In conclusion, we present the first example of inorganic phosphate transmembrane transport using the neutral bisurea-strapped calix [4]pyrrole 1. The unique ability of receptor 1 to transport phosphate was demonstrated using two complementary assays in which the entry of phosphate into vesicles is monitored directly using emission spectroscopy ([Eu.pBOH2] + assay) and 31 P NMR spectroscopy. Receptor 1 was found to be active as a H2PO4 -/Cl -antiporter, a H2PO4 -uniporter, and a Cs + H2PO4 -symporter. The higher transport activity observed in the 31 P NMR assay at pH 5 compared to pH 7 and 8 indicates that phosphate is mainly transported in the form of H2PO4 -. This work represents a breakthrough for the development of new phosphate transporters, as well as a milestone towards transmembrane transport of other biological phosphates.