Selective Crystallization Separation Driven by Structural Divergence in Lanthanide Mixed-Organic Systems

Abstract

Lanthanide separation remains challenging due to their shielded 4f orbitals, which prevent bonding with ligand orbitals. The slight decrease in the Ln³⁺ ionic radii from La³⁺ to Lu³⁺ leads to highly similar coordination environments, making their differentiation even more difficult. In this study, a unique complex organic system based on 1,10-phenanthroline-2,9-dicarboxylic acid (H₂PDA), N,N′-dimethylformamide (DMF), and its decomposition products was developed to achieve selective crystallization separation of lanthanide elements. Through the study of the crystallization periodicity of lanthanides in the solvothermal systems, we enabled the efficient crystallization separation of lanthanides such as La/Ce, La/Sm and La/Lu, with binary separation factors of 2.0 ± 0.1, 8.9 ± 0.1, and 26.9 ± 3.1, respectively.