Unlocking Efficient High‐Order Multiphoton‐Excited Fluorescence of Metal‐Organic Framework via Octupolar Module In Situ Formation

Abstract

AbstractEngineering high‐order multiphoton excited fluorescent (H‐MPEF) materials is of significant importance for sensing, 3D optical data storage and bioimaging. However, it remains a challenging endeavor due to a lack of appropriate construction strategies. This study demonstrates that incorporating octupolar modules within metal‐organic framework (MOF) offers new possibilities for the design of highly attractive H‐MPEF materials. Constructed from a typical MOF (UiO(bpdc)), the in situ formation of multibranched octupolar cyclometallated iridium(III) modules via post‐ligand coordination modification endowed the framework with enlarged static hyperpolarizabilities, an extended conjugated system, and enhanced charge transfer, ultimately unlocking its second near‐infrared (NIR‐II, 1000–1700 nm) light activated H‐MPEF performance including three‐ and four‐photon activity. Moreover, these exciting features, combined with subsequent orotic acid‐capping, enabled its application in cancer cell‐specific targeting oncotherapy using tissue‐penetrating NIR‐II light. This finding highlights the vital role of octupoles in H‐MPEF performance and sets a benchmark for unlocking the multiphoton activity of MOFs at the molecular level for deep‐seated tumor fluorescence imaging and therapy.