Fluorinated Tripodal Chalcogen Bonding Receptor for Recyclable Iodine Adsorption in Water

The development of robust and regenerable molecular adsorbents for iodine removal from water medium remains a major challenge because of the limited aqueous stability and weak binding interactions exhibited by most existing systems. Here, we report Se₃-PentF, a fluorination-enhanced chalcogen bonding (ChB) receptor engineered to maximize the σ-hole intensity and thereby promote strong Se···I^- interactions. The introduction of pentafluorophenyl groups deepens the selenium σ-hole via an electron withdrawing inductive effect, while simultaneously enabling C-F···π contacts that promote layered supramolecular organization in the solid state. Moreover, Se₃-PentF exhibits substantially higher iodine affinity compared to its phenyl (Se₃-Benz) and electron-rich tert-butyl (Se₃-TBu) analogues. Both the solution-phase studies via NMR, ITC, and solid-phase X-ray crystallographic analyses confirm pronounced Se···I^- interactions and fluorine-assisted π-stacking that stabilize iodide binding. At ambient conditions, Se₃-PentF efficiently captures iodine (I₂/I₃^-) from water and can be regenerated simply by ethanol treatment, enabling repeated reuse. Importantly, in a dynamic column-flow setup, Se₃-PentF maintains its high iodine removal efficiency for at least 20 consecutive adsorption-desorption cycles without exhibiting any discernible performance loss.