Perfluoroalkyl Functionalized Superhydrophobic Covalent Organic Frameworks for Excellent Oil–Water Membrane Separation and Anhydrous Proton Conduction

Rapid economic development has led to oil pollution and energy shortage. Membrane separation has attracted much attention due to its simplicity and efficiency in oil-water-separation. The development of membrane materials with enhanced separation properties is essential to improve the separation-efficiency. Proton exchange membrane fuel cells (PEMFCs) are expected to replace conventional engines due to their high-power-conversion rates and other favorable properties. Anhydrous-proton-conducting materials are vital components of PEMFCs. However, developing stable proton-conducting materials that exhibit high conductivity at varying temperatures remains challenging. Herein, two covalent organic frameworks (COFs) with long-side-chains are synthesized, and their corresponding COF@SSN membranes. Both membranes can effectively separate oil-water mixtures and water-in-oil emulsions. The TFPT-AF membrane achieves a maximum oil-flux of 6.05 × 10⁵ g h^-1 m^-2 with an oil-water separation efficiency of above 99%, which is almost unchanged after 20 consecutive uses. COF@H₃PO₄ doped with different ratios of H₃PO₄ is prepared, the results show that the perfluorocarbon-chain system has excellent anhydrous proton conductivity , achieving an ultra-high proton-conductivity of 3.98 × 10^-1 S cm^-1 at 125 °C. This study lays the foundation for tailor-made-functionalization of COF through pre-engineering and surface-modification, highlighting the great potential of COFs for oil-water separation and anhydrous-proton-conductivity.