Excited State Absorption Upconversion Induced by Structural Defects for Photocatalysis with a Breakthrough Efficiency

Abstract The nitrogen‐deficient graphitic carbon nitride (g‐C 3 N 4 ) has been prepared, a new excited state absorption (ESA) up‐conversion mode is discovered, which is directly induced by structural defects, showing distinct chemical characteristics from those based on lanthanide ions and triplet states chromophores. The abundant N 2C vacancies in g‐C 3 N 4 nanosheets work as the crucial intermediate excitation states, which lead to g‐C 3 N 4 upconverted emitting at the wavelength of 436 nm excited by the light with the wavelength of 800 nm. This process is proven to proceed via a two‐photon involved ESA mode with a breakthrough quantum efficiency of 0.64 %. Further, we combine N 2C vacancies enriched g‐C 3 N 4 with In 2 S 3 and CdS, and successfully achieved an infrared light driven photocatalytic reactions. These findings offered a new family of up‐conversion materials; more semiconductors with various structural defects are potential complementary members.