Ultralong-Lived Excitons in Metallo-Quinoline-Incorporated Covalent Organic Frameworks Promote Photoreductive...

Designing long-lived excitons in photocatalysts is crucial for efficient charge separation. However, most of the current organic photocatalysts are characterized by a relatively short exciton lifetime within the range of picoseconds due to localized excitons with large binding energies. Herein, we report the design of ultralong-lived excitons with a lifetime exceeding 8000 ps by constructing metallo-quinoline-incorporated covalent organic frameworks (COFs). Post-synthetic metalation into the quinoline-containing skeletons of COFs allows the cooperative metal chelation at the COF interlayers to form monodispersed MN₂O₂ species, ensuring the incorporation of metallo-quinoline complexes into the COF structures at the molecular level. Diverse metal types are utilized to confirm the synthetic versatility, with the Fe(III)-chelated one exhibiting the highest electrophilicity, distinctive orbital distribution, ultralong exciton lifetimes, and photostability. These features empower their use as efficient and robust heterogeneous photocatalysts for a challenging but desirable olefin-carbonyl reductive cross-coupling reaction, achieving remarkable conversion efficiencies and isolated yields for various substrates and good recyclability. This metallo-quinoline complex-incorporated strategy establishes a feasible way to elongate the lifetime of excitons in COF platforms for future photocatalytic research, which can cause a ripple effect for the metal-incorporated COF field.