Study of cyano and hydroxyl groups modification on the properties of porous carbon nitride synthesized by using a salt assistant method

Porous carbon nitride integrated with the cyano and hydroxyl functional groups are obtained through simple KCl assisted thermal treatment of urea. The existence of cyano and hydroxyl groups were confirmed through FTIR, NMR, and XPS characterizations. Easily removed KCl powders play a key role to produce a porous carbon nitride with cyano and hydroxyl groups. The DFT calculation was employed to estimate the band gap structure of the modified carbon nitride. It is shown that the cyano and hydroxyl groups take an important role to narrow the bandgap, positively shift band energy and enhance the spatial separation of the HOMO and LUMO states, which well explains the much improved optical and electrochemical properties and the photocatalytic performance in degradation of Methyl Orange and NO. This work provides important insights in designing highly efficient carbon nitride based visible light photocatalysts.