Dual-functional asymmetric CuO@NC-based janus hydrogel membrane for integrated oil–water separation and solar-driven desalination for sustainable use

Janus membrane was integrated with oil separation and solar-driven desalination • Janus CuO@NC-PVDF hydrogel membrane achieved remarkable oil rejection • CuO@NC-PVDF layer demonstrated high surface temperature of ∼72 °C • Janus hydrogel membrane resulted in a high evaporation rate of 1.29 kg m -2 h -1 • Janus membrane can show remarkable long-term performance Solar-driven desalination has emerged as a promising strategy to address freshwater scarcity; however, its practical application is often hindered by severe performance deterioration under oily seawater conditions. To overcome the limitations of conventional interfacial evaporation systems, this study presents an asymmetric Janus hydrogel membrane based on copper oxide nanoparticles encapsulated within a nitrogen-doped carbon shell (CuO@NC), integrated into a polyvinylidene fluoride (PVDF) matrix. The CuO@NC-PVDF Janus membrane features a hydrophilic–hydrophobic dual-layer architecture, enabling the functional decoupling of oil rejection and solar-driven evaporation. The hydrophobic layer effectively prevents oil penetration, while the hydrophilic photothermal layer facilitates efficient water evaporation. As a result, the membrane achieved outstanding oil rejection (>99.99%) across various oil-contaminated feed conditions. Under 1 sun irradiation, the membrane exhibited a high surface temperature (∼45 °C), along with an enhanced evaporation rate of 1.29 kg m −2  h −1 and a solar-to-vapor efficiency of 86.4%. The Janus configuration improved the evaporation performance by approximately 2.8 times compared to conventional single-function systems. Moreover, the membrane maintained high evaporation and thermal efficiencies under realistic oily seawater conditions and demonstrated stable long-term operation over repeated cycles (∼10 cycles). These findings highlight the effectiveness of integrating photothermal functionality with asymmetric wettability in a Janus architecture, providing a robust and scalable platform for simultaneous oil–water separation and solar-driven desalination. This approach offers strong potential for practical applications in sustainable oily wastewater treatment and resource recovery. Download: Download high-res image (202KB) Download: Download full-size image