Z-scheme HPMoVO/g-CN heterojunction with strong photooxidative capacity for promoting efficient cleavage of C-C bond in lignin models and lignin.

The efficient photocatalytic breakage of C-C bonds has great significance for the valorization of lignin into value-added aromatic chemicals, but remains challenging owing to their demanding depolymerization conditions and high bond dissociation energies. In this study, the Z-scheme heterojunction HPMoVO/g-CN (HPA/CN) photocatalyst was elaborately developed for the selective and efficient cleaving of C-C bonds in real lignin and its β-O-4 models under mild conditions. The construction of Z-scheme heterojunction with irregular sheet micromorphology not only enhanced the charge separation and redox abilities, but also broadened the light absorption range and promoted charge-to-surface transfer in two redox components. Notably, 35 % HPA/CN could completely convert the 2-phenoxy-1-phenylethanol with C-C bond cleavage selectivity of 97.4 %, achieving approximately 50.0- and 2.2-times higher conversion rates compared to HPA and CN, respectively. Meanwhile, this strategy also offered a wide substrate scope containing various β-O-4 model compounds and native lignin, leading to the generation of corresponding aromatics. The mechanism experiments revealed that photoinduced holes and superoxide radicals synergistically triggered the oxidative cleavage of C-C bond. This study could provide a reference for photocatalytic production of value-added aromatic monomers by exploiting both renewable feedstocks and solar energy.