Preparation and characterization of sulpho-functionalized ordered mesoporous silica

Abstract

Sulpho groups have been successfully embedded in mesoporous silica with an ordered two-dimensional hexagonal structure. The sulpho-functionalized mesoporous silica was prepared by the oxidation of a thiol-functionalized mesoporous silica which was obtained via the hydrolysis and co-condensation of tetramethoxysilane (TMOS) and mercaptopropyl trimethoxysilane (MPTMS). The samples exhibited an ordered two-dimensional hexagonal pore array up to 30 mol% MPTMS loading. The large surface area of MCM-41 (ca. 1000 m2/g) was maintained after incorporation of the mercaptopropyl group and oxidation of its thiol group. Solid-state 29Si NMR spectra showed the existence a mercaptopropyl group in a silica framework and 13C NMR studies further proved that treatment with hydrogen peroxide led to oxidation of the sulpho groups. High ammonia uptakes with high differential heats of adsorption revealed the strong acidity of sulpho-functionalized mesoporous silica. The amounts of acid sites may be controlled by regulating the amount of MPTMS employed in the synthesis. The sulpho-functionalized mesoporous silica behaved as an acid catalysis for the isomerization reaction of but-1-ene to cis- and trans-but-2-ene.