Supramolecular liquid-liquid extraction enabled by Cy2Q[6] for highly selective separation of benzene/cyclohexane mixtures.

The efficient separation of benzene (C6H6) from cyclohexane (C6H6) remains a longstanding challenge due to their similar molecular structures and nearly identical boiling points. Herein, we report a supramolecular liquid-liquid extraction strategy based on a water-soluble dicyclohexyl-substituted cucurbit[6]uril (Cy2Q[6]) for this demanding separation. Spectroscopic studies reveal that Cy2Q[6] can encapsulate both guests individually, while competitive binding experiments demonstrate a pronounced preference for C6H6 in binary systems. Density functional theory (DFT) calculations further confirm the higher thermodynamic stability of the Cy2Q[6]⊃C6H6 complex compared to Cy2Q[6]⊃C6H12. Exploiting this selective molecular recognition, complete separation of an equimolar C6H6/C6H12 mixture is achieved in a single extraction step under ambient conditions, affording quantitative selectivity toward C6H6. The aqueous Cy2Q[6] phase exhibits excellent recyclability with minimal performance loss over multiple cycles. Furthermore, simulated industrial experiments demonstrate efficient removal of trace C6H6 impurities, highlighting the practical applicability of this system. This work establishes a sustainable supramolecular extraction paradigm and provides an energy-efficient alternative to conventional distillation for the separation of structurally similar hydrocarbon mixtures.