Aminated ZIF-8 to facilitate CO2 sieving through polyvinyl alcohol/ionic liquid membranes

Abstract

CO₂ separation technology at low pressure is most desirable in carbon capture projects to mitigate global warming. Facilitated transport membranes offer selective and effective CO₂ permeation using a wide range of carbon carriers at low pressure. Porous fillers were recently included as they can carry abundant fixed carriers besides offering open channels for CO₂ permeation. This study investigates the effects of amine-modified zeolitic imidazolate framework-8 (ZIF-8) with well-defined micropores and gas sieving ability in polyvinyl alcohol (PVA) membranes containing an ionic liquid that worked as mobile carriers. The effects of amine-modified ZIF-8 and silica nanoparticles on membrane properties and separation performance were also compared. Fourier transform infrared spectra confirmed the incorporation of ZIF-8, secondary amine, IL anions, and silica nanoparticles in PVA membranes. Energy dispersive analysis showed the good dispersion of inorganic fillers. The amine-modified silica nanoparticles resulted in higher thermal stability compared to the amine-modified ZIF-8 in PVA membranes containing [bmin][Ac] ionic liquid, as shown in the thermogravimetric analysis. However, the CO₂ separation performance of PVA membranes containing [bmim][Ac] ionic liquid was improved more significantly by the amine-modified ZIF-8 with microporous structure. A CO₂/N₂ ideal selectivity of 85.65 and CO₂ permeance up to 4,502.91 GPU were attained. Unlike the CO₂/N₂ ideal selectivity, the CO₂ permeance was not significantly affected either using [bmin][Ac] or [bmin][BF₄]. The humid gas greatly enhanced the CO₂ permeance without much changes in the CO₂/N₂ ideal selectivity due to the promotion of facilitated transport. © 2024 Society of Chemical Industry and John Wiley & Sons, Ltd.