Perfect Separation of <i>n</i>-Pentane and <i>Iso</i>-pentane by Nonporous Adaptive Crystals of Perethylated Pillar[5]arene

The separation of n-pentane (n-PT) and iso-pentane (iso-PT) mixtures represents a significant challenge in the petrochemical industry. In this study, we propose an innovative, efficient, and energy-saving method for the adsorptive separation of n-PT and iso-PT mixtures using nonporous adaptive crystals (NACs) based on perethylated pillar[5]arene (EtP5), achieving 100% purity. The single crystal structure suggests that the high selectivity is due to multiple noncovalent interactions between EtP5 and n-PT as well as the formation of newly stable crystals of n-PT@EtP5. Density functional theory demonstrates that the host–guest interaction of n-PT@EtP5 is mainly concentrated in the cavity center of EtP5, and the aromatic area of EtP5 contributes the most. Additionally, NACs of EtP5 exhibit recyclability due to the reversible transformation between the guest-free and guest-loaded structures.