JP5316988B2 - Regular mesoporous fullerene having a large specific surface area and method for producing the same - Google Patents

Description

  The present invention relates to an ordered mesoporous fullerene having a large specific surface area that can be used in various electrochemical applications. The present invention also relates to a method for producing the mesoporous fullerene.

Regular mesoporous materials have received particular attention in many fields due to their favorable structural properties, and their pore size must be controlled to meet several application requirements (1). reference). The mesopore size can be adjusted in many ways, but with these methods it was only possible to enlarge the pores.
Multi-scale pores that are independently controlled in larger or smaller sizes and well-connected pores may be beneficial for some applications, such as catalysts. Another most rapidly developing trend in modern chemical physics is related to the discovery and research of fullerenes, which are novel carbon allotropes (see Non-Patent Documents 2-7). The carbon atoms in the fullerene molecule are located at the vertices of regular hexagons and regular pentagons and cover the surface of the sphere or spheroid in a regular manner. The most spread and complex ones of molecules belonging to the fullerene system is C _60, this structure is truncated icosahedron. The surface of this molecule is composed of 20 regular hexagons and 12 regular pentagons so that each pentagon is adjacent only to the hexagon, whereas each hexagon is composed of 3 pentagons alternately. And adjacent to the hexagon. Also the fullerene system, in addition to C _60, also molecules such as _{C 70,} C _78, C ₈₄ are included, these and poorer symmetry, distinguished by there are hexagonal larger number of surface Is done. Thus, fullerenes form a unique molecular species with a closed two-dimensional structure.

The object of the present invention is to provide a novel and extremely versatile morphology, a large specific surface area (greater than 200 m ² / g) and spherical dimensions (about 70 nm), which can be used for various electrochemical applications. It is to provide mesoporous fullerenes. Another object of the present invention is to provide a method for producing the mesoporous fullerene.

In order to achieve the above object, we came up with the use of a very regular KIT-6 mesoporous material as a template and completed the present invention.
That is, the present invention provides an ordered mesoporous fullerene having a large surface area whose structure is composed of fullerene aggregates.
The term “meso” in this specification means a size between 2 nm and 50 nm.

The present invention also provides a method of making ordered mesoporous fullerenes having a large specific surface area whose structure is composed of fullerene aggregates. This fabrication method consists of the following steps:
(1) a step of dissolving a predetermined amount of fullerene in an organic solvent,
(2) A step of adding a predetermined amount of three-dimensional large pore mesoporous silica (KIT-6) having cubic Ia3d symmetry to the fullerene dissolved in an organic solvent and mixing.
(3) heating the mixture under a nitrogen atmosphere and maintaining the mixture at about 900 ° C. to obtain a composite;
(4) A step of washing the composite with HF to remove silica, and (5) a step of drying the obtained composite.

The ordered mesoporous fullerene of the present invention having a large specific surface area is a novel material and can be used in various electrochemical applications such as fuel cells, rechargeable cells, and electroforming.
By using the production method of the present invention, the mesoporous fullerene of the present invention having a large specific surface area whose structure is composed of fullerene aggregates can be produced.

3 is a powder XRD pattern at a low angle of MF-1 obtained in Example 1. FIG. 2 is a powder XRD pattern of MF-1 obtained in Example 1 at a wide angle. It is a nitrogen adsorption isotherm of MF-1. It is a HRSEM image of MF-1. It is a HRTEM image of MF-1.

First, a regular method for producing mesoporous fullerene will be described.
As described above, the regular mesoporous fullerene of the present invention is produced as follows.
(1) A predetermined amount of fullerene is dissolved in an organic solvent;
(2) Three-dimensional large pore mesoporous silica (KIT) with cubic Ia3d symmetry
-6) is added to the fullerene dissolved in an organic solvent and mixed;
(3) The composite is obtained by heating the mixture under a nitrogen atmosphere and maintaining the mixture at about 900 ° C;
(4) washing the composite with HF to remove silica; and
(5) The obtained composite is dried.

  Here, KIT-6 is a three-dimensional large pore mesoporous silica with cubic Ia3d symmetry, and a very regular pore structure with large specific surface area, large pore volume and adjustable large pore diameter have. This material has received much attention because it has a three-dimensional structure with a large pore diameter, which is described in the references (T.-W. Kim, F. Kleitz). B. Paul, R. Ryoo, Journal of the American Chemical Society (J. Am. Chem. Soc.), 127, 7601-7610 (2005)). Can do.

