Polystyrene Sulfonate Threaded through a Metal–Organic Framework Membrane for Fast and Selective Lithium‐Ion Separation

Abstract

Extraction of lithium ions from salt-lake brines is very important to produce lithium compounds. Herein, we report a new approach to construct polystyrene sulfonate (PSS) threaded HKUST-1 metal-organic framework (MOF) membranes through an in situ confinement conversion process. The resulting membrane PSS@HKUST-1-6.7, with unique anchored three-dimensional sulfonate networks, shows a very high Li⁺ conductivity of 5.53×10^-4 S cm^-1 at 25 °C, 1.89×10^-3 S cm^-1 at 70 °C, and Li⁺ flux of 6.75 mol m^-2 h^-1 , which are five orders higher than that of the pristine HKUST-1 membrane. Attributed to the different size sieving effects and the affinity differences of the Li⁺ , Na⁺ , K⁺ , and Mg²⁺ ions to the sulfonate groups, the PSS@HKUST-1-6.7 membrane exhibits ideal selectivities of 78, 99, and 10296 for Li⁺ /Na⁺ , Li⁺ /K⁺ , Li⁺ /Mg²⁺ and real binary ion selectivities of 35, 67, and 1815, respectively, the highest ever reported among ionic conductors and Li⁺ extraction membranes.