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 CO

2

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 CO

2

permeability and CO

2

/CH

4

selectivity increased from 402.7 Barrer (1 Barrer = 1.33×10

-14

m

3

(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 CO

2

separation performance. Permeability tests at different temperatures revealed that as temperature was raised

at constant pressure

CO

2

permeability for the membrane containing the mixed ligand increased from 682.2 Barrer to 733.5 Barrer

While CO

2

/CH

4

selectivity decreased from 15.46 to 13.43.