Epoxides hydration on CoIII(salen)-OTs encapsulated in silica nanocages modified with prehydrolyzed TMOS

The silylation for reducing the pore entrance size is crucial for the success encapsulation of molecular catalysts. Herein, we reported the preparation of an efficient solid catalyst for epoxide hydration via encapsulation of Co-III(salen)-OTs in the nanocages of FDU-12 using prehydrolyzed tetramethylorthosilicate (TMOS) as silylation reagent under mild condition. Co-III(salen)-OTs in nanocages could afford TOF of 2760 h(-1) in the hydration of propylene epoxide (PO), which is the highest ever reported at low PO/H2O molar ratio. Comparison of the activity of Co-III(salen)-OTs accommodated in nanocages with different microenvironments suggests that Co-III(salen)-OTs in hydrophilic microenvironment was more active than that in hydrophobic microenvironment in the hydration of propylene epoxide. Moreover, studies show that the deactivation rate of Co-III(salen)-OAc is lower than that of Co-III(salen)-OTs in nanocages due to the confinement effect of the nanoreactor. (C) 2016 Elsevier Inc. All rights reserved.