Composite material, method for producing the same, and quartz crystal resonator gas sensor using the same

Abstract

To provide a composite material using fullerene and a metal-organic framework, a method for producing the same, and a quartz crystal resonator sensor using the same.SOLUTION: The composite material of the present invention comprises fullerene nanotubes and a zeolitic imidazolate framework (ZIF) containing metal ions positioned on surfaces of the fullerene nanotubes. The method for producing the composite material of the present invention comprises acid-treating fullerene nanotubes, mixing and reacting the fullerene nanotubes, imidazole or a derivative of the same, and a salt of a metal element in a solvent, and washing and drying an obtained product.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a composite material, a method for producing the same, and a quartz crystal resonator sensor using the same. [Background technology]

[0002] In recent years, composite materials using fullerenes and metal-organic frameworks (MOFs) have been developed, and their functionality has attracted attention (see, for example, Patent Document 1). According to Patent Document 1, a gas adsorption material has been developed that contains a specific metal-organic framework and a fullerene therein. Such gas adsorption materials can be used for gas storage and gas separation. In addition to the composite material described in Patent Document 1, it is expected that composite materials with unique properties and functionality will be developed by combining fullerenes and metal-organic frameworks. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-514530 Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above, an object of the present invention is to provide a composite material using a fullerene and a metal organic framework, a method for producing the same, and a quartz oscillator sensor using the same. [Means for solving the problem]

[0005] The composite material of the present invention comprises fullerene nanotubes and zeolite-like imidazolate structures (ZIFs) containing metal ions located on the surface of the fullerene nanotubes, thereby solving the above-mentioned problems. The fullerene constituting the fullerene nanotube is C 60 Fullerene, C 70 Fullerene, C 76 Fullerene, C78 Fullerene, C 82 Fullerene, C 84 Fullerene, C 90 Fullerene, C 94 It may be selected from the group consisting of fullerenes and derivatives thereof. The fullerene is C 60 It may be fullerene or a derivative thereof. The metal ions may be selected from the group consisting of zinc ions, cobalt ions, cadmium ions, lithium ions, manganese ions, mercury ions, iron ions, copper ions, and indium ions. The molar ratio of the fullerenes constituting the fullerene nanotube to the metal ions may be in the range of 0.1 or more and 2.5 or less. The molar ratio may be in the range of 0.5 or more and 2.0 or less. The molar ratio may be in the range of 0.75 to 1.25. The zeolite-like imidazolate structure may be selected from the group consisting of ZIF-7, ZIF-22, ZIF-8, ZIF-67, ZIF-69, ZIF-71, ZIF-78, ZIF-90, and ZIF-95. The BET specific surface area is 150m 2 / g or more 700m 2 / g or less. The total pore volume is 0.15 cm 3 / g or more 0.7cm 3 / g or less, and the pore volume of micropores having a pore diameter of 1 nm or less may be in the range of 40% to 70% of the total pore volume. The method for producing the above-mentioned composite according to the present invention comprises treating fullerene nanotubes with an acid, mixing and reacting the acid-treated fullerene nanotubes with imidazole or a derivative thereof and a salt of a metal element in a solvent, and washing and drying the product obtained by the mixing and reaction, thereby solving the above-mentioned problem. The acid treatment may use an acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid. The salt of the metal element may be an inorganic acid salt or an inorganic halide salt of a metal element selected from the group consisting of zinc, cobalt, cadmium, lithium, manganese, mercury, iron, copper, nickel, platinum, and indium. In the mixing and reaction, the acid-treated fullerene nanotubes, the imidazole or its derivative, and the salt of the metal element may satisfy a molar ratio of 1-5:10-100:1-10. The quartz crystal resonator gas sensor according to the present invention comprises a gas sensor film, and the gas sensor film contains the composite material described above, thereby solving the above-mentioned problems. Volatile organic compounds selected from the group consisting of formic acid, acetic acid, toluene, benzene, cyclohexane, hexane, pyridine, acetone, and aniline may be detected. [Effects of the Invention]

[0006] The composite material of the present invention contains fullerene nanotubes and zeolite-like imidazolate structures (ZIFs) containing metal ions located on the surface of the fullerene nanotubes. The composite material of the present invention exhibits excellent selectivity for volatile organic compounds and is applicable to quartz crystal resonator gas sensors. [Brief explanation of the drawings]

[0007] [Figure 1] Schematic diagram showing the composite material of the present invention. [Figure 2] Flowchart showing the steps for producing the composite material of the present invention [Figure 3A] Front view of a quartz crystal resonator gas sensor using the composite material of the present invention. [Figure 3B] Side view of a quartz crystal resonator gas sensor using the composite material of the present invention [Figure 4] 1 shows SEM images of the products of Examples 1 to 4. [Figure 5] STEM and TEM images of the product of Example 2 [Figure 6] Figure showing the XRD pattern of the product of Example 2 [Figure 7]FITR spectrum of the product of Example 2 [Figure 8] FIG. 1 shows the Raman spectrum of the product of Example 2. [Figure 9] 1 shows the thermogravimetric profile of the product of Example 2. [Figure 10] Figure showing XPS spectra of the product of Example 2 and FNT-ox [Figure 11] XPS core level spectrum of FNT-ox [Figure 12] Figure 1 shows the XPS core level spectrum of the product of Example 2 [Figure 13] FIG. 1 shows nitrogen adsorption / desorption isotherms for the products of Examples 1 to 4. [Figure 14] FIG. 1 shows the time dependence of the frequency shift when the QCM electrodes using the products of Examples 1 to 4 are exposed to formic acid. [Figure 15] Figure 1 shows the results of repeated frequency shift tests when a QCM electrode using the product of Example 2 was exposed to formic acid. [Figure 16] A table showing the frequency shifts observed when a QCM electrode using the product from Example 2 is exposed to various volatile organic compounds. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are given like reference numerals and their description will be omitted. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits.

