Growing ZIF-L seeds in graphene oxide interlayers towards synthesizing efficient cation sieving membranes

Designing and synthesizing membranes with fast and selective cation transport remains extremely challenging. Herein, ZGO membranes are conceived via a two-dimensional zeolitic imidazolate framework (ZIF-L) in situ grown on graphene oxide (GO), with ZIF-L as an interlayer that increases both vertical interlayer spacing and lateral tortuous path spacing of GO, thus improving the stability, selectivity, and ion permeation of the ZGO lamellar membrane. Structural analyses reveal that GO surfaces with abundant oxygen functional groups favored the formation of ZIF-L with 316 crystal planes and offered a high ion-accessible surface area. More importantly, the ZGO membrane delivers an excellent K + permeability of 86.9 mmol m −2  h −1 and K + /Mg 2+ selectivity up to 266, outperforming state-of-the-art GO-based membranes. Furthermore, molecular simulations confirm that the hydrogen bonding between hydrated cations and polar functional groups of ZGO membranes substantially restricted the dynamical transport of bivalent cation, and thus led to excellent cation selectivity. These results open a pathway to developing membranes for fast and highly selective ion separations in the future.