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.