Porous carbon composite material, method for producing the same, and catalyst prepared using the same

Abstract

To provide a porous carbon material carrying metal particles, a production method therefor, and a catalyst prepared using the same.SOLUTION: The porous carbon composite material of the present invention contains a porous carbon nanotube based on a fullerene nanotube and a porous carbon structure based on a zeolitic imidazolate framework (ZIF) positioned on the surface of the porous carbon nanotube and containing metal particles, wherein a ratio of an atomic percentage of metal particles (M) to carbon (C) constituting the porous carbon nanotube and the porous carbon structure is 0.015 or more and 0.03 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a porous carbon composite material, a method for producing the same, and a catalyst using the same. [Background technology]

[0002] Catalysts in which metal particles are supported on porous carbon materials are known (see, for example, Patent Document 1). Patent Document 1 discloses a method for producing a metal particle-supported porous carbon material, which comprises preparing a precursor of an organic compound composed of carbon, zinc, metal, hydrogen, and oxygen elements, including zinc and a metal element with a melting point and boiling point exceeding 1000°C, and then calcining the precursor at a temperature of 900 to 1000°C, thereby sublimating the zinc to form pores and dispersing and granulating the metal element, thereby converting the precursor into a porous carbon material and simultaneously supporting the dispersed and granulated metal particles on the porous carbon material. However, this method does not yet achieve control of the particle size of the metal particles, and further improvements in the catalyst function are expected. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2024-20082 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 porous carbon composite material supporting metal particles, a method for producing the same, and a catalyst using the same. [Means for solving the problem]

[0005] The porous carbon composite material of the present invention comprises porous carbon nanotubes based on fullerene nanotubes, and a porous carbon structure based on a zeolite-like imidazolate structure (ZIF) that is located on the surface of the porous carbon nanotubes and contains metal particles, and the atomic percentage ratio of the metal particles (M) to the carbon (C) that constitutes the porous carbon nanotubes and the porous carbon structure is 0.015 or more and 0.03 or less, thereby solving the above-mentioned problem. The metal particles may be made of a metal selected from the group consisting of cobalt (Co), nickel (Ni), iron (Fe), and platinum (Pt). The particle diameter of the metal particles calculated from the half width of X-ray diffraction by Scherrer's equation may be in the range of 3.5 nm to 9.0 nm. The atomic percentage ratio may be in the range of 0.018 to 0.03. The porous carbon nanotubes and / or the porous carbon structure may further contain nitrogen (N). The porous carbon nanotubes and / or the porous carbon structure may further contain oxygen (O). The atomic percentages (%) of the carbon (C), the metal particles (M), the oxygen (O), and the nitrogen (N) (where the total of C, M, O, and N is 100%) are respectively: 75≦C≦85 1.3≦M≦3.0 12≦O≦20 2.0≦N≦2.5 may be satisfied. 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 370m 2 / g or more 800m 2 / g or less. The BET specific surface area is 380m 2 / g or more 450m 2 / g or less. The total pore volume is 0.65 cm 3 / g or more 1.0cm 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 53.5% or more and 60% or less of the total pore volume. The method for producing a porous carbon composite material 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, washing and drying the product obtained by the mixing and reaction, and calcining the product obtained by the drying, wherein the molar ratio of the fullerene nanotubes to the salt of the metal element is greater than 0.5 and less than 2.0, thereby solving the above-mentioned problem. 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 It may be selected from the group consisting of fullerenes and derivatives thereof. 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 cobalt (Co), nickel (Ni), iron (Fe), and platinum (Pt). 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 1-5:10-50:1-5. The calcination may involve calcining the product in a nitrogen atmosphere at a temperature in the range of 750° C. to 1200° C. The catalyst according to the present invention contains the porous carbon composite material, thereby solving the above problems. The nitropolycyclic aromatic hydrocarbon may be reduced. [Effects of the Invention]

[0006] The porous carbon composite material of the present invention contains porous carbon nanotubes based on fullerene nanotubes and metal particles located thereon, and also contains a porous carbon structure based on a zeolite-like imidazolate structure (ZIF), in which the atomic percentage ratio of the metal particles (M) to the carbon (C) is 0.015 or more and 0.03 or less. The porous carbon material of the present invention functions as a catalyst for reducing nitropolycyclic aromatic hydrocarbons. [Brief explanation of the drawings]

