Judicious design functionalized 3D-COF to enhance CO₂ adsorption and separation

The effects of functional groups (including OH, OCH₃ , NH₂ , CH₂ NH₂ , COOH, SO₃ H, OCO(CH₂ )₂ COOH(E-COOH), and (CH₂ )₄ COOH(c-COOH)) in 3D covalent organic frameworks (3D-COFs) on CO₂ adsorption and separation are investigated by grand canonical Monte Carlo (GCMC) simulations and density functional theory calculations. The results indicate that interaction between CO₂ and the framework is the main factor for determining CO₂ uptakes at low pressure, while pore size becomes the decisive factor at high pressure. The binding energy of CO₂ with functionalized linker is correlated to CO₂ uptake at 0.3 bar and 298 K on 3D-COF-1, suggesting functional groups play a key role in CO₂ capture in microporous 3D-COFs. Moreover, CO₂ selectivity over CH₄ , N₂ , and H₂ can be significantly enhanced by functionalization, where CH₂ NH₂ , COOH, SO₃ H, and E-COOH enhance CO₂ adsorption more effectively at 1 bar. Among them, SO₃ H is the most promising functional group in 3D-COFs for CO₂ separation.