Ionic Liquid/Metal–Organic Framework Composite for CO₂ Capture: A Computational Investigation

A composite of ionic liquid [BMIM][PF 6 ] supported on metal–organic framework IRMOF-1 is investigated for CO 2 capture by molecular computation. Due to the confinement effect, IL in the composite exhibits an ordered structure as observed from radial distribution functions. The bulky [BMIM] + cation resides in the open pore of IRMOF-1, whereas the small [PF 6 ] − anion prefers to locate in the metal cluster corner and possesses a strong interaction with the framework. [BMIM] + exhibits a greater mobility than [PF 6 ] −, which is also observed in simulation and experimental studies for imidazolium-based ILs in the bulk phase. With increasing IL ratio in the composite and thus enhancing confinement effect, the mobility of [BMIM] + and [PF 6 ] − is reduced. Ions in the composite interact strongly with CO 2; in particular, the [PF 6 ] − anion is the most favorable site for CO 2 adsorption. The composite selectively adsorbs CO 2 from the CO 2 /N 2 mixture, with selectivity significantly higher than many other supported ILs. Furthermore, the selectivity increases with increasing IL ratio in the composite. This computational study, for the first time, demonstrates that IL/MOF composite might be potentially useful for CO 2 capture.