Asymmetric-Wettability Janus Sponge for Switchable Oil/Water Separation and Photocatalytic Remediation of Multipollutant Wastewater

The escalating issue of oil contamination and aqueous persistent pollutants necessitates advanced remediation materials. In this study, an asymmetric Janus sponge was synthesized using a synthetic BiOBr semiconductor to in situ grow CAU-17 metal-organic frameworks (MOFs) and serve as a Bi³⁺ donor. One side of the melamine sponge (MS) was functionalized with hydrophilic BiOBr/CAU-17, while the opposite side was modified with polydimethylsiloxane (PDMS) to achieve superhydrophobicity. This design resulted in a Janus sponge with contrasting wettability: the PDMS-coated side displayed a water contact angle exceeding 150.4°, attributed to low surface energy from interconnected 3D porous channels and hydrophobic PDMS carbon chains. This enabled selective oil adsorption (15-38 times its own weight) and >99% water separation efficiency. The BiOBr/CAU-17@MS interface demonstrated potent photocatalytic activity, degrading rhodamine B, methylene blue, and tetracycline hydrochloride with 97% efficiency under visible light, even at high pollutant concentrations (50 mg/L). These findings highlight the Janus sponge's dual functionality for simultaneous oil-water separation and degradation of organic contaminants, offering a promising solution for treating complex wastewater containing both oils and dissolved pollutants.