Interfacial design of polysulfone/Cu-BTC membrane using [Bmim][Tf2N] and [Dmim][Cl] RTILs for CO2 separation: Performance assessment for single and mixed gas separation

Abstract

An upsurge in searching membranes with improved perm-selectivity and long-term stability is crucial in membrane-based gas separation. Herein, we engineered the interfacial characteristics of Cu-BTC MOFs with the polysulfone (PSf) matrix using ionic liquids (ILs) at the polymer-filler interface. Two different ILs, [Bmim][Tf2N] and [Dmim][Cl], were used to prepare composite PSf/Cu-BTC/[Bmim][Tf2N] and PSf/Cu-BTC/[Dmim][Cl] membranes. The membranes micro and chemical structures were characterized using XRD, FESEM, and XPS techniques. Results indicated that the multifunctional properties of ILs and Cu-BTC particles influenced the membrane formation mechanism. The uniform dispersion of Cu-BTC filler particles with the inclusion of [Bmim][Tf2N] and [Dmim][Cl] ILs on the membrane surface was evident from the morphological studies. The absence of a leaky interface by the ILs integration in the PSf/Cu-BTC/[Bmim][Tf2N] and PSf/Cu-BTC/[Dmim][Cl] membranes results in a pronounced increase in selectivities. For instance, PSf/Cu-BTC/[Dmim][Cl] membranes, the CO2 permeance was noticed to be 29.35 ± 0.35 GPU, and their corresponding gas pair selectivities were noted to be significantly higher than the neat and PSf/Cu-BTC membranes. Similarly, in PSf/Cu-BTC/[Bmim][Tf2N] membrane exhibited optimum CO2 permeance of 30.44 ± 0.49 GPU with the CO2/N2 and CO2/CH4 selectivities of 61 and 59.70%, respectively, higher than neat PSf membrane. Furthermore, these membranes showed better anti-aging resistance and long-term stability than the neat PSf membranes. The merits of a simultaneous increase in permeance and selectivities and the good stability and scalable properties make the proposed PSf/Cu-BTC/IL membranes of great interest for the industrial CO2 separation from the gas exhausts.