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

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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.