(697e) Ultra-Permeable Mixed Matrix Membranes Containing ZIF Nanoparticles for CO2 Capture

Membrane technology is an attractive approach for CO₂ capture from flue gas or syngas derived from coal-fired plants, due to its inherent advantages such as high energy-efficiency, small footprint, and potentially low cost. The state-of-the-art membranes are based on polar poly(ethylene oxide) (PEO), which exhibit high CO₂ permeability and high CO₂/N₂ and CO₂/H₂ selectivity. In this work, these PEO containing materials were doped with zeolitic imidazolate framework (ZIF) nanoparticles to improve CO₂ permeability. Specifically, ZIF-8 with uniform particle sizes of ~100 nm were synthesized and incorporated into polymers prepared from poly(ethylene glycol) diacrylate (PEGDA). Increasing the ZIF-8 loading dramatically increased CO₂ permeability and slightly decreased the CO₂/N₂ selectivity. For example, adding 10 wt% ZIF-8 increased the CO₂ permeability from 130 Barrers in a polymer prepared from PEGDA to 320 Barrers without changing the CO₂/N₂ selectivity. At a loading of 50 wt%, the mixed matrix membranes (MMMs) exhibited a CO₂ permeability of 1300 Barrers and CO₂/N₂ selectivity of 33 at 35 ^oC, which was one of the best separation properties reported in the literature. Furthermore, an open-cocoon-like ZIF with particle sizes of ~500 nm were synthesized and incorporated into the polymer. Adding 10 wt% open-cocoon ZIF nanoparticles in the polymer increased CO₂ permeability to 370 Barrers with a 15% increase in CO₂/H₂ selectivity and a 10% decrease in CO₂/N₂ selectivity. While the CO₂/light gas selectivity in these MMMs can be satisfactorily described using the Lewis-Nielsen model, the model underestimates the gas permeability. Despite a body of studies of MMMs comprising ZIFs, this work represents one of the few on the MMMs based on amorphous rubbery polymers elucidating the effect of ZIF loading on the polymer properties and demonstrating their impact in achieving superior CO₂/H₂ and CO₂/N₂ separation properties.