Concurrent enhancement of CO2-philic pathway and interfacial compatibilization in ZIF-67 based polysulfone membranes through [Bmim][Tf2N] for CO2 separation

Abstract

To date, it remains a tedious task to concussively control the preferred gas transport pathways in metal–organic frameworks (MOFs) membranes. Herein, we demonstrate highly selective CO2 transport in polysulfone (PSf) membrane using [Bmim][Tf2N] ionic liquid (IL) modified ZIF-67 nanoparticles with 0.5–2 wt% loading. Membrane structure, surface, and chemical properties were investigated through FTIR, XRD, SEM-EDX, and XPS analysis. The membrane morphological studies showed uniform and non-defective selective thin layers followed by a well-defined porous sublayer. The [Bmim][Tf2N]@ZIF-67 nanoparticles ensured the uniform dispersion in the PSf, resulting from a wetting and interfacial binding act of [Bmim][Tf2N] between ZIF-67 and PSf matrices. The ultimate stress of [Bmim][Tf2N]@ZIF-67 membranes, observed at a 1.5 wt%, was 8.73 % greater than those of pristine PSf membrane. In the PSf/2% [Tf2N]@ZIF-67 membrane, the CO2 permeance was 60.5 GPU with a substantial increment in CO2/CH4 and CO2/N2 selectivities of 62.66 and 52.97 %, respectively, over to pristine PSf membrane. The membrane performance was closer and approaching towards the Robeson upper bound for both CO2/N2 and CO2/CH4 gas pairs. This simultaneous increase in permeance and selectivities of PSf/[Tf2N]@ZIF-67 membrane could open a new avenue in mitigating the CO2 emission.