Green-engineered superhydrophobic and photothermal CuO nanofiber membranes for solar-assisted membrane distillation

The practical implementation of membrane distillation (MD) for hypersaline brine treatment is often severely hindered by membrane fouling. To address these challenges, we report a robust, fluorine-free strategy for fabricating self-cleaning superhydrophobic nanofibrous membranes via a scalable electrospinning and in-situ structural engineering approach. By embedding copper nanoparticles within porous polystyrene nanofibers, we successfully tailored two distinct hierarchical copper oxide (CuO) architectures—nanoneedles and nanosheets—through controlled chemical growth and thermal transformation. Without the need for low-surface-energy fluorination, the resulting membranes exhibit exceptional superhydrophobicity, with the nanosheet-structured membrane achieving a remarkable water contact angle of 159.6°. These hierarchical CuO nanostructures not only confer superior anti-fouling capabilities but also serve as highly efficient photothermal converters. Under one-sun irradiation, the membrane rapidly generates a surface temperature of 83.4 °C within 3 min. Consequently, it delivers a stable and high water flux of 35.2 LMH during continuous 24-h desalination of hypersaline brine. This work presents a sustainable, high-performance nanofibrous platform for next-generation solar-thermal freshwater production.