Abstract Mn-decavanadate cluster [Mn(mIM)4]2[H2V10O28] (1) (mIM = 1-methylimidazole) was synthesized using a neutral hexanuclear V6O15(mIM)8 as a synthon and further acted as heterogeneous catalyst in sulfoxidation of sulfide using H2O2 as terminal oxidant. 1 shows excellent catalytic performance and can be recycled at least 3 times without considerable decrease in activity.