Fabrication of NanoCOF/Polyoxometallate Composites for Photocatalytic NADH Regeneration via Cascade Electron Relay

Covalent organic frameworks (COFs) as novel visible‐light responsive photocatalysts confront the problem of low photocatalytic activity due to the difficulty in separation of photogenerated charge carriers. Herein, the fabrication of nanoCOF/polyoxometallate (POM) composites to enhance the charge separation efficiency via cascade electron relay is reported. It is found that the photogenerated electrons in the π orbitals of nanoCOF quickly transfer to POM (electron mediator and electron storage tank) to form heteropolyblue (HPB), which is verified by electron paramagnetic resonance and ultraviolet (UV)–vis characterizations. In photocatalytic NADH regeneration, nanoCOF/POM composites afford NADH yield of 97% with turnover frequency of 72.0 mmolg COF −1 h −1 , which is the highest ever reported for COFs and is more than 360‐fold that of COF counterpart. The high photocatalytic activity of nanoCOF/POM composites is mainly attributed to the high concentration of charge carriers and long lifetime of photogenerated charges on the basis of transient absorption spectroscopy, which are achieved by the cascade relay of photogenerated electrons. The primary results suggest that the integration of COFs with electron mediators is an efficient approach to increase the photocatalytic activity via promoted charge separation efficiency.