Development of new ligand systems that selectively extract and release critical elements, such as lanthanides, in the presence of other metal ions at significantly higher concentrations can provide a sustainable alternative to conventional mining and ligand-based flotation reagents. In this work, the rational design of a highly tunable molecular scaffold based on tris(2-aminoethyl)amine is elaborated. When functionalized with salicylaldehydes, the corresponding imine ligands were observed to effectively extract Ce from aqueous solutions in the presence of a large excess of both Mg and Ca. Furthermore, the re-extraction and reactive separation of Ce was observed using CO 2 as a stimulus trigger for release and precipitation, synthesizing cerium carbonate and high-purity ceria that could be used for a wide range of applications. The pH swing driven by the controlled partial pressure of CO 2 allowed the efficient recovery of energy-relevant elements from unconventional resources through green chemistry.