Hybrid of Polyoxometalate-Based Ionic Salt and N-Doped Carbon toward Reductant-Free Aerobic Hydroxylation of Benzene to Phenol

A novel carbon-based hybrid is composed of N-doped ordered mesoporous carbon (NC) and polyoxometalate (POM) based ionic salt (IL-POM), constructing the first efficient non-noble metal heterogeneous catalyst for reductant-free hydroxylation of benzene to phenol with molecular oxygen. Enhanced activity and reusability were achieved and were even better than the previous noble metal involved system. The newly task-specifically designed dicationic ionic liquid tethered with the nitrile group contributed to the high efficiency and heterogeneous property. Systematic structure–activity analysis revealed that the superior activity for this difficult reaction came from the simultaneous activation of benzene by NC and O2 by V species of IL-POM. This work suggests a new green reaction pathway toward heterogeneous aerobic hydroxylation of the Csp2-H bond in π-conjugated aromatic molecules.