Selection of a suitable ZIF-8/ionic liquid (IL) based composite for selective CO2 capture: the role of anions at the interface. Issue 64 (26th October 2020)

• Record Type: Journal Article
• Authors: Thomas, Anoopa; Ahamed, Rafiq; Prakash, Muthuramalingam
• Is Part Of: RSC advances. Volume 10:Issue 64(2020)
• Page Start: 39160
• Page End: 39170
• Publication Date: 2020-10-26
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0ra07927h
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : The interfacial stability of hydrophilic/hydrophobic IL incorporated ZIF-8 is identified and the CO2 selectivity depends on the fluorinated anions in the IL. Abstract : The effective capture of CO2 from the atmosphere is much needed to reduce its environmental impact. The design and development of CO2 capturing materials is getting much attention. A zeolitic imidazolate framework (ZIF) can replace many of the conventional materials in gas separation due to its stability and high performance. Here, we analyzed the effect of encapsulation of ionic liquids (ILs) into the pores of ZIF-8 for selective CO2 capture and separation. The [BMIM] + cation with a series of anions was selected to study suitable carbon capture materials using density functional theory (DFT) approaches. Our calculations suggest that the nitrogen containing anions are not well adsorbed on the ZIF-8 surface but their gas separation performance is not affected by these interfacial interactions. This is confirmed from the CO2 /N2 and CO2 /CH4 selectivity of these composites, calculated using grand canonical Monte Carlo (GCMC) simulations. A suitable force field for the composites was identified by comparing the available force fields with the experiments. The IL@ZIF-8 composite shows better CO2 selectivity compared to pristine ZIF-8. Fluorinated hydrophobic anions (such as [BF4 ] −, [PF6 ] − and [Tf2 N] − ) in the composites show better CO2 adsorption and significant CO2 selectivity than pristine ZIF-8, especially at low pressure. The nature of the anion plays an important role in CO2 separation, rather than its stability at the pores of ZIF-8. Close scrutiny of the results reveal that the CO2 selectivity of these composite materials depends on the anion of the IL and thus through the selection of a suitable anion we can significantly enhance the CO2 selectivity for different flue gas mixtures. Our molecular level design shows that the selection of suitable anions in IL based composites is very important in identifying potential carbon capture materials for industrial applications.