[0007] [Figure 1] Schematic diagram showing a porous carbon composite material of the present invention. [Figure 2] Flowchart showing the steps for producing the porous carbon composite material of the present invention [Figure 3] Figure showing SEM images of MOFOF-0.5, MOFOF-1.0, MOFOF-1.5 and MOFOF-2.0 [Figure 4] Figure showing electron beam images such as SEM images of Co@HC-1.0 [Figure 5] XRD patterns and Raman spectra of Co@HC-0.5~2.0 [Figure 6] XPS spectrum of Co@HC-1.0 [Figure 7] Nitrogen adsorption / desorption isotherms for Co@HC-0.5~2.0 [Figure 8] Figure showing the reaction time dependence of the reduction rate of 4-nitrophenol with Co@HC-1.0~1.5 [Figure 9] Pseudo-first-order kinetic plots of Fig. 8 [Figure 10] Figure showing the reaction time dependence of the reduction rate of various nitropolycyclic aromatic hydrocarbons by Co@HC-1.0 [Figure 11] Pseudo-first-order kinetic plots of Fig. 10 [Figure 12]Figure showing the cycle test of the reduction of 4-nitrophenol by Co@HC-1.0 [Figure 13] Figure showing nitrogen adsorption / desorption isotherms of Co@HC-1.0 before and after the reduction test. 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] FIG. 1 is a schematic diagram showing a porous carbon composite material of the present invention.

[0010] The porous carbon composite material 100 of the present invention comprises porous carbon nanotubes 110 based on fullerene nanotubes, and a porous carbon structure 130 based on zeolitic imidazolate framework (ZIF) that is located on the surface of the porous carbon nanotubes and contains metal particles 120. Hereinafter, the zeolitic imidazolate framework may be simply referred to as ZIF. The porous carbon composite material 100 of the present invention is composed of a porous carbon material having a hierarchical structure as a base material, on which metal particles are supported.

[0011] In the porous carbon composite material 100 of the present invention, the ratio of the atomic percentage of the metal particles 120 to the carbon (C) constituting the porous carbon nanotubes 110 and the porous carbon structure 130 is 0.015 or more and 0.03 or less. This allows the porous carbon composite material 100 of the present invention to function as a catalyst. If the ratio is outside this range, the catalytic function may be reduced. More preferably, the ratio is 0.018 or more and 0.03 or less. This can further improve the catalytic performance of the porous carbon composite material 100 of the present invention.

[0012] The porous carbon nanotubes 110 based on fullerene nanotubes are graphitic (specifically, sp 2 Hybridized carbon and disordered sp 3 The porous carbon nanotube 110 has a wall made of a carbon nanotube (hybrid carbon). As shown in Figure 1, the porous carbon nanotube 110 has a hollow structure and its cross-sectional shape is circular, elliptical, or the like. The surface of the porous carbon nanotube 110 refers to the outer surface as well as the surface inside the hollow structure.

[0013] Here, the fullerene nanotube is not particularly limited as long as it is a spherical molecule containing fullerene as the main component and carbon atoms with and / or without a substituent.

[0014] The fullerene constituting the fullerene nanotube 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.

[0015] The porous carbon 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. This size appropriately reflects the size of a fullerene nanotube.

[0016] The ZIF-based porous carbon structure 130 is a graphite-like structure in which organic components are removed and the structure is rearranged (specifically, sp 2 Hybridized carbon and disordered sp3 As shown in Figure 1, the porous carbon structure 130 reflects the structure of ZIF and has a particulate shape.

[0017] ZIF 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.

[0018] Known ZIFs include 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.

[0019] Such a ZIF-based porous carbon structure 130 preferably has a particle size in the range of 50 nm to 300 nm. The porous carbon structure 130 more preferably has a particle size in the range of 75 nm to 150 nm. This can improve the functionality of the porous carbon composite material 100 of the present invention. In this specification, the particle size of the porous carbon structure 130 is the average of the longest diameters of 100 particles observed in an electron microscope image at 15,000x magnification.

[0020] The metal particles 120 supported on the porous carbon structure 130 are selected from the group consisting of cobalt (Co), nickel (Ni), iron (Fe), and platinum (Pt), which can improve the catalytic performance of the porous carbon composite material 100 of the present invention.

[0021] The metal particles 120 are extremely small particles on the nano-order. Preferably, the metal particles 120 have a particle size in the range of 3.5 nm or more and 9.0 nm or less. This can improve the catalytic performance of the porous carbon composite material 100 of the present invention. More preferably, the metal particles 120 have a particle size in the range of 5 nm or more and 8 nm or less. This can further improve the catalytic performance of the porous carbon composite material 100 of the present invention. In this specification, the particle size of the metal particles 120 is calculated from the half-width of X-ray diffraction using the Scherrer equation.

[0022] When the metal particles 120 are cobalt, the metal particles 120 may have a face-centered cubic crystal structure (FCC).

[0023] The porous carbon nanotubes 110 and the porous carbon structure 130 may further contain nitrogen (N), which stabilizes the structure. The porous carbon nanotubes 110 and the porous carbon structure 130 may further contain oxygen (O), which further stabilizes the structure.

