Advances in Photocatalytic Biomass Valorization to Organic Acids Coupled with Reduction Reactions

The photocatalytic conversion of biomass derivatives into high-value organic acids and fuels represents a sustainable green synthetic strategy, playing a pivotal role in achieving carbon neutrality objectives. This review examines recent advances in the photocatalytic oxidation of biomass-derived platform molecules (such as sugars and alcohols) to produce high-value organic acids (including monobasic acid and polybasic acid). It further explores coupled pathways integrating with reduction reactions (such as H₂, CO, and H₂O₂ production) to enhance charge carrier utilization efficiency and overall redox reaction synergy. Secondly, an in-depth analysis was conducted on the fundamental photocatalysis reaction mechanisms, including the direct oxidation of oxygen-containing functional groups in biomass-derived substrates, radical-mediated selective cleavage of C-C/C-H/C-O bonds, proton-coupled electron transfer, and electron-mediated reduction pathways. This elucidates processes including light absorption, charge carrier migration, substrate adsorption-activation, and surface dynamic evolution. Furthermore, this review highlights the optimization of catalyst design strategies, such as crystal plane defects, heterostructure construction, co-catalyst loading, and organic framework assembly, to enhance interfacial charge transfer kinetics and reaction dynamics. Finally, the challenges and opportunities in photocatalytic biomass upgrading were discussed, including the development of multifunctional photocatalysts, enhancing the coupling efficiency of redox reactions, and improving substrate specificity and product selectivity. The summary of innovative researches will further advance the application of photocatalytic technology in sustainable biofuels and green chemistry, providing crucial support for achieving efficient biomass valorization and environmental protection objectives.