[0009] (Embodiment 1) In the first embodiment, a composite material and a method for producing the same of the present invention will be described. FIG. 1 is a schematic diagram showing the composite material of the present invention.

[0010] The composite material 100 of the present invention contains a fullerene nanotube 110 and a zeolitic imidazolate framework (ZIF) 120 containing metal ions, which is located on the surface of the fullerene nanotube 110. Hereinafter, the zeolitic imidazolate framework containing metal ions may be simply referred to as ZIF.

[0011] 1, the fullerene nanotube 110 has a hollow structure and its cross-sectional shape is circular, elliptical, etc. The surface of the fullerene nanotube 110 refers to the surface inside the hollow structure as well as the outer surface.

[0012] There are no particular limitations on the fullerene nanotube 110, as long as it is a spherical molecule containing fullerene as its main component and carbon atoms with and / or without a substituent.

[0013] The fullerene constituting the fullerene nanotube 110 is, for example, C 60 Fullerene, C 70 Fullerene, C 76 Fullerene, C 78 Fullerene, C 82 Fullerene, C 84 Fullerene, C 90 Fullerene, C 94 The fullerene may be selected from the group consisting of fullerenes and derivatives thereof. Note that the fullerene derivative refers to a compound in which at least a part of a fullerene is modified.

[0014] Among them, fullerene is more preferably C 60 Fullerene and / or its derivatives. 60 In the case of fullerene and its derivatives, the fullerene nanotube can have a hollow structure without being partially blocked.

[0015] The surface of the fullerene nanotube 110 may be hydrophilic, which allows the ZIF 120 to be immobilized on the surface. The fullerene nanotube 110 preferably exhibits peaks derived from the stretching bands of CO and / or C—OH in the infrared absorption spectrum. The hydrophilicity can be improved by oxy-functionalizing the surface of the fullerene nanotube 110.

[0016] The fullerene nanotubes 110 preferably have the following dimensions: The length in the longitudinal direction is in the range of 1 μm to 10 μm. The wall thickness is in the range of 100 nm to 300 nm. The diameter is in the range of 450 nm to 1.5 μm. Such a size makes it easier to position ZIF120 on the surface.

[0017] The metal ions contained in ZIF120 are selected from the group consisting of zinc ions, cobalt ions, cadmium ions, lithium ions, manganese ions, mercury ions, iron ions, copper ions, and indium ions. These metal ions can be incorporated into ZIF120. Furthermore, the composite material 100 of the present invention can exhibit functionality depending on the selected metal ion. In particular, when cobalt (Co) ions are selected as the metal ion, high selectivity for volatile organic compounds (VOCs) can be exhibited.

[0018] ZIF120 is a type of material based on metal-organic frameworks (MOFs), a three-dimensional microporous material similar to zeolites, in which the organic bridging ligands that bridge the metal ions are imidazole-substituted.

[0019] ZIF120 is known as ZIF-7, ZIF-22, ZIF-8, ZIF-67, ZIF-69, ZIF-71, ZIF-78, ZIF-90, ZIF-95, etc., depending on the pore size, type of imidazole substituent, etc. Among them, ZIF-67, i.e., a sodalite-type crystal structure in which metal ions are crosslinked with 2-methylimidazole, is preferred from the viewpoint of pore size and yield.

[0020] The ZIF 120 is particulate and adheres to the fullerene nanotube 110. The ZIF 120 preferably has a particle size in the range of 50 nm or more and 200 nm or less. This can improve the functionality of the composite material 100 of the present invention. The ZIF 120 more preferably has a particle size in the range of 75 nm or more and 125 nm or less. This can further improve the functionality of the composite material 100 of the present invention. In this specification, the particle size of ZIF is the average of the longest diameters of 100 particles observed in an electron microscope image at 15,000x magnification.

[0021] In the composite material 100, the molar ratio of fullerenes constituting the fullerene nanotubes 110 to the metal ions in the ZIF 120 preferably falls within the range of 0.1 to 2.5, thereby stabilizing the composite material 100.

[0022] The molar ratio more preferably falls within the range of 0.5 or more and 2.0 or less, thereby improving the functionality of the composite material 100 of the present invention. The molar ratio even more preferably falls within the range of 0.75 or more and 1.25 or less, thereby further improving the functionality of the composite material 100 of the present invention.

[0023] The composite material 100 of the present invention is preferably 150 mm 2 / g or more 700m 2 The composite material 100 of the present invention more preferably has a BET specific surface area of ​​180 m / g or less. 2 / g or more 600m 2 / g or less, which may improve the functionality of the composite material 100. Even more preferably, the composite material 100 of the present invention has a BET surface area of ​​250 m 2 / g or more 350m 2 / g or less, which can further improve the functionality of the composite material 100.

