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

Abstract Two-dimensional (2D) MOF named Cu(BPY)2(OTF)2 (OTF = trifluoromethanesulfonic acid anion (CF3SO3−), 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 CO2/CH4 gas mixtures. The inherent microporous structure and interlayer nanochannel that constructed by axial coordination anion CF3SO3− of Cu(BPY)2(OTF)2 nanosheets provide selective transfer channels for CO2. In addition, the group that has an affinity for CO2, such as pyridine group and CF3SO3− anion, locating in the surface and the interlayer of Cu(BPY)2(OTF)2 nanosheets, present better binding affinity and molecule selectivity for CO2. Owing to the synergistic effect between structure and functional groups of Cu(BPY)2(OTF)2 nanosheets, the optimized CO2 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.