Evolution of functional feed-side interfaces in membrane distillation: From stability to selectivity and reactivity

Membrane distillation (MD) has emerged as a promising technology for the concentration of hypersaline wastewater. Nevertheless, its practical deployment remains constrained by persistent interfacial challenges, including membrane wetting, fouling, scaling, and the co-transport of volatile organic compounds (VOCs) with water vapor. This review systematically examines the evolution of functional feed-side interfaces in MD, highlighting their conceptual progression from interfacial stability to molecular selectivity and ultimately to interfacial reactivity. Specifically, hydrophobic, superhydrophobic, omniphobic, and Janus interfaces are designed to mitigate membrane wetting, fouling, and scaling. Beyond stability-oriented engineering, selective interfaces incorporate dense, hydrated, or nanoconfined layers to regulate molecular sorption, diffusion, and evaporation, thereby enabling precise discrimination between water and volatile contaminants. Reactive interfaces further introduce localized catalytic domains within the feed-side region to enable in situ transformation of accumulated contaminants. This trajectory reflects a broader shift from passive capillary protection to active molecular transport regulation and chemical transformation, while presenting new trade-offs under complex hypersaline conditions. By consolidating these advances within a unified stability-selectivity-reactivity framework, this review elucidates fundamental design principles and outlines strategic priorities for the practical translation of next-generation MD membranes.