Engineering atomic MnN4 sites in g-C3N4 for promoting the photocatalytic oxidation of glucose to glucaric acid

Photocatalysis has demonstrated great potential in the conversion of biomass, but the design of single-atom photocatalysts for the selective upgrading of glucose is rarely achieved. Here, we report a manganese doped g-C 3 N 4 (Mn SA -CN) single-atom photocatalyst by the impregnation-pyrolysis method, which achieves 34.6% glucaric acid (GAA) yield and 72.6% glucose conversion. Physicochemical characterizations indicate that the atomically dispersed Mn N 4 sites serve as the key catalytic centers, which not only optimize the electronic structure by narrowing the band gap, but also significantly promote the separation of photo-generated charge carriers. Additionally, the free radical scavenging experiments indicated that the hydroxyl radical is the main species for promoting the photocatalytic conversion of glucose. Furthermore, the GAA yield maintained over 33.0% after the catalyst was recycled five times. DFT calculation reveals that the Mn N 4 coordination structure increases the glucose adsorption and electron transfer, thereby reducing the overall reaction energy barrier and promoting the photocatalytic synthesis of GAA. This work offers fundamental insights at the atomic level for the rational design of single-atom photocatalysts toward sustainable biomass conversion.