[0024] The composite material 100 of the present invention is preferably 0.15 cm 3 / g or more 0.7cm 3 / g or less, and the pore volume of micropores with pore diameters of 1 nm or less is in the range of 40% to 70% of the total pore volume. This can improve the functionality of the composite material 100. The composite material 100 of the present invention more preferably has a pore volume of 0.5 cm 3 / g or more 0.67cm 3 / g or less, and the pore volume of micropores with pore diameters of 1 nm or less is in the range of 40% to 50% of the total pore volume. This can further improve the functionality of the composite material 100.

[0025] The composite material 100 of the present invention preferably comprises carbon atoms (C), oxygen atoms (O), metal (here cobalt) atoms (M) and nitrogen atoms (N), and is composed of the following atomic percentages (%): 70≦C≦85 10≦0≦20 0.5≦M≦20 2.5≦N≦10 This stabilizes the composite material 100 and improves its functionality.

[0026] The composite material 100 of the present invention exhibits various functions depending on the type of metal ion, and is applicable to gas storage, gas separation, catalysis, gas detection, energy storage, etc. In particular, the composite material 100 of the present invention has defect sites, uncoordinated metal atoms, and / or basic N (nitrogen) sites, and these sites interact with guest molecules such as volatile organic compounds (VOCs), enabling the detection of guest molecules.

[0027] Next, a method for producing the composite material 100 of the present invention will be described. FIG. 2 is a flow chart showing the steps for producing the composite material of the present invention.

[0028] The composite material 100 of the present invention is manufactured by the following steps. Step S210: The fullerene nanotubes are treated with acid. Step S220: The fullerene nanotubes treated with acid in step S210, imidazole or a derivative thereof, and a salt of a metal element are mixed in a solvent and reacted with each other. Step S230: The product obtained by mixing and reacting in step S220 is washed and dried.

[0029] Each step will be described in detail. In step S210, the fullerene nanotube may be a fullerene nanotube having the above-described characteristics. Such fullerene nanotubes may be produced by, for example, the liquid-liquid interface precipitation method described in Japanese Patent Laid-Open No. 2022-18133.

[0030] In step S210, the acid treatment makes the surface of the fullerene nanotube hydrophilic, allowing for uniform growth of ZIF. Any acid can be used for the acid treatment as long as the surface of the fullerene nanotube is oxy-functionalized. For example, an acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid is used. A combination of acids may also be used.

[0031] In step S210, the acid treatment may be performed by ultrasonically treating the fullerene nanotubes in an acid solution, washing, and drying them in a vacuum at a temperature of 50° C. to 100° C. for 5 hours to 24 hours.

[0032] In step S220, imidazole or a derivative thereof refers to imidazole with or without a substituent, imidazole having 1 to 3 substituents selected from the group consisting of an alkyl group having 1 to 6 carbon atoms (e.g., 1 to 4 carbon atoms, 1 to 3 carbon atoms), a halogen group, and a nitro group on at least one or more carbon atoms at the 2-, 4-, or 5-positions on the imidazole, or imidazole in which adjacent substituents at the 4- and 5-positions on the imidazole may be joined together to form a fused 5- or 6-membered aromatic carbon ring or aromatic hetero ring which may have a substituent.

[0033] 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, and n-hexyl. Among these, methyl, ethyl, n-propyl, and isopropyl are more preferred, methyl and ethyl are even more preferred, and methyl is particularly preferred. Examples of the halogen group include fluoro, chloro, bromo, and iodo, with chloro being preferred.

[0034] Examples of fused 5- or 6-membered aromatic carbocyclic rings include a benzo group. Examples of fused 5- or 6-membered aromatic heterocyclic rings include a furo group, a thiopheno group, a pyrrolo group, an imidazolo group, a pyrazolo group, an isoxazolo group, a tetrazolo group, a pyrido group, a pyrazino group, a pyrimidino group, a pyridazino group, and the like, each containing at least one heteroatom selected from the group consisting of oxygen, nitrogen, and sulfur atoms.

[0035] Among them, imidazole or its derivative is preferably 2-methylimidazole, which is commercially available, easily available, and can be synthesized by existing methods.

[0036] In step S220, the salt of the metal element may be an inorganic salt or an organic salt of the metal element, preferably an inorganic salt of the metal element, such as an inorganic acid salt or an inorganic halide salt of a metal element selected from the group consisting of zinc, cobalt, cadmium, lithium, manganese, mercury, iron, copper, nickel, platinum, and indium.

[0037] In step S220, the solvent may be ultrapure water, ion-exchanged water, distilled water, or the like.

[0038] In step S220, the fullerene constituting the fullerene nanotube treated with acid in step S210, imidazole or its derivative, and salt of a metal element are mixed in a molar ratio of 1-5:10-100:1-10. If this ratio is satisfied, the reaction is promoted.

[0039] In step S220, the molar ratio of the fullerene constituting the fullerene nanotube to the salt of the metal element preferably falls within the range of 0.1 to 2.5, thereby stabilizing the composite material 100.

[0040] The molar ratio more preferably falls within the range of 0.5 or more and 2.0 or less, thereby improving the functionality of the composite material 100 of the present invention. The molar ratio even more preferably falls within the range of 0.75 or more and 1.25 or less, thereby further improving the functionality of the composite material 100 of the present invention.

