Atomistic Insights into the Reactive Diffusion of CO2 in Guanidine-Based Facilitated Transport Membranes

Abstract

The pressing need to address climate change has led to significant advancements in carbon dioxide (CO₂) capture technologies. Notably, facilitated transport membranes (FTMs) are distinguished by their exceptional selectivity and permeance, attributed to their reversible chemical reactions with CO₂. This study, for the first time, sheds light on the reactive diffusion mechanism of CO₂ in FTMs, utilizing 1,1,3,3-tetramethylguanidine (TMG) as a mobile carrier. Specifically, state-of-the-art molecular dynamics (MD) simulations, augmented by a reparameterized reactive force field (ReaxFF) capable of describing atomistic interactions and reaction pathways, are conducted to investigate the transport of CO₂ in TMG. The analysis of mean squared displacement (MSD) and diffusion coefficients reveals a clear hierarchy in the mobility of reaction components. Our findings highlight a unique hopping diffusion mechanism between bicarbonate ions and TMG molecules, increasing the diffusivity of reacted CO₂ by 1.4 times. The hopping events observed not only enhance our understanding of molecular mobility but also offer a means to boost the performance of FTMs in CO₂ capture applications. Overall, this research lays the groundwork for the future design of FTMs with optimal carrier properties.