Emerging as a type of promising materials for proton conduction, covalent organic frameworks (COFs) assembled from dynamic imine bonds face a challenge of surmounting hydrolytic instability to achieve long-term performance in humid environments. In this work, we report a post-synthetic strategy to simultaneously enhance the hydrolytic stability and hydrophilicity of a pyridine-imine-based COF, COF-LIFM7, without compromising its crystallinity and porosity. A bifunctional monomer containing amino and acetal groups was employed to construct the primary framework, which was subsequently modified via amide formation and pyridine N-oxidation to yield COF-LIFM7-Amide and COF-LIFM7-Amide-N+O-. These stepwise modifications increased the polarity and hydrogen-binding sites within COF pores to improve water affinity, leading to a three-order-of-magnitude enhancement in the proton conductivity for COF-LIFM7-Amide-N+O-, reaching 1.9 × 10-3 S/cm at 95% relative humidity and 70 °C. This study highlights a generalizable post-synthetic approach for tuning the pore chemistry of COFs to achieve high performance in proton-conducting applications under humid conditions.
Keywords: Proton conduction; Pyridine-imine; Stepwise post-modification; covalent organic framework; water adsorption.
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