Three compounds, [(CH 3 ) 2 NH 2 ][M 3 (BTC)(HCOO) 4 (H 2 O)]·H 2 O (M=Mn (1), Co (2), Ni (3), H 3 BTC=1,3,5-benzenetricarboxylic acid), were synthesized under hydrothermal conditions and were characterized by single crystal and powder X-ray diffraction, IR spectra, elemental analysis, coupled TG-MS and magnetic measurements. Compounds 1–3 are isostructural analogues and crystallize in monoclinic space group P2 1 /c. Each metal ion in these compounds connects to six oxygen atoms to form a MO 6 octahedron. Six MO 6 octahedra link to each other to form a corner-shared hexameric M 6 cluster, which is linked by BTC ligands to form two-dimensional layers. The two-dimensional layers are further connected by formic ions to form a three-dimensional network with channels, where (CH 3 ) 2 NH 2 + ions and water molecular are located. Magnetic measurements indicate that anti-ferromagnetic ordering occurs at low temperature for these compounds.