Pebax-Based Composite Membranes with High Transport Properties Enhanced by ZIF-8 for CO2 Separation

A series of mixed matrix membranes containing poly (ether-block-amide) Pebax 1657 as matrix and polyethylene glycol (PEG) and Zeolitic Imidazolate Framework-8 (ZIF-8) as additives, were prepared and tested for CO<INF>2</INF> separation. The membranes were prepared by solvent evaporation method and were characterized by TGA, DSC, SEM, and gas permeation measurements. The effects of PEG and its molecular weight, and the percentage of ZIF-8 into Pebax matrix were investigated. The results showed that the addition of PEG to Pebax/ZIF-8 blends avoid the agglomeration of ZIF-8 particles. A synergic effect between PEG and ZIF was particularly observed for high ZIF-8 content, because the initial permeability of pristine Pebax was multiplied by three (from 54 to 161 Barrers) while keeping the CO<INF>2</INF> selectivity (alpha<INF>CO<INF>2</INF>/N<INF>2</INF></INF> = 61, alpha<INF>CO<INF>2</INF>/CH<INF>4</INF></INF> = 12 and alpha<INF>CO<INF>2</INF>/O<INF>2</INF></INF> = 23). Finally, the mechanism of CO<INF>2</INF> transport is essentially governed by the solubility of CO<INF>2</INF> into the membranes. Therefore, this new Pebax/PEG/ZIF-8 system seems to be a promising approach to develop new selective membranes for CO<INF>2</INF> with high permeability.