Selective hydrogenolysis of lignin over hierarchical CoNC catalysts for the sustainable production of 4-propylsyringol†

Production of chemicals through the conversion of lignin can not only improve the utilization of renewable biomass resources but also reduce the dependence on traditional fossil resources. In this work, 4-propylsyringol (), a high value-added chemical for medicine and materials, was obtained via selective hydrogenolysis of lignin in the presence of a novel hierarchical Co, N co-doped carbon (CoNC) catalyst. When organosolv bagasse lignin was depolymerized at 230 °C for 4 h, the yield of monophenols reached 28.8 wt%, and 34.3% of the products were (yield of 9.9 wt%). Extensive characterizations demonstrated that the high ratio of mesopores (92.9%) and the suitable pore-size (>1.9 nm) distribution of CoNC promoted the adsorption and mass transfer of lignin on the catalyst, while the synergistic catalytic effect between the Co single atom and acid site (pyrrolic–N) played a key role in the superior catalytic activity of CoNC. The structural evolution of lignin, control experiments with lignin models, and DFT calculations showed that the β-O-4 bond in the S unit of lignin was the most reactive amongst the lignin fragments, and it was responsible for the excellent selectivity of . In addition, a plausible reaction mechanism was proposed, where the β-O-4 bond cleaved according to a carbon center radical pathway, as revealed by electron paramagnetic resonance (EPR) spectroscopy results. Therefore, this work provides a sustainable alternative strategy to petroleum routes for producing typical value-added fine chemicals.