A biomass-derived nickel-based nanomaterial as a sustainable and reusable catalyst for hydrogenation of arenes and heteroarenes†

Selective hydrogenation of functionalized aromatic- and hetero-aromatic hydrocarbons is an essential research area in synthetic chemistry, which gives straightforward access to an array of saturated carbo- and heterocyclic compounds. To accomplish this hydrogenation process in a more resourceful and cost-effective manner, the development and applicability of potential catalytic materials, particularly based on earth-abundant metals, are crucial. From the viewpoint of sustainability and circular economy, such catalytic systems should be derived from waste biomass. Here, we report the preparation and application of plant-based waste biomass such as pine needle-derived Ni-nanoparticles as an efficient catalyst for the hydrogenation of (hetero)arenes. The immobilization of Ni-nitrate on pine needles and subsequent pyrolysis generates zero-valent Ni-nanoparticles (5–8 nm), which are embedded in a highly mesoporous N-doped graphitic matrix. The resulting nickel nanoparticles exhibited high activity and selectivity as well as stability and reusability for the hydrogenation of functionalized arenes as well as nitrogen and oxygen-containing heteroarenes to obtain various cyclo-aliphatic compounds including tetrahydroquinolines, tetrahydroquinoxalines and dihydrobenzofurans as well as key starting materials of pharmaceutical agents. DFT calculations have been made for this Ni-catalytic (hetero)arene hydrogenation process, which revealed favorable reaction thermodynamic and kinetic as well as mechanistic feasibility for selective ring reduction.