Fully conjugated two-dimensional sp 2 -carbon covalent organic frameworks for efficient photocatalytic hydrogen generation

In this paper, two types of conjugated, triazine-based covalent organic frameworks (COFs) with different connected linkages (imine bond and sp 2 -carbon-CN bond) are presented. The insignificant difference in the linkages creates a remarkable difference in their performance in visible-light-driven hydrogen generation. The fully π-conjugated two-dimensional (2D) COF with sp 2 -carbon-CN linkages showed an external quantum efficiency of 13.48% at 450 nm, which is an unprecedented result for COF photocatalysts. In contrast, the imine-linked 2D COF displayed almost no photoactivity. Further photoelectrochemical and quantum chemical studies provide an in-depth understanding of the catalytic mechanism. This finding provides new insight into preparing high-performance organic photocatalysts for solar energy conversion.