Introducing two-dimensional metal-organic frameworks with axial coordination anion into Pebax for CO2/CH4 separation

Two-dimensional (2D) MOF named Cu(BPY) 2 (OTF) 2 (OTF = trifluoromethanesulfonic acid anion (CF 3 SO 3 − ), BPY = 4,4-bipyridine) possessing axial coordination anion was prepared, and then combined into Pebax® MH 1657 (Pebax) polymer to fabricate mixed matrix membranes (MMMs) for the separation of CO 2 /CH 4 gas mixtures. The inherent microporous structure and interlayer nanochannel that constructed by axial coordination anion CF 3 SO 3 − of Cu(BPY) 2 (OTF) 2 nanosheets provide selective transfer channels for CO 2 . In addition, the group that has an affinity for CO 2 , such as pyridine group and CF 3 SO 3 − anion, locating in the surface and the interlayer of Cu(BPY) 2 (OTF) 2 nanosheets, present better binding affinity and molecule selectivity for CO 2 . Owing to the synergistic effect between structure and functional groups of Cu(BPY) 2 (OTF) 2 nanosheets, the optimized CO 2 separation performance (permeability and selectivity) of the MMMs compared with that of pure Pebax were increased by 86.65% and 47.59%, respectively, under the conditions of pure gas, 0.1 MPa and 25 °C. The open narrow nanochannels and axial coordination anion in Cu(BPY) 2 (OTF) 2 nanosheet, making Cu(BPY) 2 (OTF) 2 a promising material to prepare efficient mixed matrix membrane.