Reaction-condition-controlled formation of secondary-building-units in three cadmium metal–organic frameworks with an orthogonal tetrakis(tetrazolate) ligand

Three metal–organic frameworks (MOFs) have been isolated using an orthogonal tetrakis(tetrazolate) ligand, ttbf (the tetra-anion of 2,2′,7,7′-tetrakis(2H-tetrazol-5-yl)-9,9′-spirobi[fluorene], H4ttbf). These three MOFs were constructed using only (ttbf)4− and Cd2+ by changing metal:ligand ratio, solvent, and source of anions. MOF 3 contains a very rare square–planar Cd4 cluster bridged by a μ4-Cl atom. MOFs 1 and 3 have saturated metal centers prior to drying and do not thermally decompose until 315 °C. MOF 2, however, has an unsaturated metal center prior to drying and its thermal-decomposition temperature is around 250 °C.