Fe3O4@SiO2/[Ru(bpy)3]2+ nanoscale stir bars as recyclable photocatalysts

Core-shell nanoscale stir bars doped with [Ru(bpy) 3 ] 2+ are successfully synthesized via magnetic-field-induced self-assembly of Fe 3 O 4 nanoparticles combined with classic Stöber method. The obtained Fe 3 O 4 @SiO 2 /[Ru(bpy) 3 ] 2+ nanoscale stir bars (NSBs) are applied to the photocatalytic amidation of aniline and the Friedel-Crafts amidoalkylation of trimethoxybenzene with no use of conventional stir bars, yielding the target products in 89% (at 4 mol% catalyst loading) and 94% (at 4 mol% catalyst loading), respectively. Furthermore, above NSBs allow rapid and quantitative recycling simply via the help of an external magnetic field, and maintain excellent catalytic ability after 7–8 rounds of catalysis. This work provides an effective strategy for the efficient heterogenization and recycling of [Ru(bpy) 3 ] 2+ . And it offers a new insight into the design of catalytic systems combining high activity and nanoscale stirring.