Divalent Fe Atom Coordination in Two-Dimensional Microporous Graphitic Carbon Nitride

Graphitic carbon nitride (g-C₃N₄) is a rising two-dimensional material possessing intrinsic semiconducting property with unique geometric configuration featuring superimposed heterocyclic sp² carbon and nitrogen network, nonplanar layer chain structure, and alternating buckling. The inherent porous structure of heptazine-based g-C₃N₄ features electron-rich sp² nitrogen, which can be exploited as a stable transition metal coordination site. Multiple metal-functionalized g-C₃N₄ systems have been reported for versatile applications, but local coordination as well as its electronic structure variation upon incoming metal species is not well understood. Here we present detailed bond coordination of divalent iron (Fe²⁺) through micropore sites of graphitic carbon nitride and provide both experimental and computational evidence supporting the aforementioned proposition. In addition, the utilization of electronic structure variation is demonstrated through comparative photocatalytic activities of pristine and Fe-g-C₃N₄.