Selective Partial Oxidation of Methyl Groups by Electrochemically Generated Ceric Ions.

Activation of saturated C-H bonds, particularly the partial oxidation of methyl groups, remains a major challenge in modern catalysis due to their high bond dissociation energies and low polarity, and it currently relies heavily on costly catalysts, oxidants, and harsh conditions. In this work, we report a sustainable strategy for the selective partial oxidation of methyl groups using electrochemically generated ceric ions (Ce4+). Using toluene as a model system, we construct a Pickering emulsion stabilized by hydrophobized SiO2 microspheres, which markedly increases the interfacial area between the organic toluene phase and the aqueous Ce4+ phase. As a result, the system achieves a high benzaldehyde selectivity (∼80%) with a production rate of ∼10 mM h-1, nearly a 2-fold enhancement compared with a nonemulsified biphasic system. The reduced Ce3+ species is efficiently regenerated via electrochemical oxidation with a high electron utilization efficiency exceeding 95%, enabling a closed-loop oxidation-regeneration cycle under mild conditions. We also demonstrate that the solid emulsifier can be readily recovered and reused for ten cycles without noticeable performance degradation. Moreover, we extend this strategy to a broad range of aromatic and aliphatic methyl-containing substrates, demonstrating its broad applicability. When powered by renewable electricity, the process provides a green and cost-effective alternative to conventional methyl oxidation routes.