Functionalized 3D Covalent Organic Frameworks for High‐Performance CO2 Capture and Separation over N2

Covalent organic frameworks (COFs) are emerging adsorbent materials for CO2 capture and separation due to their tunable pore size, periodic permutation, and chemical thermal stability. Herein, four functionalized 3D COF‐300s (COF‐300‐X, X = –SO3H, –NO2, –OH, and –NH2) for CO2 adsorption and separation are studied by using density functional theory and grand canonical Monte Carlo simulation. The results show that four functionalized COF‐300s could create a feasible environment for CO2 adsorption with high accessible surface area, suitable pore size, and high porosity. The CO2 adsorption capacity in COF‐300s could be significantly improved by functionalization. In comparison, the best performing COF‐300‐SO3H shows a superior CO2 adsorption capacity of 6.23 mmol g−1 and a high CO2/N2 selectivity of 393 at 298 K and 100 kPa. The adsorption heat and interaction analyses demonstrate that the CO2 affinity in COF‐300s is enhanced by the introduction of polar functional groups, which renders great CO2 adsorption and separation performances. The gas distribution shows that the adsorption sites are concentrated near the functional groups and the distribution of CO2 in COF‐300‐SO3H has a characteristic of multilayer adsorptions. This work highlights COF‐300‐SO3H as an outperforming adsorbent candidate for CO2 capture and separation. Functionalized 3D COF‐300s (COF‐300‐X, X = –SO3H, –NO2, –OH, and –NH2) possess excellent CO2 adsorption and separation performances over N2. In‐depth analyses on pore physical characteristics, gas–framework interaction, and gas distribution elucidate the promotion essence from the introduction of functionalized groups.