Imidazole-Mediated Size-Tunable ZIF(Cu) Particles Enhance the CO2 Separation Performance of Pebax-Based MMMs

Abstract The particle size of ZIFs has a significant effect on the CO2 separation performance of mixed matrix membranes (MMMs). Herein, an imidazole-mediated protonation strategy was developed to regulate the particle size of ZIF(Cu), achieving tunable sizes spanning more than one order of magnitude (37 nm, 400 nm, and 18 μm). Subsequently, Pebax-based MMMs were fabricated, and the relationship between ZIF particle size and interfacial properties, as well as the effects of particle size and residual imidazole on the CO2 separation performance of MMMs, was systematically investigated. The incorporation of ZIF(Cu) establishes efficient CO2 transport pathways within MMMs, enabling the MMMs containing 5 wt % ZIF (400 nm) particles to achieve a CO2 permeability of 170.7 Barrer and a CO2/N2 separation factor of 54.86 under humid conditions, corresponding to 90.27% and 32.75% improvements over Pebax, respectively. This strategy provides a new approach for controlling ZIF particle size and optimizing MMMs performance.