Two octamolybdate-based complexes formulated by [M2(H2O)4(γ-Mo8O26)(HDIBA)2]·H2O [M = Co (1), Zn (2), DIBA = 3,5-di(1H-imidazol-1-yl)benzoic acid], were synthesized successfully by using hydrothermal method in the presence of 3,5-di(1H-imidazol-1-yl) benzonitrile (DICN) as initial ligand. The DIBA ligand was generated in situ from the hydrolysis of DICN ligand. The γ-octamolybdate polyoxoanion was decorated by two DIBA ligands relying on Mo−O covalent bonds between the carboxyl oxygen atom of DIBA ligand and Mo atom of polyoxoanion. The transition metal centers joined in pairs these modified γ-octamolybdate polyoxoanions into a 1D chain, which were further aggregated to result in a 2D layer. The investigations on the electrochemical performances indicated that the two complexes displayed electrocatalytic and electrochemical sensing activities for bromate and Cr(VI), which provide potential electrode materials in preparing the electrochemical sensors and electrocatalysts.