Photocatalytic Selective Oxidation of Toluene over Chlorine-Coordinated MIL-101(Fe) under Ambient Conditions

The activation of an inert C(sp³)-H bond in selective oxidation of hydrocarbons under mild conditions is a critical and challenging process. Herein, we report a stable chlorine-coordinated metal-organic framework (MOF) photocatalyst, MIL-101(Fe), for efficient visible-light-driven photocatalytic selective oxidation of toluene to benzaldehyde in air under ambient conditions. Encouragingly, a benzaldehyde formation yield of 3.11 mmol·g^-1·h^-1 with a selectivity of 92.1% is achieved in 5 h, which is superior to most of the reported works. Based on the experimental results and characterizations, the high catalytic performance is mainly due to the promoted rate-limiting step of C(sp³)-H bond activation by a chlorine radical (Cl·) from the coordinated -Cl in the MIL-101(Fe) structure. In addition, the present photocatalyst possesses good substrate tolerance for photocatalytic selective oxidation of various toluene derivatives under optimized conditions.