Catechol Quinone as an Electron-Shuttling Spot Conjugated to Graphitic Carbon Nitride for Enhancing Photocatalytic Reduction

Carbon nitride (CN) has emerged as a promising photocatalyst, recognized for its visible-light sensitivity, high conduction band-edge position, tunable electronic configuration, and environmental friendliness. Despite these attributes, the practical application of CN is hindered by challenges such as inefficient charge carrier separation, a narrow light absorption range, and inherent n-type characteristics due to nonstoichiometry. Here, we introduce a new postsynthetic functionalization strategy that modifies CN with catechol quinone (CQ) to substantially improve its photocatalytic performance through light-induced electron polarization and extended light absorption. The key mechanism involves promoted spatial charge separation at the CN–CQ interface, leveraging the light-triggered oscillation of CQ between its electron donor and acceptor states, corroborated by density functional theory calculations. Moreover, CN–CQ conjugation broadens the photoactive range of CN across the full spectrum of visible light due to lower-energy electronic excitations arising from the midgap states introduced by CQ. Under sunlight illumination, the CN–CQ conjugation increased the photocatalytic activities of CN 2-fold for photochemical gold ion reduction and hydrogen evolution. Our findings suggest that postsynthetic functionalization with a redox-active moiety is a promising strategy for enhancing the photocatalytic activity of CN.