[0041] In step S220, triethylamine, sodium hydroxide, etc. may be added as a reaction accelerator. The amount of the accelerator added may be in the range of 1.0 to 8.0 with respect to the metal ions.

[0042] In step S220, the reaction can be carried out by simply stirring at a temperature ranging from 15°C to 40°C. Ultrasonic treatment for 5 to 60 minutes may be used for stirring. The progress of the reaction can be confirmed by the precipitation of colored solid crystals, such as brown crystals.

[0043] In step S230, washing may be performed using water such as ultrapure water, ion-exchanged water, or distilled water, followed by alcohol such as isopropanol or ethanol to remove unreacted substances from the product of step S220.

[0044] In step S230, the drying is not particularly limited as long as the solvent can be removed, but drying may be performed in a vacuum at a temperature range of 50° C. to 100° C. for 5 hours to 24 hours.

[0045] (Embodiment 2) In the second embodiment, a quartz crystal resonator gas sensor using the composite material of the present invention described in the first embodiment will be described. FIG. 3A shows a front view of a quartz crystal gas sensor using the composite material of the present invention. FIG. 3B shows a side view of a quartz crystal gas sensor using the composite material of the present invention.

[0046] A quartz crystal microbalance (QCM) electrode 310 of a QCM gas sensor 300 according to the present invention is provided with a gas sensor film 320 containing the composite material described in the first embodiment.

[0047] Specifically, the QCM electrode 310 includes a quartz crystal substrate 330, electrodes 340a and 340b formed on the front and back principal surfaces thereof, and lead wires 350a and 350b connected to the electrodes 340a and 340b, respectively. The quartz crystal substrate 330 is an AT-cut substrate having a substantially circular plate shape. The electrodes 340a and 340b are made of gold, platinum, chromium, nickel, or the like, and are formed by physical vapor deposition or the like. The lead wires 350a and 350b are connected to an AC power source or the like to apply a potential to the quartz crystal substrate 330 and may also be connected to a frequency counter or the like capable of measuring changes in frequency. The gas sensor film 320 is provided on at least one of the electrodes 340a and 340b, but may also be formed on both the electrodes 340a and 340b.

[0048] The gas sensor film 320 may be in the form of a film containing the composite material 100. Such a film can be obtained by dispersing the composite material 100 in water or an organic solvent and applying the resulting dispersion to the quartz crystal substrate 330 on which the electrodes 340a and 340b are formed. Examples of organic solvents include ethanol, ethylene glycol, and α-terpineol. The application can be performed by coating, drop casting, spraying, immersion, spin coating, screen printing, or the like. Preferably, heating is performed to remove the solvent after application. The gas sensor film 320 has a thickness in the range of 50 nm to 500 nm, which enhances sensor sensitivity. The gas sensor film 320 may consist of the composite material 100 alone, or may additionally contain an organic binder resin, an organic solvent, or the like.

[0049] The operation of the QCM gas sensor 300 of the present invention will now be described. A potential is applied to the quartz crystal substrate 330 via the lead wires 350a and 350b and electrodes 340a and 340b of the QCM gas sensor 300. This causes the quartz crystal substrate 330 to vibrate at a predetermined resonant frequency using thickness-shear vibration. When an acidic gas is passed through the QCM gas sensor 300, the acid in the gas is adsorbed by the composite material in the gas sensor film 320. This causes an energy loss equivalent to the mass of the adsorbed acid, resulting in a change in the predetermined resonant frequency. The frequency change is measured via the lead wires 350a and 350b using a frequency counter or the like. In this way, the QCM gas sensor 300 of the present invention can detect acid in gas by measuring the frequency change.

[0050] In particular, when the metal ion of the composite material 100 of the present invention is cobalt, the QCM gas sensor 300 of the present invention detects volatile organic compounds (VOCs) selected from the group consisting of formic acid, acetic acid, toluene, benzene, cyclohexane, hexane, pyridine, acetone, and aniline with high accuracy.

[0051] Next, the present invention will be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples. [Example]

[0052] [Preparation of fullerene nanotubes] Using fullerene C60, fullerene nanotubes were produced by a liquid-liquid interface precipitation method with reference to JP-A-2022-18133.

[0053] Fullerene C 60 The powder (purity 99.5%, manufactured by MTR Ltd.) was dispersed in 1,3,5-trimethylbenzene (purity 98.0%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a good solvent, and ultrasonicated for 1 hour to prepare a fullerene dispersion. The fullerene concentration in the fullerene dispersion was 1.4 mg / mL.

[0054] The fullerene dispersion (1 mL) was placed in a 13.5 mL cleaned glass bottle, which was placed in an ultrasonic bath and sonicated. Next, methanol (5 mL, purity 99.7%, manufactured by Nacalai Tesque, Inc.) was added as a poor solvent to the fullerene dispersion quickly (approximately 2 seconds). Sonication was continued for 1 minute, and the glass bottle was removed from the ultrasonic bath and kept at 25 °C for 5 minutes.

[0055] Ethylenediamine (EDA, purity 99.0%, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added to the fullerene dispersion. Then, the mixture was sonicated for 10 minutes in an ultrasonic bath. This mixture was incubated at 25°C for 24 hours to obtain fullerene nanotubes (FNTs).

