Checkerboard-Like Bimetallic Covalent Organic Frameworks as Efficient Electrocatalysts for Oxygen Reduction Reaction

Covalent organic frameworks (COFs) have been widely employed as an excellent scaffold for the electrocatalytic oxygen reduction reaction (ORR). To reach high activity and selectivity, various metal complexes have been imbedded into COFs via imine bonds to obtain ORR electrocatalysts. However, most of them suffer from passable performance and low stability due to the lack of active sites and decomposable linkage. In this work, we developed a series of dioxin-linked bimetallic COFs, which are constructed by phthalocyanine and perfluorinated phthalocyanine in checkerboard mode. The rational combination of different active metals, including Fe3+, Cu2+, Ni2+, and Co2+, as well as highly stable dioxin linkage renders these COFs as high-performance ORR electrocatalysts through a synergistic effect. Among these COFs, FePcF8-CoPc-COF exhibited the highest half-wave potential of 0.87 V, which constitutes a new record value among COFs and is comparable to that of commercial Pt/C catalysts. In addition, this COF can be recycled up to 10,000 runs without significant change in half-wave potential. This work not only developed an efficient and stable ORR electrocatalyst but also developed a strategy for the construction of functional COFs for practical applications.