Elucidating the tandem synergistic roles of Cs-O dual sites confined in carbon nitride toward selective photoreduction H2O2 production coupled with xylose oxidation

The in-situ photocatalytic selective reduction of O2 to produce H2O2 is a promising green and sustainable production technique. However, it faces significant challenges due to the high reaction energy barrier of the H2O oxidation half-reaction, which inhibits the reaction and leads to undesirable oxidative by-products. In this study, we have the first time developed a O/Cs dual-functional carbon nitride material for the simultaneous photocatalytic reduction of O2 to synthesize H2O2 and the selective oxidation of xylose to produce xylonic acid. The CN-O/Cs material exhibits excellent photocatalytic activity for H2O2 production at 820.6 mu molh- 1 (41.03 mmolh1g- 1), while achieving a xylose oxidation rate of 359.5 mu molh- 1 to xylonic acid, surpassing most reported catalytic systems and enabling biomass upgrading. It is elucidated that the introduction of Cs atoms serves as new reduction active sites, significantly enhancing the adsorption of O2 with the transitioning Pauling type adsorption configuration. And the Cs atoms facilitate the deprotonation capability of H2O to form the crucial *OOH while lowering the reaction energy barrier. The presence of oxygen atoms plays a role in redistribution of electron density, and promotes the selective oxidation of the aldehyde group at the edge of xylose. The synergistic functionalities of Cs and O atoms enable the efficient utilization of electron-hole pairs for the simultaneous synthesis of H2O2 and xylonic acid. This study demonstrates that the rational design of multifunctional tandem sites materials at the atomic scale for the synergistic synthesis of H2O2 and selective oxidation of biomass holds promising prospects.