Advancing solar-driven redox processes: pyrene-based covalent organic frameworks for efficient environmental remediation and H2O2 production

Abstract

The rational design of efficient photocatalysts is critical for solar-driven chemical conversions. Pyrene-based covalent organic frameworks (COFs) are promising candidates due to pyrene's excellent electron-donating ability and planar π-conjugation, making them potentially powerful photocatalysts. However, the limited availability of pyrene monomers hinders the design of such COFs. This study explores COFs incorporating a novel pyrene monomer for selective two-electron oxygen reduction (2e⁻ ORR) and two-electron water oxidation (2e⁻ WOR) to produce hydrogen peroxide (H₂O₂). Under visible light irradiation, COF-Pytri achieves a remarkable H₂O₂ production rate of 1046 μmol g⁻¹ h⁻¹, representing 4-fold and 5-fold enhancements over the COFs without pyrene or triazine units, respectively. Density functional theory (DFT) calculations reveal that the triazine unit acts as an electron acceptor site for selective O₂ adsorption and reduction and the pyrene unit provides the site for the water oxidation reaction as an electron donor, and the combination of D–A structure improves the efficiency of charge carrier separation and enables the reaction to proceed in an orderly manner. Furthermore, COF-Pytri exhibits rapid photocatalytic degradation of environmental pollutants, as demonstrated with Rhodamine B (RhB). This work provides a design strategy for developing advanced pyrene-based photocatalysts for energy and environmental applications.