An ultrasonic-assisted rapid approach for sustainable fabrication of antibacterial and anti-biofouling membranes via metal-organic frameworks

Biofouling is a pivotal problem for polymeric membranes used in water treatment and reuse. Surface functionalization is a promising practice to improve the resistance of membranes to biofouling. Diverse materials, synthesis methods, and functionalization techniques will be needed to address different applications. Herein, we employed a novel ultrasonic-assisted technique to functionalize polyvinylidene fluoride microfiltration membranes by silver-based metal-organic frameworks (AgMOFs). Polydopamine (PDA) coating was also used to carry out this surface modification. In this study, AgMOFs were synthesized and in-situ grafted on the membrane surface simultaneously using ultrasonication for the first time. Unlike the conventional methods in which AgMOFs are prone to be washed away, the AgMOFs synthesized by ultrasonic-assisted method strongly bonded with the PDA-coated membrane. In addition, the MOF-PDA membrane fabricated by this method showed more uniform and size-controlled AgMOFs on the membrane surface than other conventional methods with large MOF clusters. The AgMOF-functionalized membrane displayed enhanced static antibacterial activity and dynamic biofouling resistance compared to those of the PDA-coated and pristine membranes while in contact with the model bacteria, Escherichia coli and Staphylococcus aureus. These results were evidenced by a larger inhibition zone area, a decline in viable cells observed in static antibacterial experiments, and more retained water flux in dynamic biofouling experiments. Altogether, our findings indicate that the in-situ synthesis of AgMOFs on membrane surfaces was successful by this facile and environmentally friendly method which can be considered in future studies with the purpose of surface modification for diverse applications.