Mesoporous Silica Supported Unsymmetric Chiral Mn(III) Salen Complex: Synthesis, Characterization and Effect of Pore Size on Catalytic Performance
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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.
KeywordsUnsymmetric chiral Mn(III) salen complex Mesoporous silica Fine-tuning of pore size Heterogeneous catalysts Asymmetric epoxidation
This work obtained the financial support from the National Natural Science Foundation of China (grant 20773069), the Specialized Research Fund for the Doctoral Program of Higher Education (grant 200800551017) and the Fundamental Research Funds for the Central Universities.
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