Boron-doped C6N8 monolayer as a promising nanosensor for ultrafast and selective detection of HF and NO: DFT and...

The adsorption and sensing behavior of pristine and boron-doped C₆N₈ monolayers (BC₆N₇) toward CO, HF, and NO were systematically investigated using DFT, TD-DFT, NBO, NCI, and QTAIM analyses. The pristine C₆N₈ displayed a cohesive energy of -142.7 kcal mol^-1 with a HOMO-LUMO gap of 2.94 eV, whereas boron doping reduced the gap to 1.55 eV and enhanced charge-transfer ability (ΔNmax = 5.09). Adsorption energies revealed strong binding for BC6N7@HF (-3.53 eV) and BC6N7@NO (-2.95 eV), both with fast recovery times. Electrical conductivity increased up to 2.47 × 10⁹ A.m^-2 upon NO adsorption. Dipole moment and polarizability reached maxima of 9.99 D and 149.97 a.u., respectively. Optical analyses showed notable redshifts, particularly C₆N₈@NO (λ_max = 434 nm) and BC₆N₇@NO (442 nm). NBO analysis confirmed strong π→π∗ and n→π∗ interactions with stabilization energies up to 29.09 kcal mol^-1, while QTAIM revealed the highest bond critical point density (ρ(r) = 0.271 a.u.) for C6N8@CO. These results highlight BC₆N₇, especially in HF and NO adsorption, as a promising candidate for fast, selective, and reusable toxic gas sensors.