Recent Advances in Photocatalytic Conversion of Lignocellulosic Biomass: Routes, Limitations, and Outlook

Lignocellulosic biomass (LCB) is an abundant resource for recovering fuels and value-added products. Despite extensive investigations and research, the complete unlocking of LCB potency has yet to be accomplished. The photocatalytic conversion of LCB, which utilizes renewable solar light under mild conditions, has been recognized as the hottest current research topic receiving attention for sustainable development. Numerous technical challenges have been identified for effective practical implementations. In brief, photocatalytic conversion oxidizes Cβ─O/Cα─Cβ linkages in LCB to recover fuels and biochemicals. From a chemical viewpoint, optimizing the exclusive interaction of oxidizing radical groups and radical intermediates through suitable regulation of their type and recovery is crucial for selectively generating desirable products. This review provides recent insights into the mechanistic pathways of the selective conversion of LCB via reactive oxygen species (ROS) behavior optimization and system design. In addition, this review highlights the up-to-date achievements in the photocatalysis of LCB and its components as well as the selective oxidation of the prominent linkages of lignin, native biomass valorization, cellulose, hemicellulose, and its derivatives. Further, upgrading of bioplatforms and electricity generation via LCB photocatalysis is discussed in detail as a novel approach. The prospects and opportunities of using LCB photocatalysis to improve the viability of photocatalytic conversion of LCB are also discussed.