Non‐Stop Switching Separation of Superfine Solid/Liquid Dispersed Phases in Oil and Water Systems Using Polymer‐Assisted Framework Fiber Membranes

Abstract Fabricating filtration membranes with wide applicability and high efficiency is always a challenge in the precise separation of small colloidal particles under mild conditions. For this purpose, a strategy mixing supramolecular framework fiber with polymer is adopted. The fibrous assembly in the gel state provides uniform nanopores for both channel and interception and controlled wettability for lyophilic/lyophobic switching. The used polymer fills the gaps between fiber assemblies and improves the mechanical property. The composite membrane shows both under‐oil superhydrophobic and underwater superoleophobic nature, which allows the conversions via in situ modulation of joystick solvents. Based on surface wetting and size‐sieving, ultrafine hard nanoparticles dispersing in both hydrophobic organic solvents and water are selectively sieved. In addition, on‐demand separation of water‐in‐oil and oil‐in‐water microemulsions without and with surfactants as systems containing soft droplets are realized. The smallest cut‐off size of ≈3 nm is achieved for both hard and soft emulsions, while separation efficiency maintains during sustained in situ reversible switches.