Terephthalaldehyde-based covalent organic frameworks as photocatalysts for CO2 reduction under visible light

As a new type of porous organic materials, two-dimensional covalent organic frameworks (2D COFs) show superior visible-light harvesting and effective separation and transport of the photogenerated charges, which ensures COFs to be promising platforms for photocatalysis. In the current work, two 2D imine-linked COFs (PDA-TAB and PDA-TTA), having the same framework with benzene and/or triazine units, were synthesized to investigate the effects of the introduced triazine units in the skeleton of COFs on photocatalytic CO2 reduction. Compared to PDA-TAB, PDA-TTA exhibits a much higher photocatalytic activity with a HCOOH yield of 65.7 μmol gcat-1h−1. Further studies indicate the introduction of triazine units in the skeleton of PDA-TTA not only can enhance the visible-light absorption due to the high conjugation degree, but also can promote the charge separation and migration, thus improving the photocatalytic performance. The current work facilitates to understand the roles of the key structural units in 2D COFs on photocatalysis and provides some insights to develop efficient photocatalysts for the conversion of CO2.