First‐Principles Insights Into the CO Adsorption Mechanism on Cu‐Doped C ₂₁

Density functional theory (DFT) calculations were employed to investigate the CO adsorption mechanism on Cu‐doped C ₂₁ (C ₂₁ Cu). The adsorption configurations, adsorption energies, adsorption heights, electronic structures, and charge transfer characteristics were systematically analyzed to reveal the interaction between CO molecules and the C ₂₁ Cu substrate. The results show that C ₂₁ Cu exhibits strong adsorption toward CO molecules. Among the investigated configurations, C‐end adsorption is more favorable than O‐end adsorption, with adsorption energies of −3.36 and −1.62 eV, respectively. The corresponding adsorption heights are 0.73 and 3.36 Å, and the most stable adsorption sites are identified as H2 and T sites. The stronger interaction and shorter adsorption distance of the C‐end configuration indicate enhanced adsorption activity. Although the O‐end configuration exhibits relatively weaker adsorption, it still belongs to the chemisorption regime. This study provides theoretical insights into the CO adsorption mechanism on Cu‐doped C ₂₁ and suggests its potential application as a CO gas adsorption and sensing material.