Determination of heat capacities and thermodynamic properties of two structurally unrelated but isotypic calcium and manganese(II) 2,6-naphthalene dicarboxylate-based MOFs

Two metal-organic frameworks, Ca(2,6-NDC)(DMF) (1) and Mn3(2,6-NDC)3(DMF)4 (2) (where 2,6-NDC = 2,6-naphthalene dicarboxylate and DMF = N,N′-dimethylformamide) have been solvothermally synthesized under optimized conditions and characterized by X-ray powder diffraction, elemental analysis, FT-IR spectroscopy, and TG analysis. The thermal decomposition characteristics were investigated under air atmosphere from 300 to 1,170 K (for 1) and from 300 to 971 K (for 2). The molar heat capacities were measured from 198 to 548 K (for 1) and from 198 to 448 K (for 2) by temperature modulated differential scanning calorimetry (TMDSC) for the first time. The fundamental thermodynamic parameters such as entropy and enthalpy variations with temperature were calculated based on the experimentally determined molar heat capacities.