Carbon Dioxide Capture by Amino Acids through an Arginine-Arginine Carbamate Ion Pair

A novel complex comprising an ion pair of arginine-arginine carbamate is reported herein, which is isolated from an aqueous L-arginine solution after reacting with CO2. Its structure was unambiguously elucidated via single-crystal X-ray diffraction, and its phase purity was confirmed by powder X-ray diffraction (PXRD) analysis. Nuclear magnetic resonance (NMR) studies suggested that the arginine carbamate complex hydrolyzed in aqueous conditions with a rate directly proportional to its concentration. Furthermore, density functional theory (DFT) calculations revealed how the amino group acted as a nucleophile to attack CO2 to enable the ion-pair formation through a proton transfer between the arginine and arginine carbamate. The discovery of the arginine-CO2 adduct expands our understanding of CO2 fixation and can lead to the development of new methods of implementing L-arginine or other amino acids for CO2 capture technology.

Automated summary

This study reports a novel complex consisting of an ion pair of arginine-arginine carbamate, isolated from an aqueous solution after reacting with CO2. The structure was elucidated through X-ray diffraction, and NMR studies revealed the hydrolysis rate of the complex in aqueous conditions. Density functional theory calculations showed how the amino group acted as a nucleophile to attack CO2, leading to the formation of the ion pair. The discovery expands understanding of CO2 fixation and can potentially lead to new methods for CO2 capture using amino acids.