Semiconductor/Covalent-Organic-Framework Z-Scheme Heterojunctions for Artificial Photosynthesis

Abstract

A strategy to covalently connect crystalline covalent organic frameworks (COFs) with semiconductors to create stable organic-inorganic Z-scheme heterojunctions for artificial photosynthesis is presented. A series of COF-semiconductor Z-scheme photocatalysts combining water-oxidation semiconductors (TiO2, Bi2WO6, and alpha-Fe2O3) with CO2 reduction COFs (COF-316/318) was synthesized and exhibited high photocatalytic CO2-to-CO conversion efficiencies (up to 69.67 mu mol g(-1) h(-1)), with H2O as the electron donor in the gas-solid CO2 reduction, without additional photosensitizers and sacrificial agents. This is the first report of covalently bonded COF/inorganic-semiconductor systems utilizing the Z-scheme applied for artificial photosynthesis. Experiments and calculations confirmed efficient semiconductor-to-COF electron transfer by covalent coupling, resulting in electron accumulation in the cyano/pyridine moieties of the COF for CO2 reduction and holes in the semiconductor for H2O oxidation, thus mimicking natural photosynthesis.