Selective adsorptive separation of xylene isomers in vapor and liquid phases by nonporous adaptive crystals of leaning pillar[6]arenes

The efficient separation of xylene isomers is a vital yet energy-intensive process in the petrochemical industry due to their nearly identical physical properties. Here, we report the first use of nonporous adaptive crystals (NACs) of leaning pillar[6]arenes (EtLP6 and EtFLP6) for selective xylene isomer separation. EtLP6 exhibited excellent p-xylene (pX) selectivity via solid–vapor adsorption, achieving purities of 97.1 % in binary mixtures and 94.0 % in ternary systems. In contrast, EtFLP6 functioned effectively in solid–liquid systems, affording pX purities of up to 92.4 % and 91.1 %, respectively. Single-crystal X-ray diffraction and DFT calculations revealed that pX uniquely induced guest-driven phase transformations, forming stable host–guest complexes, while o-xylene and m-xylene failed to do so. Additionally, both materials exhibited outstanding recyclability, fully regenerating after guest removal without performance loss. These findings highlight the potential of leaning pillar[6]arene-based NACs as recyclable, high-performance adsorbents for energy-efficient xylene isomer separations.