Synergistic effect of cyano defects and CaCO in graphitic carbon nitride nanosheets for efficient visible-light-driven photocatalytic NO removal.

Photo-oxidation with semiconductor photocatalysts provides a sustainable and green solution for NO elimination. Nevertheless, the utilization of traditional photocatalysts in efficient and safe photocatalytic NO removal is still a challenge due to the slow charge kinetic process and insufficient optical absorption. In this paper, we report a novel porous g-CN nanosheet photocatalyst modified with cyano defects and CaCO (xCa-CN). The best performing sample (0.5Ca-CN) exhibits an enhanced photo-oxidation NO removal rate (51.18 %) under visible light irradiation, largely surpassing the value of pristine g-CN nanosheets (34.05 %). Such an enhancement is mainly derived from an extended visible-light response, improved electron excitation and transfer, which are associated with the synergy of cyano defects and CaCO, as evidenced by a series of spectroscopic analyses. More importantly, in-situ DRIFTS and density functional theory (DFT) results suggest that the introduction of cyano defects and CaCO enables control over NO adsorption and activation processes, making it possible to implement a preference pathway (NO → NO → NO¯) and reduce the emission of toxic intermediate NO. This work demonstrates the potential of integrating defect engineering and insulator modification to design highly efficient g-CN-based photocatalysts for air purification.