Thermal decomposition of inclusion compounds on the base of the metal–organic framework [Zn2(bdc)2(dabco)

Abstract

Metal–organic frameworks (MOFs) have promising practical applications in gas storage, separation and fine purification of substances, and also in catalysis. These MOFs are crystalline compounds consisting of metal ions coordinated by bridging organic ligands with the formation of porous structures. We study the kinetic stability of two inclusion compounds on the base of a such framework: [Zn2(bdc)2(dabco)]·nL (bdc2− = terephthalate, dabco = 1,4-diazabicyclo[2.2.2]octane, L = cyclohexane and benzene). The cyclohexane compound is more stable than the benzene compound, although the kinetic diameters of the guest molecules are almost equal. So as the centrosymmetrical cyclohexane molecule can easily transform the chair conformation to the bath conformation, it can have the influence on the steric hindrance (as well as on the activation barrier) for the guest molecules removal. Therefore, the entropy contribution is as favorable factor, as the energetic one in the kinetic stability of the supramolecular compounds.