Efficient and cost-effective CO2 capture from air requires new methodologies to overcome the challenges associated with the low concentration of CO2 in the atmosphere. We have posited that a hybrid material that combines the best attributes of two materials common for CO2 capture could enable the design of more efficient carbon capture approaches. Our system is comprised of a CO2-selective membrane and a CO2 capture solvent acting as a draw solution to provide the driving force to pull CO2 through the membrane. While independently, these materials have been studied quite thoroughly, little is known regarding the compatibility between them and more importantly, the speciation and dynamics of CO2 within. Here, we detail a combined experimental and theoretical approach to study the interactions between a prominent water-lean carbon-capture solvent, and a novel polyether ether ketone (PEEK) ionene membrane, CO2, and combinations thereof. Our approach details how advanced nuclear magnetic resonance (NMR) techniques, coupled with advanced atomistic simulations can aid us in the detection and quantification of speciation and dynamics of the solvent, membrane, and CO2. Our first finding indicates that CO2 diffusion in the PEEK ionene membrane does not move through spaces in the ionic lattice as expected, rather CO2 diffuses through benzylic regions within the PEEK ionene membrane, giving us new knowledge in membrane design. A second key finding was the change in dynamics of the system when the water-lean carbon-capture solvent was introduced. The amine-based solvent reacts with CO2 to produce a carbamic acid, which then alters the interactions between the imidazolium (Im+) cations and the bistriflimide anions within the PEEK-ionene membrane. The resulting structural changes within the interface, create regions at the interface through which CO2 can diffuse more readily, where interestingly, CO2 diffusion is faster than in the bulk carbon-capture solvent. We detail how combined experimental and theoretical approaches such as this provide unprecedented level of detail of the molecular interactions allowing us to design the next generation of membranes that selectively could move CO2 at unprecedented rates.

Enhanced transport of CO2 across the interface between a PEEK ionene membrane and a water-lean solvent: An experimental and theoretical study

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