Two‐photon Absorption in a Defect‐engineered Carbon Nitride Polymer Drives Red‐light Photocatalysis

Abstract Exploiting photocatalysts that harvest the solar spectrum as broadly as possible remains a high‐priority target, but is a grand challenge. Herein, for the first time, we found that bulky polymer carbon nitride (denoted as PCN) possessed excellent two‐photon absorption behavior and confirmed that the bulky PCN can efficiently drive red‐light photocatalysis by two‐photon absorption processes. Long‐wavelength‐excited fluorescence measurements and confocal laser scanning microscopy clearly revealed the existence of two‐photon absorption in PCN. Moreover, we created nitrogen vacancies on the PCN surface by increasing the polymerization temperature and confirmed the nitrogen vacancies can efficiency accelerate charge separation. As a result, bulky PCN with nitrogen vacancies showed unexpected pollutant degradation and water splitting activity under 660 nm. Additionally, PCN obtained from other precursors also exhibited competent red‐light photocatalytic performance. This work represents an important step toward developing two‐photon‐absorption PCN photocatalysts for wide solar‐spectrum utilization.