Lanthanide-Selective Artificial Channels

Lanthanides serve as essential elements for modern technology, playing critical roles in batteries, wind turbines, portable electronics, and energy-efficient lighting. Purifying lanthanides from ores and recycling them from end-of-life consumer materials are costly and damaging to the environment due to inefficient separation technologies. In this study, we present a new approach for lanthanide separations using supramolecular membrane channel nanopores based on a pillar[5]arene scaffold with appended diphenylphosphine oxide (DPP) ligands. These channels show high transport selectivity (>18:1) of the middle lanthanides, europium (Eu3+) and terbium (Tb3+) ions, over monovalent K+ ions and also excluded other common mono- and divalent metal ions (Na+, Ca2+, and Mg2+) including protons. These membrane channels also have high lanthanide-lanthanide transport selectivity with Eu3+/La3+ selectivity of >40 and Eu3+/Yb3+ selectivity of ∼30. Additionally, they demonstrated significantly higher selectivities between middle lanthanides and both light and heavy lanthanides: Tb3+/La3+ (∼140), Tb3+/Yb3+ (∼72), Tb3+/Nd3+ (∼58), and Eu3+/Nd3+ (∼17), which are considerably higher than selectivities reported in studies using traditional solvent extraction methods. Molecular dynamics simulations indicate that the high selectivity observed is due to specific water-mediated interactions between the hydrated ions and the channel. Our findings could contribute to ongoing efforts to improve lanthanide separation efficiency and reduce the environmental impact associated with current methods.