Two-Dimensional Covalent Organic Frameworks with Pentagonal Pores.

The pore shapes of two-dimensional covalent organic frameworks (2D COFs) significantly limit their practical applications in separation and catalysis. Although various 2D COFs with polygonal pores have been well developed, constructing COFs with pentagonal pores remains an enormous challenge. In this work, we developed one kind of pentagonal COFs with the mcm topological structure for the first time, through the rational combination of C 4 and C 2 symmetric building blocks. The resulting pentagonal COFs exhibit high crystallinity, excellent porosity, and strong robustness. Moreover, the inbuilt porphyrin units render these COFs as efficient electrocatalytic catalysts toward oxygen reduction reaction with a half-wave potential of up to 0.81 V, which ranks as one of the highest values among COFs-based electrocatalysts. This work not only verified the possibility of constructing 2D COFs with pentagonal pores but also developed a strategy for the construction of functional 2D COFs for interesting applications.