Theoretical insights into sensing of hexavalent chromium on buckled and planar polymeric carbon nitride nanosheets of heptazine and triazine structures

The applicability of four surface models of graphitic carbon nitride (planar and corrugated nanosheets of triazine and heptazine structures) to detect hexavalent chromium from contaminated environments was investigated theoretically. The sensing was most favourable on hollow sites but with different coordination numbers and geometrical configurations. A substantial variation in the gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 2D material (e.g. from 4.12 to 0.36eV in the case of buckled heptazine structure) delineated the high capability of the sensor toward the detection of the chromium ion. Remarkable charge transfers (4.466-4.558 e) from the sensor to the analyte were evident from the topological analysis. Neglecting the surface corrugation could overestimate the adsorption energy while underestimating the HOMO-LUMO gap of both types of graphitic carbon nitride. The localised orbital locator (LOL) profiles revealed the ionic nature of the interactions.