Randomly oriented covalent organic framework membrane for selective Li⁺ sieving from other ions

Area of Science:

• Materials Science
• Chemical Engineering
• Environmental Science

Background:

• Biological ion channels demonstrate high selectivity for ion transport.
• Artificial membranes are needed for efficient lithium extraction and sustainable technologies.
• Current methods struggle with precise differentiation of lithium from competing ions.

Purpose of the Study:

• To develop a covalent organic framework (COF) membrane for selective separation of lithium ions (Li+) from competing cations.
• To investigate the mechanisms behind the membrane's selectivity and ion transport.
• To assess the membrane's performance under electrical potential for enhanced ion flux.

Main Methods:

• Fabrication of a randomly oriented covalent organic framework (COF) membrane.
• Incorporation of sulfonic acid groups within the COF structure.
• Evaluation of ion selectivity for Li+, Na+, K+, Mg2+, and Ca2+.
• Measurement of ion flux under applied electrical potential.

Main Results:

• The COF membrane exhibits narrow pores, enabling size-based selectivity among alkaline ions.
• Sulfonic groups facilitate preferential binding and transport of Na+ and K+ while retaining Li+.
• The membrane achieves selectivity beyond detection limits for K+ and Na+ over Li+.
• Electrical potential enhances ion flux through the membrane by over an order of magnitude.
• The membrane effectively rejects Li+ while allowing transport of Mg2+ and Ca2+.

Conclusions:

• The developed COF membrane demonstrates high selectivity for Li+ separation from major competing ions.
• Synergistic effects of pore size and functional groups drive the selective ion transport.
• The membrane shows potential for advancing biomimetic materials for resource extraction from aqueous sources.