Generation, Capture, Storage, and Release of Singlet Oxygen from a Perylene Diimide‐Based Metallacage for Oxygen Sensing

The controlled generation and utilization of singlet oxygen (¹O₂) are crucial for its diverse applications but remain challenging due to its high reactivity and short-lived nature. Here, we report a box-shaped metallacage prepared via multicomponent coordination-driven self-assembly using tetrapyridyl perylene diimide (PDI) and tetracarboxylate anthracene as building blocks. Upon photo-irradiation, the PDI faces act as photosensitizers to generate ¹O₂, which reacts with the anthracene pillars to form a peroxidized metallacage, where ¹O₂ is captured and stored as anthracene peroxides. Heating releases ¹O₂ quantitatively, restoring the original metallacage structure. Both states are stable at room temperature, as confirmed by X-ray diffraction. Additionally, photoinduced electron transfer (PET) from anthracene pillars to PDI faces quenches the emission of the metallacage, while oxidation of anthracene inhibits PET, yielding bright fluorescence for the peroxidized metallacage. This reversible emission change enables the metallacage to function as a "turn-on" fluorescence sensor for dissolved oxygen, with a detection limit of 1.1 × 10^-3 mg L^-1. This study demonstrates a metallacage that can generate, capture, store, and release ¹O₂ for oxygen sensing, offering insights for designing stimuli-responsive smart materials.