[0024] When the porous carbon composite material 100 of the present invention is composed of carbon (C), metal particles (M), oxygen (O), and nitrogen (N), the atomic percentages (%) of these preferably satisfy the following, with the proviso that the total of C, M, O, and N is 100%. 75≦C≦85 1.3≦M≦3.0 12≦O≦20 2.0≦N≦2.5 This can stabilize the structure of the porous carbon composite material 100 of the present invention and improve the catalytic performance.

[0025] The porous carbon composite material 100 of the present invention is preferably 370 mm 2 / g or more 800m 2 / g or less, thereby stabilizing the porous carbon composite material 100. The porous carbon composite material 100 of the present invention more preferably has a BET specific surface area of ​​380 m 2 / g or more 450m 2 / g or less, thereby improving the catalytic performance of the porous carbon composite material 100.

[0026] The porous carbon composite material 100 of the present invention preferably has a thickness of 0.65 cm 3 / g or more 1.0cm 3 / g or less, and the pore volume of micropores with pore diameters of 1 nm or less is in the range of 53.5% to 60% of the total pore volume. This can improve the catalytic performance of the porous carbon composite material 100. The porous carbon composite material 100 of the present invention more preferably has a pore volume of 0.65 cm 3 / g or more 0.8cm 3 / g or less, and the pore volume of micropores with pore diameters of 1 nm or less satisfies the range of 53.5% to 57% of the total pore volume. This can further improve the catalytic performance of the porous carbon composite material 100.

[0027] The porous carbon composite material 100 of the present invention exhibits various catalytic performances depending on the type of metal particles 120. When the metal particles 120 are cobalt, the porous carbon composite material 100 of the present invention is particularly advantageous as a catalyst for reducing nitropolycyclic aromatic hydrocarbons. When the metal particles 120 are nickel, the porous carbon composite material 100 of the present invention is particularly advantageous as a catalyst for energy conversion. When the metal particles 120 are iron, the porous carbon composite material 100 of the present invention is particularly advantageous as a catalyst for the electrochemical reduction of oxygen and nitrates. When the metal particles 120 are platinum, the porous carbon composite material 100 of the present invention is particularly advantageous as an electrode catalyst for oxygen reduction reactions. The metal particles may be of one type, or two or more types may be combined depending on the application.

[0028] Next, a method for producing the porous carbon composite material 100 of the present invention will be described. FIG. 2 is a flow chart showing the steps for producing the porous carbon composite material of the present invention.

[0029] The porous carbon 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. Step S240: The product dried in step S230 is calcined. However, in step S220, the fullerene nanotubes and the salt of the metal element are mixed so that the molar ratio of the fullerene nanotubes to the salt of the metal element is greater than 0.5 and less than 2.0.

[0030] Each step will be described in detail. In step S210, the fullerene nanotube may have the above-mentioned characteristics. Such a fullerene nanotube may be, 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 produced by the liquid-liquid interface deposition method described in JP-A-2022-18133 using a fullerene selected from the group consisting of fullerenes and derivatives thereof.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Among them, imidazole or its derivative is preferably 2-methylimidazole, which is commercially available, easily available, and can be synthesized by existing methods.

[0037] 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, which may be an inorganic acid salt or an inorganic halide salt of a metal element selected from the group consisting of cobalt (Co), nickel (Ni), iron (Fe), and platinum (Pt).

[0038] In step S220, the solvent may be ultrapure water, ion-exchanged water, distilled water, or the like.

[0039] In step S220, the fullerene nanotubes and the salt of the metal element are mixed so that the molar ratio of the fullerenes constituting the fullerene nanotubes to the salt of the metal element is greater than 0.5 and less than 2.0, thereby providing a porous carbon composite material 100 having catalytic properties.

[0040] The molar ratio more preferably falls within the range of 0.75 or more and 1.75 or less, thereby improving the catalytic performance of the porous carbon composite material 100 of the present invention. The molar ratio even more preferably falls within the range of 1.0 or more and 1.5 or less, thereby further improving the catalytic performance of the porous carbon composite material 100 of the present invention.

[0041] In step S220, in addition to the above molar ratio, the fullerene constituting the fullerene nanotube treated with acid in step S210, imidazole or its derivative, and salt of a metal element may be mixed to satisfy a molar ratio of 1-5:10-50:1-5. If this ratio is satisfied, the reaction is promoted.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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 in the range of 50° C. to 100° C. for 5 hours to 24 hours.

[0046] Steps S210 to S230 produce a precursor composite material containing fullerene nanotubes and zeolite-like imidazolate structures (ZIFs) located on the surface of the fullerene nanotubes and containing metal ions. As mentioned above, ZIFs obtained by these steps include ZIF-7, ZIF-22, ZIF-8, ZIF-67, ZIF-69, ZIF-71, ZIF-78, ZIF-90, ZIF-95, etc. Among these, from the viewpoint of pore size and yield, ZIF-67, i.e., a sodalite-type crystal structure in which metal ions are crosslinked with 2-methylimidazole, is preferred.

