Steering Amine-CO₂ Chemistry: A Molecular Insight into the Amino Site Relationship of Carbamate and Protonated Amine

The chemical absorption of carbon dioxide (CO₂) using amine solvents is set to be a prominent technology for large-scale point source carbon capture, yet its development encounters significant challenges, such as the inherent instability of carbamate intermediates that are crucial to the CO₂ capture process. Traditionally, amine solvent development has been focusing on stringent process controls and optimizing the structure of amino sites that form carbamates. Our study introduces an innovative concept of intersite stability, which enhances the relative structural arrangement and positioning between amino sites, specifically between carbamate and its counter-protonated amine. Our approach not only stabilizes the carbamate itself but also leverages synergistic effects to improve overall system performance under higher CO₂ loadings. We demonstrate that strategic increases in structural differences between amino sites can significantly augment stability, effectively mitigating the traditional pathways of carbamate decomposition to bicarbonate, especially under high-temperature CO₂ loading conditions. We optimize the amine system's resilience against decomposition by designating specific roles for amino sites, increasing protonation and carbamate stabilization, and strategically modifying their structural relationships, both within and between molecules. Our detailed analysis and validation of this concept includes the study of structural positioning in blends of cyclic amines, multialkylamines, and alkanolamines, which are candidates for commercialization. These modifications made to traditional amine systems, which usually form less stable carbamates, follow the logic of our intersite stability framework, showcasing enhanced stability even in aqueous environments. This study paves the way for more reliable and efficient CO₂ capture technologies by fundamentally rethinking the dynamics within the amino sites of these amine-based solvents.