Rationally designed nanotrap structures for efficient separation of rare earth elements over a single step

Abstract Extracting rare earth elements (REEs) from wastewater is essential for the growth and an eco-friendly sustainable economy. However, it is a daunting challenge to separate individual rare earth elements by their subtle differences. To overcome this difficulty, we report a unique REE nanotrap that features dense uncoordinated carboxyl groups and triazole N atoms in a two-fold interpenetrated metal organic framework (named NCU-1). Notably, the synergistic effect of suitable pore sizes and REE nanotraps in NCU-1 is highly responsive to the size variation of rare-earth ions and shows high selectivity toward light REE. As a proof of concept, Pr/Lu and Nd/Er were used as binary models, which gave a high separation factor of SFPr/Lu = 579 and SFNd/Er = 273, demonstrating highly efficient separation over a single step. This ability achieves efficient and selective extraction and separation of REEs from mine tailings for the first time, establishing this platform as an important advance for sustainable obtaining high purity REEs.