[0047] Again, the fullerene nanotubes 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. Furthermore, the ZIF preferably has a particle size in the range of 50 nm or more and 300 nm or less.

[0048] The precursor composite is preferably 200 mm 2 / g or more 500m 2The precursor composite material more preferably satisfies a BET specific surface area in the range of 300 m / g or less. 2 / g or more 420m 2 / g or less, thereby stabilizing the porous carbon composite material 100.

[0049] The precursor composite is preferably 0.5 cm 3 / g or more 1.0cm 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 60% of the total pore volume. This makes it easy to obtain the porous carbon composite material 100. The precursor composite material is more preferably 0.6 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 52% of the total pore volume. This can stabilize the porous carbon composite material 100.

[0050] In step S240, the product obtained in step S230, i.e., the precursor composite material, is calcined and carbonized. There are no particular limitations on the conditions as long as carbonization is possible, but calcination is preferably performed in a nitrogen atmosphere at a temperature range of 750°C to 1200°C. This promotes carbonization of the porous carbon composite material 100. More preferably, calcination is performed in a nitrogen atmosphere at a temperature range of 750°C to 850°C for 1 hour to 10 hours. This allows the porous carbon composite material 100 to be obtained with a high yield.

[0051] Following step S240, the resulting product may be subjected to an acid treatment. This etches the surface, removes impurities, and improves catalytic performance. An acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid can be used. The acid treatment may be performed at a temperature ranging from 40°C to 80°C for 1 hour to 24 hours. This produces a porous carbon composite material 100 suitable as a catalyst for reducing nitroarenes.

[0052] 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]

[0053] [Preparation of fullerene nanotubes] Fullerene C 60 Using this, fullerene nanotubes were produced by a liquid-liquid interface precipitation method with reference to JP-A-2022-18133.

[0054] 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.

[0055] 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.

[0056] 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).

[0057] 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.

[0058] [Example 1 to Example 4] In Examples 1 to 4, porous carbon composite materials were produced using the prepared fullerene nanotubes (FNTs).

[0059] 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.

[0060] Acid-treated fullerene nanotubes (FNTox), imidazole or its derivative, and a salt of a metal element were mixed in a solvent and reacted (step S220 in FIG. 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. Here, the molar ratio of FNT to cobalt salt in Examples 2 and 3 was greater than 0.5 and less than 2.0, but the molar ratio in Examples 1 and 4 did not satisfy this range.

[0061] Specifically, the acid-treated fullerene was added to an aqueous solution of 2-methylimidazole and triethylamine, and ultrasonicated for 10 minutes. Cobalt nitrate hexahydrate was then added, and ultrasonicated for an additional 30 minutes, resulting in the formation of purple-brown solid crystals (product).

[0062] The product was washed and dried to obtain a precursor composite material (step S230 in FIG. 2). Specifically, the precursor composite material was washed with distilled water and then with isopropanol, and dried in vacuum at 80° C. for 12 hours.

[0063] The dried precursor composite materials 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 / Co), they are called MOFOF-0.5, MOFOF-1.0, MOFOF-1.5, and MOFOF-2.0, respectively.

[0064] The precursor composite materials of Examples 1 to 4 were fired (Step S240 in FIG. 2). Specifically, MOFOF-0.5 to 2.0 were fired in a nitrogen atmosphere at 800°C for 4 hours. The fired products were then acid-treated with hydrofluoric acid (HF, 0.2M) at 60°C for 12 hours to remove soluble impurities.

[0065] The products of Examples 1 to 4 after firing were treated with C, which constitutes fullerene nanotubes. 60 The molar ratio of cobalt in cobalt nitrate hexahydrate to that in nitrate (C 60 / Co), they are called Co@HC-0.5, Co@HC-1.0, Co@HC-1.5, and Co@HC-2.0, respectively.

[0066] [Table 1]

[0067] MOFOF-0.5 to 2.0 and Co@HC-0.5 to 2.0 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). MOFOF-0.5 to 2.0 and Co@HC-0.5 to 2.0 were characterized using an X-ray diffractometer (XRD, Rigaku Corporation, RINT-Ultima III).

[0068] The Raman spectra of Co@HC-0.5 to 2.0 were measured using a triple laser Raman spectrometer (Jobin Yvon, T64000) using a laser with an output of 0.01 mW and a wavelength of 514.5 nm.

[0069] X-ray photoelectron spectra of Co@HC-0.5 to 2.0 were measured using a Theta Probe Spectrometer (Thermo Electron). The Al-Kα monochromatic line (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. To avoid charge accumulation on the measurement sample, a built-in electroflood gun was used for the measurements.

