Highly Selective Separation of Isopropylbenzene and α-Methylstyrene by Nonporous Adaptive Crystals of Perbromoethylated Pillararene via Vapor- and Liquid-Phase Adsorptions.

Isopropylbenzene () and α-methylstyrene (), two members of C9 aromatics, are important in both industrial production and laboratory research, but the separation of / mixtures is still a big challenge. Here, we provide a new strategy to separate and using nonporous adaptive crystals of four pillararenes, perethylated pillar[5]arene, perethylated pillar[6]arene, perbromoethylated pillar[5]arene, and perbromoethylated pillar[6]arene (). Among them, selectively adsorbs from an equal volume mixture of and with >95% purity for solid-vapor phase adsorption and >94% purity for solid-liquid phase adsorption, while the selectivities for the other three pillararenes are unsatisfactory. Single-crystal structural analyses combined with powder X-ray diffraction and differential scanning calorimetry experiments demonstrate that the selectivity arises from the different stabilities of guest-loaded crystals. Moreover, the reversible transitions between guest-free and -loaded structures indicate the preeminent recycling performance of crystals.