Properties of metal species in square-shape mesopores of KSW-2-based silica

Abstract

Properties arising from 2-D orthorhombic mesoporous silica (KSW-2) were investigated for each structural feature: (1) periodicity in silicate framework and (2) square-shape mesopore. Titanium species were grafted onto the periodic silica walls of KSW-2-based mesoporous silica through silylation with octylmethyldichlorosilane in the presence of organotitanium compounds with cyclopentadienyl ligands. The surface TiO₄ units formed after calcination at 550 °C showed a higher activity in the oxidation of cyclohexene with peroxides than those onto FSM-16 and MCM-41 grafted in the same manner, indicating that (1) the periodicity in the framework influenced the catalytic activity due to the heteroatoms fixed at the silicate surfaces. The synthesis of metallic Pt species inside square-shape mesopores of KSW-2-based silica was conducted by reduction of impregnated H₂PtCl₆. Considering the morphology of metallic Pt species formed through wet H₂ and UV reduction, it is considered that (2) the square-shape mesopore is useful for suppressing the sintering of metallic Pt species.