Synergy of Single Atoms and Lewis Acid Sites for Efficient and Selective Lignin Disassembly into Monolignol Derivatives.

Lignin is the most abundant aromatic polymer from the natural and renewable lignocellulosic biomass resource. Developing highly efficient catalysts for lignin depolymerization to produce valuable monophenols with high yield and selectivity remains a desirable but challenging target in this field. Here, we design a synergistic catalyst combining atomically dispersed Mo centers and Al Lewis acid sites on a MgO substrate (Mo1Al/MgO) for the depolymerization of Eucalyptus lignin via the β-aryl ether bond cleavage. A near-theoretical monophenol yield of 46% with an ultrahigh selectivity of 92% for coniferyl and sinapyl methyl ether, as well as good cycling durability, was achieved simultaneously by Mo1Al/MgO in an inert N2 atmosphere. First-principles calculations and control catalytic experiments confirmed the synergistic catalysis mechanism between Mo1-O5 single-atom centers and the neighboring Al Lewis acid sites with the participation of a methanol solvent. This study validates the feasibility of designing better-performing catalysts with synergistic multiactive sites for the efficient and selective disassembly of complex renewable biopolymers into highly value-added products with lower cost and greater security.