A facile structural engineering of porous coordination polymers for enhanced gas separation performance

Membrane-based gas separation technique is attractive due to its good energy efficiency and small footprint. Especially, polymeric membranes incorporated with homogeneously distributed nanofillers, called mixed matrix membranes (MMMs), are an attractive platform owing to potential scalability and excellent molecular size/shape-sieving ability. However, several technical challenges, including the fine-tuning of molecular structures and the suppression of interfacial voids between polymer and nanofillers should be addressed for industrial applications. Zeolitic imidazolate frameworks (ZIFs) are attractive porous coordination polymers constructed from zinc metal ions and organic ligands for gas separations. The purpose of the current study is to engineer the desired molecular structure of ZIF nanofillers for enhanced gas separation performance. A facile defect engineering is proposed to suppress the formation of non-selective interfacial voids around nanofillers and enhance the molecular sieving behaviour of ZIFs by introducing Zn-alkyl amine coordination into the framework. In addition, the fine-tuning of molecular structures of ZIF nanofillers is realized either by in-situ synthesis or by post-synthetic modification for excellent gas separation performance.