In Situ Surface Engineering of Mesoporous Silica GeneratesInterfacial Activity and CatalyticAcceleration Effect

摘要

Mesoporous structured catalysts featuring interfacial activity are the most promising candidates for biphasic interface catalysis because their nanopores can concurrently accommodate catalytic active components and provide countless permeable channels for mass transfer between the interior and the exterior of Pickering droplets. However, to date, a convenient and effective strategy for the preparation of an anchor site-containing interfacial active mesoporous catalyst is still lacking. In the present work, we report a novel and efficient interfacial active mesoporous silica (MS) catalyst, which is prepared by a facile cocondensation of two types of organosilanes and subsequent anchoring of Pd NPs onto its surface through the confinement and coordination interactions. The as-prepared catalyst is then applied as emulsifier to stabilize the water-in-oil (W/O) Pickering emulsion and investigated as an interfacial catalyst for the hydrogenation of nitroarenes. An obviously enhanced rate toward the nitrobenzene hydrogenation is observed for the 0.8mol% Pd/PAP-functionalized mesoporous silica-20 catalyst in the emulsionsystem (both conversion and selectivity are >99% within 30 min)incomparison to a single aqueous solution. Moreover, the emulsion catalyticsystem can be easily recycled six times without the separation ofthe catalyst from the water phase during the recycling process. Thisfinding demonstrates that the incorporation of phenylaminopropyl trimethoxysilaneamphiphilic groups during the hydrolysis of tetramethyl orthosilicatenot only endows MS with interfacial activity but also improves thecatalytic activity and stability.