Solar-Light-Driven Lignin Conversion via Depolymerization and Dimerization Domino Reactions for Concurrent Production of Phenolics and Biodiesel Components

Photocatalytic valorization of lignin, featuring the selective cleavage of lignin linkages and subsequent upgrading of resulting monomers, is an emerging and promising approach for utilizing this natural renewable aromatic polymer. However, existing photocatalytic conversion strategies typically perform singular functions (either depolymerization or monomer upgrading) and face pronounced separation challenges since phenolic and acetophenone intermediates derived from lignin monomers often exhibit similar physical properties. This work introduces a domino conversion strategy combining lignin β–O–4 dimer cleavage and acetophenone dimerization using a ZnS/Zn2In2S4 composite photocatalyst constructed via a light-induced phase segregation method. The ZnS/Zn2In2S4 composite exhibits synergistically enhanced redox capability and charge separation, enabling hole-driven Cβ–O scission and electron-mediated pinacol coupling of acetophenone under mild conditions. This approach achieves near-quantitative conversion of acetophenone to C16+ vicinal diols (biodiesel precursors) along with phenolic monomers. Scalable reactions demonstrate 91% phenolic and 90% C16+ yields after hydro-deoxygenation, circumventing distillation-based separation. The integrated strategy presents an efficient, step-economical route for coproducing value-added aromatics and biofuels, advancing photocatalytic lignin valorization.