Preparation and Performance Study of Strong and Tough Polyacrylonitrile/Polyurethane Composite Electrospun Janus Fiber Membranes for Oil/Water Emulsion Separation

Oil pollution poses a persistent threat to ecosystems and human habitats. The development of high‐performance oil–water separation membranes must address the inherent challenge of high energy consumption while ensuring high throughput and durability. In this study, we present an electrospun Janus membrane (PPNM) with an asymmetric hydrophilic–hydrophobic structure. The hydrophilic layer consists of polyacrylonitrile (PAN), polyurethane (PU), and tannic acid (TA), whereas the hydrophobic layer is composed of PAN, PU, and carbon nanotubes (CNTs). The microstructure, mechanical properties, wettability, and oil–water separation performance of the membrane were systematically investigated, with emphasis on elucidating the influence of the hydrophilic/hydrophobic layer thickness ratio on separation efficiency. By tuning this ratio in the Janus membrane, efficient selective separation was achieved for both oil‐in‐water (O/W) emulsions (flux up to 1179.5 L m −2 h −1 ) and water‐in‐oil (W/O) emulsions (flux up to 1450 L m −2 h −1 ), with separation efficiencies exceeding 99% for both types. After 10 separation cycles, the membrane showed no significant decline in performance, demonstrating excellent cycling stability. The structural advantages of this Janus membrane in separating O/W emulsions provide both theoretical insight and experimental support for its potential application in complex oil–water systems.