Alkaline earth metal-regulated In-S heterojunctions enable selective photocatalytic C-C bond cleavage of lignin

Photocatalytic lignin depolymerization offers a promising strategy for producing value-added aromatic chemicals but remains limited by inefficient charge transfer and poor control over radical-mediated bond cleavage. Herein, alkaline-earth-metal regulated ZnIn 2 S 4 /MIn 2 S 4 (M = Ca, Mg, Ba) heterojunctions photocatalysts were rationally constructed to enable efficient and selective lignin depolymerization under near-UV irradiation. The optimized ZnIn 2 S 4 /MIn 2 S 4 (ZIS 7 /MIS 3 ) photocatalyst achieves nearly complete conversion of a lignin β -1 model compound with a benzoic acid yield of 119.4 mol%, and promotes selective C α -C β bond cleavage in organosolv lignin. Mechanistic investigations reveal that alkaline earth metal incorporation regulates interfacial electronic structure and establishes an internal electric field, enabling a charge transfer pathway with enhanced charge separation while preserving redox potentials. Control experiments confirm that the photocatalytic process proceeds via an interfacial charge-transfer-driven single-electron-transfer/proton-coupled electron transfer (SET-PCET) mechanism, promoting controlled generation of reactive oxygen species and selective radical-mediated bond cleavage. This work establishes alkaline-earth-metal-regulated heterojunctions as an effective strategy for modulating interfacial charge transfer and radical reactivity, providing new insights into the design of efficient photocatalysts for selective lignin valorization.