Graphene hydrogel supported palladium nanoparticles as an efficient and reusable heterogeneous catalysts in the transfer hydrogenation of nitroarenes using ammonia borane as a hydrogen source

Addressed herein is a facile one-pot synthesis of graphene hydrogel (GHJ) supported Pd nanoparticles (NPs), namely Pd-GHJ nanocomposites, via a novel method that comprises the combination of hydrothermal treatment and polyol reduction protocols in water. The structure Pd-GHJ nanocomposites were characterized by TEM, HR-TEM, XRD, XPS, Raman spectroscopy and BET surface area analysis. Then, Pd-GHJ nanocomposites were used as a heterogeneous catalysts in the tandem dehydrogenation of ammonia borane and hydrogenation of nitroarenes (Ar-NO2) to anilines (Ar-NH2) in the water/methanol mixture at room temperature. A variety of Ar-NO2 derivatives (total 9 examples) were successfully converted to the corresponding Ar-NH2 by the help of Pd-GHJ nanocomposites catalyzed tandem reactions with the conversion yields reaching up to 99 % in only 20 min reaction time. Moreover, Pd-GHJ nanocomposites were demonstrated to be the reusable catalysts in the tandem reactions by preserving their initial catalytic performance after five consecutive catalytic cycles. It is believed that the presented synthesis protocol for the Pd-GHJ nanocomposites and the catalytic tandem hydrogenation reactions will make a significant contribution to the catalysis and synthetic organic chemistry fields.