Band-structure and morphology regulation in CdZnS photocatalysts for efficient visible-light-driven cleavage of lignin model compounds

The selective cleavage of β-O-4 linkages in lignin under mild conditions remains a major challenge for the sustainable production of aromatic chemicals. In this work, CdZnS photocatalysts were synthesized via co-precipitation (CP), hydrothermal (HT), and template-assisted solvothermal ion-exchange (TP) methods and applied to the photocatalytic cleavage of the β-O-4 linkage in 2-phenoxy-1-phenylethanol (PP-ol). Cd 0.5 Zn 0.5 S-CP exhibited outstanding photocatalytic performance under visible-light irradiation, achieving complete conversion of PP-ol with high molar yields of phenol and acetophenone reaching 92.2% and 86.6%, respectively. Comprehensive characterizations revealed that the superior activity of Cd 0.5 Zn 0.5 S-CP originates from the synergistic interplay between its suitably negative conduction band potential (−1.26 eV) and a mesoporous structure with a large accessible surface area. In contrast, Cd 0.5 Zn 0.5 S-HT showed lower activity mainly because of its limited accessible surface area. Cd 0.5 Zn 0.5 S-TP also exhibited inferior performance, which was mainly attributed to its overly positive conduction band potential (−0.60 eV) and insufficient reductive driving force for C–O bond cleavage. Mechanistic investigations demonstrate that the reaction proceeds via a self-hydrogen transfer pathway, with photogenerated electrons playing a dominant role in driving C β –O bond cleavage. This study provides fundamental insights into the rational design of efficient photocatalysts for lignin valorization under mild conditions.