Self-assembly superwetting supramolecular nanofiber membrane via metal-coordination reinforced hydrogen-bonding for high-efficiency oil/water separation

Polymeric nanofibrous membranes attract significant interest in oil/water separation due to high porosity, tunable pore size and customizable surfaces, while their intrinsic hydrophilicity deficits compromise their separation performance and anti-fouling properties. Owing to its intrinsic hydrophilic nature and biocompatibility, polyvinylpyrrolidone (PVP) is commonly used to improve antifouling performance. However, the excessive hydrophilicity of PVP hinders its structural integrity, preventing its widespread deployment in aqueous environments. Herein, a metal-phenolic network (Tannic acid-Ca²⁺, TA-Ca²⁺) was used for hydrogen-bonding assembly with PVP to design freestanding membrane material. Subsequently, the coordination assembly of natural phytic acid (PA) endowed the membrane a potent hydration barrier against oil-fouling and enhanced mechanical strength by 491 %(1.83 → 9.03 MPa). The resulting nanofiber membrane exhibited intrinsic superhydrophilicity and good swelling stability, achieving 2.9 × 10⁴ L·m⁻²·h⁻¹·bar⁻¹ permeability for oil/water emulsions with separation efficiency above 99.7 % under gravity (∼1 KPa). Moreover, through altering coordination metal ions, a series of self-assembly PVP-based membranes can be constructed with both internal and external super-wettability, providing a source of inspiration for the development of advanced separation membranes with high separation efficiency, long-lasting anti-fouling properties, and low energy consumption.