Palladium nanoparticles supported carbon based graphene oxide monolith as catalyst for sonogashira coupling and hydrogenation of nitrobenzene and alkenes

Abstract

Synthesis of palladium nanoparticles supported on carbon based graphene oxide monolith (Pd@CGO monolith) is reported here. It was prepared by solvothermal carbonization of glucose with small amount of graphene oxide (GO) as structure directing agent. It provides large and flat surface for anchoring Pd nanoparticles. CGO monolith impedes Pd particles migration and increases interaction between Pd nanoparticles and support, which leads to enhanced activity. It was used in Sonogashira coupling and hydrogenation of alkenes and nitrobenzene. The activity of Pd@CGO monolith was compared with 5 % Pd@GO and 5 % Pd/C for Sonogashira coupling of phenylacetylene with iodobenzene. Pd@CGO monolith showed excellent conversion (93 %) at 90 °C with low catalyst loading (1×10⁻³ g/cm³) under ligand and copper free reaction conditions. Pd@CGO monolith was well characterized by different analytical techniques. The effect of solvent, base, speed of agitation, mole ratio, catalyst loading and temperature was studied using Pd@CGO monolith. Also, a reaction mechanism was proposed and kinetic model developed. The catalyst was recycled up to four times with no loss of activity. It was highly stable showing no Pd leaching.