Magnetic yolk-shell mesoporous silica microspheres with supported Au nanoparticles as recyclable high-performance nanocatalysts

Based on the surface engineering strategy, multifunctional yolk-shell microspheres with a magnetic core encapsulated in hollow mesoporous silica have been rationally synthesized through a stepwise solution-phase interface deposition approach by combining the sol-gel chemistry and surfactant-involved co-assembly process. The resulting microspheres possess a well-defined yolk-shell structure, uniform sizes, high magnetization (similar to 23.5 emu g(-1)), perpendicularly aligned mesopore channels (similar to 2.2 nm in diameter), high surface area (similar to 405 m(2) g(-1)) and controllable void space size (320-430 nm in diameter). Gold nanoparticles of 4.2 nm are incorporated into the yolk-shell microspheres, leading to a novel magnetically recyclable nanocatalyst. The obtained catalyst exhibits an excellent catalytic performance for styrene epoxidation with high conversion (91.4%) and selectivity (83.1%) in 12 h, much better than its counterpart, Au-loaded magnetic mesoporous silica catalyst. The multifunctional yolk-shell microspheres possess superior stability in terms of catalysis performance and porous yolk-shell structure even after 12 cycles of catalysis.