Photo: PMRC Postdoctoral Fellow Ah-Young Song carefully introduces 13CO2 to the sample to investigate the reaction mechanisms of CO2 adsorption within an amine-modified sorbent using solid-state NMR.
A study led by PMRC Postdoctoral Fellow Ah-Young Song has provided a detailed molecular-level understanding of how water influences carbon dioxide adsorption in a materials considered for direct air capture (DAC) technologies. Using an amine-functionalized benchmark capture material, the H2O-CO2 co-adsorption chemical mechanism was explored to inform the optimization of DAC processes and sorbent material design. Water "outnumbers" CO2 in direct air capture by about 50-to-1 and thus plays a pivotal role in adsorbent-based DAC. Here water not only competes with CO2 for adsorption sites but also induces swelling in the adsorbent material presenting a time-varying reaction medium. Dr. Song's study revealed that water facilitates the opening of pores in the adsorbent, making more adsorption sites available up to a specific relative humidity (RH), thereby enhancing CO2 capture capacity. At high humidities, however, Dr. Song showed that water condenses on the polymer surface and decreases adsorption capacity. Notably, water does not chemically interact with CO2 when both are adsorbed within the adsorbent.
This research was led by the Reimer Lab at the College of Chemistry, utilizing advanced nuclear magnetic resonance spectroscopy techniques. Solid-state NMR applications at the PMRC Core Facility were used to investigate how varying levels of relative humidity influence the binding of CO2 molecules and H2O molecules, as well as swelling induced by H2O. The results were published in the Journal of Materials Chemistry A.