Dipole induction by structural engineering of supports for Fe single-atom photocatalysts toward excellent photocatalytic ozonation

Efforts in designing efficient polymer-based single atom photocatalysts (SAPs) have primarily focused on selecting specific metal atoms with tailored geometries and properties to control functionality. However, the impact of the light-harvesting units that bridge these single metal atoms, crucial for light absorption and energy transfer, has been largely overlooked. In this work, two carbon nitride (CN)-based iron SAPs with a similar FeN₄ coordination environment are synthesized: triazine-based CN (C₃N₄) and nitrogen-rich triazole-based CN (C₃N₅), differing in the unit cell structure. C₃N₅ exhibits better photocatalytic ozonation performance than C₃N₄ due to its unit cell asymmetry, which induces a dipole field that facilitates charge transfer. The addition of iron single atoms breaks the symmetry of C₃N₄ to enhance the dipole moment, while they weaken the separation and migration of bulk charge carriers in the Fe-C₃N₅ SAP. The iron atoms act as active sites in both Fe-C₃N₄ and Fe-C₃N₅ SAPs, accelerating interfacial reaction kinetics. These findings demonstrate the importance of the light-harvesting unit structures of CN-based SAPs in regulating photogenerated charge kinetics and offering valuable insights for the rational design of effective photocatalysts.