Molecular Perspective Reveal Enhanced CO 2 Transport in Modified Polymer and Mixed Matrix Membranes

ABSTRACT Microscopic properties are crucial determinants of macroscopic performance in gas separation processes. Molecular simulation technology, which allows for the precise calculation of microscopic properties, holds significant value in advancing the understanding of separation mechanisms. In previous research, our group developed polyimide membranes (PI), 1‐aminoethyl‐3‐butylimidazolium hexafluorophosphate‐grafted polyimide membranes (IL‐GPI), and mixed matrix membranes containing graphene oxide (IL‐GPI/GO) for CO 2 separation, achieving favorable macroscopic separation results. However, a detailed understanding of the microscopic mechanisms remained limited. This study investigates the microscopic properties of these three types of membranes, offering insights into their gas transport mechanisms at the molecular level. Key microscopic properties, including free volume fraction and radial distribution functions, were calculated to explain variations in diffusion coefficient and solubility coefficient, thereby bridging microscopic phenomena with macroscopic observations. The results demonstrate that for polymer membranes, the free volume and pore size are critical factors influencing separation performance. Enhancing gas separation can be achieved by increasing the spacing between polymer chains and modifying the pore structure. Incorporating fillers to increase adsorption sites can lower the energy required for gas absorption, thereby enhancing membrane permeability. These findings contribute valuable guidance for experimental researchers aiming to optimize membrane performance and improve gas separation efficiency.