[0070] Nitrogen adsorption isotherms for MOFOF-0.5 to 2.0 and Co@HC-0.5 to 2.0 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. Measurements were performed at 77.35 K, the temperature of liquid nitrogen. From the obtained nitrogen adsorption isotherms, the specific surface area (Brunauer-Emmett-Teller) was calculated, the pore volume (BJH) was calculated, the pore size distribution (DFT) was calculated, the surface area of ​​micropores with a pore size of 1 nm or less, the pore volume of ultramicropores with a pore size 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.

[0071] The catalytic performance of the products (Co@HC-0.5 to 2.0) from Examples 1 to 4 was investigated. Specifically, using Co@HC-0.5 to 2.0, reduction of nitropolycyclic aromatic hydrocarbons (4-nitrophenol (4-NP), nitrobenzene (NB), 2-nitrophenol (2-NP), 4-methylnitrobenzene (4Me-NB), and 4-chloronitrobenzene (4Cl-NB) was carried out in a quartz cell (4 mL).

[0072] First, a NaBH4 aqueous solution (0.5 mL, 0.3 M) was mixed with various aqueous solutions of nitropolycyclic aromatic hydrocarbons (3 mL, 5 mM) in a quartz cell. Then, aqueous solutions of Co@HC-0.5–2.0 (1 mg mL) were added. -1 50 μL of the solution was added to the mixture and allowed to react. After the addition, the UV absorbance (wavelength 400 nm) of the reaction mixture was measured at 1-minute intervals using a spectrophotometer (Shimadzu Corporation, UV2550). A cycle test (5 times) was performed on Co@HC-1.0. Nitrogen adsorption isotherms were also measured for samples that underwent four cycle tests.

[0073] The above results are shown in FIGS. 3 to 13 and Tables 2 to 5 and will be explained together.

[0074] FIG. 3 shows SEM images of MOFOF-0.5, MOFOF-1.0, MOFOF-1.5, and MOFOF-2.0.

[0075] SEM images of fullerene nanotubes (FNT) before and after acid treatment (FNTox) are also shown in Figure 3. Figures 3(a) to 3(f) are SEM images of FNT, FNTox, MOFOF-0.5, MOFOF-1.0, MOFOF-1.5, and MOFOF-2.0, respectively.

[0076] 3(a) and (b), it was found that the surface morphology of the fullerene nanotubes was maintained even after the acid treatment, and that the FNTox had a smooth surface.

[0077] Figure 3(c)-(f) shows that ZIF was uniformly distributed on the surface of FNTox, and a MOFOF was obtained. ZIF was also located on the surface of the hollow structure of FNTox. The particle size of the particulate ZIF 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.

[0078] [Table 2]

[0079] Table 2 shows the pore characteristics of the precursor composite materials (MOFOF-0.5 to 2.0) calculated from the nitrogen adsorption / desorption isotherms. According to Table 2, MOFOF-1.0 and MOFOF-1.5 had a pore size of 200 m 2 / g or more 500m 2 / g or less, in detail, 300m 2 / g or more 420m 2 The MOFOF-1.0 and MOFOF-1.5 had a BET specific surface area of ​​0.6 cm / g or less. 3 / g or more 0.7cm 3 / g or less, and the pore volume of micropores with pore diameters of 1 nm or less was in the range of 40% to 52% of the total pore volume.

[0080] FIG. 4 shows electron beam images such as SEM images of Co@HC-1.0.

[0081] Figures 4(a)–(f) show the SEM, STEM, TEM, HAADF, and HR-TEM images and SAED patterns of Co@HC-1.0, respectively. Comparing Figures 4(a) and (b) with Figure 3, it was found that Co@HC-1.0 maintained a complex consisting of a tubular structure and particulate structures located on its surface, even after the heat treatment of MOFOF-1.0 and the subsequent acid treatment.

[0082] The tubular structure was confirmed to appropriately reflect the size of the FNT and to have the following dimensions: The length in the longitudinal direction was in the range of 1 μm or more and 10 μm or less. The wall thickness ranged from 100 nm to 300 nm. The diameters were in the range of 450 nm to 1.5 μm.

[0083] The particulate structure favorably reflected the size of the ZIF, with a particle size of 50 nm to 300 nm, specifically 75 nm to 150 nm. Although not shown, the SEM and STEM images of Co@HC-1.5 also showed similar results.

[0084] The black dots in Figure 4(c) and the white dots in (d) are cobalt particles within the particulate structure, and were located on the outer surface of the tube as well as on the surface within the hollow structure, and were uniformly distributed throughout.

