Two new organic–inorganic hybrid compounds based on polyoxometallates, [Ni(im) 6 ][Him] 2 [(im) 2 Mo 8 O 26 ]·2DMF·2H 2 O (1) and [Ni(im) 4 (DMF) 2 ] 2 [(im) 2 Mo 8 O 26 ]·2DMF·3H 2 O (2) (im=imidazole, DMF=N,N-dimethylformamide), have been synthesized and characterized by single crystal X-ray analysis, elemental analysis and IR spectra. The thermal properties were studied by TG analysis. Both of the two compounds consist of imidazole coordinated γ-octamolybdate anions, which firstly link to one-dimensional chains via hydrogen bonding. Then, the metal complex cations link the 1D hydrogen bonding chains to 3D frameworks by abundant hydrogen bondings.