Direct air capture (DAC) and sequestration of CO₂: Dramatic effect of coordinated Cu(II) onto a chelating weak base ion exchanger.

Abstract

Direct air capture (DAC) is important for achieving net-zero greenhouse gas emissions by 2050. However, the ultradilute atmospheric CO₂ concentration (~400 parts per million) poses a formidable hurdle for high CO₂ capture capacities using sorption-desorption processes. Here, we present a Lewis acid-base interaction-derived hybrid sorbent with polyamine-Cu(II) complex enabling over 5.0 mol of CO₂ capture/kg sorbent, nearly two to three times greater capacity than most of the DAC sorbents reported to date. The hybrid sorbent, such as other amine-based sorbents, is amenable to thermal desorption at less than 90°C. In addition, seawater was validated as a viable regenerant, and the desorbed CO₂ is simultaneously sequestered as innocuous, chemically stable alkalinity (NaHCO₃). The dual-mode regeneration offers unique flexibility and facilitates using oceans as decarbonizing sinks to widen DAC application opportunities.