ZIF-filler incorporated mixed matrix membranes (MMMs) for efficient gas separation: A review

Gas separation by employing polymeric membranes is one of the most developed branches of membrane based separation technology. But, polymeric materials are unable to meet the demands of present day membrane technology. Mixed matrix membranes (MMMs) which are combination of both polymeric and inorganic materials have appeared as an emerging membrane material as it combines the dimensional stability and efficient gas separation ability of inorganic material along with facile fabrication and low cost of polymeric material. In this review, main challenges that are encountered during fabrication of MMMs and the steps taken to overcome these challenges are reviewed in detail. Also, the basic criteria for the selection of suitable polymer and inorganic material for fabrication of MMMs is also discussed pertaining to chemical and physical compatibility between them. Zeolite imidazolate frameworks (ZIFs) because of their good compatibility with polymers along with their beneficial properties such as unsaturated sites, adjustable pore channels and simple functionalization are widely incorporated into polymer matrix for fabrication of MMMs. Influence of various types of ZIFs on MMMs fabrication along with their gas separation performances are also put together in this review article from different reports. Moreover, ZIF modification techniques in order to enhance the gas separation performance of MMMs are also discussed. This study reveals that modified filler’s synergic effect can alter membrane’s structure by improving interfacial voids and thus can overcome the trade-off effect. Besides this, the influence of ZIFs morphology on gas separation performance of MMMs is also analysed in this article.