N-Methylpyrrolidone　is　widely　used　across　various　sectors;　however,　the　energy　-efficient　removal　of　1,4-butyrolactone　impurity　from　NMP　remains　a　significant　challenge　due　to　their　nearly　identical　molecular　size　and　properties.　Herein,　we　synthesize　a　series　of　flexible　molecular　materials,　perethylated　pillar[　n　]arene　(　n　=　5,　6)　with　enhanced　crystallization　efficiency　under　the　induce　of　dichloromethane　solvent.　Through　a　size　-specific　recognition　and　varied　host　-guest　interaction,　EtP5　demonstrates　exceptional　99　%　selectivity　for　GBL　against　NMP;　single　-crystal　structure　analyses　and　theoretical　calculations　unveil　intricate　C-H　center　dot　center　dot　center　dot　O　hydrogen　bonding　interactions,　and　7C　-7C　stacking　interactions　between　EtP5　and　GBL.　The　single　-crystal　structure　of　the　two　-guest　complexes　has　proved　the　existence　of　adsorption　transition　states,　and　it　comprehensively　elucidates　the　dynamic　adsorption　process　of　EtP5　with　GBL,　supported　by　theoretical　calculations.　Reuse　experiments　validate　these　crystals　could　be　fully　reused　without　loss　of　performance.