Yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres with tunable shell thickness and ultrahigh surface area for biomass-derived levulinic acid hydrogenation under mild conditions

Aiming to efficiently upgrade renewable biomass-derived levulinic acid (LA) into.-valerolactone (GVL), we have devised yolk-shell electron-rich Ru@hollow pyridinic-N-doped carbon nanospheres, featuring a tunable shell thickness (20 70 nm) and an ultrahigh surface area (4016 m(2) g(-1)). Experimental and theoretical investigations reveal that the strategic formation of the yolk-shell structure and appropriate thinning of the carbon shell facilitate the generation of electron-rich Ru-0 and a positive shift of the d-band center towards the Fermi level by increasing surface pyridinic-N species. These modifications suitably intensify Ru-0 -H interaction, promote reactant adsorption, stimulate electron transfer between active H and the C=O group of LA, and ultimately reduce apparent activation energy. Consequently, a high LA turnover frequency (18733.4 h(-1) at 30 degrees C) and GVL selectivity (99.9%), alongside excellent stability up to eight cycles, are achieved, markedly outperforming externally-supported analogues. These findings afford valuable insights into designing yolk-shell nanostructures for biomass upgrading through microenvironment engineering.