A New Method for Mixed Matrix Composite Membranes Preparation Using Direct Spray‐Coating Technique

The development of membranes has evolved over the last years as an effective CO2 separation technology to fight the environmental impact of post‐combustion processes. In this regard, the upgrade of conventional polymers has been approached through different strategies to overcome their permeance‐selectivity trade‐off. Mixed matrix membranes (MMMs) combine the benefits of fillers within a polymeric matrix to increase the CO2 perm‐selectivity. More specifically, the coupling of metal‐organic frameworks (MOFs) with high CO2 sorption capacity and CO2‐selective plasticizers, such as ionic liquids (ILs), has the potential to further improve the mechanical stability of membranes and their performance concerning CO2 transport. In this work, Pebax1657‐based membranes combining the MOF ZIF‐8 and 1‐ethyl‐3‐methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][Tf2N]) IL have been optimized in terms of materials loading in a self‐standing framework. Then, their transition to a composite material using the spray‐coating technique has been addressed with a simple double‐step protocol, avoiding the need of an intermediate gutter layer. Composite membranes, as thin‐film composite (TFC) membranes, have the appeal of increasing the membrane permeance while maintaining the selectivity of self‐standing membranes. Here, it is described the capacity of the spray‐coating technique to convert advanced MMMs into TFC‐MMMs to further evaluate them in CO2 separation processes.