日本ゼオライト学会　刊行物 Publication of Japan Zeolite Association

Covalent organic frameworks (COFs) are porous materials with ordered pores composed of highly symmetrical units. Since conventional methods for synthesizing COF thin films typically require complex, low-concentration, and time-consuming conditions, the development of a rapid and controllable film fabrication technique garners attention. In this study, we propose an indirect electrochemical synthesis method for imine-based COFs using electrogenerated acid (EGA) as a catalyst. EGAs are locally generated on the electrode surface through electrochemical reactions, promoting imine bond formation at the neighboring electrode surface. By employing 1,2-diphenylhydrazine as the EGA source and conducting electrolysis in the presence of multifunctional amines and aldehyde monomers, we successfully synthesized imine-based COFs on the electrode surface at room temperature within a short time. The resulting COF thin films exhibited crystallinity and porosity, and this method was applicable to various imine-based COFs. As an application of the resultant materials, the COF thin films demonstrated their potential for hydrophobic coatings. The COF thin films with sponge-like structures obtained by short-duration electrolysis showed superhydrophobic properties. Furthermore, this method enabled the fabrication of COF/nanocarbon composites with a single-nanometer-scale COF layer. The COF/nanocarbon composite electrodes displayed improved activity as organic oxygen reduction catalysts. This method is expected to accelerate the electrochemical applications of COF thin films.