Carbon dioxide (CO₂) capture has become of great importance for industrial processes due to the adverse environmental effects of gas emissions. Mixed matrix membranes (MMMs) have been studied as an alternative to traditional technologies, especially due to their potential to overcome the practical limitations of conventional polymeric and inorganic membranes. In this work, the effect of using different ionic liquids (ILs) with the stable metal–organic framework (MOF) ZIF-8 was evaluated. Several IL@ZIF-8 composites and IL@ZIF-8 MMMs were prepared to improve the selective CO₂ sorption and permeation over other gases such as methane (CH₄) and nitrogen (N₂). Different ILs and two distinct loadings were prepared to study not only the effect of IL concentration, but also the impact of the IL structure and affinity towards a specific gas mixture separation. Single gas sorption studies showed an improvement in CO₂/CH₄ and CO₂/N₂ selectivities, compared with the ones for the pristine ZIF-8, increasing with IL loading. In addition, the prepared IL@ZIF-8 MMMs showed improved CO₂ selective behavior and mechanical strength with respect to ZIF-8 MMMs, with a strong dependence on the intrinsic IL CO₂ selectivity. Therefore, the selection of high affinity ILs can lead to the improvement of CO₂ selective separation for IL@ZIF-8 MMMs.

Composite sorbent materials (IL@MOF) with a metal-organic framework (MOF) ZIF-8 and [B(CN)₄]⁻-based ionic liquids (ILs) were produced for the first time. Characterization results indicate the successful IL impregnation and conservation of the ZIF-8 crystalline structure and morphology. The data collected from the nitrogen (N₂) physisorption at 77 K suggest that these IL@ZIF-8 materials are nonporous as their textural properties, such as BET specific surface area and total pore volume, are negligible. However, CO₂, CH_4, and N₂ adsorption/desorption measurements in the IL@ZIF-8 composites at 303 and 273 K contradict the N₂ data at 77 K, given that the obtained isotherms are Type I, typical of (micro)porous materials. Their gas adsorption capacity and ultramicroporous volume are in the same order of magnitude as the pristine microporous ZIF-8. The case study [C₆MIM][B(CN)₄] IL revealed a high affinity to both CO₂ and CH₄. This compromised the selectivity performance of its respective composite when compared with pristine ZIF-8. This work highlights the importance of accurate experimental gas adsorption/desorption equilibrium measurements to characterize the adsorption uptake and the porous nature of adsorbent materials.

Adsorption therapies in hemodialysis have emerged as an innovative approach for removing protein-bound uremic toxins (PBUTs). The present work focused on the enhancement of the adsorption capacity of hemodialysis membranes through the incorporation of Metal-Organic Frameworks (MOFs).The removal capacity of PBUT p-cresyl sulfate (pCS) by cellulose acetate (CA)/silica (SiO2)/MOF mixed matrix membranes was investigated with two types of MOFs, UiO-66 and UiO-66-NH2. The MOFs were synthesized and characterized by infrared spectroscopy, X-ray diffraction, nitrogen adsorption-desorption equilibrium at -196 °C, and thermogravimetry analysis. The mixed matrix membranes were synthesized by coupling the phase inversion technique with the sol-gel method and with casting solutions incorporating the MOF dispersions. They were characterized in terms of hydraulic permeability, molecular weight cut-off, and rejection coefficients to pCS and bovine serum albumin (BSA).The mixed matrix membranes CA/SiO2/UiO-66-NH2 exhibited lower permeability and molecular weight cut-off when compared to the CA/SiO2/UiO-66 ones. In permeation tests simulating a hemodialysis session with a feed solution of 100 ppm pCS and 35 g/L BSA, the membranes without MOF showed a pCS rejection coefficients of 24.8-30.4%. The incorporation of MOFs significantly improved performance, with rejection coefficients to pCS of 0.2% for the CA22/SiO2/UiO-66 membrane with 1.5% of MOF and 2.6% for the CA22/SiO2/UiO-66-NH2 membrane with 2% of MOF.Upon quantification of the pCS free and bound to BSA it is concluded that the removal capacity of pCS bound to BSA is 99.8% for the CA22/SiO2/UiO-66 membrane with 1.5% of MOF and 95.9% for the CA22/SiO2/UiO-66-NH2 membrane with 2% of MOF. Based on these results, the mixed matrix membranes CA22/SiO2/UiO-66 and CA22/SiO2/UiO-66-NH2 are promising candidates for PBUTs removal in hemodialysis.