Metal-Doped Bipyridine-Linked Covalent Organic Framework Nanosheets As a Novel Platform for Photoelectrocatalysts

摘要

Light-driven conversion of chemical substances has attracted much attention with respect to the photogeneration of valuable chemicals and the photodegradation of pollutants. Covalent organic frameworks (COFs), which are crystalline porous polymers, have attracted much attention as novel platforms for photo-energy conversion materials because of their unique physiological properties, including their nano-porous structure, high design flexibility and visible light absorption. In addition, as COFs possess abundant hetero atoms with a lone electron pair, such as N, O and S, they can support metal atoms via coordination bonds and exhibit various functions originated from supported metals. For example, our group has recently demonstrated metal-doped COFs (M-COFs) exhibited various unique elctrocatalytic functions depending on the metal species. Cu- and Ni-doped COFs serve as the electrocatalysts for oxygen reduction reaction (ORR) and carbon dioxide reduction (CRR), respectively. In this study, we newly synthesized various metal-doped bipyridine-linked COFs (bpy-COF) and evaluated their photoelectrocatalytic activity. First, the details in the photo-induced charge transfer process were investigated using photoelectrochemical action spectrum, photoluminescence and in situ spectroscopy by employing the ORR mediated by Cu sites doped in bpy-COF (Cu-bpy-COF) as a model system. We subsequently attempted to expand metal-doped COFs as the photo electrocatalysts for CRR toward the application in artificial photosynthesis.