An Operationally Simple Method for Separating the Rare‐Earth Elements Neodymium and Dysprosium

Rare‐earth metals are critical components of electronic materials and permanent magnets. Recycling of consumer materials is a promising new source of rare earths. To incentivize recycling there is a clear need for simple methods for targeted separations of mixtures of rare‐earth metal salts. Metal complexes of a tripodal nitroxide ligand [{(2‐ t BuNO)C 6 H 4 CH 2 } 3 N] 3− (TriNOx 3− ), feature a size‐sensitive aperture formed of its three η 2 ‐(N,O) ligand arms. Exposure of metal cations in the aperture induces a self‐associative equilibrium comprising [M(TriNOx)thf]/ [M(TriNOx)] 2 (M=rare‐earth metal). Differences in the equilibrium constants ( K eq ) for early and late metals enables simple Nd/Dy separations through leaching with a separation ratio S Nd/Dy =359.