Bioinspired Polyimide Membranes with Sponge-Like Networks for Capillarity-Assisted Ultralow-Pressure Dye/Salt Separation

Achieving efficient and stable separation of complex dye/salt systems under ultra-low driving pressures is crucial for reducing energy consumption in membrane processes and advancing sustainable water treatment technologies. However, conventional membrane systems are still constrained by high transport resistance, interfacial instability, and severe fouling, which collectively hinder their long-term separation performance. Herein, inspired by natural capillary transport, we report a biomimetic PI–SiO 2 –TA@Fe composite membrane fabricated via a synergistic combination of solvent-induced phase separation and in situ coordination chemistry. The resulting sponge-like, hierarchically interconnected porous architecture, together with a functional hydrated interfacial layer, enables continuous low-resistance transport pathways and capillary-assisted water permeation under ultra-low pressures. Meanwhile, the stable hydration interface effectively suppresses fouling while maintaining high separation selectivity. Benefiting from these synergistic structural and interfacial regulations, the membrane exhibits a water flux of 110 L m -2 h -1 , high dye rejection (>98%), and low salt rejection. Remarkably, efficient separation can still be achieved under simple manual pressure without external pumping. This integrated strategy, combining capillary-assisted transport, hierarchical pore engineering, and interfacial hydration defense, establishes a biomimetic design paradigm for low cost, low energy, and high stability separation membranes. It demonstrates strong potential for industrial wastewater treatment, portable water purification, and sustainable desalination. Download: Download high-res image (230KB) Download: Download full-size image