Sensing potential of C₆N₈ for ammonia (NH₃) and nitrogen triflouride (NF₃): A DFT study

The detection of toxic gases (NH₃ and NF₃) in regulating and monitoring air quality in the atmosphere has drawn a lot of attention. Herein, we explored a novel material (C₆N₈) for the detection of the important but toxic gases (NH₃ and NF₃). We investigated the interactions of the NH₃ and NF₃ with C₆N₈ through DFT at B3LYP, ωB97XD, and non-DFT M06-2X. Counterpoise interaction energy values (E_{int. cp.}) of NH₃@C₆N₈ and NF₃@C₆N₈ are -0.45 eV and -3.51 eV (for B3LYP), -0.42 eV and 2.11 eV (for ωB97XD) and -0.44 eV and -3.41eV (for M06-2X), respectively. Complexes having the most stable configurations were then subjected to further analyses including frontier molecular orbitals, H-L gap, and conductivity of complexes. An increase in the H-L gap in complexes (NH₃@C₆N₈ and NF₃@C₆N₈) is observed. The conductivity of NH₃@C₆N₈ and NF₃@C₆N₈ decreases as compared to C₆N₈. A considerable change in dipole moment was seen in C₆N₈ before and after complex formation. This is because of the shifting of charge between C₆N₈ and gases (NH₃ and NF₃). CHELPG and NBO charge analysis were used to evaluate the amount of charge transfer between C₆N₈ and gases. These analyses demonstrate that NH₃ and NF₃ withdraw electron density from C₆N₈. It was found that NH₃ tends to be physically adsorbed on C₆N₈ while NF₃ adsorbs chemically on C₆N₈. NCI and QTAIM analyses were performed to investigate the kind of interactions between the surface (C₆N₈) and gases (NH₃ and NF₃). Furthermore, the recovery time of NH₃@C₆N₈ and NF₃@C₆N₈ shows that C₆N₈ can be a better choice for sensing NH₃ and NF₃ gases.