Negative emission technologies, including direct air capture (DAC) of carbon dioxide, are now considered essential for mitigating climate change, but existing DAC processes tend to have excessively high energy requirements, mostly associated with sorbent regeneration. Here we demonstrate a new approach to DAC that combines atmospheric CO<sub>2</sub> absorption by an aqueous oligopeptide (i.e., glycylglycine) with bicarbonate crystallization by a simple guanidine compound (i.e., glyoxal-bis-iminoguanidine). In this phase-changing system, the peptide and the guanidine compounds work in synergy, and the cyclic CO<sub>2</sub> capacity can be maximized by matching the p<i>K</i><sub>a</sub> values of the two components. The resulting DAC process has a significantly lower regeneration energy compared to state-of-the-art solvent-based DAC technologies.
Negative Emission Potential of Direct Air Capture Powered by Renewable Excess Electricity in Europe
