A novel Fe3O4@nSiO2@NiPd–PVP@mSiO2 multi-shell core–shell nanocomposite for cinnamic acid hydrogenation in water

Abstract

A novel Fe₃O₄@nSiO₂@NiPd–PVP@mSiO₂ multi-shell core–shell nanocomposite, with a Brunauer–Emmet–Teller surface area as high as 304.5 m² g⁻¹, has been prepared by the combination of a modified Stöber method, an impregnation–reduction method and a surfactant-templating method. It has a multi-shell structure with ferroferric oxide as the core, an inner nonporous silica shell, polyvinylpyrrolidone (PVP) dispersed Ni and Pd active species, and an outer mesoporous silica shell in sequence, as confirmed by transmission electron microscopy and nitrogen adsorption–desorption. It showed excellent catalytic performance in the selective hydrogenation of cinnamic acid to hydrocinnamic acid under relatively mild reaction conditions and can be recycled efficiently. Furthermore, it also exhibited good catalytic activity and stability in the hydrogenation of a number of unsaturated substrates in water. It was demonstrated that addition of small amounts of Pd can markedly improve its activity. The combination of PVP and the outer mesoporous silica shell can not only disperse the active species but also suppress their loss or aggregation during the reaction, accounting for its good stability in water.