Poly(ionic liquid)–Ionic Liquid Membranes with Fluorosulfonyl-Derived Anions: Characterization and Biohydrogen Separation

Abstract

Clean and sustainable energy production has become a key global issue concerning the world's energy shortage and environmental problems. Despite the recognized potential of biohydrogen (bioH2) for sustainable development, there are still issues regarding its production and purification, such as the elimination of CO2, N2, and other impurities (H2O and H2S), so that an enriched H2 stream can be obtained for efficient energy generation. The use of poly(ionic liquid)s (PILs) and their derived composite materials incorporating ionic liquids (PIL–IL) has been considered a highly promising strategy to design membranes with improved CO2 separation. In this study, membranes of pyrrolidinium-based PILs containing symmetric or asymmetric fluorosulfonyl-derived anions, namely, bis(fluorosulfonyl)amide ([FSI]−), (trifluoromethyl)sulfonyl-N-cyanoamide ([TFSAM]−), and (trifluoromethyl)sulfonyl-N-trifluoroacetamide ([TSAC]−), were prepared by the incorporation of different amounts of structurally similar ILs. The PIL–IL membranes were characterized by different techniques (thermogravimetric analysis, differential scanning calorimetry, Fourier-transform infrared, and Raman), and their CO2/H2 and H2/N2 separation performances were investigated. Higher CO2/H2 selectivities were obtained for PIL FSI–40 [C2mim][FSI] (αCO2/H2 = 9.0) and PIL TFSAM–40 [C2mim][TFSAM] (αCO2/H2 = 7.1) compared to those of PIL–IL membranes containing the conventional [TFSI]− anion at similar or even higher amounts of IL incorporation.