Oxygen-Activated Boron Nitride for Selective Photocatalytic Coupling of Methanol to Ethylene Glycol.

The controllable photocatalytic C-C coupling of methanol to produce ethylene glycol (EG) is a highly desirable but challenging objective for replacing the current energy-intensive thermocatalytic process. Here, we develop a metal-free porous boron nitride catalyst that demonstrates exceptional selectivity in the photocatalytic production of EG from methanol under mild conditions. Comprehensive experiments and calculations are conducted to thoroughly investigate the reaction mechanism, revealing that the OB unit in the porous BN plays a critical role in the preferential activation of C-H bond in methanol to form ⋅CHOH via a concerted proton-electron transfer mechanism. More prominent energy barriers are observed for the further dehydrogenation of the ⋅CHOH intermediate on the OB unit, inhibiting the formation of some other by-products during the catalytic process. Additionally, a small downhill energy barrier for the coupling of ⋅CHOH in the OB unit promotes the selective generation of EG. This study provides valuable insights into the underlying mechanisms and can serve as a guide for the design and optimization of photocatalysts for efficient and selective EG production under mild conditions.