Computational Study of Pristine, Al- and P-Doped B12N12 Nanocages for BrCN Adsorption and Detection under Electrostatic Fields Using Density Functional Theory, Time-Dependent-Density Functional Theory, and Reduced Density Gradient.

This study presents a comprehensive computational investigation of the adsorption and sensing potential of pristine and doped B12N12 nanocages B12N12, AlB11N12, and B12N11P toward cyanogen bromide (BrCN), a highly toxic gas. Equilibrium structures of the BrCN complexes are optimized at the ωB97XD/6-31 G (d, p) level, and adsorption energies, thermodynamic parameters (ΔH, ΔG), and electronic descriptors are calculated. Interaction analyses are performed using atoms in molecules, reduced density gradient, molecular electrostatic potential, and electron localization function approaches. The effects of solvents, nonlinear optical properties, and UV-visible spectra are examined under neutral conditions and external static electric fields (SEF, z + 0.01 to z + 0.04 au). Results reveal that BrCN adsorption is strongest on AlB11N12, exhibiting favorable thermodynamics in both gas and aqueous phases, highlighting its potential for realistic sensing applications. While increasing SEF generally reduces adsorption energies, the pristine B12N12 complex shows an exception. Reactivity and conductivity analyses indicate a superior electronic response for AlB11N12, with noncovalent interactions, primarily van der Waals forces, governing the binding. Overall, AlB11N12 is identified as a promising candidate for the design of selective and sensitive BrCN gas sensors.