Tuned Oxidation Potential of Continuous Defective Photocatalyst for Selective Biomass Conversion

Photocatalytic biomass conversion offers an energy-efficient, low-carbon route for the sustainable production of fine chemicals. However, selectivity control of biomass valorization is challenging due to the presence of multiple functional groups and competing reaction pathways. Herein, we report a wavelength-controlled photocatalytic strategy with adaptive oxidative capability for regulating biomass conversion selectivity. Using black TiO₂ with continuous defect energy levels as a model photocatalyst, the wavelength-dependent excitation of defect states confers adaptive oxidative behavior, enabling selective conversion of xylose into high-value xylonic acid under visible light, avoiding over-oxidation into low-value C1 products under UV irradiation. The high selectivity is attributed to the tunable photooxidation capability of defect states, where the oxidation potential of defect states excited by visible light is appropriate to suppress the production of non-selective highly oxidative hydroxyl radicals. This work reveals the correlation between the defect energy-level distribution and the selective biomass oxidation behavior, offering a self-tuning approach for directional biomass conversion through catalyst design. The strategy is further validated across a range of biomass-derived substrates, highlighting its broad applicability in selective chemical synthesis using adaptive photocatalysis.