College of Science & Engineering
Twin Cities
As a key ingredient in fertilizers, significant concentrations of phosphates can accumulate in agricultural runoffs. The resulting surplus of nutrients causes eutrophication of surface and coastal waters, boosts algal growth, and creates dead zones that have significant economic and health impacts. On an industrial scale, purification of water can be performed with porous membranes that can separate out a desired species. Unfortunately, such technologies have yet to be successfully developed for inorganic phosphates. Part of the problem hindering their development arises from the general paucity of receptors that can sequester inorganic phosphates with sufficient affinity directly in complex aqueous media, with high selectivity over competing anions, and in a reversible manner such that both the device and the phosphates can be recycled.
This group is currently designing such lanthanide-based supramolecular receptors for phosphate remediation. The ability of these complexes to catch and release phosphate upon addition of a trigger such as pH makes them promising candidates for the development of recyclable membranes. Although complexes of lanthanide ions with open coordination sites are known to bind phosphates, they do not all do so with the same affinity and selectivity. Even minor differences in ligand can lead to substantial changes in anion recognition. The group is studying how the structure of the ligand L, the geometry of the lanthanide complex, its charge, and the presence of a hydrogen-bonding network all affect anion recognition, binding, and selectivity, and how to design a lanthanide complex for catch-and-release applications.