Highly permeable poly(4-methyl-1-pentyne)/NH2-MIL 53 (Al) mixed matrix membrane for CO2/CH4 separation

Abstract

Poly(4-methyl-1-pentyne) (PMP) as a polymer matrix together with synthesized NH₂-MIL 53 metal organic framework (MOF) as a filler were used to fabricate a mixed matrix membrane (MMM). Various characterization methods as well as a series of CO₂/CH₄ gas separation tests (i.e. pure and mixed gas tests) were conducted in order to determine the effect of NH₂-MIL 53 on the properties of the prepared MMMs and their gas transport characteristics. The results of TGA and DMA showed that both degradation temperature (T_d) and glass transition temperature (T_g) increased by increasing the NH₂-MIL 53 loading. SEM images also demonstrated that uniform dispersion of NH₂-MIL 53 particles in the PMP matrix was achieved with no noticeable voids in the polymer-filler interfaces. It was also found that incorporation of NH₂-MIL 53 in PMP results in an increase of gas permeability (especially for CO₂) and higher CO₂/CH₄ selectivity. In contrast with the increment of CO₂ solubility due to the presence of MOF in the polymer matrix, the solubility of CH₄ decreases. Although the CO₂ solubility was improved with the addition of NH₂-MIL 53, its diffusivity remained almost constant with no significant changes. Lastly, it was observed that increasing the MOF loading along with higher feed pressure provide a condition to overcome the Robeson upper bound.