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

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.