Enhancing CO 2 Transport Across a PEEK-Ionene Membrane and Water-Lean Solvent Interface

Efficient direct air capture (DAC) of CO will require strategies to deal with the relatively low concentration in the atmosphere. One such strategy is to employ the combination of a CO -selective membrane coupled with a CO 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, CO , and combinations were probed using advanced NMR techniques coupled with advanced simulations. We identify the speciation and dynamics of the solvent, membrane, and CO , presenting spectroscopic evidence of CO 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 CO 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 CO 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 CO can diffuse more readily. Consequently, this restructuring results in CO diffusion at the interface that is faster than CO diffusion in the bulk carbon-capture solvent.