Overcoming Photochemical Limitations in Covalent Organic Frameworks: Low-Energy Light Driven Selective 1O2 Generation Achieved by Donor-Acceptor Strategy

Abstract

Singlet oxygen (1O2) plays a crucial role in various photocatalytic oxidation reactions; however, achieving high-efficiency and selective 1O2 production under low-energy light remains a challenge. Herein, we present a novel donor-acceptor (D-A) strategy in covalent organic frameworks (COFs) to regulate the localized electronic state structures for efficient and selective 1O2 generation under low-energy light. Notably, the rationally incorporation of the negatively charged carbonyl groups into the basal plane of the COF strengthens the D-A interaction, improves light harvesting in the lower-energy region, and facilitates highly selective 1O2 generation through a coupled charge-transfer mechanism. As a result, the engineered COF demonstrates exceptional photocatalytic performance in 1O2 driven advanced oxidation, enabling gram-scale production under red light, even when operating through translucent barriers. A mechanistic study revealed that the distinct 1O2 production under low-energy light is attributed to the spatially locked structure and charge localization around active centers. These features enhance strong pi-pi stacking interaction, promote effective charge separation and transport properties, and ultimately facilitate the activation of O2 to 1O2. This study paves the way for the development of high-performance COF photocatalysts for low-energy light-driven reactive oxygen species generation in advanced oxidation processes.