In-Depth Understanding of Highly Crystalline Carbon Nitride for Near-Infrared Photocatalysis: From n→π* Transition to Midgap State Engineering

Abstract

Graphitic carbon nitride (GCN) has been widely applied in the field of photocatalysis due to its excellent chemical stability, low toxicity, and environmental friendliness. However, its intrinsic bandgap of 2.7 eV limits the absorption edge to approximately 460 nm, thereby hindering the effective utilization of near-infrared (NIR) light and resulting in low solar energy conversion efficiency. This paper systematically reviews recent progress in the development of highly crystalline carbon nitride (HCCN) for NIR applications. Specifically, this review discusses the changing the structural symmetry to induce spatially forbidden n→π* electron transition, as well as the regulation of midgap states through multi-photon absorption mechanisms to broaden the spectral response range. Furthermore, the diverse applications of HCCN-based photocatalysts under NIR light are summarized. Finally, the current challenges and future perspectives of highly crystalline carbon nitride in the NIR region are highlighted.