Enhancing CO2 Transport Across a PEEK‐Ionene Membrane and Water‐Lean Solvent Interface

• Published in: ChemSusChem 2023-07, Vol.16 (13), p.e202300157-n/a
• Main Authors: Walter, Eric D., Zhang, Difan, Chen, Ying, Sung Han, Kee, Bazak, J. David, Burton, Sarah, O'Harra, Kathryn, Hoyt, David W., Bara, Jason E., Malhotra, Deepika, Allec, Sarah I., Glezakou, Vassiliki‐Alexandra, Heldebrant, David J., Rousseau, Roger
• Format: Article
• Language: English
• Subjects: absorption; Carbon; Carbon dioxide; carbon dioxide capture; Carbon sequestration; Diffusion rate; Ionenes; Membranes; NMR; NMR spectroscopy; Nuclear magnetic resonance; Polyether ether ketones; Solvents; Speciation; water-lean solvent
• ISSN: 1864-5631; 1864-564X
• DOI: 10.1002/cssc.202300157

Efficient direct air capture (DAC) of CO2 will require strategies to deal with the relatively low concentration in the atmosphere. One such strategy is to employ the combination of a CO2‐selective membrane coupled with a CO2 capture solvent acting as a draw solution. Here, the interactions between a leading water‐lean carbon‐capture solvent, a polyether ether ketone (PEEK)‐ionene membrane, CO2, and combinations were probed using advanced NMR techniques coupled with advanced simulations. We identify the speciation and dynamics of the solvent, membrane, and CO2, presenting spectroscopic evidence of CO2 diffusion through benzylic regions within the PEEK‐ionene membrane, not spaces in the ionic lattice as expected. Our results demonstrate that water‐lean capture solvents provide a thermodynamic and kinetic funnel to draw CO2 from the air through the membrane and into the bulk solvent, thus enhancing the performance of the membrane. The reaction between the carbon‐capture solvent and CO2 produces carbamic acid, disrupting interactions between the imidazolium (Im+) cations and the bistriflimide anions within the PEEK‐ionene membrane, thereby creating structural changes through which CO2 can diffuse more readily. Consequently, this restructuring results in CO2 diffusion at the interface that is faster than CO2 diffusion in the bulk carbon‐capture solvent. Favorable conditions! For selective membranes to perform when in contact with a carbon capture solvent, their chemical and physical interactions need to be studied. The interactions between a water‐lean solvent and polyether ether ketone (PEEK) ionene membrane show that not only are these materials compatible, but that the CO2 bound solvent increases diffusion in the membrane.