Vapor silylation of Ta-HMS mesoporous molecular sieve

Abstract

Ta-HMS mesoporous molecular sieve was synthesized hydrothermally and vapor-silylated using hexamethyldisilazane. Two samples were characterized by Fourier transform infrared spectrometry, ²⁹Si cross-polarization and magic angle spinning nuclear magnetic resonance, hydrophilicity–lipophilicity tests, X-ray diffraction, N₂ adsorption, and diffuse reflectance ultraviolet–visible spectroscopy (DR UV–Vis), respectively. They were also evaluated by the epoxidation of cyclohexene using tert-butyl hydroperoxide as oxidant. Trimethylsilyl groups have been anchored on the surface of Ta-HMS after silylation treatment. The silylated Ta-HMS keeps a typical mesoporous structure, whereas it has a less pore diameter and a less specific area than Ta-HMS. On the other hand, the silylated Ta-HMS gives the less hydrophilicity and higher lipophilicity as well as the higher dispersity of Ta sites than Ta-HMS, and as a result, the silylated Ta-HMS exhibits the more excellent catalytic performance in epoxidation of cyclohexene than Ta-HMS.

Graphical Abstract

Ta-HMS mesoporous molecular sieve was synthesized hydrothermally and vapor-silylated using hexamethyldisilazane. Trimethylsilyl groups have been anchored on the surface of Ta-HMS after silylation treatment. The silylated Ta-HMS keeps the typical mesoporous structure, whereas it has the less pore diameter and specific area compared with Ta-HMS. On the other hand, the silylated Ta-HMS gives the less hydrophilicity and higher lipophilicity as well as the higher dispersity of Ta sites than Ta-HMS, and as a result, the silylated Ta-HMS exhibits more excellent catalytic performance in epoxidation of cyclohexene than Ta-HMS.