Polyoxovanadate Building Units in Metal–Organic Frameworks: Coordination Connectivity and Selective Oxidation of Aromatic Thioether

Polyoxovanadate (POV) clusters, with their diverse vanadium-oxo coordination modes, provide structurally well-defined inorganic nodes for constructing functional metal–organic frameworks (MOFs). In this work, four polyoxovanadate-based metal–organic frameworks [Co2(DPP)4(V4O12)]·0.25H2O (1), [M3(DPP)4(H2O)4(V6O18)]·2H2O (M = Co (2) and Ni (3)), and [Zn3(DPP)3(V6O18)] (4) (DPP = 1,3-Di(4-pyridyl)propane) were reported and structurally characterized by single-crystal X-ray diffraction. These materials feature distinct POV motifs, including cyclic {V4} units and extended {V3}/{V6} vanadium-oxo chains, providing well-defined coordination environments around the metal nodes. All four MOFs efficiently catalyzed the oxidation of aromatic thioethers using H2O2 with high selectivity for sulfoxide formation. Among them, compound 4 exhibited the highest activity and excellent recyclability over at least five cycles, consistent with its robust structural stability. Comparative catalytic and structural analyses suggest that the superior performance of 4 originates from the parallel and independent action of unsaturated V and Zn centers within its zigzag V–Zn chains. This study demonstrates that tuning POV building units and their coordination connectivity provides an effective strategy for controlling activity and selectivity in oxidation reactions.