Fabrication of hydrophilic defective MOF-801 thin-film nanocomposite membranes via interfacial polymerization for efficient chromium removal from water

Addressing the challenge of utilizing defect-rich MOFs as materials for thin-film nanocomposite membranes functional layers, particularly to expose more pores and functional sites to enhance pollutant selectivity, is a critical scientific issue in the current field of nanofiltration. In this study, we have innovatively employed modulators and ultrasonic techniques to synthesize a highly defective, hydrophilic MOF-801. This was then incorporated into a polyamide (PA) functional layer on a PVDF substrate through interfacial polymerization, creating a membrane specifically designed for chromium separation. Advanced characterization techniques confirmed that the PA@DMOF-801 membrane exhibits a distinct interlayer water channel structure, which facilitates the complete exposure of functional sites due to the open nature of the pores. The findings reveal that the resulting membrane exhibits pronounced hydrophilic pore characteristics, achieving a permeability coefficient of 14.5 L m⁻² h⁻¹ bar⁻¹ and a Cr³⁺ retention rate of 98 % for ions with larger hydrated radii, along with high separation efficiency. The hydrophilic sites and porous features exposed by defects ensure the membrane excels in both permeability and selectivity. The primary contribution of this work lies in demonstrating that increasing MOF defect sites enhances the membrane's functional layer more significantly than any potential drawbacks, providing valuable insights for future research on exploiting MOF defects in membrane development.