Alkyl amine functionalized triphenylamine-based covalent organic frameworks for high-efficiency CO2 capture and separation over N2

High-efficiency absorbent is a prerequisite for CO2 capture from the atmosphere to alleviate environmental degradation. Herein, grand canonical Monte Carlo (GCMC) was used to investigate the CO2 adsorption and separation behaviors in four alkyl anime functionalized triphenylamine-based covalent organic frameworks (TPA-xC-NH2, x = 1–4). Results show that a longer alkyl anime chain has a more remarkable effect on the CO2 adsorption capacity and separation over N2. The alkyl amine chain owning four carbon atoms of TPA-4C-NH2 exhibits the best performance. The CO2 adsorption capacity in TPA-4C-NH2 is 3.41 mmol/g at 298 K and 5.26 mmol/g at 273 K and 1 bar, thereby enhancing the CO2 adsorption capacity by 50.2% and 30.5%, respectively, with a 121% selectivity increase compared with that of the pristine TPA-COF. The pore characteristic, isosteric heat, coulomb/non-coulomb interaction, and selectivity are analyzed to elucidate the enhancement mechanisms.