Near Infrared Light‐Triggered Photocatalytic Decaging for Remote‐Controlled Spatiotemporal Activation in Living Mice**

Abstract Spatiotemporal manipulation of biological processes in living animals using noninvasive, remote‐controlled stimuli is a captivating but challenging endeavor. Herein, we present the development of a biocompatible photocatalytic technology termed CAT‐NIR, which uses external near infrared light (NIR, 740 nm) to trigger decaging reactions in living mice. The Os(II) terpyridine complex was identified as an efficient NIR photocatalyst for promoting deboronative hydroxylation reactions via superoxide generation in the presence of NIR light, resulting in the deprotection of phenol groups and the release of bioactive molecules under living conditions. The validation of the CAT‐NIR system was demonstrated through the NIR‐triggered rescue of fluorophores, prodrugs as well as biomolecules ranging from amino acids, peptides to proteins. Furthermore, by combining genetic code expansion and computer‐aided screening, CAT‐NIR could regulate affibody binding to the cell surface receptor HER2, providing a selective cell tagging technology through external NIR light. In particular, the tissue‐penetrating ability of NIR light allowed for facile prodrug activation in living mice, enabling noninvasive, remote‐controlled rescue of drug molecules. Given its broad adaptability, this CAT‐NIR system may open new opportunities for manipulating the functions of bioactive molecules in living animals using external NIR light with spatiotemporal resolution.