Theoretical Study of SO₂ Selective Detection from the Cr-Modified B₁₂N₁₂

Sulfur dioxide is a toxic gas with serious environmental and health implications, making the development of selective and efficient sensors an urgent need. In this work, we investigate, using density functional theory (DFT)/B3LYP-D3/6-31G-(d,p) calculations, the potential of B₁₂N₁₂ nanocages functionalized with Cr in different configurations (doped, decorated, and encapsulated) for application in SO₂ chemical sensing. The results show that the encapsulated configuration (Cr@B₁₂N₁₂) exhibits the best combination of properties, including high electronic sensitivity (ΔE _gap = 79.3%), moderate adsorption energy (E _ads = -0.96 eV), and an appropriate recovery time (τ = 167 s), key parameters for reusable sensors under atmospheric conditions. In addition, the system demonstrates high selectivity toward interfering gases such as CO, CO₂, COCl₂, CH₄, H₂S, N₂, and H₂O, corroborated by molecular dynamics simulations. The data analysis suggests that Cr functionalization represents a promising strategy for SO₂ sensor design, although the system's performance remains dependent on the adsorption energy range and the experimental feasibility of metal encapsulation.