Three new metal–organic coordination polymers, [Co 2 (bbix) 3 (dnba) 4 (H 2 O)]·0.5bbix (1), [Co(bbix) 1.5 (aip)]·H 2 O (2) and [Co(bbix)(fma)]·3H 2 O (3) (bbix=1,4-bis(benzimidazol-1-ylmethyl)benzene, Hdnba=3,5-dinitrobenzoate acid, H 2 aip=5-amino-isophthalic acid and H 2 fma=fumaric acid), were obtained under hydrothermal conditions and structurally characterized. Coordination polymer 1 shows a linear chain formed by dinuclear [Co 2 (dnba) 4 (H 2 O)] units and bbix ligands. The chains are further extended into a supramolecular layer by π–π stacking interactions between dnba and bbix. Coordination polymer 2 features a layer constructed from Co II ions and bbix ligands, and the aip anions only consolidate the layer structure. Coordination polymer 3 possesses a three-dimensional (3D) 3-fold interpenetrated diamond framework. In 3, the fma anions link the Co II ions to form a wave-like chain, which is further extended into a 3D architecture by the bbix ligands. The structural analyses clearly indicate that the nature of the secondary auxiliary ligands can effectively influence the coordination environments of the Co II ions and the dimensionality of the coordination polymers 1–3. In addition, the electrochemical and photoluminescent properties of 1–3, as well as magnetic properties of 1, have been investigated.