1D continuous ZIF-8 tubes incorporated PDMS mixed matrix membrane for superior ethyl acetate pervaporation separation

Abstract

• 1D ZIF-8 tubes were incorporated in PDMS for membrane preparation. • Continuous permselective molecular pathways constructed by ZIF-8 tubes. • Superior separation performances by tubes than conventional nanoparticles. • Longer ZIF-8 tubes contributed more for enhancing ethyl acetate pervaporation. Mixed matrix membranes (MMMs) filled with dispersed nanoparticles may not favor all requirements for high separation performances due to the discontinuity in molecular permeation pathways. Here, we reported polydimethylsiloxane (PDMS) based MMMs by incorporating one-dimensional (1D) ZIF-8 tubes for the pervaporation (PV) recovery of ethyl acetate (EtOAc) from its diluted aqueous solution. The 1D ZIF-8 is a tubular structure formed by the ZIF-8 crystal particles inlaying each other, some windows between the ZIF-8 crystal particles are seamlessly connected, so that the cavities of the ZIF-8 are connected through the windows. The ZIF-8 tubes not merely possess microporous and molecular sieving properties, but also are inherently continuous in the integral morphology. The morphological continuity renders docking micropores along the tube body, which can act as efficient molecular permselective pathways for EtOAc molecules. Both the short and long-sized ZIF-8 tubes (STZIF-8 and LTZIF-8) played greater roles in facilitating PV performances than that of dispersed nanoparticles. Importantly, the most remarkable effect of the LTZIF-8 on separation performance was obtained since their micron-sized continuous structure, connected cavities and lumen, is more conductive to the separation process. The MMMs with 8% loading of the LTZIF-8 exhibited superior separation factor of 591.9 and EtOAc flux of 0.82 kg·m −2 ·h −1 for separating 1 wt% feed solution at 30 °C, which are 3.11 and 3.45 times of that of PDMS membrane, respectively. This study may give inspiration for developing high-performance MMMs by incorporating such morphologically continuous, microstructurally porous and molecular sieving fillers as permselective pathways for guest molecules.