Hyaluronic Acid-Guided Synthesis of Pd Nanocatalysts for Transfer Hydrogenation of 4-Nitrophenol

Abstract

Herein Pd nanocatalysts for transfer hydrogenation were synthesized by using hyaluronic acid (HA) as both the reductant and the stabilizer. The effects of molecular weight of HA, molar ratio of [HA]/[Na2PdCl4] and reduction temperature, were evaluated in Pd-catalyzed transfer hydrogenation of 4-nitrophenol. The most active Pd NPs show the TOF value of 131.07 h−1 at 50 °C with the equimolar mixture of formic acid and sodium formate. Further, uniformly distributed Pd NPs were successfully synthesized through the reduction of Pd (II) precursors on HA-modified magnetic NPs, which were constructed through electrostatic layer-by-layer assembly. The hybrid catalysts also exhibit high activity with the mixed hydrogen source. This work paves a promising way to construct highly active hybrid catalysts through the combination of in-situ reduction and electrostatic layer-by-layer methods.