Cellulose nanocrystal-assisted microphase separation for constructing multi-scale electrospun membrane toward W/O emulsion separation

Efficient separation of water-in-oil (W/O) emulsions is essential for wastewater treatment, yet conventional electrospun membranes often suffer from poor mechanical properties, large inter-fiber pores and structural instability. Here, we propose a coaxial electrospinning strategy that combines a PVDF/CNC core with a PDMS shell to construct a hierarchical superhydrophobic membrane. The incorporation of CNC induces nonsolvent-driven microphase separation during electrospinning, generating spindle- and nanosphere-like surface structures while reinforcing the fibrous network. Meanwhile, the PDMS shell contributes to inter-fiber connectivity and enhances surface hydrophobicity. These synergistic effects result in an interlocked porous architecture that supports gravity-driven separation of W/O emulsions. At 4 wt% CNC, the membrane achieves a water contact angle of 158°, an average pore size of 1.93 μm and a flux of 2890 L m⁻² h⁻¹, while maintaining over 94 % separation efficiency over 20 cycles. This work provides a sustainable strategy for tailoring structures for effective W/O emulsion separation.