pH-Dependent phosphate separation using a tripodal hexaurea receptor

Abstract

We demonstrate that a tripodal hexaurea receptor can selectively bind PO₄³⁻ anions via 12 hydrogen bonds with up to 3.8 × 10⁶ M⁻¹ binding affinity in DMSO, which is 38-fold stronger than SO₄²⁻. This receptor facilitates the extraction of PO₄³⁻ from strongly basic aqueous solutions into chloroform using liquid–liquid extraction, followed by its release as the H₂PO₄⁻ anion into an acidic solution. This pH-dependent phosphate extraction successfully enables selective separation of phosphate and sulfate anions.