A new family of trinuclear transition-metal (TM)-sandwiched heteropolyoxovanadates (hetero-POVs) {(SeV10O28(SeO3)(3)M(H2O)(3))(2)(M(H2O)(4))(10-) (Se8V20M3, where M = Mn2+, Co2+, and Zn2+) were prepared using two feasible approaches: a stepwise assembly strategy atop the POV precursor Se4V10 and a one-pot reaction approach of KVO3, SeO2, and a proline ligand. The crystallographic studies reveal that Se8V20M3 consist of two asymmetric {SeV10O28(SeO3)(3)M(H2O)(3))](6-)units, linked by another TM2+ ion, thus forming an interesting staggered sandwich-type arrangement. Additionally, Se8V20M3 and Se8V20M4 present strong correlations between their structures and catalytic properties. In particular, Se8V20M3 demonstrate an analogical heterogeneous catalytic performance as Se8V20M in the sulfoxidation reaction of thioethers owing to their structural similarities.