Liquid-liquid phase separation of designer EF-hand peptides for selective and enhanced recovery of rare earth...

The sustainable and selective separation of rare earth elements (REE) remains a pressing challenge owing to their nearly identical chemical properties. Here, we develop a bioinspired liquid-liquid phase separation (LLPS) system based on engineered EF-hand peptides, enabling highly efficient and selective recovery of REE through a fully aqueous, green, and low-cost process. By incorporating a hydrophobic Nap-FF motif, these peptides readily undergo rapid LLPS upon REE binding, yielding dense liquid-like condensates. This LLPS platform enhances REE binding capacity by over 30%, significantly outperforming conventional immobilization approaches. Moreover, the system achieves selective separation of adjacent light REE (Nd/Ce) with a separation factor exceeding 2.8 at pH 5.6, surpassing most reported liquid-liquid extraction systems. With excellent reusability, broad pH tolerance, and strong resistance to competing ions, this LLPS strategy provides a sustainable, efficient, and selective route for the recovery and enrichment of REE.