Two new Keggin-based organic-inorganic hybrid compounds, namely [Cu8(H2biim)8(SiW12O40)2]·7H2O (1) and [Cu2(H2biim)4(H2O)2(SiMo12O40)] (2) (H2biim = 2,2′-biimidazole), were hydrothermally synthesized by using the bi-imidazole ligand and Keggin anions, and characterized by single-crystal X-ray diffraction, elemental analyses, IR spectra, and cyclic voltammetry. In compound 1, two H2biim ligands are fused by two Cu+ ions to form a dinuclear [Cu2(H2biim)2]4+ subunit. The Cu3-based dinuclear subunits are further connected by [SiW12O40]4– anions to construct a 1D chain. The other Cu1-based dimer acts as a supporting unit of the anion. Through changing [SiW12O40]4– to [SiMo12O40]4–, compound 2 was obtained, including discrete anions and mononuclear subunits [Cu(H2biim)2(H2O)]2+. The electrochemical behaviors of compounds 1 and 2 bulk-modified carbon paste electrodes (1- and 2-CPE) were studied.