Novel PTFE / PI Nanofibrous Composite Membranes Enabling High‐Flux Desalination and Durable Anti‐Scaling in Membrane Distillation

Polytetrafluoroethylene (PTFE) membranes are widely recognized for their low surface energy and strong resistance to salt accumulation in membrane distillation (MD) processes. However, challenges such as limited interfacial adhesion and unfavorable morphological characteristics hinder the fabrication of fibrous membranes and compromise vapor flux and long‐term stability. This study introduces a simple and efficient one‐step fabrication method for PTFE nanofibrous membranes. By incorporating a water‐soluble precursor of polyimide (PI) into an aqueous PTFE emulsion, followed by thermal imidization during PTFE sintering, a uniformly distributed PI microphase is formed within the PTFE matrix. This approach enhanced nanofiber surface roughness, controlled fiber morphology and membrane porosity, and prevented fiber fusion and shrinkage. The resultant PTFE/PI membranes exhibit strong three‐dimensional super‐hydrophobicity and self‐cleaning capabilities, with a water contact angle of 156 ± 4°. Under direct contact membrane distillation (DCMD) with 3.5 wt% NaCl feed at a temperature difference of 40 °C, the membranes delivered a high water vapor flux of 52.2 ± 2 L m −2 h −1 , approximately 206% higher than pure PTFE nanofibrous membranes, while maintaining salt rejection nearly 100%. Moreover, the membranes demonstrate stable performance over 168 hours of continuous operation.