Synthesis and structural determination of three metal-organic frameworks in a Co-3-amino-1,2,4-triazole system

The hydrothermal reactions of cobalt(II) salts with 3-amine-1H-1,2,4-triazole (Hatrz) result in two kinds of coordination polymers, namely, 2D isoreticular layers based on a binuclear unit Co(atrz)Br (1) and Co(atrz)I (2), and 3D alternating layer architecture of Co₅(atrz)₇(N₃)₃ (3), which were structurally characterized by single-crystal X-ray diffraction techniques. Thermostabilities of all compounds were examined by thermogravimetric analysis. Isostructural compounds 1 and 2 display a two-dimensional layer structure where Co centers are linked by μ_1,2,4-atrz anions to form isoreticular layers containing sixteen-membered rings. Compound 3 is a 3D alternating layer architecture, which are based on parallel 1D chains and bimetal unit N₃Co-(μ_1,4-atrz)-CoN₃]. The thermogravimetric analysis results of compounds 3 show that tremendous heat is released from its thermal decomposition, which indicates that the compound qualifies as a high-energy candidate.