[0085] The d-spacings calculated from the intensity profile of the crystal lattice in Figure 4(e) were 0.349 nm and 0.205 nm, respectively. The d-spacings calculated from Figure 4(f) were 0.346 nm and 0.205 nm, which were in good agreement with each other. These values ​​corresponded to the d-spacings of the 002 plane of graphitic carbon (0.336 nm) and the d-spacings of the 111 plane of a cobalt crystal with a face-centered cubic (FCC) crystal structure (0.206 nm), respectively. Although not shown, Co@HC-0.5, Co@HC-1.5, and Co@HC-2.0 also had similar d-spacings.

[0086] FIG. 5 shows XRD patterns and Raman spectra of Co@HC-0.5 to 2.0.

[0087] Figure 5(a) shows the XRD patterns of FNT, FNTox, pZIF-67, and MOFOF-1.0. The XRD patterns of FNT and FNT-ox showed no change in the crystalline phase even after acid treatment. The XRD pattern of MOFOF-1.0 contained the peaks of ZIF-67 in addition to the XRD pattern of FNT-ox. This indicates that MOFOF-1.0 was a precursor composite material containing fullerene nanotubes and zeolite-like imidazolate structures (ZIFs) containing metal ions located on their surfaces.

[0088] Figure 5(b) shows the XRD patterns of Co@HC-0.5~2.0. The XRD patterns in Figure 5(b) are completely different from those in Figure 5(a), and contain new peaks at 26.0°, 44.2°, and 51.6°. The peak at 26.0° corresponds to the 002 plane of graphitic carbon, and the peaks at 44.2° and 51.6° correspond to the 111 and 200 planes of FCC cobalt crystals, respectively.

[0089] Figures 4 and 5(b) show that the Co@HC-0.5-2.0 obtained by heat-treating the precursor composite is a carbon composite material containing carbon nanotubes based on fullerene nanotubes and ZIF-based carbon structures containing cobalt particles located on the surface. In particular, the carbon after combustion is sp 2 Hybrid graphitic carbon and disordered sp 3 It was found that the cobalt particles have a face-centered cubic crystal structure (FCC), while the carbon is hybridized.

[0090] In Figure 5(b), the particle size of the cobalt particles was calculated from the half-width of the X-ray diffraction by Scherrer's equation. The particle sizes of Co@HC-0.5 to 2.0 were 3.3 nm, 5.8 nm, 7.3 nm, and 9.6 nm. This means that the particle size of the metal particles is 60 The tendency was that the solubility increased as the molar ratio of HCl / Co increased.

[0091] Figure 5(c) shows the Raman spectra of Co@HC-0.5 to 2.0. All of the Raman spectra show a peak at 1353 cm -1 and 1587 cm -1 These bands correspond to the disordered sp 3 D band and sp band associated with hybridized carbon atoms 2 This corresponds to the G band associated with the hybridized carbon atoms.

[0092] Intensity ratio of D band and G band (I D / I G) were 1.28, 1.32, 1.37, and 1.42, respectively, indicating that the more ZIF-67, the more graphitic carbon there was.

[0093] FIG. 6 shows the XPS spectrum of Co@HC-1.0.

[0094] Figure 6 also shows the XPS spectrum of MOFOF-1.0. According to Figure 6(a), MOFOF-1.0 is composed of carbon, oxygen, metal (cobalt in this case), and nitrogen atoms, with atomic percentages (%) of 78.3%, 14.8%, 1.0%, and 5.9%, respectively. Co@HC-1.0, based on MOFOF-1.0, is also composed of carbon, oxygen, cobalt, and nitrogen atoms, with atomic percentages (%) of 80.1%, 16.2%, 1.5%, and 2.2%, respectively.

[0095] Although not shown, the XPS spectrum of Co@HC-1.5 was similar to that of Co@HC-1.0, and had the composition shown in Table 3. From this, it can be seen that the product obtained by the manufacturing process shown in Figure 2 is composed of carbon atoms (C), oxygen atoms (O), metal (cobalt in this case) atoms (M), and nitrogen atoms (N), and the atomic percentage (%) is 75≦C≦85 12≦O≦20 1.5≦M≦3.0 2.0≦N≦2.5 It was found that

[0096] [Table 3]

[0097] Figures 6(b) to (e) show the XPS core level spectra of Co@HC-1.0. The C1s spectrum of MOFOF-1.0 (lower panel of Figure 6(b)) has peaks at 284.1 eV, 285.6 eV, and 286.4 eV, which correspond to C=C(sp 2 ), CC(sp 3), and C-OH or C-N bonds. The C1s spectrum of Co@HC-1.0 (upper panel of Figure 6(b)) has peaks at 284.3 eV, 285.6 eV, 286.3 eV, and 288.7 eV, which correspond to C-V, C-OH, CO / CN, and O-C=O bonds, respectively.

[0098] The O1s spectra of MOFOF-1.0 and Co@HC-1.0 (Fig. 6(c)) both had C-OH and C-O-C bonding states.

