Urchin-like Nb2O5 hollow microspheres enabling efficient and selective photocatalytic C-C bond cleavage in lignin models under ambient conditions

Selective cleavage of robust C-C bonds to harvest value-added aromatic oxygenates is an intriguing but challenging task in lignin depolymerization. Photocatalysis is a promising technology with the advan- tages of mild reaction conditions and strong sustainability. Herein, we show a novel urchin-like Nb2O5 hollow microsphere (U-Nb2O5 HM), prepared by one-pot hydrothermal method, are highly active and selective for C-alpha-C-beta bond cleavage of lignin beta-O-4 model compounds under mild conditions, achieving 94% substrate conversion and 96% C-C bond cleavage selectivity. Systematic experimental studies and den- sity functional theory (DFT) calculations revealed that the superior performance of U-Nb2O5 HMs arises from more exposed active sites, more efficient free charge separation and the active (001) facet, which facilitates the activation of C-beta-H bond of lignin models and generate key C-beta radical intermediates by photogenerated holes, further inducing the C-alpha-C-beta bond cleavage to produce aromatic oxygenates. This work could provide some suggestions for the fabrication of hierarchical photocatalysts in the lignin de- polymerization system. (C) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.