Thermodynamic properties of 3D copper(II)-MOFs assembled by 1H-tetrazole

Abstract

Three-dimensional MOFs, {[Cu₃(tz)₄Cl₂] 2CH₃OH}_n (Htz = 1H-1,2,3,4-tetrazole), have been synthesized in methanol. It was characterized by chemical analysis, element analysis, IR spectroscopy, single-crystal X-ray diffraction and thermal analysis. Thermogravimetric analysis demonstrated that the MOFs after removing methanol molecules possessed good thermostability with decomposition temperature up to 533 K. The enthalpy change of liquid-phase formation reaction was determined by a RD496–2000 microcalorimeter at 298.15 K with the value of (−46.63 ± 0.26) kJ mol⁻¹. The enthalpy change of solid-phase formation reaction was calculated as (−573.89 ± 0.89) kJ mol⁻¹ on the basis of a designed thermochemical cycle. The thermodynamics of formation reaction of the MOFs was investigated by changing the temperature of liquid-phase reaction. Based on the experimental results, fundamental kinetic and thermodynamic parameters k, n, E, $\Delta H_{ \ne }^{\theta }$, $\Delta S_{ \ne }^{\theta }$ and $\Delta G_{ \ne }^{\theta }$ were obtained. The specific heat capacity at 298.15 K was determined to be (1.87 ± 0.08) J K⁻¹ g⁻¹ by a RD496-2000 calorimeter. In addition, the constant volume combustion energy of title MOFs was determined by a RBC-II rotating-bomb calorimeter at 298.15 K. The standard molar enthalpy of combustion and standard molar enthalpy of formation were calculated to be (−4736.43 ± 4.03) kJ mol⁻¹ and (293.42 ± 4.11) kJ mol⁻¹, respectively.