Integration of Earth-Abundant Photosensitizers and Catalysts in Metal-Organic Frameworks Enhances Photocatalytic Aerobic Oxidation

We report here the construction of two metal-organic frameworks (MOFs), Zr-6-Cu/Fe-1 and Zr-6--Cu/Fe-2, by integrating earth-abundant cuprous photosensitizers (Cu-PSs) and Fe catalysts for photocatalytic aerobic oxidation. Site isolation and pore confinement stabilize both Cu-PSs and Fe catalysts, while the proximity between active centers facilitates electron and mass transfer. Upon visible light irradiation and using O-2 as the only oxidant, Zr-6-Cu/Fe-1 and Zr-6-Cu/ Fe-2 efficiently oxidize alcohols and benzylic compounds to afford corresponding carbonyl products with broad substrate scopes, high turnover numbers of up to 500 with a 9.4-fold enhancement over homogeneous analogues, and excellent recyclability in four consecutive runs. Control experiments, spectroscopic evidence, and computational studies revealed the photooxidation mechanism: oxidative quenching of [Cu-PS]* by O-2 affords [Cu-II-PS], which efficiently oxidizes Fe-III-OH to generate a hydroxyl radical for substrate oxidation. This work highlights the potential of MOFs in promoting earth-abundant metal-based photocatalysis.

Automated summary

In this study, two metal-organic frameworks were constructed to facilitate the photocatalytic oxidation reactions of copper and iron. The materials showed high catalytic efficiency and good recyclability. Analysis of the photooxidation mechanism provided insights into the catalytic mechanism.