Fabrication of organic solvent nanofiltration membranes through magnetic field-induced surface segregation of Fe3O4@ZIF8 for salt/dye separation

Inserting metal–organic frameworks into polymer matrix to prepare mixed matrix membranes (MMMs) is a promise strategy for the preparation of organic solvent nanofiltration (OSN) membranes. However, MMMs prepared via traditional physical blending strategy exhibits the disadvantage of uneven dispersion of MOFs particles, resulting in a decrease in organic solvent resistance and membrane performances. In this work, the magnetically responsive nanomaterials (Fe 3 O 4 @ZIF8) were successfully prepared via growing ZIF8 functional layer upon Fe 3 O 4 nanoparticles. Then, the OSN membranes were fabricated via embedding the Fe 3 O 4 @ZIF8 into polymer matrix under a magnetic condition during non-solvent induced phase separation. The magnetically responsive Fe 3 O 4 @ZIF8 particles were compelled to segregate and enrich in membrane surface, optimizing the arrangement of Fe 3 O 4 @ZIF8 within the membrane. This strategic modification significantly improves the porosity and solvent resistance property of membrane. The optimized M−Fe 3 O 4 @ZIF8(0.3)/PAN membrane exhibited an increased permeance of methanol from 40.5 m -2 h −1 bar −1 to 55.5 m -2 h −1 bar −1 compared to the pristine PAN membrane while the retention to Congo Red increased above 99 %. The M−Fe 3 O 4 @ZIF8(0.3)/PAN membrane also possesses excellent permeation of organic solvent and a selectivity (NaCl/Congo Red) of 232, which makes these MMMs promising for salt/dye separation in organic solvent nanofiltration.