pH-Dependent phosphate separation using a tripodal hexaurea receptor

We demonstrate that a tripodal hexaurea receptor can selectively bind PO43- anions via 12 hydrogen bonds with up to 3.8 x 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. A tripodal hexaurea receptor enables reversible uptake and release of phosphate anions from water under the control of pH.