Publications

Rimsza, Jessica R.; Nenoff, T.M.; Christian, Matthew S.; Hurlock, Matthew H.

Direct air capture (DAC) of CO₂ is one of the negative emission technologies under development to limit the impacts of climate change. The dilute concentration of CO₂ in the atmosphere (~400 ppm) requires new materials for carbon capture with increased CO₂ selectivity that is not met with current materials. Porous liquids (PLs) are an emerging material that consist of a combination of solvents and porous hosts creating a liquid with permanent porosity. PLs have demonstrated excellent CO₂ selectivity, but the features that control how and why PLs selectively capture CO₂ is unknown. To elucidate these mechanisms, density functional theory (DFT) simulations were used to investigate two different PLs. The first is a ZIF-8 porous host in a water/glycol/2-methylimidazole solvent. The second is the CC13 porous organic cage with multiple bulky solvents. DFT simulations identified that in both systems, CO₂ preferentially bound in the pore window rather than in the internal pore space, identifying that the solvent-porous host interface controls the CO₂ selectivity. Additionally, SNL synthesized ZIF-8 based PL compositions. Evaluation of the long-term stability of the PL identified no change in the ZIF-8 crystallinity after multiple agitation cycles, identifying its potential for use in carbon capture systems. Through this project, SNL has developed a fundamental understanding of solvent-host interactions, as well as how and where CO₂ binds in PLs. Through these results, future efforts will focus not on how CO₂ behaves inside the pore, but on the porous host-solvent interface as the driving force for PL stability and CO₂ selectivity.