High pressure gas separation performance of mixed-matrix polymer membranes containing mesoporous Fe(BTC)

Abstract

Mixed-matrix membranes (MMMs), filled with inorganic particles, provide a means to improve the gas separation performance of polymeric membranes. In this work, MMMs containing the mesoporous metal organic framework (MOF) Fe(BTC) in a Matrimid®-PI matrix were characterized in terms of their carbon dioxide (CO2) and methane (CH4) separation performance at low and high pressures. Physical properties (density, thermal degradation, and glass transition) of Fe(BTC) and prepared MMMs were analyzed. An optimized priming and suspension mixing protocol resulted in a homogeneous distribution of MOF particles in the Matrimid®-PI matrix, as observed by scanning electron microscopy (SEM). Experimental results showed decreased thermal degradation but increased membrane density and glass transition with increased Fe(BTC) loading, as well as improvement in CO2 permeability and CO2/CH4 selectivity. At high pressures, the native Matrimid®-PI membrane showed typical plasticization behavior, but as the MOF loading increased gas transport properties seem to be controlled by MOF particles leading to reduced plasticization tendencies. The favorable performance of MOF containing membranes can be attributed to the strong increase in the sorption capacity and chain rigidity by the Fe(BTC) particles which suppressed plasticization. At a mixed gas feed pressure of 40bar, MMMs with 30wt% MOF showed a CO2/CH4 selectivity increase of 62% compared to the native Matrimid®-PI membrane, while the permeability was about 30% higher than that of native polymer.