Sequential Separation of Metal Cations Using Nor-seco-cucurbit[10]uril as a Supramolecular Material

The treatment of metal-bearing wastewater is a critical step in safeguarding aquatic ecosystems and human health. In this study, the coordination characteristics of nor-seco-cucurbit[10]uril (ns-Q[10]) were systematically examined with various metal cations, encompassing alkali metal, alkaline earth metal, and rare earth metals, in HCl aqueous solution. Through X-ray single-crystal diffraction analysis, 12 distinct ns-Q[10]-based coordination complexes were identified, incorporating Ca²⁺, Y³⁺, La³⁺, Ce³⁺, Pr³⁺, Sm³⁺, Eu³⁺, Gd³⁺, Tb³⁺, Dy³⁺, Ho³⁺, and Er³⁺ metal ions. Based on these findings, a sequential separation method for metal ions was developed. This method uses ns-Q[10] to selectively capture metal ions in a HCl solution, forming a precipitate. The captured metal ions can then be released in a HNO₃ solution. The proposed approach demonstrated potential applications in cation capture and release, offering a promising strategy for metal separation and recovery in environmental and industrial contexts.