Solar-Driven Photocatalytic Reforming of Lignocellulose into H2 and Value-Added Biochemicals

Lignocellulose is the most abundant form of biomass on earth, and its efficient valorization for H-2 generation and value-added biochemical production provides a promising strategy to alleviate the currently faced energy shortages. However, the requirements of toxic organic solvents, unsatisfactory conversion, and poor selectivity of biochemicals make the effective biomass photorefinery challenging. Herein, we report the efficient lignocellulose photoreforming including cellulose, hemicellulose, and lignin, using polymeric carbon nitride photocatalyst that was prepared via the pyrolysis of a preorganized supramolecular assembly between cyanuric acid, melamine, and Pt-(NH2-bpy)(2). The optimized catalyst exhibits a superior H-2 evolution rate of 3.39 mmol g(-1) h(-1) from the aqueous glucose solution under irradiation of a 427 nm LED light source, which is more than nine times higher than that of the pristine carbon nitride. Furthermore, 100% conversion of glucose and 86% selectivity toward lactic acid are achieved with the system. Density functional theory calculations verify that the introduction of Pt significantly lowers the activation energy barrier for water reduction into hydrogen and facilitates the selective cleavage of the C-C bond of fructose generated by glucose isomerization, which is weakened by electron density shift to the adjacent bond, the essential step to promote lactic acid production. This work presents an effective and promising strategy to couple the H-2 generation and value-added biochemical production through biomass photorefinery.

Automated summary

Lignocellulose is the most abundant form of biomass on earth, and efficient valorization for H-2 generation and value-added biochemical production provides a promising strategy. Photoreforming of lignocellulose using a polymeric carbon nitride photocatalyst is reported, achieving high H-2 evolution rate and selectivity towards lactic acid production.