Selective Hydrodeoxygenation\nof Lignin via Aryl Ether\nC–O Bond Cleavage: Cs-Mediated Cu Surface Engineering

Lignin is a pivotal building block of lignocellulose\nbiomass and\nthe most abundant aromatic polymer in nature. Selective hydrodeoxygenation\n(HDO) via the target cleavage of aryl ether C–O bonds is of\ngreat importance for lignin biorefinery. However, preserving aromaticity\nduring HDO for efficient production of arenes remains a challenge.\nHerein, the low electronegativity of Cs was utilized to customize\nthe chemical environment and geometric construction of highly dispersed\nCu sites on mesoporous SiO<sub>2</sub> nanospheres. The electron density\naround Cu sites evidently increased while the coordination environment\nof Cu was precisely tailored. The hydrogenation and deoxygenation\nactivities were effectively balanced. Owing to the synergy between\nelectron-rich Cu<sup>δ−</sup> sites and the Cs center,\nthe saturated hydrogenation of aromatic rings was efficiently inhibited,\nand preferential selectivity toward aryl ether C–O bond cleavage\nwas obtained. The selectivity of arenes from anisole reached 83% on\n2Cs/Cu@NS-SiO<sub>2</sub>, while the intrinsic production activity\nof arenes based on active Cu sites significantly increased to 0.34\nmmol·m<sub>Cu</sub><sup>–2</sup>·h<sup>–1</sup>, more than doubled that of Cu@NS-SiO<sub>2</sub> without Cs modification.\nBesides, a remarkable arene selectivity of 76.3% was achieved among\nthe depolymerized monomers from the HDO of organic solvent-extracted\nlignin. This study offers a promising approach for valorizing lignin\ninto high-value arenes.