Two cobalt coordination polymers, namely{［Co(DTA) (1,4-DIB)(H2O)］·H2O}n (1) and ［Co(DTA)(1,3-BMIB)］n(2) were constructed by 2,5-dimethoxyterephthalic acid (H2DTA), Co(Ⅱ) ions and different imidazole derivatives 1,4-di(1H-imidazol-1-yl)benzene (1,4-DIB) and 1,3-bis(4-methyl-1H- imidazol-1-yl)benzene (1,3-BMIB) under hydrothermal reaction, respectively. Complexes 1 and 2 were characterized by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analysis, thermo-gravimetric analysis and UV-Vis spectra. Single-crystal X-ray diffraction reveals that complexes 1 and 2 are three-dimensional supra molecular frameworks packed by two-dimensional layers. The powder X-ray diffraction confirms that complexes 1 and 2 are stable in water under UV light. The UV-Vis spectra indicate that complexes 1 and 2 are semiconductors with high absorbing ability for UV-Vis light. Photocatalytic tests further confirm the complex 1 and 2 have catalytic activity for the degradation of methylene blue (MB) in water.