Sensing toxic gas molecules is crucial for environmental monitoring and human safety. In this spin-polarized DFT study, we introduce BCN nanocage, a hybrid analogue of C₂₀ nanocage, for sensing Cl2, COCl2, H2S, and NH3 gas molecules. BCN is functionalized with a series of metal adatoms (Li, Be, Al, Si, P, Sc, Ti, V, Mn, Fe, Ni, and Cu), chosen for their diverse electronic configurations and potential to interact strongly with the substrate. Among these, only the Li-, Al-, Sc-, Fe-, and Cu-decorated BCN complexes were found to be thermodynamically stable and energetically favourable. Sc exhibits the strongest binding with the nanocage, followed by Fe, Al, Li, and Cu, due to bond formation and significant charge transfer from adatoms to the nanocage. Among the studied candidates, BCNCu emerges as the most promising for Cl2 sensing under dry conditions, exhibiting an adsorption energy of 0.66 eV, a recovery time of 0.02s, and a -37.16% band gap variation. Compared with previously reported nanocage-based sensors, BCNCu demonstrates a balanced combination of suitable adsorption energy, rapid recovery time, and appreciable sensitivity, highlighting its potential for efficient Cl2 detection under dry conditions. However, its sensing performance is influenced by humidity, indicating that BCNCu operates more effectively under dry conditions than in humid atmospheres. AIMD simulations and vibrational spectra analysis confirm the thermal stability of the substrate at 400 K and its dynamical stability. This study advances the field by establishing BCNCu as a promising Cl2 sensor while highlighting its limitations in humid environments, offering valuable insights for experimental fabrication and real-world applications.

Metal-functionalized BCN nanocages for Cl2, COCl2, H2S, and NH3 detection: a DFT study on sensing efficiency, humidity effects, and thermal stability
    Abstract
    Highlights
    1 Introduction
    2 Computational details
    3 Results and discussion
        3.1 Adsorption of gas molecule
        3.2 Interaction analysis: RDG, NBO charge transfer and QTAIM analyses
        3.3 Vibrational spectra: dynamic stability
        3.4 AIMD: thermal stability
        3.5 Effects of humidity
        3.6 Comparison of sensing performance
    4 Conclusion
    References

• Unnati Jethawa(Department of Physics, The Institute of Science, Dr. Homi Bhabha State University, Mumbai 400032, India)
• Ajay Chaudhari(Department of Physics, The Institute of Science, Dr. Homi Bhabha State University, Mumbai 400032, India) Corresponding author