Using pyrazine and 4,4’-bipyrine as co-ligand, respectively, two metal-organic frameworks (MOFs) were synthesized by complexzation of Cd2+ and Zn2+ with 4,4’-azobenzoic acid (H2(4,4’-azo)). X-ray single crystal diffraction shows that their crystal structures are as same as those of the previously published ［Cd(4,4’-azo)(H2O)］n (1) and ［Zn(4,4’-azo)(H2O)2］n (2) where the co-ligands are not involved into the structures. Varying the co-ligand to 1,3-bi(tetrapyridyl)propane (bpp) with larger size and metal ions to Co2+, a co-crystal ［H2(4,4’-azo)(bpp)］n (3) was isolated successfully, which is monoclinic, space group of C2/c with crystal cell parameters a=3.216 8(19) nm, b=0.475 5(3) nm and c=1.873 2(14) nm. The thermal stabilities of the three compounds were investigated by thermal gravimetric analyzer and the fluorescence of two MOFs were examined by fluorescence spectrometer, respectively. Both 1 and 2 display excellent thermal stabilities. Especially, 2 keeps stable up to 247 ℃. UV-Vis spectra and fluorescence spectra of 1 and 2 are different, which are ascribed to that 1 is a 3D network formed by 4,4’-azo bi-dentated coordinating with two Cd2+ whereas 2 is a 1D zig-zag chain constructed by 4,4’-azo mono-dentated coordinating with Zn2+. In addition to the ligand emission at 359 nm, 2 exhibits a new enhanced emission at 420 nm due to the ligand to metal charge transfer (LMCT) upon Zn2+ coordination with 4,4’-azo.