Identification of Two-Dimensional Covalent Organic Frameworks with mcm Topology and their Application in Photocatalytic Hydrogen Evolution

Covalent organic frameworks have attracted considerable attention in recent years as a distinct class of crystalline porous organic materials. Their functional properties are inherently linked to their structural characteristics. Although hundreds of COFs have been reported so far, the types of their topologic structure are still limited. In this article, we report the identification of mcm topology for three porphyrin-based two-dimensional COFs which are constructed from [4 + 4] imine condensation reactions. The mcm net is generated by pentagonal tiling which has not yet been identified for COFs before. The structure of the COFs is elucidated by a variety of experimental characterization and structural simulations, by which their reticular frameworks comprised of pentagonal pores have been confirm. Moreover, the COFs exhibit high performance in photocatalytic hydrogen evolution from water, with the best one up to 10.0 mmol g-1 h-1 after deposited 0.76 wt.% Pt as a co-catalyst. This study identifies mcm topology for COFs for the first time, and highlights the potential of these COFs as promising photocatalysts for sustainable hydrogen production from water.