Vanadium-containing ethane–silica hybrid periodic mesoporous organosilicas: Synthesis, structural characterization and catalytic applications

Vanadium-containing ethane–silica hybrid mesoporous silsesquioxane materials (V-HMM) with uniform hexagonal arrangement were prepared using C18-, C16- and C14-alkyl trimethyl ammonium (ATMA) surfactants under basic conditions. The materials were characterized by PXRD, N2 adsorption–desorption, UV–Visible spectroscopy, Raman, 29Si, 13C and 51V solid-state MAS NMR, TEM and SEM techniques. The characterization techniques revealed that the structural ordering, morphology as well as the percentage of metal incorporation depends strongly on the hydrophobic chain length of the surfactant. PXRD, electron microscopy and N2 adsorption–desorption analysis confirmed that the original hexagonal structure of the material is maintained after vanadium substitution. UV–Visible, 51V NMR and Raman analysis certified that vanadium exists in a highly dispersed state and had tetrahedral coordination with the support surface. Liquid-phase epoxidation reaction of styrene using aqueous H2O2 and TBHP as oxidants, showed that the hybrid materials were highly active and more stable than conventional vanadosilicates. The high catalytic activity and improved epoxide selectivity of the V-HMM samples is related to the more hydrophobic environment inside the pore channels than the silica channels in V-MCM-41.