Boosting exciton dissociation in anion and cation co-doped polymeric semiconductor for selective oxidation reaction.

The inherently low dielectric properties and weak shielding effect of polymeric semiconductors cause excitons to dominate their photoexcitation process, which greatly restricts the photocatalytic performances mediated by charge carriers. Here, an anion and cation co-doping strategy was proposed to weaken the binding energy of excitons by forming distinct positive and negative charge regions, where the charge asymmetry produced an external potential to drive exciton dissociation. Using polymeric carbon nitride as a typical model framework, we show that the incorporation of anions (Cl, Br, I) and cations (Na, K) could create a significant spatial separation of electrons and holes, thereby promoting exciton dissociation. Specifically, K and Cl co-doped polymeric carbon nitride could effectively promote the dissociation of excitons into hot carriers, contributing to the outstanding efficiency in hot-electron-involved photocatalytic processes, such as the generation of superoxide radicals (O˙) and the oxidation of phenylboric acid under visible light. This work presents a practical approach for promoting excitons dissociation through the introduction of charge asymmetry.