(158a) 3D Covalent-Organic Framework Membranes for Li+/Mg2+ Separation: Microscopic Insights into Effects of Charge and Interpenetration

In this study, molecular simulation is utilized to explore the effects of charge and interpenetration in COF-300-NH₃⁺ on Li⁺/Mg²⁺ separation. We design 2, 3, and 4-fold interpenetrated membranes with fully charged, partially charged, or neutral frameworks. The fully charged 2-fold interpenetrated membrane shows excellent separation performance in both Li⁺ flux and Li⁺/Mg²⁺ selectivity. It is revealed the presence of charges induces electrostatic repulsion within framework, which has a great effect on the pore size of the membrane. Additionally, framework flexibility and distribution of counterions (Cl^- ions) in the membranes also play a crucial role in membrane separation performance. The structure-performance relationships unravelled by molecular simulation is microscopically insightful toward the design of new COF membranes for high-performance ion separation.