Introducing defect-engineering 2D layered MOF nanosheets into Pebax matrix for CO2/CH4 separation

The layered Ni-MOF nanosheets (Ni-NS) with defective structure were used as fillers to prepare mixed matrix membranes (MMMs) for CO2 separation. In this work, the defect structure of Ni-MOF nanosheets was manipulated by adjusting the molar ratio of metal source to organic linker (RM/L), and the influence of defects at the Ni-MOF nanocrystal on the gas separation performance of MMMs was investigated. The characterization of filler and membranes showed that Ni-MOF nanosheets with defective structure could improve the gas separation performance mainly through the enlarged pore size and the increased adsorption sites. Compared with the Ni-NS-2 with complete crystal structure, the Ni-NS-8 with defective structure showed better interfacial compatibility with poly(ether-block-amide) (Pebax® MH 1657) matrix. The Pebax/Ni-NS-8-6 MMM showed the best CO2/CH4 separation performance. The CO2 permeability and CO2/CH4 selectivity were 436.1 Barrer and 33.1, which were 115% and 18% higher than those of pure Pebax membrane, respectively. The results showed that defect-engineering in MOF nanocrystals was an important strategy to optimize the gas separation performance of 2D MOF-based MMMs.