Construction of Cobalt-Containing Polyoxovanadate-Based Inorganic–Organic Hybrids as Heterogeneous Catalysts for the Selective Oxidation of Sulfides

In order to develop efficient catalysts for the selective oxidation of sulfides, in this work, two polyoxovanadate-based inorganic-organic hybrids, [Co(H₂O)₃(3-bpfb)_0.5(V₂O₆)]·(3-bpfb)_0.5 (1) and [Co(H₂O)₂(4-bpfb)_0.5(V₂O₆)] (2) [3-bpfb = N, N'-bis(3-pyridylformamide)-1, 4-benzenediamine, 4-bpfb = N, N'-bis(4-pyridylformamide)-1, 4-benzenediamine], were isolated under hydrothermal conditions. The structures of 1 and 2 embodied two kinds of different cobalt-containing polyoxovanadate-based inorganic chains. Compound 1 contained a one-dimensional inorganic zigzag chain created by the aggregation of {V₂O₆} clusters with each other, on which Co (II) ions were fixed. But it was an inorganic dimeric chain constructed from two linear {V₂O₆} cluster-based chains gathered by Co (II) ions in 2. The 3-bpfb and 4-bpfb ligands, as the bidentate linkers, coordinated with two Co (II) ions from adjacent chains to organize them into two-dimensional layers. The hydrogen bonds made important contributions to the formation of supramolecular structures of the two compounds. The two compounds served as heterogeneous catalysts and exhibited efficient activity for the selective oxidation of sulfide to sulfoxide and could be reused at least six times without loss of catalytic activity and stability.