Highly Water-Selective Hybrid Membrane By Incorporating Lamellar ZIF-8 into Polymer Matrix

Inspired by the structure and function of aquaporins in bio-membrane, novel water-selective hybrid membranes with superior water/ethanol separation performance were fabricated by incorporating lamellar ZIF-8 into sodium alginate (SA) matrix. The as-synthesized lamellar ZIF-8 exhibited a two-dimensional morphology and hydrophobic nanoporous structure. Due to the reinforcement effect of ZIF-8, the hybrid membranes exhibited higher mechanical strength, thermal stability, and swelling resistance. On one hand, the horizontally aligned structure of lamellar ZIF-8 within the hybrid membranes and could constructed ordered water channels; on the other hand, the selective and hydrophobic nanopores of lamellar ZIF-8 could render water channels with molecular sieving effect and fast water permeation. Moreover, the lamellar ZIF-8 could interfere the polymer chain packing and create additional interfacial channels. Accordingly, the hybrid membranes exhibited high water permeability and selectivity for water/ethanol mixture separation. Especially, for the membrane containing 4 wt% of lamellar ZIF-8, the separation factor was as high as 1840, while the permeation flux was 1218 g/m² h under 76 ^oC and 10 wt% feed water concentration. This study also revealed the lamellar ZIF-8 was more efficient than hexagonally shaped ZIF-8 as a filler of hybrid membrane for dehydration of aqueous solution.