Nonsacrificial Self-Template Synthesis of Colloidal Magnetic Yolk-Shell Mesoporous Organosilicas for Efficient Oil/Water Interface Catalysis

Using interfacial reaction systems for biphasic catalytic reactions is attracting more and more attention due to their simple reaction process and low environmental pollution. Yolk-shell structured materials have broad applications in biomedicine, catalysis, and environmental remediation owing to their open channels and large space for guest molecules. Conventional methods to obtain yolk-shell mesoporous materials rely on costly and complex hard-template strategies. In this study, a mild and convenient nonsacrificial self-template strategy is developed to construct yolk-shell magnetic periodic mesoporous organosilica (YS-mPMO) particles by using the unique swelling-deswelling property of low-crosslinking density resorcinol formaldehyde (RF). The obtained YS-mPMO microspheres possess an amphiphilic outer shell, high surface area (393 m(2) g(-1)), uniform mesopores (2.58 nm), a tunable middle hollow space (50-156 nm), and high superparamagnetism (34.4-37.1 emu g(-1)). By tuning the synthesis conditions, heterojunction structured yolk-shell Fe3O4@RF@void@PMO particles with different morphologies can be produced. Owing to the amphipathy of PMO framworks, the YS-mPMO particles show great emulsion stabilization ability and recyclability under a magnetic field. YS-mPMO microspheres with immobilized Au nanoparticles (approximate to 3 nm) act as both solid emulsifier for dispersing styrene (St) in water and interface catalysts for selective conversion of St into styrene oxide with a high selectivity of 86%, and yields of over 97%.