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

The nitrogen-deficient graphitic carbon nitride (g-C₃ N₄ ) 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-C₃ N₄ nanosheets work as the crucial intermediate excitation states, which lead to g-C₃ N₄ 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-C₃ N₄ with In₂ S₃ 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.