Electron-rich Cuδ+-O-Con+ boosts active site reconfiguration to trigger multi-pathway C-O bond hydrogenolysis activation in lignin

The abundant bridging bonds and side chains in lignin make the selective cleavage of its C-O bonds a promising approach for achieving efficient conversion. Herein, Cu/CoOx-CeO 2 catalysts were prepared and the effects of their physical and chemical structures on C-O bond hydrogenolysis activity were investigated. The results indicated that incorporating an appropriate amount of CeO 2 as a support facilitated the doping of Co n+ cations into the CeO 2 lattice, enhancing oxygen vacancy concentration. Additionally, the Cu K-edge X-ray absorption near-edge structure (XANES) spectra revealed that Cu exists in a mixed valence state (Cu δ+ , 0 < δ < 2) within the catalyst. Reaction pathway regulation was achieved through strategic modulation of reaction conditions. When isopropanol was used as the solvent under a N 2 atmosphere, 2-phenoxy-1-phenylethanol (2-PPE-ol) was completely converted at 180 °C within 2 h, yielding ethylbenzene and cyclohexanol with 100 % selectivity. Conversely, when n -hexane was employed as the solvent, dehydrogenation of the C α -OH group generated hydrogen radicals, which promoted cleavage of the C β -O bond in the β-O-4 ketone intermediate, resulting in phenol and 1-phenylethanol with 100 % selectivity. Isotopic labeling and active hydrogen tracking experiments revealed that the active hydrogen in catalyst transfer hydrogenolysis (CTH) originated from the solvent, whereas self-hydrogen-transfer hydrogenolysis (SHTH) relied on hydrogen derived from the C α -OH group of 2-PPE-ol. This work provides valuable insights into the directional conversion of lignin into high-value chemicals and efficient energy utilization.