[0056] The obtained fullerene nanotubes were confirmed by scanning transmission electron microscopy to have a hollow structure and the following dimensions: Longitudinal length: 1 μm to 10 μm Wall thickness: 100nm or more and 300nm or less Diameter: 450nm or more and 1.5μm or less Furthermore, it was confirmed by X-ray diffraction that the fullerene nanotubes have a hexagonal close-packed (hcp) structure.

[0057] [Example 1 to Example 4] In Examples 1 to 4, the prepared fullerene nanotubes (FNTs) were used to produce composite materials supporting ZIF-67.

[0058] The prepared fullerene nanotubes were subjected to acid treatment (step S210 in Figure 2). Specifically, the fullerene nanotubes were immersed in an acid solution containing nitric acid and sulfuric acid (volume ratio 1:1) and ultrasonicated for 20 minutes. The fullerene nanotubes were then washed with distilled water and dried in vacuum at 80°C for 12 hours.

[0059] Acid-treated fullerene nanotubes (FNT-ox), imidazole or its derivative, and a metal salt were mixed in a solvent and reacted (step S220 in Figure 2). As shown in Table 1, the acid-treated fullerene nanotubes, 2-methylimidazole (Tokyo Chemical Industry Co., Ltd.), and cobalt nitrate hexahydrate (Fujifilm Wako Pure Chemical Industries, Ltd.) were weighed, mixed in distilled water, and reacted. Specifically, the acid-treated fullerene was added to an aqueous solution of 2-methylimidazole and triethylamine, and ultrasonicated for 10 minutes. Next, cobalt nitrate hexahydrate was added, and ultrasonicated for an additional 30 minutes, resulting in the production of purple-brown solid crystals (product).

[0060] The product was washed and dried (step S230 in FIG. 2). Specifically, the product was washed with distilled water and then with isopropanol, and dried in vacuum at 80° C. for 12 hours.

[0061] The products of Examples 1 to 4 were treated with C, which constitutes fullerene nanotubes. 60 The molar ratio of cobalt in cobalt nitrate hexahydrate to that in nitrate (C 60 Depending on the composition (weight / Co), they may be referred to as MOFOF-0.5, MOFOF-1.0, MOFOF-1.5, and MOFOF-2.0, respectively.

[0062] [Table 1]

[0063] The products of Examples 1 to 4 were observed using a field-emission scanning electron microscope (SEM, Hitachi High-Tech Corporation, S-4800) and a field-emission transmission electron microscope (TEM, JEOL Ltd., JEM-2100F). The products of Examples 1 to 4 were evaluated using an X-ray diffractometer (XRD, Rigaku Corporation, RINT-Ultima III). The surface functional groups of the products of Examples 1 to 4 were identified using an attenuated total reflection Fourier transform infrared spectrophotometer (ATR-FTIR, Thermo Fisher Scientific K.K., Nexus 670).

[0064] The Raman spectra of the products of Examples 1 to 4 were measured using a triple laser Raman spectrometer (Jobin Yvon, T64000). A laser with a wavelength of 514.5 nm and an output of 0.01 mW was used for the measurements. The thermogravimetric analyses of the products of Examples 1 to 4 were measured using a thermogravimetric analyzer (NETZSCH-Geratebau GmbH, STA2500 Regulus).

[0065] X-ray photoelectron spectra of the products of Examples 1 to 4 were measured using a Theta Probe Spectrometer (manufactured by Thermo Electron). Al-Kα monochromatic radiation (energy 15 keV) was used for the measurements. Core-level XPS C1s (energy peak position of the C 1s orbital), O1s (energy peak position of the O 1s orbital), N1s (energy peak position of the N 1s orbital), and Co2p (energy peak position of the Co 2p orbital) were recorded in 0.05 eV steps. A built-in electroflood gun was used for the measurements to prevent charge accumulation on the measurement sample.

[0066] The nitrogen adsorption isotherms of the products of Examples 1 to 4 were measured using an automatic adsorption apparatus (Quantachrome Instruments, Autosorb-1). Each sample (20 mg) was degassed at 120°C for 24 hours before measurement to prepare the measurement sample. Measurement was performed at 77.35 K, the temperature of liquid nitrogen. From the obtained nitrogen adsorption isotherms, the specific surface area determined by the Brunauer-Emmett-Teller (BET) method, the pore volume determined by the Barrett-Joyner-Halend (BJH) method, the pore distribution determined by the Density Functional Theory (DFT) method, the surface area of ​​micropores with a pore diameter of 1 nm or less, the pore volume of ultramicropores with a pore diameter of 1 nm or less, the average pore diameter Dp, and the half pore width Wp were calculated using the software (BET tool) provided with the apparatus.

[0067] The gas sensor capabilities of the products of Examples 1 to 4 were investigated using a quartz crystal microbalance (QCM). Using a resonant frequency of 9 MHz (AT-cut), the frequency change upon adsorption / desorption of various guest gases was recorded for Au resonators (QCM electrodes) coated with the products of Examples 1 to 4. The QCM electrodes were prepared as follows: 0.5 mg of the products of Examples 1 to 4 were dispersed in 1 mL of isopropanol and stirred for 30 seconds. A 2 μL aliquot of the resulting suspension was drop-cast onto a QCM electrode and dried in vacuum at 80°C for 12 hours. The guest gases used were formic acid, acetic acid, toluene, benzene, cyclohexane, hexane, pyridine, acetone, and aniline.

