N-S vacancy sites on heteroatomic doping metal-free carbo-catalyst for efficient biomass hydrodeoxygenation

The development of excellent performance catalysts for the hydrodeoxygenation of renewable biomass into value-added chemicals is essential but remains extremely challenging. Herein, a series of novel metal-free carbo-catalyst catalysts through one-step-pyrolysis strategy were fabricated for the hydrodeoxygenation (HDO) of lignin-derived vanillin (VAN) to produce 2-methoxy-4-methylphenol (MMP). It has been demonstrated that 81.32 % VAN conversion could be acquired with a high selectivity of 77.30 % of MMP under the condition of 240 °C, 1 MPa H 2 and 4 h with the assistance of the optimized NSCC-800-7 catalyst. After characterization of the catalyst and density functional theory (DFT) calculations, the outstanding catalytic activity is attributed to the synergistic effect between nitrogen and sulfur dopants, which effectively regulates the number of active sites. N-S vacancy (NSVs) in the N-doped carbon catalysts is found to play an active site for the VAN HDO reaction, which is greatly beneficial to activating hydrogen molecules. Meanwhile, sulfur doping can promote the formation of defect sites and high specific surface area, while enabling to stabilization of NSVs. Additionally, isopropanol was both the reaction medium and the secondary hydrogen donor, which contributed to reducing the external hydrogen supplication. This finding can open broad opportunities for the rational design of novel metal-free catalysts for challenging chemical reactions.