Dibenzo-15-crown-5-based Tröger's Base membrane for 6Li+/7Li+ separation

The separation of lithium isotopes through membrane-based technologies has become an increasingly attractive research direction, considering the application of lithium isotopes as potential energy sources. However, the very similar physicochemical properties of 6Li+ and 7Li+ pose a significant challenge in developing capable membranes and the separation performance is currently not satisfactory. Here we report a dibenzo-15-crown-5-based polymeric membrane synthesized from Tröger's Base (TB) polymerization, namely PIM-DB15C5-TB, for lithium isotope separations. The introduction of dibenzo-15-crown-5 enables PIM-DB15C5-TB to manifest good 6Li+/7Li+ selectivity, and the TB units having rigid and contorted structure conformation provide PIM-DB15C5-TB with abundant free volumes for 6Li+/7Li+ transport. When applied in electrodialysis for the separation of 6Li+/7Li+, PIM-DB15C5-TB demonstrates a 6Li+/7Li+ selectivity of 1.16. The current work proposes a strategy for developing polymeric membranes for the selective separation of lithium isotopes.