Advances in membrane technologies that combine greatly improved carbon dioxide (CO ₂ ) separation efficacy with low costs, facile fabrication, feasible upscaling, and mechanical robustness are needed to help mitigate global climate change. We introduce a hybrid-integrated membrane strategy wherein a high-permeability thin film is chemically functionalized with a patchy CO ₂ -philic grafted chain surface layer. A high-solubility mechanism enriches the concentration of CO ₂ in the surface layer hydrated by water vapor naturally present in target gas streams, followed by fast CO ₂ transport through a highly permeable (but low-selectivity) polymer substrate. Analytical methods confirm the existence of an amine surface layer. Integrated multilayer membranes prepared in this way are not diffusion limited and retain much of their high CO ₂ permeability, and their CO ₂ selectivity is concurrently increased in some cases by more than ~150-fold.

The mixture of the ionic liquid 1-ethyl-3-methylimidazolium acetate (EmimAc) and dimethylsulfoxide (DMSO) was employed to dissolve microcrystalline cellulose (MCC). A 10 wt % cellulose dope solution was prepared for spinning cellulose hollow fibers (CHFs) under a mild temperature of 50 °C by a dry–wet spinning method. The defect-free CHFs were obtained with an average diameter and thickness of 270 and 38 µm, respectively. Both the XRD and FTIR characterization confirmed that a crystalline structure transition from cellulose I (MCC) to cellulose II (regenerated CHFs) occurred during the cellulose dissolution in ionic liquids and spinning processes. The thermogravimetric analysis (TGA) indicated that regenerated CHFs presented a similar pyrolysis behavior with deacetylated cellulose acetate during pyrolysis process. This study provided a suitable way to directly fabricate hollow fiber carbon membranes using cellulose hollow fiber precursors spun from cellulose/(EmimAc + DMSO)/H₂O ternary system.

The capture of CO ₂ is of high interest in our society representing an essential tool to mitigate man-made climate warming. Membrane technology applied for CO ₂ capture offers several advantages in terms of energy savings, simple operation, and easy scale-up. Glassy membranes are associated with low gas permeability that negatively affect on their industrial implementation. Oppositely, rubbery membranes offer high permeability, but their selectivity is low. Here we report rubbery organic frameworks (ROFs) combining the high permeability of soft matrices with the high sieving selectivity of molecular frameworks. The best performing membranes provide a CO ₂ /N ₂ selectivity up to 104 with a CO ₂ permeability up to 1000 Barrer, representing relevant performances for industrial implementation. Water vapors have a positive effect on CO ₂ permeability, and the CO ₂ /N ₂ selectivity is higher than in dry conditions, as most of CO ₂ gas emissions are present in fully humidified gas streams. The synergetic high permeability/selectivity performances are superior to that observed with current state-of-the-art polymeric membranes.

A poly(ionic-liquid) (PIL) matrix can be altered by incorporating additives that will disrupt the polymer chain packing, such as an ionic liquid (IL) and inorganic salts to boost their exploitation as materials for membrane production to be used in CO₂ capture. Herein, potential of PIL/IL/salt blends is investigated on the example of poly(diallyldimethyl ammonium) bis(trifluoromethylsulfonyl)imide (P[DADMA][Tf₂N]) with N-butyl-N-methyl pyrrolidinium bis(trifluoromethylsulfonyl)imide ([Pyrr₁₄][Tf₂N]) and zinc di-bis(trifluoromethylsulfonyl)imide (Zn[Tf₂N]₂). Composite material with IL and a higher amount of Zn²⁺ showed an increase in the equilibrium CO₂ sorption capacity to 2.77 cm³ (STP)cm ⁻³ bar⁻¹. Prepared blends were successfully processed into thick, dense membranes and thin-film composite membranes. Their CO₂ separation efficiency was determined using ideal and mixed-gas feed (vol% CO₂ $=50$ , dry and with 90% relative humidity). The dominant role of solubility in the transport mechanism is confirmed by combining direct gravimetric sorption measurements and indirect estimations from time-lag experiments. The maximum incorporated amount of Zn²⁺ salts increased equilibrium solubility selectivity by at least 50% in comparison to the parent PIL. All materials showed increased CO₂ permeance values by at least 30% in dry conditions, and 60% in humidified conditions when compared to the parent PIL; the performance of pure PIL remained unchanged upon addition of water vapor to the feed stream. Mixed-gas selectivities for all materials rose by 10% in humidified conditions when compared to dry feed experiments. Our results confirm that the addition of IL improves the performance of PIL-based composites due to lower stiffness of the membrane matrix. The addition of Zn²⁺-based salt had a marginal effect on CO₂ separation efficiency, suggesting that the cation participates in the facilitated transport of CO₂.