Processing of poly(ionic liquid)–ionic liquid membranes using femtosecond (fs) laser radiation: Effect on CO₂ separation performance

Femtosecond (fs) laser micromachining on polymeric materials is a single-step, and contactless manufacturing technology. Knowing the potential of poly(ionic liquid)s (PILs) and their derived composite materials incorporating ionic liquids (PIL–IL) to design membranes with improved CO₂ separation, we here explore for the first time the creation of microchannels on the surface of PIL–IL materials by laser ablation using femtosecond laser radiation. PIL–IL membranes composed of pyrrolidinium-based PILs containing the [NTf₂]^– and [C(CN)₃]^– anions and different amounts of their corresponding ILs (40 and 60 wt%) were prepared and micromachined using fs laser pulses varying the pulse repetition rate, scanning speed, and pulse energy. The morphology of the fs laser modified PIL–IL samples was investigated through scanning electron microscopy (SEM), while the influence of the fs laser processing on the membranes structure was analyzed by solid-state nuclear magnetic resonance (ssNMR), Fourier-transform infrared (FT-IR) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The CO₂/N₂ and CO₂/H₂ separation performances of the irradiated membranes were also evaluated and compared to those of the non-irradiated. Depending on the parameters used, fs laser processing was successful in modifying the surface of PIL–IL membranes through the formation of microchannels around 55–60 μm deep. Significant improvements in CO₂, N₂ and H₂ permeabilities were achieved for the irradiated PIL–IL membranes, maintaining their CO₂/N₂ and CO₂/H₂ permselectivities.