Efficient CO₂ capture and separation in TpPa COFs: Synergies from functional groups and metal Li

Covalent organic frameworks (COFs) have emerged as promising materials for CO₂ capture and separation owing to their exceptional structural stability. Herein, grand canonical Monte Carlo simulation (GCMC) and density functional theory (DFT) were used to first screen the most favorable functional group in the COFs consisting of 1,3,5-triformylphloroglucinol (Tp) and p-phenylenediamine (Pa) functionalized with –OH, –COOH, and –SO₃H, respectively (TpPa-X). Subsequently, the H atoms of –SO₃H, the best functional group, were replaced by Li atoms to form –SO₃Li, revealing the synergies of functional group –SO₃H and Li modification on selective CO₂ capture. TpPa-OLi/COOLi were also constructed to confirmed the universality of this synergistic effect. The introduction of functional groups enhanced the CO₂ capture and separation performances by creating a more suitable pore environment. The Li introduction increased the structural polarity and provided strong adsorption sites, further improving the selective CO₂ capture performance. Notably, TpPa-SO₃Li exhibited a remarkable CO₂ adsorption capacity of 136.11 cm³ cm⁻³ with the CO₂ over N₂/CH₄ selectivity of 264.22/164.38, respectively, at 298 K and 1.0 bar. Structural stabilities, pore characteristics, gas adsorption distribution, isothermal adsorption heat, and interactions were adopted to reveal the synergistic effect between functional groups and Li in enhancing CO₂ capture and separation. © 2024 Elsevier B.V.