Rational Construction of Cyanide-Functionalized D-A-π-D Covalent Organic Framework for Highly Efficient Overall HO Photosynthesis from Air and Water.

Sacrificial-agent-free overall photosynthesis of HO from water and air represents currently a promising route to reform the industrial anthraquinone production manner, but, still blocks by the requirement of pure O feedstock, due to the insufficient oxygen supply from water under air. Herein, we report a rational molecule design on COFs (covalent organic frameworks) equiped with cyanide-functionalized D-A-π-D system for highly efficient overall HO production from air and water through photocatalytic oxygen reduction reactions (ORR) and water oxidation reaction (WOR). Without using any sacrificial agent, the as-synthesized D-A-π-D COF is found to enable a HO production rate as high as 4742 μmol h g from water and air and an O utilization and conversion rate up to 88 %, exceeding the other D-A-π-A COF by respectively 1.9- and 1.3-fold. Such high performance is attributed to the tuned electronic structure and prolonged charge lifetime facilitated by the unique D-A-π-D structure and cyanide groups. This work highlights a fundamental molecule design on advanced photocatalytic COFs with complicated D-A system for low-cost and massive HO production.