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Robust covalent organic frameworks (COFs) with abundant redox-active sites have attracted intense attention for organic cathode materials due to the ordered structure and excellent stability. Herein, a two-dimensional (2D) crystalline copper-porphyrin covalent triazine framework (CuBCPP-CTF) was synthesized via polycondensation of 5,15-bis(4-cyanophenyl) porphyrin (H2BCPP) and followed by post-copperization. The integration of copper-porphyrin moieties and triazine linkages provides two kinds of functional sites for outstanding Li+ and PF6− ions storage. Electrochemical studies reveal a high discharge capacity of 232 mA h g−1 at 200 mA g−1 and high mid-point voltage (2.77 V vs. Li+/Li), corresponding to an outstanding energy density of 601 W h kg−1. Density functional theory calculations and ex-situ characterizations disclose the intrinsic bipolar redox mechanism for metalloporphyrin for both PF6− and Li+ accommodation and p-type triazine units for PF6− storage.
Zhou et al. (Tue,) studied this question.