Effective Separation of Phenanthrene from Isomeric Anthracene Using a Water-Soluble Macrocycle-Based Cage

Selective separation of phenanthrene (PHE) from aromatic isomer mixtures poses a significant challenge in industry due to the similar physical properties of PHE and its isomer anthracene (ANT). Herein, we report the self-assembly of a water-soluble Pd2L2 cage 1 with a large hydrophobic cavity, formed from novel macrocyclic ligands (L) and cis-Pd(II). Cage 1 can selectively encapsulate PHE instead of ANT. Based on host-guest recognition followed by extraction, we achieve a remarkable 99% purity of PHE separation from an equimolar mixture of PHE and ANT using cage 1 in aqueous solution. Importantly, the separation performance of PHE using cage 1 remains unaffected even after five extraction cycles, demonstrating its robustness. This work highlights the potential of supramolecular cages for efficient and cost-effective PHE separation from the isomer ANT in aqueous solutions using such promising host-guest strategy.