Overcoming Photochemical Limitations in Covalent Organic Frameworks: Low-Energy Light Driven Selective ¹O₂ Generation...

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 π-π 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.