Encapsulation of Hydrophobic Pollutants within a Large Water-Soluble [Fe₄L₆]^4- Cage

Hydrophobic molecules lost into water systems can have significant impacts on local ecology. Notably the discharge of unmetabolized medications, specifically hormones, and hygiene products into effluent wastewater is a pressing environmental challenge. Whilst selective capture of these molecules has been demonstrated by metal-organic cages (MOCs), these studies typically employ an organic solvent system that does not reflect aqueous environmental conditions. In this study, we report a rare, water-soluble, tetrahedral MOC bearing hydrosolvating sulfonate moieties alongside an aromatic naphthyl spacer. The MOC encloses a large (657 ų) cavity that can bind a range of polycyclic structures in aqueous media. Isothermal titration calorimetry measurements support guest binding being an enthalpically driven hydrophobic binding process. The synthetic strategy employed to prepare the MOC is extensible, and thus serves as a promising route to a range of large, water-soluble MOCs containing hydrophobic binding cavities with exciting prospects.