Robust Fe3O4/SiO2-Pt/Au/Pd magnetic nanocatalysts with multifunctional hyperbranched polyglycerol amplifiers.

Here we report a facile approach to prepare multicarboxylic hyperbranched polyglycerol (HPG)-grafted SiO(2)-coated iron oxide (Fe(3)O(4)/SiO(2)) magnetic hybrid support. This support combined the both features of Fe(3)O(4) and HPG, facile magnetic separation, and favorable molecular structure with numerous functional groups. With the use of the grafted-HPGs as templates, various noble metal nanocatalysts such as Pt, Au, and Pd were directly grown on the surfaces of magnetic support with ultrasmall and nearly monodisperse sizes (e.g., the average sizes of Pt, Au, and Pd are 4.8 +/- 0.5, 6.0 +/- 0.6, and 4.0 +/- 0.4 nm, respectively) and high coverage densities. Because of the amplification effect of HPG, high loading capacities of the nanocatalysts, around 0.296, 0.243, and 0.268 mmol/g for Pt, Au, and Pd, respectively, were achieved. Representative catalytic reactions including reduction of 4-nitrophenol, alcohol oxidation, and Heck reaction demonstrated the high catalytic activity of the noble metal nanocatalysts. Because of the stabilization of HPG templates, the nanocatalysts can be readily recycled by a magnet and reused for the next reactions with high efficiencies. The robust multifunctional magnetic hybrids will find important applications in catalysis and other fields such as drug delivery and bioseparations.