[0068] When the frequency shift reached equilibrium, the QCM electrode was exposed to air to desorb the adsorbed gas. To test the reproducibility of the QCM electrode, the time dependence of the frequency shift (Δf) was recorded when gas exposure and desorption were repeated.

[0069] The above results are shown in FIGS. 4 to 16 and Table 2, and will be explained together. FIG. 4 shows SEM images of the products of Examples 1 to 4.

[0070] SEM images of fullerene nanotubes (FNT) before and after acid treatment (FNT-ox) are also shown in Figure 4. Figures 4(a) to 4(f) are SEM images of FNT, FNT-ox, MOFOF-0.5 (Example 1), MOFOF-1.0 (Example 2), MOFOF-1.5 (Example 3), and MOFOF-2.0 (Example 4), respectively.

[0071] 4(a) and (b), it was found that the surface morphology of the fullerene nanotubes was maintained even after the acid treatment, and that the FNT-ox had a smooth surface.

[0072] Figures 4(c) to (f) show that particles were uniformly distributed and adhered to the surface of the FNT-ox. In addition, particles were also located on the surface of the hollow structure of the FNT-ox. The particle size was in the range of 50 nm to 200 nm. The amount of particles was C 60 The tendency was that the solubility increased as the molar ratio of HCl / Co increased.

[0073] FIG. 5 shows STEM and TEM images of the product of Example 2.

[0074] Figure 5(a)-(c) show STEM images of fullerene nanotubes (FNT) before acid treatment, fullerene nanotubes (FNT-ox) after acid treatment, and ZIF-67, respectively. Figure 5(d)-(f) show TEM images of MOFOF-1.0 (Example 2) at various magnifications.

[0075] Figures 5(d)-(f) show that particles are located on the surface of the fullerene nanotube and on the surface of the hollow interior, and that the particles have the same shape as in Figure 5(c). This suggests that the particles located on the surface of MOFOF-1.0 are ZIF-67.

[0076] FIG. 6 shows the XRD pattern of the product of Example 2.

[0077] In addition to the XRD pattern of the product of Example 2, Figure 6 also shows the fullerene (C 60 ), fullerene nanotubes (FNT) before acid treatment, fullerene nanotubes (FNT-ox) after acid treatment, ZIF-67, and simulated ZIF-67 XRD patterns are also shown.

[0078] The XRD patterns of FNT and FNT-ox in Figure 6 show that the acid treatment did not change the crystalline phase. On the other hand, the XRD pattern of MOFOF-1.0 had a new peak in addition to the XRD pattern of FNT-ox. The new peak was found to match the peak of ZIF-67 and the simulated ZIF-67. Although not shown, the XRD patterns of the products of Examples 1, 3, and 4 were similar to that of the product of Example 2. This indicates that the product obtained by the manufacturing process shown in Figure 2 is a composite material containing fullerene nanotubes and zeolite-like imidazolate structures (ZIFs) containing metal ions located on their surfaces.

[0079] FIG. 7 shows the FITR spectrum of the product of Example 2.

[0080] FIG. 7 shows the FTIR spectrum of the product of Example 2, as well as the FTIR spectra of fullerene nanotubes (FNT) before acid treatment, fullerene nanotubes (FNT-ox) after acid treatment, and ZIF-67.

[0081] According to the FTIR spectrum of FNT-ox in Figure 7, the peak at 1071 cm -1 , 1362cm -1 , 1636cm -1 These peaks were attributed to the CO stretching band, the C-OH stretching band, and the bending of water (HO), respectively, indicating that the surface of the fullerene nanotubes was oxy-functionalized by the acid treatment.

[0082] The FTIR spectrum of MOFOF-1.0 in Figure 7 shows a peak at 1427 cm in addition to the peak in the FTIR spectrum of FNT-ox. -1 and 1305 cm -1 These peaks were derived from the stretching vibration of the imidazole ring of ZIF-67. Although not shown, the FTIR spectra of the products of Examples 1, 3 and 4 were similar to that of the product of Example 2. This indicates that the product obtained by the manufacturing process shown in FIG. 2 is a composite material containing fullerene nanotubes and zeolite-like imidazolate structures (ZIFs) containing metal ions located on the surface thereof.

[0083] FIG. 8 shows the Raman spectrum of the product of Example 2.

[0084] FIG. 8 shows the Raman spectrum of the product of Example 2, as well as the Raman spectra of fullerene nanotubes (FNT) before acid treatment, fullerene nanotubes (FNT-ox) after acid treatment, and ZIF-67.

[0085] The Raman spectrum of MOFOF-1.0 in Figure 8 is similar to that of FNT and FNT-ox, but with a peak at 689 cm -1 The peak corresponding to the Co-N bond of ZIF-67 was also shown. Although not shown, the FTIR spectra of the products of Example 1, Example 3 and Example 4 were also similar to that of the product of Example 2. This also indicated that the product was a composite of fullerene nanotubes and ZIF.

[0086] FIG. 9 shows the thermogravimetric profile of the product of Example 2.

[0087] Figure 9 shows the thermogravimetric profile of the product of Example 2 as well as that of FNT-ox. According to Figure 9, the decomposition of ZIF-67 in MOFOF was observed at 550 °C, which is higher than the decomposition temperature of ZIF-67. This temperature was also different from the decomposition temperature of fullerene nanotubes. This indicates that the product of Example 2 is a well-organized complex of fullerene nanotubes and ZIF-67 located on their surfaces.

