Synthesis of ZIF-68 Membrane on a ZnO Modified α-Alumina Support by a Modified Reactive Seeding Method

Large-pore- ZIF-68 membranes offer adsnrp tion-based selectivity for separation of gas mixtures- or molecular sieving characteristics for the separation of large liquid molecules. ZIF-68 membranes can be grown on ZnO modified a-alumina supports by a modified reactive eeding method. The resultant membranes were around 40 mu m in thickness and were determined to have Ili-lifted nonselective defects given their adherence to Knudsen diffusion- during single gas permeation measurements. Further pervaporation experiments showed that the ZIF-68 inembranes synthesized via the modified reactive seeding method' had a p-xylene pervaporation flux: approximately 5.4 times as large as that reported for similar pore-sized MOF-S membranes; however, pervaporation flux of larger Molecule,-ditert-butylbenzene, through the same two MOF membranes showed the flux of the ZIF-68 membrane,was 3.4 times smaller than that reprirted for MOF-S. This reversal in pervaporation flux indicates the ZIF68 structure-is more readily accessible to molecules smaller than its pore size, but larger molecules are subjected to a staunch cut off in flux.