Enhanced CO2 separation performance of Pebax®2533 mixed matrix membrane incorporated by synthesized mixed-ligand UiO-67

In this study, Pebax®2533 polymer was used as the continuous phase and UiO-67 was employed as the filler to prepare mixed matrix membranes. UiO-67 is usually synthesized using two ligands: biphenyl-4,4′-dicarboxylate (bpdc) and 2,2′-bipyridine-5,5′-dicarboxylic acid (bpy). In this research, UiO-67 was synthesized not only with these two ligands but also using a mixed ligand approach (50% bpdc and 50% bpy). The synthesized UiOs were incorporated into the polymer matrix at mass percentages ranging from 0% to 2% to form the mixed matrix membranes (MMMs). Membranes containing UiO-67 with mixed ligands exhibited a greater affinity for CO₂ compared to other membranes. Various analytical techniques, including X-ray diffraction, thermogravimetric analyzer, Fourier transform infrared spectroscope (FTIR), field emission scanning electron microscope (FESEM), and differential scanning calorimetry, were used to analyze the properties of the prepared membranes. The FTIR spectrum confirmed all desired bands of Pebax®2533 and UiO-67 in the MMMs. The FESEM images showed that the pure Pebax membrane has a uniform structure, and the developed membranes are uniformly incorporated with the synthesized UiO-67 nanoparticles. Gas permeation measurements indicated that CO₂ permeability and CO₂/CH₄ selectivity increased from 402.7 Barrer (1 Barrer = 1.33 × 10⁻¹⁴ m³(STP)·m·m⁻²·s⁻¹·kPa⁻¹) and 9.32 for the pure Pebax membrane at 1.0 MPa to 770.1 Barrer and 16.96 in the modified membrane. Additionally, the gas permeation test results demonstrated that adding functionalized porous nanofillers increases the CO₂ separation performance. Permeability tests at different temperatures revealed that as temperature was raised, at constant pressure, CO₂ permeability for the membrane containing the mixed ligand increased from 682.2 Barrer to 733.5 Barrer, While CO₂/CH₄ selectivity decreased from 15.46 to 13.43.