Piperidinium functionalized poly(2,6 dimethyl 1,4 phenylene oxide) based polyionic liquid/ionic liquid (PIL/IL) composites for CO2 separation

In this study, free-standing PIL/IL composite membranes of 1-bromohexyl-1 methylpiperidinium bromide (Br-6-MPRD) grafted poly(2,6 dimethyl 1,4 phenylene oxide) (ILPPO) incorporated with different amounts of free Br-6-MPRD (0, 2, 5 and 10 wt%) were prepared and the effect of free ionic liquid on CO2, N2 and O2 transport properties were reported. The structure of piperidinium based polyionic liquid (PIL) synthesised was confirmed using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectral techniques. Gas permeation results at 1 bar pressure and 25 °C revealed the best CO2 permeability and CO2/N2 as well as CO2/O2 permselectivities of the membrane stretch to 907.20 Barrer (higher than Pebax® 1657), 12.94 and 14.90 respectively for ILPPO/Br-6-MPRD-2 which come within reach of the 2008 Robeson limit. Apart from most of the published works, ILPPO/Br-6-MPRD-2 membrane revealed an anti-trade-off permeability-selectivity performances which is most required and a great challenge for CO2 separation and capture applications.