The amount of fullerene used is preferably 30 to 100 mg with respect to 1 g of KIT-6. The key point in changing the amount of fullerene is to improve mesostructure order and crystallinity.
The amount of the organic solvent used is preferably 2.5 to 10 ml with respect to 1 g of KIT-6. A key point in changing the amount of organic solvent is to improve the solubility of fullerenes by corresponding to the mesostructure order and crystallinity of the final material.

  As fullerene solvents, various fullerene solubility, such as 1,2,4-trimethylbenzene, 1,2-dichlorobenzene, 1-methylnaphthalene, 1-phenylnaphthalene, or xylene Organic solvents can be used.

The fullerene obtained by the production method has a “very regular” mesoporous structure, and has a large specific surface area reflecting KIT-6 as a template. As used herein, “very regular” means that the material has regular path connectivity and a uniform pore size distribution.
The specific surface area of mesoporous fullerene is preferably more than 200 m ² / g, more preferably more than 300 m ² / g, and these are determined by a nitrogen adsorption method. Regarding the nitrogen adsorption method, reference literature (PI Ravikovitch, AV Nymark (AV
Neimark), Journal of the Physical Society of Japan B (J. Phys. Chem.
B.), 105, 6817-6823 (2001)).

Example 1
<Production of KIT-6>
KIT-6 with various pore diameters is P123 (poly (ethylene glycol) -block-poly (propylene glycol) -block-poly (ethylene glycol) which is a triblock copolymer (Pluronic P123, molecular weight 5800). , EO ₂₀ PO ₇₀ EO ₂₀ (Sigma-Aldrich) and n-butanol mixtures as structure directing agents, synthesized at various synthesis temperatures in strongly acidic media. In a typical synthesis, 4 g of P123 was dissolved in 144 g of distilled water and 7.9 g of 35 wt% HCl solution, and the mixture was stirred for 3 hours at 35 ° C. Further, 4.0 g of n-butanol was quickly added to the mixture. The mixture was then stirred for 1 hour at 35 ° C. Subsequently, this homogeneous clear solution was mixed with TEOS (tetraethylol). 8.6 g was quickly added and stirring was continued for 24 hours at 35 ° C. The mixture was then transferred to a polypropylene bottle and kept in an air oven at 150 ° C. for 24 hours under static conditions. This sample was named KIT-6-150, and the resulting product was filtered under high temperature conditions without washing and dried in air at 100 ° C. for 24 hours. Firing was performed at 550 ° C. in the air.

<Preparation of very regular mesoporous fullerene having a large specific surface area>
Mesoporous fullerene was prepared by solid phase reaction using an appropriate stoichiometric amount of the obtained mesoporous KIT-6-150 and fullerene. First, 60 mg of fullerene is first dissolved in 5 g of 1,2,4-trimethylbenzene and thoroughly mixed with 1 g of KIT-6-150, then the sample is transferred to a carbonization chamber and the presence of a nitrogen atmosphere at 900 ° C. for 5 hours. Held below. This complex sample was named MF-1. Mesoporous fullerene was obtained by washing the complex (MF-1) with HF to remove silica and dried at 100 ° C. for 24 hours.

<Evaluation of the obtained mesoporous fullerene>
The sample was analyzed by powder XRD (FIGS. 1 and 2). The XRD test was performed by operating a Rigaku Multisampler Diffractometer apparatus at 40 kV and 40 mA, CuKα = 1.54 Å. MF-1 was found to show two peaks at low angles that could be indexed with a three-dimensional cubic lattice (Ia3d), indicating that the sample had a very ordered mesoporous structure. Yes. The structure of the material is almost the same as that of the template (KIT-6-150) having a three-dimensional cubic structure having Ia3d symmetry. From this it is clear that the structure of MF-1 is a complete replica of the mesoporous silica template used for its synthesis. The sample also showed several peaks at high angles, which were similar to the high angle XR pattern of non-porous fullerene molecules (not shown). However, the peaks at 2θ = about 26 and 2θ = about 44 may be due to peak overlap due to bridging bonds during carbonization at 900 ° C. with actual fullerenes. This confirms that the material is indeed composed of spherical fullerene particles arranged in a regular manner by leaving a mesopore space in the center. This mesopore is very regular as confirmed by the low angle XRD pattern.

