Building well-defined magnetic channels in PIM-1 mixed matrix membranes with ZIF-8 wrapped Fe3O4 nanoparticle for effective O2/N2 separation

Magnetic mixed matrix membranes (MMMs) show great potential for enhancing O 2 /N 2 separation efficiency by leveraging the inherent magnetic property differences between O 2 (paramagnetic) and N 2 (diamagnetic). However, one of the major challenges is the establishment and precise control of magnetic channels between magnetic fillers and polymer matrix. To address this issue, herein, ZIF-8 wrapped Fe 3 O 4 nanoparticles (Fe 3 O 4 @ZIF-8) were synthesized using a step-by-step assembly method, and then integrated into polymer of intrinsic microporosity (PIM-1) matrix to develop MMMs with well-defined magnetic channels for O 2 /N 2 separation. In comparison with Fe 3 O 4 , Fe 3 O 4 @ZIF-8 nanoparticles exhibited significantly enhanced compatibility with the polymer matrix, thereby facilitating uniform dispersion and improving interfacial adhesion. Gas permeation experiments revealed that the magnetic PIM-1/Fe 3 O 4 @ZIF-8 MMMs demonstrated enhanced O 2 /N 2 separation performance due to the combined effects of magnetic responsiveness and the presence of ZIF-8 magnetic channels. Under a magnetic field strength of 56mT, the magnetic MMM with a 4 wt% loading of Fe 3 O 4 @ZIF-8 exhibited optimal O 2 /N 2 separation performance with O 2 permeability of 710 Barrer and O 2 /N 2 selectivity of 3.64. These values represented a significant improvement of 42% and 24%, respectively, compared to pure PIM-1 membrane. Moreover, the simultaneous improvement of permeability and selectivity enabled the achievement of Robeson’s 2008 upper bound for O 2 /N 2 separation, underscoring the great potential of Fe 3 O 4 @ZIF-8 nanoparticles for designing magnetic MMMs with favorable structural attributes and exceptional separation efficiency.