[0099] The N1s spectrum of MOFOF-1.0 (lower panel of Figure 6(d)) has peaks at 400.05 eV, 401.0 eV, and 401.96 eV, corresponding to NH, CN, and C=N bonds, respectively. The N1s spectrum of Co@HC-1.0 (upper panel of Figure 6(d)) has peaks at 398.2 eV, 400.2 eV, and 401.4 eV, corresponding to pyridinic nitrogen (N-6), pyrrolic nitrogen (N-5), and quaternary nitrogen (NQ), respectively.

[0100] The Co 2p spectrum of MOFOF-1.0 (lower panel of Fig. 6(e)) shows the Co-N bond at 781.1 eV and a satellite peak at 785.4 eV, which are derived from ZIF-67. On the other hand, the Co 2p spectrum of Co@HC-1.0 (upper panel of Fig. 6(e)) shows the characteristic peaks of metallic cobalt 2p at 780.35 eV and 795.95 eV, in addition to the Co-N bond state at 782.4 eV. 3 / 2 and 2p 1 / 2 The level was shown.

[0101] FIG. 7 is a diagram showing nitrogen adsorption / desorption isotherms of Co@HC-0.5 to 2.0.

[0102] According to Figure 7, all of the isotherms of Co@HC-0.5~2.0 are classified as a mixed type of Type I / Type IV in the IUPAC classification, indicating that Co@HC-0.5~2.0 has a hierarchical micro / mesoporous carbon structure.

[0103] 4, 5, and 7, it was found that Co@HC-0.5~2.0 has a hierarchical structure consisting of porous carbon nanotubes based on fullerene nanotubes and a porous carbon structure based on zeolite-like imidazolate structures (ZIFs) located on the surface of the porous carbon nanotubes, and that cobalt particles are located within the porous carbon structure.

[0104] The BET specific surface area, BJH pore volume, DFT pore distribution, etc. calculated from FIG. 7 are shown in Table 4.

[0105] [Table 4]

[0106] According to Table 4, Co@HC-1.0~1.5 is 370m 2 / g or more 800m 2 / g or less, and meets the BET surface area of ​​0.65 cm 3 / g or more 1.0cm 3 The total pore volume was 53.5% to 60% of the total pore volume, and the volume of micropores with pore diameters of 1 nm or less was 53.5% to 60% of the total pore volume. Such porous materials with metal particles are advantageous for heterogeneous catalytic reactions.

[0107] FIG. 8 is a graph showing the reaction time dependence of the reduction rate of 4-nitrophenol with Co@HC-1.0 to 1.5. FIG. 9 shows the pseudo-first order kinetic plot of FIG.

[0108] Figures 8 and 9 also show the results of catalytic tests on the carbide (referred to as FDC) obtained by calcining the prepared fullerene nanotubes (FNTs) at 800°C for 4 hours in a nitrogen atmosphere, and the carbide (referred to as Co@ZDC) obtained by calcining ZIF-67 at 800°C for 4 hours in a nitrogen atmosphere.

[0109] As shown in Table 5, the correlation coefficient R 2was close to 1, confirming that the use of the pseudo-first-order kinetic model is effective for the reduction reaction of 4-nitrophenol (4-NP) using Co@HC-1.0~1.5, FDC, and Co@ZDC.

[0110] 8 and 9, Co@HC-1.0 and Co@HC-1.5 were found to be effective in reducing 4-NP. In particular, the kinetic constants and catalytic frequencies in Table 5 indicate that Co@HC-1.0 has better catalytic performance than Co@ZDC.

[0111] [Table 5]

[0112] FIG. 10 is a graph showing the reaction time dependence of the reduction rate of various nitropolycyclic aromatic hydrocarbons with Co@HC-1.0. FIG. 11 shows the pseudo-first order kinetic plot of FIG.

[0113] 10 and 11, Co@HC-1.0 was found to function as a catalyst for the reduction of various nitropolycyclic aromatic hydrocarbons. In particular, Co@HC-1.0 showed excellent catalytic performance for the reduction of nitrobenzene (NB), 4-nitrophenol (4-NP), 2-nitrophenol (2-NP), 4-methylnitrobenzene (4Me-NB), and 4-chloronitrobenzene (4Cl-NB), in that order.

[0114] FIG. 12 shows the cycle test of the reduction of 4-nitrophenol by Co@HC-1.0.

[0115] According to Figure 12, the catalytic performance of Co@HC-1.0 was maintained even after five cycles, indicating that it was an excellent catalyst.

[0116] FIG. 13 shows nitrogen adsorption / desorption isotherms of Co@HC-1.0 before and after the reduction test.

