Selective Bicarbonate Receptors for Direct Ocean Capture of CO₂

Area of Science:

• Inorganic Chemistry
• Supramolecular Chemistry
• Environmental Science

Background:

• Ocean surface water is alkaline (pH ≈ 8), with carbon dioxide primarily present as bicarbonate (HCO3-) at 2.4 mM.
• High concentrations of competing anions like chloride and sulfate challenge selective bicarbonate capture.
• Developing efficient direct ocean capture (DOC) technologies requires supramolecular receptors with high affinity and selectivity for bicarbonate.

Purpose of the Study:

• To report the first lanthanide-based supramolecular receptors for bicarbonate.
• To achieve high selectivity and affinity for bicarbonate under oceanic conditions for DOC applications.
• To understand the mechanism of selective bicarbonate recognition and release.

Main Methods:

• Design and synthesis of lanthanide-based supramolecular receptors.
• Investigation of receptor binding affinity and selectivity using various anions.
• Elucidation of the coordination mechanism through structural and spectroscopic studies.
• Demonstration of receptor recycling and pure carbon dioxide recovery.

Main Results:

• The first lanthanide-based receptors exhibiting high selectivity and affinity for bicarbonate were developed.
• Receptor performance matches the requirements for direct ocean capture (DOC) technologies.
• Ligand design predisposes the lanthanide complex for bidentate bicarbonate coordination, ensuring high selectivity.
• The receptor facilitates efficient release of bicarbonate, enabling receptor recycling and pure CO2 recovery.

Conclusions:

• Lanthanide-based supramolecular receptors offer a promising avenue for energy-efficient direct ocean capture of carbon dioxide.
• The developed receptors demonstrate the potential for selective bicarbonate recognition and release under relevant environmental conditions.
• This work paves the way for novel technologies addressing carbon dioxide mitigation through ocean-based capture.