[0088] FIG. 10 shows XPS spectra of the product of Example 2 and FNT-ox.

[0089] Both MOFOF-1.0 and FNT-ox were found to be composed of carbon with partial surface oxidation, as shown in Figure 10. MOFOF-1.0 also had peaks corresponding to cobalt and nitrogen from ZIF-67.

[0090] From these peaks, MOFOF-1.0 consisted of carbon atoms, oxygen atoms, metal (cobalt in this case) atoms, and nitrogen atoms, with atomic percentages (%) of 78.3%, 14.8%, 1.0%, and 5.9%, respectively. On the other hand, FNT-ox consisted of carbon atoms and oxygen atoms, with atomic percentages (%) of 83.5% and 16.2%, respectively. It was found that the oxygen content of MOFOF-1.0 increased upon acid treatment of the fullerene nanotubes.

[0091] Although not shown, the XPS spectra of the products of Examples 1 and 3 to 4 were similar to that of Example 2. From this, it can be seen that the products obtained by the manufacturing process shown in FIG. 2 consist of carbon atoms (C), oxygen atoms (O), metal (cobalt in this case) atoms (M) and nitrogen atoms (N), and are expressed in atomic percentage (%) as follows: 70≦C≦85 10≦0≦20 0.5≦M≦20 2.5≦N≦10 It was found that

[0092] FIG. 11 shows the XPS core level spectrum of FNT-ox. FIG. 12 shows the XPS core level spectrum of the product of Example 2.

[0093] The convoluted C1s spectrum in Figure 11 shows three distinct curves with peaks at 284.9 eV, 286.4 eV, and 289.7 eV. These peaks are due to the C=C(sp 2 ), CC(sp 3 ) or C-OH and CO3 2- This is due to the bonding state of carbon.

[0094] The convoluted O1s spectrum in Figure 11 showed two distinct curves with peaks at 532.54 eV and 533.6 eV, which are attributed to the C-OH and C-O-C oxygen bonding states.

[0095] The convoluted C1s spectrum in Figure 12 showed three distinct curves with peaks at 285.05 eV, 286.2 eV, and 287.06 eV. These peaks correspond to C=C(sp 2 ), CC(sp 3 ) or C-OH and CN due to the carbon bonding state.

[0096] The convoluted O1s spectrum in Figure 12 showed two distinct curves with peaks at 532.5 eV and 533.8 eV, which are attributed to the C-OH and C-O-C oxygen bonding states.

[0097] The convoluted N1s spectrum in Figure 12 showed three distinct curves with peaks at 400.05 eV, 401.0 eV, and 401.96 eV, which are attributed to the nitrogen bonding states of NH, CN, and C=N.

[0098] The convoluted Co2p spectrum in Figure 12 shows a C-N4 bonding state at 781.1 eV and a satellite peak at 785.4 eV due to ZIF-67. A low intensity peak at 778.4 eV is due to Co-N x This corresponds to (x<4), indicating the presence of uncoordinated Co species. This suggests the presence of defect sites or uncoordinated Co(II) and 2-methylimidazole (basic N-sites) within ZIF-67 in MOFOF-1.0. These defect sites may interact with guest molecules, such as volatile organic compounds (VOCs), or the uncoordinated sites may sense guest molecules.

[0099] FIG. 13 is a graph showing nitrogen adsorption / desorption isotherms for the products of Examples 1 to 4.

[0100] FIG. 13 shows the nitrogen adsorption / desorption isotherms of the products of Examples 1 to 4, as well as the nitrogen adsorption / desorption isotherms of the fullerene nanotubes (FNT-ox) after acid treatment and ZIF-67.

[0101] According to Figure 13, the isotherms of MOFOF-0.5 to MOFOF-2.0 were all classified as Type I in the IUPAC classification, while the isotherm of FNT-ox was classified as Type IV in the IUPAC classification. That is, MOFOF-0.5 to MOFOF-2.0 were microporous materials, and the micropores increased as the ZIF-67 content increased. On the other hand, FNT-ox did not exhibit a porous structure. The BET specific surface area, BJH pore volume, DFT pore distribution, and other data calculated from Figure 13 are shown in Table 2.

[0102] [Table 2]

[0103] According to Table 2, MOFOF-0.5 to MOFOF-2.0 are 180m 2 / g or more 600m 2 / g or less, and meets the BET surface area of ​​0.15 cm 3 / g or more 0.7cm3 The total pore volume was 1000µm / g or less, and the volume of micropores with pore diameters of 1nm or less was in the range of 40% to 70% of the total pore volume. Furthermore, MOFOF-0.5 to MOFOF-2.0 were found to have a bimodal pore structure within their structure. This structure is advantageous for detecting volatile organic compounds (VOCs).

[0104] FIG. 14 is a graph showing the time dependence of the frequency shift when the QCM electrodes using the products of Examples 1 to 4 are exposed to formic acid.

