Selective lanthanide-based receptors for direct ocean capture of bicarbonate

Presenter(s)

Tristen Garner, Alexander Sunne, Logan Olson

Abstract or Description

Rising concentrations of carbon dioxide (CO₂) in the atmosphere leads to an overabundance of aqueous bicarbonate (HCO₃^-) and acidic protons, a process better known as ocean acidification. In an effort to mitigate this, an efficient direct ocean capture (DOC) recycling scheme that sequesters HCO₃^- is being explored. This system relies on pH-mediated receptors that utilize rare-earth metals, like lanthanides, to selectively capture and transform HCO₃^-. Structural parameters including receptor size, geometry, electronic properties, and aqueous pH were assessed to examine their influence on HCO₃^- binding affinity and selectivity. Addition of a benzyl group to the receptor increased its affinity for HCO₃^- (K_a = 2.8×10⁴) when compared to its unbenzylated counterpart (K_a = 4.1×10³). Further modulation of the benzyl substituent had no change on affinity (K_a = 2.9×10⁴), signifying that spatial constraints at the binding site play a more important role in anion binding. The affinity of the complex for anions with varying basicity was also explored, displaying a slight correlation between anion pK_a and binding affinity with the receptor. This work provides fundamental insights toward the design of receptors and membrane-based materials that fulfill the requirements for direct ocean capture of HCO₃^- against its concentration gradient. Future applications include the development of systems capable capturing and separating HCO₃^- that counter the effects of rising atmospheric CO₂ levels and climate change. 

Mentor

Katie Peterson