Distinct Pathways Determined by Photocatalytic C─H or O─H Bond Activation for Hydroxyl Compounds Conversion Paired With Hydrogen Production

Abstract

Selective control of C─H or O─H bond activation in photocatalytic conversion coupled with hydrogen production is a promising yet challenging goal. Here, an efficient photocatalytic system is reported that can produce high-valued tartaric acid or formaldehyde and simultaneous producing hydrogen. At optimized conditions, the directional conversion of glycolic acid into tartaric acid is achieved with a selectivity of 76.24%, and the selectivity of methanol oxidation into formaldehyde reaches 88.21%. A high hydrogen production rate of 21.43 mmol·g⁻¹·h⁻¹ is obtained using glycolic acid as substrate. Mechanism studies reveal that α-C─H bond is preferentially activated in glycolic acid adsorbed on the photocatalyst, while O─H bond is preferentially activated in methanol, forming carbon-centered radical (•CH(OH)COOH) or oxygen-centered radical (CH₃O•) for subsequent coupling or oxidation reactions. This work demonstrates the selective control of the photocatalytic conversion process of different hydroxyl compounds, providing a new perspective for achieving organic compounds selective activation coupled with hydrogen production.