Gas separation performance of 6FDA-DAM-ZIF-11 mixed-matrix membranes for H2/CH4 and CO2/CH4 separation

In this study, gas separation performance of 6FDA-DAM-ZIF-11 mixed matrix membranes (MMMs) with various ZIF-11 percentages (0, 10, 20, 30 wt.%) were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and particle size analysis were achieved to investigate ZIF-11 structure. SEM, Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and thermogravimetric (TGA) analysis were also carried out to characterize the membranes. In the SEM images of the MMMs, no apparent agglomeration between ZIF-11 particles and the 6FDA-DAM matrix was observed, even at 30 wt.% loading of the ZIF-11. The measured permeabilities for H2, CO2 and CH4 gases were found to be 272, 257 and 8.3 Barrers for 20 wt.% ZIF-11 containing MMMs measured at 30 °C and 4 bar. Pure gas permeation tests showed improvement in permeability of the MMMs but the ideal selectivity of gases remained almost constant for the various loadings. The permeability values increased as the ZIF-11 loading increased up to 20 wt.%. However, at higher loadings, 30 wt.%, the permeability decreased for all gases. The ideal selectivities of MMMs did not show significant change but the selectivity of 6FDA-DAM-ZIF-11 at 20 wt.% loading approached to the 2008 Robeson upper bound.