Metal@COFs Possess High Proton Conductivity with Mixed Conducting Mechanisms

The inherent porous structures and aligned functional units inside the skeleton of covalent organic frameworks (COFs) provide an extraordinary promise for post-modification and deservedly expand their application in the field of proton conduction. Herein, we tactfully introduced copper ions into a two-dimensional COF (TpTta) furnished with ample N,O-chelating sites by a post-modification strategy to achieve two copper(II)-modified products, namely, CuCl2@TpTta-3 and CuCl2@TpTta-10. Inspiringly, the two modified COFs demonstrated the higher conductivities of 1.77 × 10-3 and 8.81 × 10-3 S cm-1 under 100 °C and 98% relative humidity, respectively, among the previously reported COFs with higher σ values. In comparison to the pristine COFs, the σ values of CuCl2@TpTta-3 and CuCl2@TpTta-10 are boosted by 2 orders of magnitude. On the basis of structural analyses, nitrogen and water vapor adsorption tests, and proton conduction mechanism analysis, we deeply analyzed the reason why the conductivity of the modified COFs was significantly increased. To the best of our knowledge, it is the first time to employ the CuCl2-modified strategy to boost the conductivity of COFs, which offers a wise idea for the fabrication of highly conductive materials in the field of fuel cells.