Tailor-made iron-organic molecular cage embedded polydimethylsiloxane membranes via emulsion casting technique for efficient VOCs removal

Urgent needs for the removal of volatile organic compounds (VOCs) from gas streams has stimulated a vigorous research for high-performance separation membranes. Herein, porous iron-organic molecular cage (Fe-cage) embedded polydimethylsiloxane (PDMS) mixed miatrix membranes (MMMs) were fabricated through emulsion casting method for efficient VOCs removal. The membrane separation performance was systematically investigated by separating VOC/N 2 gas mixtures under various operating conditions (e.g., feed concentration, operating temperature) using n -hexane, n -heptane, and cyclohexane as model organic vapors. It was found that the resultant membranes demonstrated homogeneous Fe-cage dispersion and intimate interfacial adhesion. With the increase of the Fe-cage loading, the MMMs demonstrated obviously improved permselectivity for the separation of n -hexane/N 2 and n -heptane/N 2 . The MMM containing 4 wt% Fe-cage showed a n -heptane permeability of 1657 × 10 −8 mol μm m −2 s −1 Pa −1 and a n -heptane/N 2 selectivity of 145 at 25°C when the feed concentration is 4.3 mol%. These values were 231% and 158% of those for the pristine PDMS membrane, respectively. Furthermore, the VOC permeability and VOC/N 2 selectivity of the membranes increased with decreasing operating temperature or increasing feed concentration. Because of its excellent mixed-gas VOC/N 2 permselectivity, the Fe-cage embedded PDMS membrane could find use in petrochemical applications such as gasoline vapor recovery.