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 (Eu 3+ ) and terbium (Tb 3+ ) ions, over monovalent K + ions and also excluded other common mono- and divalent metal ions (Na +, Ca 2+, and Mg 2+ ) including protons. These membrane channels also have high lanthanide–lanthanide transport selectivity with Eu 3+ /La 3+ selectivity of >40 and Eu 3+ /Yb 3+ selectivity of ∼30. Additionally, they demonstrated significantly higher selectivities between middle lanthanides and both light and heavy lanthanides: Tb 3+ /La 3+ (∼140), Tb 3+ /Yb 3+ (∼72), Tb 3+ /Nd 3+ (∼58), and Eu 3+ /Nd 3+ (∼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.