Boosting Photocatalytic Overall Water Splitting Activity of Phosphorene Through Five-Coordinate Passivation Enabled by Carbene Addition.

Phosphorene is a promising two-dimensional semiconductor for solar-driven redox reactions, yet its practical deployment is severely restricted by rapid degradation under ambient conditions. Conventional covalent functionalization typically forms phosphorus-carbon single bonds (P─C), leaving phosphorus atoms in a four-coordinate environment and thus failing to fully quench the intrinsic reactivity associated with one residual unpaired electron. Here, we develop a selective strategy to achieve five-coordinate passivation of phosphorene by constructing phosphorus-carbon double bonds (P═C) through a one-step photochemical carbene addition reaction. Using a carbene precursor, adamantane groups are grafted onto phosphorene to afford a robust P═C-bonded architecture. Comprehensive spectroscopic analyses, together with density functional theory (DFT) calculations, validate the preferential formation of the P═C bonds. The resulting P═C-passivated phosphorene exhibits markedly improved ambient stability compared to the pristine and four-coordinate-passivated phosphorene. When utilized as a metal-free photocatalyst, the P═C-passivated phosphorene enables highly efficient overall water splitting without sacrificial agents under visible light, delivering record-high evolution of H