In order to further verify the morphology, structural order, and excellent tissue parameters, the material was characterized by HRTEM, HREM and nitrogen adsorption isotherms. FIG. 3 shows the nitrogen adsorption isotherm of MF-1, and FIG. 4 shows the obtained HRSEM image of MF-1 (observed with Hitachi-S 4800).
From the SEM photograph (FIG. 4), it is very clear that MF-1 (mesoporous fullerene) is oriented in the Z-direction with respect to this paper surface, and the particle size of mesoporous fullerene is about 70 nm. It is also clear. This material exhibits an excellent morphology with a spherical shape. The mesoporous fullerene particles have uniform dimensions. The mesoporous fullerene not only has a nano-sized particle size but also has a specific surface area of 0.9 m ² / g [Y. Y. Ye et al., Applied Physics Letters (Appl. Phys. Lett., Vol. 77 (14), 2117-2173 (2000)) has a very large specific surface area. is there. The structural parameters of the material, such as specific surface area, pore volume and pore diameter, were obtained from nitrogen adsorption measurements. In this isotherm (FIG. 3), a sharp capillary condensation stage is represented by a broader H1-hysteresis loop at higher relative pressure, which indicates that the material has a large, very regular, uniform mesopore It shows that it has. The specific surface area of this material reaches 310.5 m ² / g, which is 300 times greater than the specific surface area of the non-porous fullerene. On the other hand, the pore diameter of this material is about 3.53 nm. Conjugation between fullerene molecules not only has a very large specific surface area, but also exhibits very high conductivity, which is due to the interaction between π orbitals present in the fullerene molecule. .

  Structural order and morphology were further confirmed by HRTEM images. The sample exhibits a spherical morphology similar to non-porous fullerene. This shows that the pores are arranged in a regular fashion with a honeycomb-like structure and a uniform mesoporous pathway (FIG. 5). HRTEM images were taken with a JEOL-3000F device. The particle size is very small, which is extremely essential for various electrochemical applications.

    The mesoporous fullerene of the present invention can be used for various electrochemical applications. Further, since the mesoporous fullerene of the present invention has a very strong π-π interaction, it may be used as a support for a fuel cell.

Martin Hartman: Chem. Mater., Vol. 17, 4577-4593 (2005). Kroto HW et al .: Nature (London), vol. 318, 162 (1985). KraE tschmer W et al .: Nature (London), vol.347, 354 (1990). Taylor R et al .: J. Chem. Soc. Chem. Commun. 1423 (1990). Haufler R E et al .: J. Phys. Chem., Vol. 94, 8634 (1990). Eletskii A V, Smirnov B M: Usp. Fiz. Nauk 163 (2) 33 (1993) [Phys. Usp. 36202 (1993)]. Eletskii A V, Smirnov B M: Usp. Fiz. Nauk, vol. 165, 977 (1995) [Phys. Usp., Vol. 38, 935 (1995).].

Claims (4)

Mesoporous fullerene having a structure composed of fullerene aggregates , a specific surface area greater than 200 m ² / g, and cubic Ia3d symmetry . The mesoporous fullerene according to claim 1 , wherein the 200 m ² / g is measured by a nitrogen adsorption method. A method for producing mesoporous fullerene having a cubic Ia3d symmetry, the structure of which is composed of fullerene aggregates , the specific surface area is larger than 200 m ² / g ,
(1) a step of dissolving a predetermined amount of fullerene in an organic solvent,
(2) A step of adding a predetermined amount of three-dimensional large pore mesoporous silica (KIT-6) having cubic Ia3d symmetry to the fullerene dissolved in the organic solvent, and mixing.
(3) A step of obtaining a composite by heating and carbonizing the mixture in a nitrogen atmosphere,
(4) A method for producing the composite comprising a step of washing the composite with HF to remove silica, and (5) a step of drying the obtained composite. The method for producing mesoporous fullerene according to claim 3, wherein the carbonization is performed at 900 ° C.

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