pH-Dependent phosphate separation using a tripodal hexaurea receptor.

We demonstrate that a tripodal hexaurea receptor can selectively bind PO 4 3- anions via 12 hydrogen bonds with up to 3.8 × 10 6 M -1 binding affinity in DMSO, which is 38-fold stronger than SO 4 2- . This receptor facilitates the extraction of PO 4 3- from strongly basic aqueous solutions into chloroform using liquid-liquid extraction, followed by its release as the H 2 PO 4 - anion into an acidic solution. This pH-dependent phosphate extraction successfully enables selective separation of phosphate and sulfate anions.