Molecularly Engineered Covalent Organic Frameworks for Hydrogen Peroxide Photosynthesis

Synthesizing H₂ O₂ from water and air via a photocatalytic approach is ideal for efficient production of this chemical at small-scale. However, the poor activity and selectivity of the 2 e^- water oxidation reaction (WOR) greatly restricts the efficiency of photocatalytic H₂ O₂ production. Herein we prepare a bipyridine-based covalent organic framework photocatalyst (denoted as COF-TfpBpy) for H₂ O₂ production from water and air. The solar-to-chemical conversion (SCC) efficiency at 298 K and 333 K is 0.57 % and 1.08 %, respectively, which are higher than the current reported highest value. The resulting H₂ O₂ solution is capable of degrading pollutants. A mechanistic study revealed that the excellent photocatalytic activity of COF-TfpBpy is due to the protonation of bipyridine monomer, which promotes the rate-determining reaction (2 e^- WOR) and then enhances Yeager-type oxygen adsorption to accelerate 2 e^- one-step oxygen reduction. This work demonstrates, for the first time, the COF-catalyzed photosynthesis of H₂ O₂ from water and air; and paves the way for wastewater treatment using photocatalytic H₂ O₂ solution.