Cyclic olefin copolymer (COC)-metal organic framework (MOF) mixed matrix membranes (MMMs) for H-2/CO2 separation

Abstract

In this study, thermoplastic based mixed matrix membranes (MMMs) were prepared by using cyclic olefin copolymer (COC) and two different metal organic frameworks (MOFs), HKUST-1 and MIL-53(Al) via solution mixing (SM) and melt processing (MP) methods. Structural and physical properties of COC, MOFs, and MMMs were characterized by SEM, XRD, TGA, and DMA methods. H-2 and CO2 permeability values of MMMs were measured and ideal selectivity values (alpha) for H-2/CO2 were determined. Characterization studies confirmed that the both preparation methods yielded a strong interfacial adhesion between MOF particles and COC. Different semi-empirical gas permeation models including the Maxwell, Maxwell-Wagner-Sillar, Bruggeman, Pal, Lewis-Nielson, and Higuchi equations were used to fit relative increase in the gas permeation values of H-2 as a function of volume fraction of HKUST-1. It was found that the Higuchi model was successfully fit the increase in H-2 permeability. Loadings of 40 wt% of HKUST-1 and MIL-53 (Al) increased the H-2 permeability by 85 % and 59 %, respectively and significantly improved the ideal selectivity (alpha) of H-2/CO2, compared to COC. The gas separation performances of MMMs implied that the both series of COC/MOF membranes surpassed the Robeson's 2008 upper bound for H-2/CO2 separation.