Superhydrophilic/underwater superoleophobic ZIF-8@PMIA nanofibrous membranes with hierarchical structure for the efficient separation of oil-in-water emulsion

Nanofibrous membranes are considered ideal candidates for water purification. However, the membrane fouling results in an irreversible decline in separation flux, while the slippage of nanofibers leads to an increase in pore size under driving pressure, subsequently inducing a decline in separation efficiency. Rational structure design and material selection are crucial for separation performance improvement. In this study, we report double-layer hierarchical structured nanofibrous membranes that demonstrate simultaneous superhydrophilicity and underwater superoleophobicity for oil-water separation via a combination of electrospinning and seed-mediated solvothermal strategy. The double-layered hierarchical structure comprises an upper layer of ZIF-8@PMIA composite nanofibers and a bottom layer of PMIA nanofibers. Notably, the incorporation of ZIF-8 species confers several advantages, such as increased surface roughness, reduced pore size, and enhanced superhydrophilicity, collectively contributing to superior anti-fouling performance and high separation efficiency. Meanwhile, the bottom PMIA nanofibers, with larger diameters, ensure robust mechanical integrity for the entire membrane. Due to the rational structural design, the membrane achieves outstanding separation performance, including a 99.91 % separation efficiency for diesel-in-water emulsions and an ultrahigh flux of 3821.7 L m − 2 h −1 for dichloromethane-in-water emulsions. Therefore, this membrane has broad application prospects in the oil–water separation field.