Organic-Soluble Palladium Nanoparticles Costabilized by Hyperbranched Polymer and Dispersants as Highly Efficient and Reusable Catalysts in Biphasic Solution

A series of organic-soluble and size-controllable palladium nanoparticles (PdNPs) costabilized by alkyl-modified hyperbranched poly(amide-ester) (HP) and different dispersants were prepared by chemical reduction. Their catalytic activities and stabilities were investigated by the reduction of 4-nitrophenol to 4-aminophenol in an organic/aqueous biphasic solution. It was found that high concentration HP and long alkyl chain dispersants reduce the particle sizes of PdNPs and improve their organic solubility, accounting for their good activity and stability in the organic/aqueous biphasic solution. A HP and oleylamine costabilized PdNPs showed the best catalytic performance in the reduction of 4-nitrophenol, and it can be easily separated from the biphasic solution and recycled 10 times with a conversion efficiency of around 100%. Notably, all the costabilized PdNPs showed excellent time-dependent stability and exhibited good activity and stability even after 35 days of storage.