Synthesis and characterization of methyl- and vinyl-functionalized ordered mesoporous silicas with high organic content

摘要

Methyl- and vinyl-functionalized ordered mesoporous silicas were synthesized via a co-condensation method from tetraethyl orthosilicate (TEOS) and methyltriethoxysilane (MTES) or vinyltriethoxysilane (VTES) in the presence of cetyltrimethylammonium bromide surfactant as a structure-directing agent using the synthesis procedure we have recently elaborated. The surfactant was removed via solvent extraction. The organosilane was incorporated in proportions corresponding to its content in the synthesis mixture. The materials with up to 70 molar % of VTES and 50% of MTES exhibited at least one peak in their powder X-ray diffraction patterns, and up to 3 peaks were observed for loadings of 33 and 43%. The (100) interplanar spacing, the primary pore volume and the pore diameter tended to systematically decrease as the organic group loading increased, whereas the specific surface area was relatively constant, although it appreciably decreased for high loadings of VTES. In particular, the pore diameter shifted from the mesopore to the micropore range for higher loadings of vinyl groups, allowing functionalized ordered microporous materials to be obtained. The synthesis of vinyl-functionalized silicas was found to be highly reproducible. It was concluded that vinyl-functionalized silicas can be synthesized in a reproducible way with retention of ordered structure and without phase separation for up to about 65% organic group loading, which is the highest hitherto attained loading of pendent organics in ordered silicas.