ZIF-8 derived ZnO@NC supported Ru nanoparticles for efficient low-temperature hydrogenation of levulinic acid to -valerolactone

Highly efficient synthesis of valuable gamma-valerolactone (GVL) by levulinic acid (LA) hydrogenation is of interest for biomass refinery, but it suffers from great challenge to design highly active Ru-based catalyst at low temperature. ZIF-8 derived ZnO@NC nanocomposite can firmly anchor Ru nanoparticles to create strong Ru-ZnO interfacial structure, as revealed by characterization techniques and DFT calculations. By optimizing Ru content and ZnO particle size, Ru/ZnO@NC achieved excellent reaction activity with a turnover frequency (TOF) of 6032 h(-1) at low temperature of 40 degrees C, which is never reported before. After etching the accessible ZnO, the TOF value was significantly declined to 125 h(-1) on Ru/ZnO@NC-HF owing to the lack of effective Ru-ZnO interface. DFT calculation results demonstrate that the Ru-ZnO interfacial structure can facilitate the activation of intermediate CH3CHOCH2CH2COOH* and remarkably decline the activation energy barrier of rate-determining step (CH3CHOCH2CH2COOH + H = HPA) from 1.28 eV to 0.82 eV, thus leading to excellent activity of LA hydrogenation at low temperature.