isotherm (relationship between equilibrium pressure and nitrogen adsorption amount) of the composite obtained in Example 1. 3 hours, 6 hours, 24 hours, 120 hours, when produced in 240 hours, about 460 m ² / g, respectively complex, about 670m ² / g, about 1310m _² / g, _N ² surface area of about 1290m ² / g (Langmuir).
As a comparative example, measurement was performed using a ZIF-8 single crystal prepared by a solution method (water).
From the above results, as a result of examining the adsorption amount of nitrogen gas for each composite obtained after various fixed times in Example 1 above, the composite obtained after 24 hours is comparable to ZIF-8 single crystal particles. The composites obtained after 120 hours and 240 hours showed higher nitrogen gas adsorption. Zinc oxide is known not to have nitrogen adsorption ability.

Measurement of adsorptive capacity of complex to rhodamine B 0.04 g of the complex produced in Example 1 in 6 hours was added to 20 ml of rhodamine B aqueous solution prepared to 1.0 × 10 ⁻⁵ M, and 20 ° C. in a dark room. The sample was allowed to stand for 20 minutes, and an adsorption experiment for rhodamine B was conducted. The absorbance (absorption wavelength = 554 nm) of the rhodamine B aqueous solution was measured using a commercially available ultraviolet-visible spectrophotometer (UV) apparatus (manufactured by Shimadzu Corporation, UV-2450), and the concentration of rhodamine B was calculated. As a comparative example, measurement was carried out in the same manner using ZIF-8 single crystal prepared by zinc oxide (0.02 μm) and a solution method (water). FIG. 13 shows the result of spectrum measurement using the UV-visible spectrophotometer. Table 1 below shows the amount of rhodamine B adsorbed on zinc oxide, a ZIF-8 single crystal obtained by a solution method (water), and a complex produced in 6 hours. Since the presence ratio of ZIF-8 in the complex produced in 6 hours was about 49%, the adsorption amount converted to ZIF-8 was calculated to be 9.6 μmol / g complex. From the above results, the amount of adsorption of Rhodamine B of the complex of the present invention was markedly increased.
As a result, the composite showed a marked increase in the amount of rhodamine B adsorbed compared to the ZIF-8 single crystal particles obtained by the solution method.

  The composite obtained by the present invention contains polycrystalline composite particles that cannot be obtained by a conventional method, and has a very high adsorbing ability for a gas (for example, nitrogen gas) and a dye (for example, rhodamine B). It can be used as a new functional material for various uses. For example, it is useful as a gas storage, gas separation, gas sensor device, catalyst, and the like, and has high industrial utility value. In addition, the dry production method of the present invention is a clean production method with low environmental impact, high cost performance, suitable for mass production, excellent production processing, and industrially useful. high.

Claims (9)

A composite comprising composite particles containing metal oxide particles in the center of the composite particles and polycrystalline particles of a zeolite-like imidazolate structure in the outer shell of the metal oxide particles,
The metal in the metal oxide particles and the zeolite-like imidazolate structure is a metal selected from the group consisting of zinc and cobalt,
The imidazolate ligand is an imidazolate ligand derived from imidazole which may have a substituent or a derivative thereof, wherein the substituent includes a C _1-6 alkyl group, a halogen group and a nitro group. 1 to 3 substituents selected from the group consisting of groups, or adjacent substituents at positions 4 and 5 on the imidazolate ligand may be combined to have a substituent. The complex, which may form a condensed 5- or 6-membered aromatic carbocyclic ring or aromatic heterocyclic ring.   The composite of claim 1, wherein the metal is zinc and the zeolite-like imidazolate structure is ZIF-8.   The abundance ratio of the metal oxide particles in the composite particles and the total number of polycrystalline particles of the zeolite-like imidazolate structure is 9: 1 to 2: 8 in molar ratio. The complex according to any one of the above.   The composite according to any one of claims 1 to 3, wherein the composite is a composite comprising composite particles and metal oxide particles. The manufacturing method of the composite_body | complex of any one of Claims 1 thru | or 4 including the following processes;
1) a step of blending and mixing a metal oxide and imidazole or a derivative thereof in a molar ratio of 1: 0.1 to 1: 5.0; and 2) i) a step of grinding and mixing the reaction mixture; or ,
ii) A step of heating and standing the reaction mixture.   The process according to claim 5, wherein the metal oxide is zinc oxide, and the imidazole or derivative thereof is 2-methylimidazole.   An adsorbent containing the composite according to any one of claims 1 to 4.   The adsorbent of Claim 7 with respect to gas, dye, or an organic solvent.   Use of a composite according to any one of claims 1 to 4 for gas storage, gas separation, gas sensor device or heterogeneous reaction catalyst.