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.

Automated summary

This study demonstrates the high activity and selectivity of novel urchin-like Nb2O5 hollow microspheres for cleaving C-α-C-β bonds of lignin model compounds to produce aromatic oxygenates. The superior performance of the material is attributed to the presence of more exposed active sites, efficient charge separation, and active crystal facets.