Engineering Photocatalytic Porous Organic Materials for Directing Redox versus Energy Transfer Processes

Abstract

Two organic materials containing phenanthroline and triazine fragments, but connected in different ways, are presented. The imine‐based material Phen–Tz–covalent organic framework (COF) preferentially shows photocatalytic activity through an energy transfer pathway as observed for olefin photoisomerization. However, an analogous covalent triazine framework (Phen–CTF) behaves as a powerful photoredox catalyst able to activate CX (X=Br, Cl) bonds. The analysis of this phenomenon by means of theoretical calculations enables the rationalization of the different photocatalytic behavior observed. Phen–CTF behaves as a donor–acceptor material resulting in efficient charge separation upon excitation, while the imine groups present in Phen–Tz–COF hamper charge separation contributing to the rapid recombination between electrons and holes. This justifies a better activation via electron transfer in Phen–CTF and via energy transfer in Phen–Tz–COF.