A new two-dimensional metal-organic framework (MOF) structure has been synthesized by mild solvothermal reaction of MnCl 2 •4H 2 O with 1H-benzimidazole-5,6-dicarboxylic acid (H 3 bidc) at 85 ℃. The structure has been characterized by single-crystal X-ray diffraction, powder X-ray diffraction (PXRD), infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). Single-crystal X-ray diffraction analysis revealed that this MOF is a five-coordinated Mn(II) compound exhibiting a layered 2D network, in which the hydrogen-bonding interactions between uncoordinated carboxylic oxygen atoms and N-H groups in the imidazole rings play a key role in the final 3D supramolecular architecture. This MOF shows high thermal stability up to 400 ℃. Furthermore, XRD pattern of the MOF structure was retained for up to 20 d after soaked in water, and only 2.8 wt% of the MOF was decomposed within the first 48 h in water.