Innovative lignin photocatalyst system motivated by intramolecular charge dynamics for H2O2 production

Lignin is the most abundant renewable resource with aromatic ring structures on earth, however, its intrinsic redox functional region for H2O2 production has not been fully identified due to the source diversity and structure complexity. Herein, the charge dynamics between the HOMO level with electron-donating capability and the LOMO level with electron-accepting capability are comprehensively clarified by using 14 types of customized lignin models as photocatalytic systems. The electron-transport patterns are modulated by the structure–activity relationship of effective oxygen-containing functional groups, including conjugation effects of methoxy groups, induced effects of hydroxyl or carbonyl groups, and ether bonds determining the overlap ratio of energy levels. A comprehensive evaluation and screening system is established to identify efficient lignin photocatalysts extracted from various sources and processes that are suitable for specific application scenarios, combined with theoretical calculations and molecular dynamics simulations. The fledgling H2O2 production efficiency is expected to be further improved through constructive guidance on interfering factors. The report on direct H2O2 production by O2 reduction and the action mechanism of the novel lignin photocatalyst will draw a new blueprint for the breakthrough of bio-photocatalytic functionalization.