Selective photocatalytic glucaric acid production from TEMPO-mediated glucose oxidation on alkalized carbon nitride

Biomass photorefining is a promising approach for sustainable clean energy and high-value chemical production. However, selectively converting glucose into glucaric acid, the most valuable derivative, still poses a significant challenge due to the difficulty in transforming the terminal hydroxyl group into a carboxy group. Here, we demonstrate that highly selective glucose photorefining into glucaric acid can be achieved by synergistically coupling alkalizing modification of polymeric carbon nitride (CN) with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) mediation, which promotes the oxidation of the primary alcohol group attached to the C6 site of gluconic acid. Density functional theory (DFT) calculations affirm the enhanced performance of modified CN in glucaric acid production. When medicated with TEMPO, the optimized photocatalysis achieves ∼ 100 % glucose conversion and > 30 % glucaric acid yield, setting a record for photocatalytic glucaric acid production. This work showcases the significance of combining photocatalyst modification and redox mediation for inspiring high-efficiency photocatalysis systems for biomass photorefining.