Aqueous Separation of Styrene from Ethylbenzene Using a Water‐Soluble Cyclophane

The selective separation of hydrocarbons such as styrene ( ST ) and ethylbenzene ( EB ) remains a formidable challenge in the petrochemical industry due to their nearly identical molecular structures and physicochemical properties. Herein, we report a robust, water‐soluble, metal‐free tetracationic cyclophane ( B ) capable of achieving >99% selective extraction of ST from EB in aqueous media with excellent recyclability. B features a hydrophobic, conformationally adaptive cavity (∼6.5 Å × 14.3 Å) that selectively recognizes planar over nonplanar guests in aqueous medium. Solution‐state and solid‐state analyses confirm that the preferential binding of ST is driven by favorable interactions with its vinyl group and induced planarization of the host. B also distinguishes phenanthrene ( P ) from 9,10‐dihydroanthracene ( DHA ), further validating its precision in shape‐selective molecular recognition. Our findings demonstrate a unique aqueous separation of ST from EB employing a metal‐free receptor that advances the design of selective host–guest systems and supports greener alternatives for hydrocarbon purification.