Highly active dimeric Mn(salen) catalysts entrapped within nanocages of periodic mesoporous organosilica for epoxidation of alkenes

A couple of robust and reusable diamine-bridged dimeric Mn(salen) complexes were prepared by the encapsulation of homogeneous dimeric Mn(salen) complexes into nanocages of three-dimensionally (3D) periodic mesoporous organosilica (PMO) support followed by the silylation of the support with organosilane. The materials exhibited 3D periodic mesostructure with body-centered Im3m symmetry, and the confined Mn(salen) complexes maintained their original structure. As-prepared heterogeneous dimeric Mn(salen) complexes were successfully applied in the epoxidation of three alkenes (i.e. styrene, cyclohexene, and 1-phenylcyclohexene) by using NaClO as the oxygen donor and CH2Cl2 as a solvent, and the reusability of the materials was evaluated through three times' catalytic runs.

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► A couple of diamine-bridged dimeric Mn(salen) complexes were prepared.
► The materials were successfully applied in the epoxidation of three alkenes.
► Heterogeneous dimeric Mn(salen) complexes showed higher catalytic activity.
► Heterogeneous dimeric Mn(salen) complexes could be reused by simplified separation.