Predicting gas selectivity in organic ionic plastic crystals by free energy calculations

Abstract

The free energy calculation shows the different free energy changes of the adsorption and absorption of gas molecules into an organic ionic plastic crystal, successfully predicting the gas selectivity of this new type of gas separation material.

Highly Selective and Tunable CO2/N2 Separation Performance in Ammonium-Based Organic Ionic Plastic Crystal Composite Membranes with Self-Healing Properties

“…43,44 These salts possess analogous chemistry to RTILs, although OIPC ions instead form disordered crystal structures that evolve with temperature into different plastic crystal phases until they finally melt above ambient temperature with a low enthalpy of fusion. 45 The promise of OIPC-based materials for gas separation has recently been demonstrated by using OIPCs such as methyl(diethyl)isobutylphosphonium hexafluorophosphate ([P 122i4 ][PF 6 ]) and N-methyl-N-ethylpyrrolidinium bis(fluorosulfonyl)imide ([C 2 mpyr][FSI]), combined with poly-(vinylidene fluoride) (PVDF), demonstrating their potential in achieving high CO 2 /N 2 selectivity in prior experimental 43,46 and simulated 47,48 work. Additionally, previous work revealed insights into the effect of the cation type and polymer support in gas separation, reporting four OIPCs based on triethyl-(methyl)phosphonium ([P 1222 ] + ), hexamethylguanidinium ([HMG] + ), tetramethylammonium ([N 11 11 ] + ), and (cyanomethyl)trimethylammonium ([N 111CN ] + ) cations, all paired with the [FSI] − anion.…”