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

Abstract

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 (∼23.5 emu g⁻¹), perpendicularly aligned mesopore channels (∼2.2 nm in diameter), high surface area (∼405 m² 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.