Freestanding CuBTC‐Doped Fluorine‐Containing Flexible Membrane with Ultrafast Oil‐Water Separation via Enhanced Electrostatic Repulsion Force

Abstract To address the challenge of uneven distribution of metal–organic frameworks (MOFs) within the membrane in oil‐water separation, this study demonstrates a novel copper (II) benzene‐1,3,5‐tricarboxylate (CuBTC) embedded fluorinated composite membrane fabricated through high internal phase emulsion (HIPE) templating. During polymerization, MOFs spontaneously align at porous matrix interfaces via interfacial confinement, effectively suppressing particle aggregation. The resultant MOF‐polymer composite membranes exhibit some critical advantages: ultrafast oil‐water separation kinetics (60,854.4 L·m − 2 ·h −1 ·bar −1 for n‐hexane); chemical stability in extreme pH environments (pH 1–12). Molecular dynamics simulations revealed a unique separation mechanism dominated by synergistic electrostatic repulsion‐based CuBTC and the fluoro‐polymer matrix, challenging the conventional requirement of superhydrophobicity for efficient separation. The optimized membrane achieved 99.4% separation efficiency with <2% performance decay over 20 cycles. Furthermore, a universal flux‐thickness correlation ( J = Ae − T / B + C ) enabling quantitative comparison of separation membranes independent of thickness variations is established.