Three new organic–inorganic hybrid compounds based on the Keggin polyoxometalates, [Co₂(tib)₂(H₂O)₄(α-HBW₁₂O₄₀)]·6H₂O (1), [Co₂(tib)₂(H₂O)₄(α-SiW₁₂O₄₀)]·4H₂O (2) and [Co(H₂tib)₄(α-BW₁₂O₄₀)₂]·8H₂O (3) (tib = 1,3,5-tris(1-imidazoly)benzene), were hydrothermally synthesized by utilizing a pH-dependent approach in the same POM/Co/tib reaction systems. X-ray structural analyses reveal that isostructural compounds 1 and 2, obtained at pH 3.6, have a (3,4)-connected 2D net with the (4² 6)(4² 6³ 8) topology; compound 3, isolated at pH 4.8, is a “butterfly-like” structure stemming from α-BW₁₂ polyoxoanions and Co–tib motifs. In addition, the electrocatalytic properties of compounds 1–3 were studied by cyclic voltammetry. Compounds 1–3 displayed bifunctional electrocatalytic activities toward reduction of nitrite and oxidation of ascorbic acid.