First-principles investigation of the selective adsorption mechanisms of NO ₂ , NH ₃ and CO on C ₂₁ Cu

To address the problem of hazardous gas pollution caused by industrial emissions, the exploration and development of highly selective gas-sensing and adsorption materials are of great importance. In this work, a novel Cu-doped carbon-based material (C21Cu) was constructed and systematically investigated using first-principles calculations based on density functional theory (DFT). The adsorption processes of three typical hazardous gases, NO2, NH3 and CO, on C21Cu were studied in detail, with particular emphasis on adsorption configurations, adsorption energies and electronic structure variations. The results indicate that the C21Cu structure is thermodynamically stable, and its adsorption strength follows the order NO2 > NH3 > CO. Among them, NO2 exhibits the most negative adsorption energy and the shortest adsorption distance, corresponding to strong chemisorption, while NH3 and CO show weaker interactions. Electronic structure analysis reveals that the strong adsorption of NO2 originates from significant orbital hybridization and pronounced charge transfer between NO2 and the Cu active site, leading to a sharp reduction in the band gap and a highly sensitive electronic response. In contrast, the interactions of NH3 and CO are progressively weaker. Overall, C21Cu shows excellent selectivity and high sensitivity toward NO2, demonstrating its strong potential as an NO2 gas-sensing material.