Magnetically-Separable and Thermally-Stable Au Nanoparticles Encapsulated in Mesoporous Silica for Catalytic Applications

Here, we report a synthetic strategy for fabricating silica-encapsulated gold nanoparticles (Au NPs) on magnetic particle (Fe3O4@SiO2-Au@mSiO2) for use as a magnetically-separable, thermally-stable, and easily recyclable catalyst in liquid phase reactions. Fe3O4@SiO2-Au@mSiO2 samples were prepared by synthesizing a Fe3O4@SiO2 core–shell particle followed by decoration with the Au NPs and additional mesoporous silica coating. The prepared Fe3O4@SiO2-Au@mSiO2 catalysts showed advantageous characteristics for liquid phase reaction, which are superparamagnetic properties for easy separation and recycling, the well-developed mesoporosity on the outer surface for facile diffusion of reactant molecules, and high resistance on thermal sintering of Au NPs. The resulting core–shell-type catalysts showed improved performance in terms of catalytic stability and recyclability for multiple reaction runs. In particular, the Fe3O4@SiO2-Au@mSiO2-H2O catalyst, which is treated with additional water etching, showed optimal properties such as improved molecular accessibility and Au stability, resulting in the best catalytic performance seen in this study.