Blue amine hydrates as a novel strategy for partitioning CO2

We report a novel CO2 capture and separation principle based on the unexpected formation of CO2-loaded amine hydrates. Unlike conventional amine scrubbing, which relies on energy-intensive thermal regeneration, our approach utilizes a phase change driven by cooling. We discovered that various bifunctional amines, upon capturing CO2 in aqueous solutions containing tetrahydrofuran (THF), are structurally incorporated into the hydrate crystal lattice. This phenomenon was unequivocally confirmed via solid-state NMR and FTIR spectroscopy, with some hydrates exhibiting a distinct blue coloration. This phase separation facilitates partial dehydration and the partitioning of CO2-loaded amines into the solid phase, effectively reducing the working solution’s heat capacity. Scalability was successfully demonstrated in a 150-mL system under ambient pressure. These findings establish a new regime in amine-CO2-water chemistry, offering a “cooling-based” fractionation strategy to significantly lower the energy penalty of carbon capture processes.