Integration of Earth-Abundant Photosensitizers and Catalysts in Metal–Organic Frameworks Enhances Photocatalytic Aerobic Oxidation
Xuanyu Feng, Yunhong Pi, Yang Song, Ziwan Xu, Zhong Li, Wenbin Lin
Abstract
We report here the construction of two metal–organic frameworks (MOFs), Zr6-Cu/Fe-1 and Zr6-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 O2 as the only oxidant, Zr6-Cu/Fe-1 and Zr6-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 photo-oxidation mechanism: oxidative quenching of [Cu-PS]* by O2 affords [CuII-PS], which efficiently oxidizes FeIII–OH to generate a hydroxyl radical for substrate oxidation. This work highlights the potential of MOFs in promoting earth-abundant metal-based photocatalysis.