Pervaporation Separation of Organic Mixtures by MOF-5 Membranes

Metal organic framework (MOF) membranes have received much attention for gas separation applications, with however limited information about their liquid separation properties. This paper reports a study of permeation and separation of liquid organics by a MOF-5 membrane in pervaporation mode. Multiple high quality MOF-5 membranes were reproducibly prepared by the secondary growth method for various experimental runs. The pervaporation of pure toluene, o-xylene, and 1,3,5-triisopropylbenzene (TIPB) and the separation of their binary mixtures were studied. The permeation flux and separation factors decrease with pervaporation on-stream time and steady state permeation flux could not be reached even after 10 h of pervaporation. The fouling effects do not change the crystalline structure of the MOF-5 membrane. The pervaporation flux with the mixture feed is lower than the pure component flux, and the reduction in the flux decreases with decreasing affinity of the permeating species with MOF-5. The mixture maximum separation factors for toluene/TIPB and o-xylene/TIPB are respectively about 26.7 and 14.6, significantly higher than the pure component ideal separation factor. The fluxes and separation factors cannot be restored to their original values upon membrane activation at 100 °C in vacuum.