Preparation of Pebax 1657/MAF-7 Mixed Matrix Membranes with Enhanced CO(2)/N(2) Separation by Active Site of Triazole Ligand

Fillers play a critical role in the performance of mixed matrix membranes (MMMs). Microporous metal azolate frameworks (MAFs) are a subclass material of metal–organic frameworks (MOFs). Due to the uncoordinated nitrogen of the organic ligands, MAF-7 (SOD-[Zn(mtz)(2)], Hmtz = 3-methyl-1,2,4-triazole, window: d = 0.34 nm) shows excellent CO(2) adsorption performance. In this work, Pebax 1657/MAF-7 MMMs were prepared by a sample solution casting method with MAF-7 particles as fillers for the first time. By means of X-ray diffraction (XRD), scanning electron microscope (SEM), infrared radiation (IR), and thermogravimetry (TG), the compositional and structural properties of the mixed matrix membrane with different filler content were analyzed. The results show that the compatibility of MAF-7 and Pebax is good with a filler content of 5 wt.%. The pure gas testing showed that mixed matrix membrane has a high ideal CO(2)/N(2) selectivity of 124.84 together with a better CO(2) permeability of 76.15 Barrer with the optimized filler content of 5 wt.%. The obtained membrane showed 323.04% enhancement in selectivity of CO(2)/N(2) and 27.74% increase in the permeability of CO(2) compared to the pristine membrane at 25 °C and 3 bar. The excellent separation performance may be due to the ligands that can afford a Lewis base active site for CO(2) binding with the uniform dispersion of MAF-7 particles in Pebax and the favorable interface compatibility. The obtained membrane overcomes the Robeson’s upper bound in 2008 for CO(2)/N(2) separation. This work provides a new strategy by utilizing MAFs as fillers with triazole ligand to enhance the gas separation performance of mixed matrix membranes.