Activating Triplet Excitons in COFs via Layer‐Bridging Co Single Atoms for Photocatalytic H 2 O 2 Production and Tandem C─N Coupling

ABSTRACT Covalent organic frameworks (COFs) are promising photocatalysts for solar energy conversion in energy and environmental applications. However, their performance is intrinsically limited by weak spin–orbit coupling (SOC) arising from van der Waals interlayer interactions, thereby suppressing intersystem crossing and triplet‐exciton utilization. In this study, we demonstrate that layer‐bridging Co single atoms activate triplet excitons in COFs by synergistically enhancing SOC and inducing energy‐level splitting via Co─N coordination. This layer‐bridging Co coordination markedly promotes singlet‐to‐triplet conversion, enabling efficient O 2 activation and substantially boosting the generation of both 1 O 2 and O 2 •− . Consequently, the Co‐bridged COF achieves highly efficient photocatalytic H 2 O 2 production and tandem C─N coupling. This work establishes layer‐bridging single‐atom coordination as a promising strategy for regulating triplet‐state reactivity in COFs, offering new opportunities for reactive oxygen species (ROS)‐mediated photocatalysis and tandem organic transformations.