Organic-Silica Hybrid Materials Consisting of the Double Four-Ring Silicate Structure as a Building Block
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MASANORI ISHIDA*, SEIJI MOTOJIMA*,
AND SHIGEO SATOKAWA**
*Department of Applied Chemistry, Faculty of Engineering, Gifu University, Yanagido 1-1, Gifu-City, Gifu 501-11, Japan **Tosoh Co., Kaisei-Cho 4560, Shinnanyo-City, Yamaguchi 746, Japan
ABSTRACT 8 Copolymerization of the cubic octameric silicate anion (Si 8 0 20 -) with dimethyldichlorosilane in 2,2-dimethoxypropane has yielded organic-silica 8 hybrid materials consisting of the Si 8 0 2 0 - structure as a building block. The hybrid materials have shown high surface area by calcination in air. The reaction conditions have been optimized to produce the materials with higher As a result, the hybrid materials with BET surface specific surface area. area of 406 m2 g- 1 have been obtained.
INTRODUCTI ON The silicate species with the double four-ring silicate structure (Si 8 0 2 08-, Fig. 1) is selectively formed in a methanolic solution of tetra8 The structure of Si 8 0 2 0 methylammonium [N+(CH 3 ) 4 , TMA] silicate [1,2]. corresponds to the secondary building unit of zeolite A [3], as shown in Fig. 2. From this fact, it would be expected that controlled linking and arrangement of the Si 8 0 2 0 8 - anion yield silica-based porous materials consisting of the Si 8 02 0 8 - cubic core as a building unit of their higher-order structures, which would provide an approach to design and construction of higher-order structures of silica-based materials at the molecular level. Some studies have been reported on the building block approach to 8 syntheses of silica-based materials from compounds with the Si 8 O2 0 - strucAs one of the studies, we have recently reported on producing ture [4-8]. 8 organic-silica hybrid materials by copolymerization of Si 8 02 0 - with dimethyldichlorosilane [(CH3 ) 2 SiCI 2 , DMDCS] in 2,2-dimethoxypropane (DMOP) [7]. 2 1 after The hybrid materials show specific surface area of ca. 304 m gcalcination in air. This study is aimed to investigate optimal conditions on synthesizing the hybrid materials with higher surface area. In the first two sections of this paper, the synthesis, structure, thermal property, and specific surface Procedures for area of the organic-silica hybrid materials are described. synthesizing the hybrid materials with higher surface area are described in the last section.
0
0>-0 o-S io(
I
i-'vo--s Oo.S i.L0Fig. 1.
8 The structure of Si 8 0 2 0 -.
Fig. 2.
The framework of zeolite A.
163 Mat. Res. Soc. Symp. Proc. Vol. 346. 01994 Materials Research Society
SYNTHESIS OF ORGANIC-SILICA HYBRID MATERIALS COMPOSED OF THE Si8020o- STRUCTUF AS A BUILDING UNIT The procedure for the reaction of Si 8 02 0 8 - with DMDCS in DMOP for pro ducing organic-silica hybrid materials is as follows. A methanolic solutic of TMA silicate at the SiO2 concentration of 1.0 mol dm- 3 , the TMA ions-to SiO2 molar ratio of 1.0, and the water-to-SiO2 molar ratio of 10.0 was use as a source of Si 8 O2 0 8 -, where the silicate species is present dominantl [1,2]. The amount of DMDCS is equal in molar quantity to that of the SiC component in t
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