Computation of Polyimine Membrane as an Alternative Absorbent for Enhanced CO2 Direct Air Capture

Direct Air Capture (DAC) of CO2 using solid-supported amines offers a promising strategy to address the escalating atmospheric carbon levels. While poly(ethylenimine) (PEI) has attracted significant attention due to its remarkable CO2 adsorption efficiency and stability, our study redirects the focus to poly(propylenimine) (PPI) and its hyperbranched form as potential alternative absorbents. Together with the PEI study, we primarily examine the distribution and transport behavior of CO2 molecules within these polymer systems under varying hydration conditions. Our results indicate that the pair correlations between CO2 and both primary and secondary amines in polyimines are reduced under hydrated conditions, suggesting a diminished role of the carbamate formation mechanism compared to the dry conditions. The diffusion behavior of CO2 is more restricted in PPI, as evidenced by its longer carbon backbone when juxtaposed with PEI simulation outcomes. We further explore the complexities of CO2 transport within these polymer systems when combined with rigid supporting material (MCM-41). For this study, we optimized new force field parameters using first-principle calculations. By elucidating local structures and molecular diffusion processes, particularly in contexts with different water content levels, we expand the understanding of CO2 capture mechanisms in amine-supported materials. Our findings not only bolster the existing knowledge base but also chart a course for discovering innovative materials and enhancing current DAC technologies.