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

Abstract

In order to facilitate CO2 transport in Pebax‐based membranes, graphene oxide (GO)/core shell ZIF‐8@ZIF‐67 nanocomposites were loaded in Pebax copolymer to improve CO2 permeability and selectivity. The 0.5 wt% GO doped core shell ZIF‐8@ZIF‐67, which gave highest CO2 adsorption capacity of 1.12 mmol/g, was used as nanocomposite. The incorporated GO/core shell ZIF enhanced CO2 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 CO2 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 CO2 permeability (173.2 barrers) and ideal selectivity of CO2/N2 (61.9) and CO2/H2 (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.

MOFs meet membrane: application in water treatment and separation

“…MMMs can be constructed using MOFs because of their excellent physicochemical properties. 133 Combining two or even more MOFs to prepare hybrid membranes has been reported. For example, to avoid the issue of difficulty in controlling the operation during the solvent heat reaction, Knebel et al prepared 180 nm ZIF-8 membranes through layer-by-layer growth on ZIF-67 membranes via the self-assembly method.…”

A robust eco-compatible microporous iron coordination polymer for CO2 capture

“…In the past few years, the series of Pebax polymers was used as a continuous phase in MMMs owing to their promising separation performances resulting from their structural flexibility and solubility-selective gas separation. 47–55 Moreover, a few rubbery Pebax-MOF MMMs have shown better MOF-polymer interfacial properties in comparison to numerous MMMs based on rigid glassy polymers. 47–55 MIL-178(Fe)-Pebax- X MMMs with different MIL-178(Fe) contents ( X = 5–25 wt%) were fabricated following a two-step protocol (polymer dissolution and filler dispersion followed by casting), as explained in the Experimental section.…”

“…47–55 Moreover, a few rubbery Pebax-MOF MMMs have shown better MOF-polymer interfacial properties in comparison to numerous MMMs based on rigid glassy polymers. 47–55 MIL-178(Fe)-Pebax- X MMMs with different MIL-178(Fe) contents ( X = 5–25 wt%) were fabricated following a two-step protocol (polymer dissolution and filler dispersion followed by casting), as explained in the Experimental section. PXRD patterns of the different MIL-178(Fe)-Pebax- X MMMs display the characteristic Bragg peaks of MIL-178(Fe), the intensity of which increases with the amount of MIL-178(Fe) (Fig.…”

How 2D Nanoflakes Improve Transport in Mixed Matrix Membranes: Insights from a Simple Lattice Model and Dynamic Mean Field Theory

“…Extensive further experimentations with polymer–filler pairs led to a discovery that filler elements that do not possess their own porosity, such as 2D graphene and GO nanoflakes, may also enhance the separation performance of the hybrid material. − …”