Selective Separation of Methylfuran and Dimethylfuran by Nonporous Adaptive Crystals of Pillararenes

The separation of 2-methylfuran (MeF) and 2,5-dimethylfuran (DMeF) mixtures is very important in the chemical industry. Herein, we offer a novel strategy for the separation of MeF and DMeF using nonporous adaptive crystals (NACs) of perethylated pillar[5]­arene (EtP5), perethylated pillar[6]­arene (EtP6), perbromoethylated pillar[5]­arene (BrP5), and perbromoethylated pillar[6]­arene (BrP6). We find that the crystals of EtP6 and BrP5 show remarkable selectivities for MeF in a 50:50 (v/v) MeF:DMeF mixture vapor, yielding purities of 94.0 and 96.3%, respectively. Single-crystal structures reveal that these different selectivities come from the different thermodynamic stabilities and binding modes of the host–guest complexes. Cycling experiments demonstrate that these crystals can be reused more than five cycles without loss of performance.