[0105] As shown in Figure 14, FNT and ZIF-67 exhibited a slight frequency shift when exposed to formic acid, but the frequency shift quickly returned to its initial state (zero) after the formic acid was removed. On the other hand, MOFOF-0.5 to MOFOF-2.0 exhibited a large frequency shift when exposed to formic acid, and the frequency shift did not return to its initial state even after the formic acid was removed. This result indicates the occurrence of a strong, irreversible interaction between the acid (formic acid) and the basic site (uncoordinated N site) of the imidazole ligand of ZIF-67 in MOFOF-0.5 to MOFOF-2.0. This suggests that the composite materials of the present invention are advantageous for adsorbing and detecting reactive species such as volatile organic compounds (VOCs) through acid-base interactions.

[0106] According to FIG. 14, it was found that composite materials in which the molar ratio of fullerenes constituting fullerene nanotubes to metal ions (cobalt in this case), as represented by MOFOF-1.0, the product of Example 2, satisfies the range of 0.75 to 1.25, exhibit excellent sensitivity and are suitable for the sensor film of a quartz crystal resonator gas sensor.

[0107] FIG. 15 shows the results of a cycle test of frequency shift when a QCM electrode using the product of Example 2 is exposed to formic acid.

[0108] FIG. 15 shows that the product of Example 2 (MOFOF-1.0) has high detection ability and excellent reproducibility for formic acid.

[0109] FIG. 16 shows a list of frequency shifts when a QCM electrode using the product of Example 2 is exposed to various volatile organic compounds.

[0110] 16, the product (MOFOF-1.0) of Example 2 has the ability to detect various volatile organic compounds (VOCs) and is suitable for use as a sensor film in a quartz crystal gas sensor. In particular, the composite material of the present invention was shown to be able to detect formic acid, acetic acid, toluene, benzene, cyclohexane, hexane, pyridine, acetone, and aniline. [Industrial Applicability]

[0111] The composite material of the present invention has selective reactivity to specific volatile organic compounds and is therefore applicable to quartz crystal gas sensors. [Explanation of symbols]

[0112] 100 Composite materials 110 Fullerene nanotubes 120 Zeolite-like imidazolate structures containing metal ions 300 QCM gas sensors 310 Quartz crystal oscillator (QCM) electrode 320 Gas sensor membrane 330 Crystal substrate 340a, 340b electrode 350a, 350b lead wires

Claims

1. fullerene nanotubes, a zeolite-like imidazolate structure (ZIF) containing metal ions located on the surface of the fullerene nanotube; A composite material comprising:

2. The fullerene constituting the fullerene nanotube is C ６０ Fullerene, C ７０ Fullerene, C ７６ Fullerene, C ７８ Fullerene, C ８２ Fullerene, C ８４ Fullerene, C ９０ Fullerene, C ９４ 10. The composite material of claim 1, selected from the group consisting of fullerenes and derivatives thereof.

3. The fullerene is C ６０ The composite material of claim 2 which is a fullerene and its derivatives.

4. 4. The composite material according to claim 1, wherein the metal ions are selected from the group consisting of zinc ions, cobalt ions, cadmium ions, lithium ions, manganese ions, mercury ions, iron ions, copper ions, and indium ions.

5. 5. The composite material according to claim 1, wherein a molar ratio of fullerenes constituting said fullerene nanotube to said metal ions is in the range of 0.1 to 2.

5.

6. The composite material according to claim 5 , wherein the molar ratio is in the range of 0.5 to 2.

0.

7. The composite material according to claim 6 , wherein the molar ratio satisfies the range of 0.75 to 1.

25.

8. 8. The composite material of claim 1, wherein the zeolite-like imidazolate structure is selected from the group consisting of ZIF-7, ZIF-22, ZIF-8, ZIF-67, ZIF-69, ZIF-71, ZIF-78, ZIF-90, and ZIF-95.

9. The BET specific surface area is 150 m ２ / g or more 700m ２ The composite material according to any one of claims 1 to 8, wherein the range of 1 / g or less is satisfied.

10. The total pore volume is 0.15 cm ３ / g or more 0.7cm ３ / g or less, 10. The composite material according to claim 1, wherein the pore volume of micropores having a pore diameter of 1 nm or less is in the range of 40% to 70% of the total pore volume.

11. treating the fullerene nanotubes with an acid; mixing the acid-treated fullerene nanotubes, imidazole or a derivative thereof, and a salt of a metal element in a solvent to cause a reaction; washing and drying the product obtained by said mixing and reacting; A method for producing the composite material according to any one of claims 1 to 10, comprising:

12. 12. The method of claim 11, wherein the acid treating uses an acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid.

13. 13. The method of claim 11 or 12, wherein the salt of the metal element is an inorganic acid salt or an inorganic halide salt of a metal element selected from the group consisting of zinc, cobalt, cadmium, lithium, manganese, mercury, iron, copper, nickel, platinum, and indium.

14. The method according to any one of claims 11 to 13, wherein in the mixing and reacting, the acid-treated fullerene nanotubes, the imidazole or its derivative, and the salt of the metal element satisfy a molar ratio of 1-5:10-100:1-10.

15. A quartz crystal gas sensor having a gas sensor membrane, A quartz crystal resonator gas sensor, wherein the gas sensor film contains the composite material according to any one of claims 1 to 10.

16. 16. The quartz crystal gas sensor according to claim 15, which detects a volatile organic compound selected from the group consisting of formic acid, acetic acid, toluene, benzene, cyclohexane, hexane, pyridine, acetone, and aniline.

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