Mesoporous Silica Supported Unsymmetric Chiral Mn(III) Salen Complex: Synthesis, Characterization and Effect of Pore Size on Catalytic Performance

Abstract

An unsymmetric chiral Mn(III) salen complex was immobilized onto a series of MCM-41 and MCM-48 mesoporous materials with different pore sizes. The as-synthesized catalysts were characterized by XRD, FT-IR, DR UV-Vis, N2 sorption and XPS. The results indicated that chiral Mn(III) salen complex was immobilized into the nanopores of supports and the long-range mesoporous ordering of parent supports was maintained after the immobilization. The heterogeneous catalysts were evaluated in the asymmetric epoxidation of styrene, indene, and 1-phenylcyclohexene, and the effect of 3-mercaptopropyltrimethoxysilane dosage and fine-tuning of pore size on the catalytic performance was studied. It was found that the activity and enantioselectivity were closely correlated with the pore sizes of heterogeneous catalysts. The larger pore sizes of supports could lead to higher conversions and ee values.