Investigation of the binding affinity gases on porous adsorbents are important for establishing understanding of effective carbon dioxide adsorption and design target specific sorbents for capturing hazardous gases for environmental protection and fuel upgrading. A density functional theory (DFT) study that highlights the impact of benzimidazole‐linked polymer structure design has been conducted to explain the molecular and electronic structure, investigate the interaction sites and elucidate the experimental results on carbon dioxide and nitrogen sorption on these porous structures. DFT calculations were used to infer the strength of the polymer – gas interaction modes as well as to quantify short‐range interactions between the polymer – gas via topological characteristics analysis of intermolecular forces. Obtained results shed light on the carbon dioxide and nitrogen affinity as well as the selectivity during the adsorption process, and yet conclusions were attained on the characteristics of the adsorption type and mechanism in this study.