Optimizing gas separation performance in polyimide mixed matrix membranes: Investigating the influence of nanofiller nature

Membrane-based gas separation technology is an efficient, energy-saving, and green separation technology for CO₂ removal. Polyimide (PI) based mixed matrix membranes (MMMs) are developed to overcome the separation performance limitations of conventional PI membranes. However, the design and preparation of high-performance MMMs are still in a trial-and-error stage. In this work, to rationally design high-performance MMMs, both porous and dense nanofillers with tunable particle size are employed to fabricate MMMs and investigate the influence of nanofiller nature on the gas permeation performance of polymer matrix itself and the overall performance of MMMs. Dense PDA@SiO₂ and porous NH₂-UiO-66 nanofillers of similar sizes are incorporated into the PI matrix, respectively, to explore the possible application in carbon capture and helium extraction from natural gas. The effect of particle size for both nanofillers types on the physical properties of polymer matrix is studied and the contribution of nanofillers and polymeric matrix on He/N₂, He/CH₄, CO₂/N₂, and CO₂/CH₄ transport properties are systematically studied. PI/NH₂-UiO-66 MMMs with superior gas separation performance demonstrates promising application prospects in industrial gas separation, such as carbon capture and He extraction.