Analysis of the CO₂ and NH₃ reaction in an aqueous solution by 2D IR COS: Formation of bicarbonate and carbamate

The two-dimensional (2D) infrared correlation spectra obtained from the reaction time- and concentrationdependent IR spectra elucidates the reaction of CO₂ and NH₃ in an aqueous solution for CO₂ absorption. In the synchronous 2D correlation spectra, the interrelation of the proton with carbamate and bicarbonate indicates that the pH level affected the formation reactions of the two products. Furthermore, the interrelation of carbamate with bicarbonate confirmed the conversion of carbamate into bicarbonate with the release of protons (or the decrease of the pH). From the experimental results including the asynchronous 2D correlation spectra, the reaction of the CO₂ and aqueous ammonia proceeded through the following steps: formation of carbamate, formation of bicarbonate, release of protons, and conversion of carbamate into bicarbonate. The analysis of the formation of carbamate and bicarbonate by 2D infrared correlation spectroscopy provides useful information on the reaction mechanism of CO₂ and NH₃ in aqueous solutions.