[0117] The recycled sample after the reduction test was prepared by washing the Co@HC-1.0 that had been reduced four times with ethanol and drying it under vacuum. As shown in Figure 13, both the as-prepared Co@HC-1.0 and the recycled Co@HC-1.0 showed similar nitrogen adsorption / desorption isotherms.

[0118] 8 to 13, it was shown that among porous carbon composite materials having a hierarchical structure of porous carbon nanotubes based on fullerene nanotubes and porous carbon structures based on zeolite-like imidazolate structures (ZIFs) that are located on the surface of the porous carbon nanotubes and contain metal particles (cobalt in this case), porous carbon composite materials in which the atomic percentage ratio of metal particles (cobalt particles in this case) (M) to carbon (C) constituting the porous carbon nanotubes and porous carbon structures is in the range of 0.015 or more and 0.03 or less function as catalysts for reducing nitropolycyclic aromatic hydrocarbons.

[0119] Furthermore, referring to Table 1, it is shown that the porous carbon composite material of the present invention satisfying the above atomic percentage ratio is produced by mixing fullerene nanotubes, imidazole or a derivative thereof, and a salt of a metal element (here, cobalt) so that the molar ratio of fullerene nanotubes to the salt of the metal element is greater than 0.5 and less than 2.0, and by the production process shown in Figure 2. [Industrial Applicability]

[0120] The porous carbon composite material of the present invention is applied to a catalyst for reducing nitropolycyclic aromatic hydrocarbons. [Explanation of symbols]

[0121] 100 Porous carbon composite material 110 Porous carbon nanotubes 120 Metal particles 130 Porous carbon structure

Claims

1. Porous carbon nanotubes based on fullerene nanotubes; a porous carbon structure based on a zeolite-like imidazolate structure (ZIF) located on the surface of the porous carbon nanotube and containing metal particles; Contains A porous carbon composite material, wherein the ratio of the atomic percentage of the metal particles (M) to the carbon (C) constituting the porous carbon nanotubes and the porous carbon structure is 0.015 or more and 0.03 or less.

2. 2. The porous carbon composite material of claim 1, wherein the metal particles are made of a metal selected from the group consisting of cobalt (Co), nickel (Ni), iron (Fe), and platinum (Pt).

3. 3. The porous carbon composite material according to claim 1, wherein the particle diameter of the metal particles calculated from the half width of X-ray diffraction using Scherrer's equation is in the range of 3.5 nm to 9.0 nm.

4. The porous carbon composite material according to any one of claims 1 to 3, wherein the atomic percentage ratio is in the range of 0.018 to 0.

03.

5. The porous carbon composite material according to any one of claims 1 to 4, wherein the porous carbon nanotubes and / or the porous carbon structure further contain nitrogen (N).

6. The porous carbon composite material according to claim 5 , wherein the porous carbon nanotubes and / or the porous carbon structure further contain oxygen (O).

7. The atomic percentages (%) of the carbon (C), the metal particles (M), the oxygen (O), and the nitrogen (N) (where the total of C, M, O, and N is 100%) are respectively: 75≦C≦85 1.3≦M≦3.0 12≦O≦20 2.0≦N≦2.5 The porous carbon composite material according to claim 6, which satisfies the above formula:

8. 8. The porous carbon composite material according to 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 370 m ２ / g or more 800m ２ The porous carbon composite material according to any one of claims 1 to 8, wherein the porous carbon composite material satisfies the range of 1 / g or less.

10. The BET specific surface area is 380 m ２ / g or more 450m ２ The porous carbon composite material according to claim 9, wherein the porous carbon composite satisfies the range of 1 / g or less.

11. The total pore volume is 0.65 cm ３ / g or more 1.0cm ３ / g or less, 11. The porous carbon 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 53.5% to 60% of the total pore volume.

12. 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 the mixing and reaction; calcining the product obtained by said drying; It encompasses 12. The method for producing a porous carbon composite material according to claim 1, wherein the molar ratio of the fullerene nanotubes to the salt of the metal element is greater than 0.5 and less than 2.

0.

13. 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 13. The method of claim 12, wherein the compound is selected from the group consisting of fullerenes and derivatives thereof.

14. The method according to claim 12 or 13, wherein the acid treatment uses an acid selected from the group consisting of hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid, and hydrofluoric acid.

15. The method according to any one of claims 12 to 14, 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 cobalt (Co), nickel (Ni), iron (Fe), and platinum (Pt).

16. The method according to any one of claims 12 to 15, 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 1-5:10-50:1-5.

17. The method according to any one of claims 12 to 16, wherein the calcination comprises calcining the product in a nitrogen atmosphere at a temperature in the range of 750°C to 1200°C.

18. A catalyst comprising the porous carbon composite material according to any one of claims 1 to 11.

19. 19. The catalyst of claim 18 for reducing nitropolycyclic aromatic hydrocarbons.

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