Computational Study of Carbon Dioxide Capture by Tertiary Amines

The reaction mechanisms and corresponding structure-activity relationships of tertiary amines with respect to CO₂ capture have been investigated using density functional theory (DFT) calculations. The reaction mechanism for CO₂ capture via base-catalyzed hydration to form bicarbonate is proposed to proceed in a single step involving proton transfer and the formation of a carbon-oxygen bond. Based on the height of the reaction barriers, we suggest that amines containing side chains with the ethyl group, along with a single hydroxyl group, and cyclic structures, are especially active for CO₂ capture. The activation barrier is shown to be a descriptor for predicting the experimental CO₂ loading values. To enhance the prediction accuracy for CO₂ loading, we employ the sure-independence screening and sparsifying operator (SISSO) method, which can scan a large pool of mathematical terms stemming from combining DFT-derived descriptors to select the superior ones. Thus, we can predict the CO₂ loading with acceptable accuracy from the obtained mathematical expression. Since the computational workload of applying this expression is negligible, this facilitates high-throughput screening and accelerates the design of tertiary amines for CO₂ capture.