Selective hydrogenation of levulinic acid at room temperature: Boosting ruthenium nanoparticle efficiency via coupling with in-situ pyridinic-N-doped carbon nanoflowers

Integrating unique morphology and tunable electronic state of supported metallic catalysts via one-step is an attractive pathway to boost their catalytic behaviors in selective hydrogenation reactions. Here, electronic state-tunable Ru nanoparticles (NPs) coupled with three-dimensional (3D) hierarchical carbon nanoflowers with in-situ generated pyridinic-nitrogen (Ru/PNC) are devised. Combining with systematical characterizations, kinetics investigations, and density functional theory (DFT) computations, the pyridinic-N species is proved to facilitate the formation of electron-rich Ru, which insures the weaker adsorption of levulinic acid but stronger adsorption of H-2 molecules on Ru, ultimately reducing the apparent activation energy of selective hydrogenation of levulinic acid (LA) to gamma-valerolactone (GVL). As a result, a high turnover frequency (TOF) of 5042.5 h(-1) and a GVL selectivity of > 99% are achieved on the most electron-rich Ru/PNC catalyst. A positive linearity between the TOFs and the surface pyridinic-N/Ru-0 ratios is recognized, further corroborating the electron-rich Ru-mediated intrinsic activity enhancement evoked by the surface pyridinic-N species on carbon nanoflowers.