Thin Film of Polyimide/Mof Nanocomposite Membrane with Substantially Improved Stability for Co2/Ch4 Separation

The development of thin-film nanocomposite (TFN) membranes is necessary due to the demand of high gas permeance for industrial applications. Nevertheless, it is a great challenge to achieve TFN membranes with stable separation performance owing to the high chain mobility in thin films. In this work, we report an efficient and less destructive coordination crosslinking strategy to improve the TFN membrane stability for CO2/CH4 separation. The selective layer of TFN membranes is made of carboxylated polyimide as matrix and UiO-66 nanoparticles as fillers. By immersing these TFN membranes in methanol solution containing Cu(NO3)2, coordination bonds are successfully constructed between Cu2+ and carboxyl groups (-COOH). The crosslinked TFN membranes exhibit high CO2/CH4 selectivity up to 29~35 with CO2 permeance of 110~350 GPU, outperforming most of previously reported TFN membranes. Moreover, the plasticization pressure of the crosslinked membranes improves from 0.3-0.9 MPa to 0.9-1.5 MPa. In the CO2/CH4 (50 v:50 v) mixed gas permeation tests, the crosslinked membranes remain constant CO2/CH4 selectivity at 23.9~25.2 with increasing feed gas pressure. The crosslinked membranes also demonstrate stable CO2/CH4 selectivity in the range of 27.2~31.2 within 100 hours testing time under 1.0 MPa CO2 partial pressure