Insights into the spontaneous multi-scale supramolecular assembly in an ionic liquid-based extraction system

Area of Science:

• Supramolecular Chemistry
• Materials Science
• Separation Science

Background:

• Ionic liquids (ILs) are versatile solvents with unique properties.
• Understanding self-assembly processes in ILs is crucial for advanced applications.
• Spontaneous assembly across multiple scales remains a significant challenge.

Purpose of the Study:

• To elucidate the mechanism of spontaneous multi-scale supramolecular assembly (MSSA) in a two-phase IL system.
• To introduce and investigate the concept of multi-scale selectivity (MSS).
• To explore the physicochemical characteristics of ILs and their solvation effects on assembly.

Main Methods:

• Four-step mechanistic investigation of supramolecular assembly.
• Utilizing experimental and theoretical calculations.
• Analysis of ionic liquid-water interface phenomena, including Marangoni effect and capillary forces.

Main Results:

• Demonstrated step-by-step formation of complex ions, elementary building blocks (EBBs), [EBB] clusters, and macroscopic assembly (MA) spheres.
• Observed transfer of porous [EBB] clusters to the IL-water interface driven by electroneutrality and amphiphilicity.
• Achieved selective separation and solidification of metal ions via MSSA and MSS.

Conclusions:

• This work presents the first report of spontaneous whole-process supramolecular assembly across microscopic, mesoscopic, and macroscopic scales in extraction systems.
• The study provides fundamental insights into IL solvation effects and phase-splitting behavior.
• The developed MSSA process offers a novel platform for selective metal ion extraction and solidification.