Biosourced mesoporous carbon with embedded palladium nanoparticles by a one pot soft-template synthesis: application to Suzuki reactions

A simple, direct and environmentally-friendly one-pot preparation of a palladium-containing mesoporous carbon (Pd@MC) from a cheap, non-hazardous and easily accessible biopolymer (tannin) as a carbon precursor, Pluronic (R) F127 surfactant as a pore structuring agent and a palladium salt is reported. This material has the peculiarity to have palladium nanoparticles entrapped in irregular voids connected to the worm-like mesoporous network limiting palladium leaching while keeping good access to the reactants. It was successfully used as a catalyst for ligand-free Suzuki-Miyaura couplings of aryl bromides in a green solvent (propane-1,2-diol) in the presence of extremely low amounts of supported palladium (usually 30 mu equiv.). It is noteworthy that almost palladium-free products (containing less than 1.5 mu equiv. of precious metal) can be obtained. The possibility to reuse the catalyst was also ascertained.