Lithium Pyrene Squarate Covalent Organic Frameworks for Efficient Lithium and Magnesium Separation from Salt Water

The increasing pressure for lithium resources from the electric vehicle and nuclear energy industries means that new technologies to separate Mg²⁺ from Li⁺ from salt water are in demand. To address this need, we fabricated lithium pyrene squarate covalent organic frameworks (Li-SQCOFs) to separate Mg²⁺/Li⁺ mixtures from salt water. We optimized the effect of the electrolyte and the amount of the adsorbent and then carried out a kinetics study on the adsorbent recovery at various pH levels using both batch and continuous flow adsorption methods. Li-SQCOF was found to have excellent selectivity for solutions containing a mixture of Mg²⁺/Li⁺ ions. This work represents a unique path for the separation of Mg²⁺/Li⁺ through direct adsorption using a covalent organic framework (COF). The COF-supported ultrafiltration bed made in this study gave a Mg²⁺ separation flux of 60.5 h^-1 m^-2.