Two-Dimensional Infrared Correlation Spectroscopy and Principal Component Analysis on the Carbonation of Sterically Hindered Alkanolamines

Despite the academic and industrial importance of the chemical reaction between carbon dioxide (CO2) and alkanolamine, the delicate and precise monitoring of the reaction dynamics by conventional one‐dimensional (1D) spectroscopy is still challenging, due to the overlapped bands and the restricted static information. Herein, we report two‐dimensional infrared correlation spectroscopy (2D IR COS) and principal component analysis (PCA) on the reaction dynamics of a sterically hindered amine, 2‐[(1,1‐dimethylethyl)amino]ethanol (TBAE) and CO2. The formation of carbonate rather than carbamate species, which contribute to the unusual high working capacity of ∼1 mole CO2 per mole of TBAE at 40 °C, occurs through deprotonation of the hydroxyl group, protonation on the nitrogen atom of the amino group, and formation of a carbonate species due to the steric hindrance of the tert‐butyl group. In particular, PCA captures the chemical transition into a carbonate species and the main contributions of ${\nu _{{\rm{CO}}_2 } }$, ${\nu _{{\rm{OH}}} }$, ${\nu _{{\rm{C - N}}} }$, and ${\nu _{{\rm{C}} = {\rm{O}}} }$ bands to the carbonation, while 2D IR COS verifies the interrelation of four bands and their changes. Therefore, these results provide a powerful analytic method to understand the complex and abnormal reaction dynamics as well as the rational design strategy for the CO2 absorbents. Monitoring CO2 absorption: Two‐dimensional infrared spectroscopy (2D IR COS) and principal component analysis (PCA) monitor the carbonation of a sterically hindered alkanolamine, 2‐[(1,1‐dimethylethyl)amino]ethanol, which contributes to the unusual high working capacity of ∼1 mole CO2 per mole of amine (see picture).