Molecularly Engineered Covalent Organic Frameworks for Hydrogen Peroxide Photosynthesis

Abstract

Synthesizing H2O2 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 H2O2 production. Herein we prepare a bipyridine‐based covalent organic framework photocatalyst (denoted as COF‐TfpBpy) for H2O2 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 H2O2 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 H2O2 from water and air; and paves the way for wastewater treatment using photocatalytic H2O2 solution.

Regulating the Tautomerization in Covalent Organic Frameworks for Efficient Sacrificial Agent-Free Photocatalytic H2O2 Production

“…Covalent organic frameworks (COFs) are another new type of emerging metal-free photocatalysts due to their well-defined pore structure, extended light-response range, and highly tunable optoelectronic property. − Although several pioneering studies have shown that COFs could be endowed with promising photocatalytic H 2 O 2 production efficiency through molecular tailoring, topology tuning, mass transfer regulating, Lewis acid site manipulating, and biocatalytic approach mimicking, several critical issues need to be addressed before their practical implementation. First, the imine bonds are susceptible to harsh conditions, as a majority of the highly crystalline COFs were prepared using the reversible Schiff-base chemistry.…”