Recovering lithium from brines is important for securing critical mineral resources but efficient recovery remains challenging because Mg2+ often coexists at high concentrations and requires effective removal to obtain high-purity lithium streams. Here, amino-functionalized ZIF-8 (ZIF-8–NH2) was incorporated into cellulose acetate (CA) to form mixed-matrix membranes with improved polymer–filler compatibility for electrically driven Li+/Mg2+ separation from brine. The CA–ZIF-8–NH2 membranes exhibited greater tensile strength than corresponding CA–ZIF-8 membranes. Temperature-dependent Raman spectroscopy and density functional theory calculations supported additional hydrogen bonding interaction between ZIF-8–NH2 and CA, providing a molecular basis for the improved interfacial affinity. In binary Li+/Mg2+ solutions, the 10 wt% CA–ZIF-8–NH2 membrane achieved the highest Li + flux of 297 ± 10 mmol m−2 h−1 at −3 V while maintaining high Li+/Mg2+ selectivity. During 48 h of continuous operation with simulated Alba Sabrina brine, Li+ flux remained at 12.1–13.4 mmol m−2 h−1, while Li+/Mg2+ selectivity reached 29.5 ± 1.6. Preferential Li+/Mg2+ separation was also maintained over four consecutive cycles. These results demonstrate that interfacial reinforcement in ZIF-based mixed-matrix membranes can improve structural integrity and suppress divalent-ion crossover, highlighting their potential for electrically driven lithium purification from complex brines.
Hydrogen purification from methane-rich streams is essential for clean-energy production and utilization. Carbon molecular sieve membranes (CMSMs) are promising for H2/CH4 separation because of their strong molecular-sieving capability ultra-micropores. However, extensive structural evolution during carbonization obscures how precursor-chain conformation governs carbon microstructure and separation performance. Herein, the dianhydride geometry (6FDA, BPDA, and PMDA) was varied within a common flexible ether-containing diamine framework to construct a related polyimide series with conformations ranging from highly twisted and sterically frustrated to regular and compact. These monomer-encoded characteristics are inherited and amplified during carbonization, producing distinct C/L-domain topologies. The bulky and non-coplanar 6FDA unit disrupts precursor packing and favors a larger fraction of interconnected, transport-rich disordered “C” phase, enabling 6F-CMS to achieve an H2 permeability of 1276 Barrer. In contrast, the planar and symmetric PMDA unit promotes compact packing and distinct molecular-sieving “L” domains, resulting in excellent H2/CH4 selectivity of 714 for PM-CMS. Atomistic simulations show that the H2-to-CH4 accessible-pore-volume ratio increases from 1.27 in 6F-CMS to 1.73 in PM-CMS, accompanied by fewer CH4 adsorption sites, directly correlating size-selective pore evolution with the experimental separation performance. These findings establish precursor-conformation memory as a design principle for tailoring CMS microstructure and tuning the permeability–selectivity balance.
