Here we show a new adsorptive separation approach using nonporous adaptive crystals of a pillar[5]arene. Desolvated perethylated pillar[5]arene crystals (EtPS alpha) with a nonporous character selectively adsorb 1-pentene (1-Pe) over its positional isomer 2-pentene (2-Pe), leading to a structural change from EtPSa to 1-Pe loaded structure (1-Pe@EtP5). The purity of 1-Pe reaches 98.7% in just one cycle and EtPSa can be reused without losing separation performance.