Theoretical Investigation on Adsorption and Separation of CO2/N2 in Hybrid Ultramicroporous Materials

Abstract

Carbon capture and storage (CCS) is a promising strategy for reduction of CO2 emissions. Herein, CO2/N2 adsorption and separation in three SIFSIX-X-Cu (arrayed via SiF62- with Cu metal center, X = 2, 3, O) hybrid ultramicroporous materials at 298 K within 0-5 kPa were investigated by using grand canonical Monte Carlo (GCMC) simulation. Results showed that, in contrast to SIFSIX-2-Cu, CO2 adsorption in SIFSIX-3-Cu and SIFSIX-O-Cu reached saturation at 0.5 kPa and their CO2 adsorption capacity were 2.70 and 2.39 mmol•g-1 at 1 kPa, respectively. The CO2 adsorption capacity in CO2/N2 mixture barely decreased. SIFSIX-3-Cu and SIFSIX-O-Cu owned close pore sizes to CO2 dynamics diameter, thereby exhibiting high CO2 affinity with adsorption heat of 59 and 66 kJ•mol-1, respectively. Density functional theory (DFT) analyses showed only one CO2 molecule could be adsorbed in each hole and located at the center of SIFSIX-3-Cu and SIFSIX-O-Cu. Our results provide a theoretical guidance for developing ultramicroporous materials in adsorption and separation of CO2 at low pressure.