Free-Standing Amphiphilic Organic Membrane toward Ultrafast and Efficient Demulsification

Conventional oil-water separation techniques, such as absorption and flocculation, are still widely employed despite their high energy demands and limited separation efficiency. Membrane-based separation has emerged as a promising alternative; however, its practical implementation is often hindered by severe fouling caused by oil and surfactants. In this regard, the first free-standing, amphiphilic organic membrane (AOM-1) is judiciously designed and interfacially fabricated for the demulsification of surfactant-stabilized water-in-oil. AOM-1 is composed of hydrophilic polyethylene glycol (PEG) - inspired core and hydrophobic alkyl chains, creating an oxymoronic structure that prevents fouling and offers excellent oil permeation even in the presence of surfactants. In comparison, a hydrophobic organic membrane (HOM-1), lacking the PEG core, exhibits inferior performance. The AOM-1 achieves a steady flow rate of ≈2550 L·m^{- 2}·h^-¹, recyclability over five cycles, and a high separation capacity of ≈7.1 × 10³ L·m^{- 2}, outperforming HOM-1 (≈1.6 × 10³ L·m^{- 2}). Mechanistic investigation using molecular dynamics simulations reveals nonpolar-nonpolar interactions (-21.09 kJ mol^-1) between surfactant and membrane, facilitating emulsion infiltration in HOM-1, while the additional strong polar-polar interactions in AOM-1 (-137.70 kJ mol^-1) prevent pore blockage. The large-scale demulsification capability and antifouling nature with better recyclability of AOM-1 open the avenue for exploring amphiphilic membranes as potential alternatives to traditional and energy-intensive methods.