Influence of Linker Identity on the Photochemistry of Uranyl-Organic Frameworks.

While uranyl-based metal-organic frameworks (MOFs) boast impressive photocatalytic abilities, significant questions remain regarding their excitation pathways and methods to fine-tune their performance due to the lack of information regarding heterogeneous uranyl catalysis. Herein, we investigated how linker identity and photoexcitation impact uranyl photocatalysis when the uranyl coordination environment remains constant. Toward this end, we prepared three uranyl-based MOFs (, , and and then examined the structural and photochemical properties of each through X-ray diffraction, X-ray absorption, and photoluminescence. We then correlated our observations to the photocatalytic performance for fluorination of cyclooctane. The excitation profile from and exhibited spin-forbidden linker transitions and uranyl vibronic progressions, with uranyl excitation and emission being most dominant in . Consequently, was a more active photocatalyst than . In contrast, the excitation profile from contained transitions associated with the porphyrin linker exclusively. Photocatalytic activity from significantly underperformed in comparison to that of the other two MOFs. These data suggest that linkers' photophysical properties can be used to predict the photocatalytic behavior of uranyl-containing MOFs.