Scientific Achievement
Energy-efficient CO2 capture from flue gas is demonstrated via crystallization of structurally unique bicarbonate-water clusters with an aqueous guanidine sorbent.
Significance and Impact
Limiting global temperature rises relies on the development of energy-efficient carbon-capture methods. This novel CO2-separation cycle requires 24% less energy than industrial benchmarks based on aqueous amines.
Research Details
X-ray structural analysis revealed the formation of (HCO3–)2 dimers in the crystals, linked by water molecules into ladder-shaped clusters.
Experimental and computational investigations support a CO2-release mechanism consisting of proton transfer from guanidinium groups to bicarbonate anions with the formation of carbonic acid dimers, followed by low-energy CO2 and H2O release in the rate-limiting step.
The minimum energy required for sorbent regeneration is 151.5 kJ/mol CO2, which is 24% lower than the regeneration energy of monoethanolamine, a benchmark industrial sorbent.