Pervaporation performance comparison of hybrid membranes filled with two-dimensional ZIF-L nanosheets and zero-dimensional ZIF-8 nanoparticles

Two kinds of zeolitic imidazolate frameworks (two-dimensional ZIF-L nanosheets and zero-dimensional ZIF-8 nanoparticles) with the same building blocks were synthesized. Both the ZIF-L and ZIF-8 materials were incorporated into sodium alginate (SA) matrix to fabricate hybrid membranes for pervaporation dehydration of ethanol. At the filler content of 4 wt%, the ZIF-L-filled membrane displayed permeation flux of 1218 g/(m² h) and separation factor of 1840, while the ZIF-8-filled membrane displayed permeation flux of 879 g/(m² h) and separation factor of 678. The superior separation performance of the ZIF-L-filled membrane is due to the following two reasons: the ordered alignment and the regular apertures of ZIF-L rendered ordered water channels for rapid transport of water molecules; the suitable apertures of ZIF-L rendered the desirable molecular sieving effect. Furthermore, the hybrid membranes exhibited both good swelling resistance as well as thermal and mechanical stability. This is a step forward in realizing superior performance of hybrid membranes incorporating two-dimensional porous fillers for separation processes.