Pebax‐based mixed matrix membranes loaded with graphene oxide/core shell <scp>ZIF</scp>‐8@<scp>ZIF</scp>‐67 nanocomposites improved <scp>CO₂</scp> permeability and selectivity

Abstract

Abstract In order to facilitate CO 2 transport in Pebax‐based membranes, graphene oxide (GO)/core shell ZIF‐8@ZIF‐67 nanocomposites were loaded in Pebax copolymer to improve CO 2 permeability and selectivity. The 0.5 wt% GO doped core shell ZIF‐8@ZIF‐67, which gave highest CO 2 adsorption capacity of 1.12 mmol/g, was used as nanocomposite. The incorporated GO/core shell ZIF enhanced CO 2 adsorption via unsaturated metal sites (Zn‐O or Co‐O), because O atoms in GO substituted for N atoms coordinated with Zn and Co single atoms in core shell ZIF‐8@ZIF‐67. Positron annihilation lifetime spectroscopy indicated that GO‐templated core shell ZIF nanocomposites generated extra free volume and provided low‐resistance channels to facilitate CO 2 transport. Fourier transform infrared spectroscopy analysis revealed that hydrogen bonds were generated between Pebax polymer chains and GO‐templated core shell ZIF which improved swelling resistance and reduced interface defects. Therefore, Pebax‐based MMMs loaded with 5 wt% GO/core shell ZIF‐8@ZIF‐67 exhibited optimum CO 2 permeability (173.2 barrers) and ideal selectivity of CO 2 /N 2 (61.9) and CO 2 /H 2 (11.6), which were 99.7%, 66.4%, and 20.8% higher than Pebax membranes and surpass Robeson 2008 upper bound. The tensile strength increased by 17.6% to 28.8 MPa and elongation at break increased by 7.61%–554.6% when pure Pebax membranes were incorporated with 2.5 wt% GO/core shell ZIF‐8@ZIF‐67.