Zr-MOF catalyzed selective oxidation of anilines to azoxybenzenes in aqueous H2O2 solution

A highly efficient and organic solvent-free synthetic strategy for the selective oxidation of anilines to azoxybenzenes was developed by employing porous Zr-MOFs as catalysts in aqueous hydrogen peroxide solution. The impact of cluster nodes, pore size, and linker functionalities on the catalytic performance of Zr-MOFs was fully evaluated and discussed. Featuring abundant bridging Zr-OH-Zr catalytic sites and confined microenvironments, the pristine UiO-66(Zr) could create abundant reactive oxygen species (ROS) with high H 2 O 2 efficiency, affording quantitative yield of azoxybenzene under mild conditions. Furthermore, the UiO-66(Zr)/H 2 O 2 heterogeneous catalytic system exhibited broad and size-selective substrate scope and excellent stability in consecutive catalytic cycles. Mechanism studies demonstrated that the azoxybenzenes were produced through radical pathway on bridging Zr-OH-Zr sites. This study provided alternative strategies exploiting green catalytic systems with porous MOFs, which might further expand the potential application of the MOFs family.