Cationic effect study in acetate-based ionic liquids/ZIF-8 composites for CO2 sorption

• Published in: Sustainable Materials and Technologies Vol. 42; p. e01122
• Main Authors: Ferreira, Tiago J., Cabral, Catarina, Carvalho, Thiago O., Pais, Joana, Esteves, Laura M., Silva, Ludmila P.C., Reis, Patrícia M., Esperança, José M.S.S., Esteves, Isabel A.A.C.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2024
• Subjects: Cationic effect; CO2 post-combustion separation; IL@MOF composites; Ionic liquid (IL); Metal-organic framework (MOF); Cationic effect; CO2 post-combustion separation; Ionic liquid (IL); Metal-organic framework (MOF); IL@MOF composites
• ISSN: 2214-9937
• DOI: 10.1016/j.susmat.2024.e01122

Several strategies can be considered for the mitigation of carbon dioxide (CO2) emissions to the atmosphere, and among them is its post-combustion capture/separation from flue gas emitted from coal-fired power plants. In this work, six imidazolium, ammonium- and DABCO-based ionic liquids (ILs) containing the acetate anion were used to impregnate the metal-organic framework (MOF) ZIF-8. The cationic effect was studied to determine how the different cationic families and side alkyl chain size influence the gas sorption performance of the produced IL@MOF composites. The combination of different characterization techniques confirmed IL impregnation, and that the composite materials were microporous and crystalline. Single-component CO2 and nitrogen (N2) sorption-desorption equilibrium measurements were performed at 303 K for ZIF-8 and the IL@ZIF-8 materials. At the low-pressure regime (0–1 bar), synergy was observed for the imidazolium-based composites, especially for the one with the long-side alkyl chain. The ideal CO2/N2 selectivity was calculated for post-combustion composition, and, at 1 bar, [C10MIM][Ac]@ZIF-8 was over four times more selective than ZIF-8, while the selectivity of [C2MIM][Ac]@ZIF-8 at this pressure almost tripled when compared to the MOF. A chemical reaction between CO2 and the imidazolium ILs explained the results. [Display omitted] •Acetate-based ILs with different cations were used to produce IL@ZIF-8 materials.•Imidazolium-based composites showed the highest CO2 sorption between 0 and 1 bar.•Cation nature and side alkyl chains size can tune the selectivity at low pressures.•[C10MIM][Ac]@ZIF-8 was over four-times more selective than pristine ZIF-8 at 1 bar.