Cascade Oxidation of Ethylene and Propylene over a Redox Heterometallic Cluster.

The selective oxidation of ethylene (C2H4) and propylene (C3H6) offers the most important route for preparing a variety of platform chemicals. However, current industrial synthesis still relies on diversified thermo-oxidation methods, resulting in complex, inefficient, and high-cost production. Herein, we report a redox heterometallic cluster (TiIV16MnII4) catalyst capable of achieving unprecedented cascade oxidation of C2H4 and C3H6 to divergent products in a simple photoassisted electrochemical system. In situ characterizations combined with theoretical calculations disclose that under photoelectrochemical (PEC) operation, different electron transfer processes between the peripheral MnII centers and the internal {TiIV16O22} "electron reservoir" produce multiple active oxidation states (MnII → MnIV and TiIV → TiIII), which are able to activate multireactants and generate stabilized bromine radical (•Br) and hydroxyl radical (•OH) intermediates. As a result, the TiIV16MnII4 enables controlled tandem oxidation of C2H4/C3H6 to bromoethanol (BrCH2CH2OH)/bromopropanol (BrCH2CHOHCH3), ethylene oxide (EO)/propylene oxide (PO), and bromoacetic acid (BrCH2COOH)/bromoacetone (BrCH2COCH3) via shared (•Br + •OH)-dominated catalytic mechanisms, with high conversions (>99%), yields (up to 87%), and Faradaic efficiencies (FEs, up to 75%). Last but not least, this cascade catalytic system is applicable to a wide olefinic substrate scope as well as sustainable scaled-up production.