Selective Li ion transport via interpenetrated crystal growth on ZIF-8 seeded nanocomposite membranes

Abstract

ZIF-8 based poly(vinylidene) difluoride (PVDF) nanocomposite mixed matrix membranes (MMMs) were successfully prepared via post-synthetic seeded growth of the ZIF-8. PVDF and 5s-MMMs, before ZIF-8 crystallization, exhibit no diffusional selectivity towards Li ions, with intrinsic hydrophobicity and ion conductivity on the order of 10⁻¹² S cm⁻¹. On the other hand, crystallized 5c-MMMs with greater hydrophilicity, exhibit diffusional selectivity favoring Li over Na and K ions, with ion conductivities on the order of 10⁻⁸ S cm⁻¹, owing to the densely interpenetrated morphology of ZIF-8 in and on the membrane, controlling mass transport at selective crystal facets.