Exploiting the effects of zirconium-based metal organic framework decorated carbon nanofibers to improve CO2/CH4 separation performance of thin film nanocomposite membranes

Abstract

The challenges of interfacial defects and filler uniform dispersion are still preventing the design of mixed matrix membranes (MMMs) for the purpose of high gas selectivity. In this study, in-situ growth of UiO-66-NH2 on the external surface of carbon nanofibers (CNFs) resulted in the synthesis of a novel CNF/metal organic framework (MOF) composite which embedded into the pebax selective layer of thin-film nanocomposite (TFN) membrane. The uniform structure and defect-free interface was observed by FE-SEM analysis that reveals superior compatibility between polymer chains and CNF/UiO composite. Gas sorption analysis was investigated for pristine thin film composite (TFC) and TFN membranes and then the obtained experimental data were analyzed by Henry–Langmuir and Henry–Freundlich model. The results illustrated that gas permeation for the membranes followed the Henry–Freundlich model. Accordingly, synthesized TFN membranes demonstrated a higher CO2 permeability as well as proper CO2/CH4 selectivity compared to pristine TFC membrane. For instance, the pure and mixed gas permeation results of TFN membrane including 3wt% of CNF/UiO composite represented a high CO2 permeability of around 328 (pure gas permeability) and 230 (mixed gas permeability) Barrer and CO2/CH4 selectivity of around 27 (ideal selectivity) and 21 (real selectivity) at feed pressure of 6bar. Consequently, the TFN membranes exhibit exceptional separation performance in terms of overcoming the Robeson upper bound. The approach of decoration of MOFs on the surface of CNFs can be effective technique to enhance TFN membranes performance.