Mixed matrix iongel membranes containing azo-porous organic polymers: Influence of temperature, pressure and water vapour on CO₂ separation

The effect of temperature, pressure, and humidity content in the gas separation performance of iongel membranes are crucial parameters that should be assessed to determine the real potential of these materials to be used in CO₂ separation processes. In this work, we present a detailed study on the impact of temperature (303, 323 and 353 K), pressure (2 and 4 bar), gas composition and water vapour content (between 11 and 21% of relative humidity) on the performance of iongels containing azo-porous organic polymers (azo-POPs), for CO₂/N₂ and CO₂/CH₄ binary gas separations. The iongels combining 80 wt% of the ionic liquid (IL) [C₂mim][TFSI], 20 wt% of poly(ethylene glycol) diacrylate (PEGDA) and 0.5 wt% of different azo-POPs were prepared by a solvent-free UV curing method. At the lower temperature, the pressure increase seems to have a negative impact on the CO₂ permeability of the prepared mixed matrix iongel membranes (MMIMs). However, the opposite behaviour was found when the temperature increases. Moreover, the presence of humidity in the feed gas stream affects the gas separation performance of the studied iongels, since the CO₂ permeability greatly increases with increasing humidity in the gas mixture, while the selectivity decreases, for both gas separations under study. In general, the high pressure and temperature, and the presence of humidity have a significant influence on the separation performance of the studied iongel membranes, due to induced alterations in their structure and overall stability.