Epoxidation of alkenes catalyzed by highly ordered mesoporous manganese–salen-based hybrid catalysts

Abstract

A series of manganese–salen-based hybrid catalysts, Mn(salen)/C3N2–Schiff–SBA-15 and Mn(salen)/C4N2–Schiff–SBA-15, were demonstrated for the first time by a multistep grafting method. As-prepared hybrid catalysts exhibited well-defined mesostructure including highly ordered 2D hexagonal p6mm pore geometry, large BET surface area (268–293m2g−1), uniform pore size (5.2–6.4nm) as well as high pore volume (0.35–0.41cm3g−1); meanwhile, the structure of the starting manganese–salen complexes and other functionalities (Schiff ligand and C3N2 or C4N2 unit) remained intact in the hybrid catalysts. These hybrid catalysts were subsequently utilized as efficient, selective and reusable catalysts in epoxidation of alkenes including styrene, cyclohexene and 1-phenylcyclohexene by using NaOCl as the oxidant, and the contribution of imidazole or piperazine and Schiff base to the overall catalytic activity of the hybrid catalysts were evaluated and explained.