Self-assembled supramolecular/Fe-MOF functionalized nanofibrous membrane with switchable superwettability and photo-Fenton activity for on-demand oily wastewater treatment

Abstract

Electrospinning fiber membranes have been developed for oily wastewater treatment, yet challenges such as membrane fouling, dull wettability and single functionality hinder their widespread application. Herein, a novel mixed matrix nanofibrous membrane was fabricated by blending self-assembled 3, 4, 9, 10-Perylenetetracarboxylic diimide/NH₂-MIL-101(Fe) (SA-PDINH/NMIL(Fe)) heterojunction photocatalyst into polyacrylonitrile (PAN) nanofibers using co-electrospinning technique. The resulting SA-PDINH/NMIL(Fe)@PAN membrane exhibited unique wettability of in-air superamphiphilicity and under-liquid dual superlyophobicity, which can be switched between under-oil superhydrophobicity and under-water superoleophobicity through a simple pre-wetting strategy. The membrane demonstrated excellent on-demand separation capabilities for both oil-in-water and water-in-oil emulsions, achieving superior permeation flux (typically 1920 and 1200 L m⁻² h⁻¹ for toluene-in-water and water-in-toluene, respectively) and separation efficiency (above 99 %) under gravity-driven conditions alone. Furthermore, SA-PDINH/NMIL(Fe)@PAN membrane can effectively remove water-insoluble high-viscosity crude oil fouling from the membrane surface and degrade water-soluble organic pollutants via photo-Fenton reactions, and also exhibited photocatalytic antibacterial property. Additionally, the resultant SA-PDINH/NMIL(Fe)@PAN possessed enhanced oil/water separation performance and photo-Fenton catalytic activity compared to bare NMIL(Fe) modified PAN membrane, which due to the incorporation of self-assembled supramolecular improved the wettability and promote photogenerated charge separation. The enhanced generation of reactive species (O₂⁻, OH and ¹O₂) in SA-PDINH/NMIL(Fe) photo-Fenton-like system through multiple pathways was confirmed. Besides, the band structure and charge transfer of SA-PDINH/NMIL(Fe) heterojunction as well as the photo-Fenton mechanism were investigated. This work provides new insights into the fabrication of Fe-MOF-based nanofibrous membranes with external stimuli-free switchable superwettability and photo-Fenton functionality for versatile applications in wastewater separation and purification.