Oil-water separation remains a pressing global challenge in light of growing industrial wastewater and marine pollution, particularly when surfactant-stabilized emulsions (SSEs) with micro-sized droplets under 20 µm are involved. Conventional separation methods are limited by low flux, high energy requirements, and fouling, emphasizing the need for more efficient and eco-friendly solutions. Janus materials with asymmetric wettability have shown promise but are largely confined to two-dimensional membranes, often requiring compromises between selectivity and permeability and struggling to handle both oil-in-water (O/W) and water-in-oil (W/O) emulsions at once. To address these shortcomings, we developed a bioinspired bilayered nanofibrous aerogel (NFA) through a directional layer-by-layer freezing process, removing the need for harsh chemical treatments or complex solvent exchanges. This technique integrates hybrid nanofibers into a robust 3D hierarchical design, endowing each side with distinct wettability. Inspired by the dual wettability found in nature (such as on lotus leaves), the aerogel enables switchable wettability, achieving over 95% removal efficiency in gravity-driven separation of both O/W and W/O emulsions across multiple cycles. We further enhanced its practicality and sustainability by incorporating magnetic nanoparticles, which allow for rapid recovery and reuse. This approach also demonstrates considerable potential for large-scale industrial deployment, as its performance remains stable under varying operational conditions. We elucidated the material’s selective sorption behavior through theoretical frameworks based on Zisman’s theory and Fowkes’ model, using surface energy measurements to predict solvent interactions within the matrix. Overall, this versatile bilayered NFA architecture not only serves as a powerful platform for environmental remediation but can also be extended into advanced multilayer designs for catalysis, pollutant adsorption, and gas separation through additional functionalization.
