Membrane distillation is a promising technology for desalination; however, membrane fouling and pore wetting remain critical challenges that limit its large-scale application. In this study, a novel Janus membrane based on an omniphobic polychlorotrifluoroethylene substrate coated with a hydrophilic polyvinyl alcohol/catechol layer was developed for direct contact membrane distillation. The asymmetric architecture enables simultaneous enhancement of water vapor transport and resistance to fouling and wetting by combining a hydration-layer-forming hydrophilic surface with a low-surface-energy omniphobic support. As a result, the Janus membrane achieved a high pure water flux of 49.12 kg m− 2 h−1, outperforming the pure (37.25 kg m−2 h−1), omniphobic (47.25 kg m−2 h−1), and commercial membranes (34.48 kg m−2 h−1). When treating a 35,000 ppm sodium chloride solution, a stable permeate flux of 45.25 kg m−2 h−1 with salt rejection exceeding 99% was obtained. Furthermore, the membrane exhibited superior resistance to organic and inorganic foulants, including humic acid, calcium salts, and surfactants. The enhanced performance is attributed to the synergistic Janus design, in which the hydrophilic top layer suppresses foulant adhesion while the omniphobic substrate effectively prevents pore wetting. These results demonstrate the strong potential of polychlorotrifluoroethylene -based Janus membranes for advanced and practical desalination applications.

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