Polyoxometalates-modified and facets-engineered TiO2 nanocomposites for selective photocatalytic cleavage of C–C bond of lignin models

Selective cleavage of C-C bond of lignin derivatives and models via oxidation is vital to realize value-added utilization of lignocellulosic biomass. Herein, based on the strategy of facet engineering and pseudo-heterojunction construction, a series of P2W17V/{001}-TiO2 heterogenous photocatalysts were constructed by loading monovanadium-substituted Dawson-type polyoxometalates P2W17V onto TiO2 with exposed {001} facets. The morphologies, structures, photoelectrical properties, and photocatalytic performances of the nanocomposites were researched. P2W17V/{001}-TiO2 could effectively photocatalyze the transformation of 2-phenoxy-1-phenylethanol, the lignin model compound with characteristic β-O-4 structure, to benzaldehyde and phenol. Photogenerated electrons and O2•- were disclosed critical to lignin model conversion that could induce C-C bond cleavage, with a selectivity above 85%, through a Cβ-centered radical. Neither pure O2 nor precious metal was required in the photocatalysis. P2W17V acted as electron pools. The engineered facets of TiO2 and the pseudo-heterojunction between P2W17V and TiO2 suppressed electron-hole recombination, facilitated charge transfer, and promoted photocatalytic performance. This work paved a new avenue to convert lignin and lignin derivatives to high-value chemicals by selectively breaking C-C bond under mild conditions.