Abstract
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, CH4, 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.
Highlights
Developing new sorbent materials for carbon dioxide (CO2 ) capture/separation is vital for responding to global warming and its impacts [1,2]
Characterization techniques of the case study [C6 MIM][B(CN)4 ]@zeolitic frameworks (ZIFs)-8 composite confirmed the incorporation of the ionic liquids (ILs) into the structure of the metal-organic framework (MOF), and that the impregnation did not significantly alter the crystalline structure and morphology of ZIF-8
Unexpected results regarding the textural properties of this and other [Cn MIM][[B(CN)4 ]@ZIF-8 composites were obtained from N2 adsorption/desorption data at 77 K, which indicated that the materials were nonporous
Summary
Developing new sorbent materials for carbon dioxide (CO2 ) capture/separation is vital for responding to global warming and its impacts [1,2]. The production of MOF-based composite materials for gas adsorption has been proposed [9]. IL@MOF composite materials, has been studied [10]. In these studies, it is frequently assessed the CO2 separation from gaseous mixtures of topical interest that include methane (CH4 ) [11] or nitrogen (N2 ) [12] in their composition. Sorbent material properties like gas sorption capacity and selectivity performance are crucial to understanding the IL impact on the gaseous mixture separation compared to the pristine MOF. The desire is that IL impregnation creates a synergistic effect that improves both the CO2 uptake and selectivity of the composite material [10]
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