Thermal degradation of coordination polymer [Cd(N-Boc-gly)(2)(H2O)(2)](n)

Abstract

Multi-step thermal degradation of coordination polymer [Cd(N-Boc-gly)(2)(H2O)(2)](n) in non-isothermal conditions was studied. The kinetic parameters were determined from the thermal decomposition data using the isoconversion and non-isoconversion techniques. It was shown that the coordination polymer is stable up to 60 C, when the multi-step process of thermal dehydration, followed by steps of degradation, starts. The kinetic triplet for the step of dehydration was established as f(alpha) = 3/2(1 - alpha)(2/3)[1 - (1 - alpha)(1/3)](-1). E-inv = 170.4 +/- 6.4 kJ mol(-1) and Z(inv) =2.6 x 10(23). The established kinetic model, known as "D3 model", was confirmed by application criteria defined by Malek, Perez-Maqueda et al. as well as Master plot method. Dehydration step is followed by two steps of dehydrated coordination polymer degradation. On the base of the dependence of Arrhenius parameters (E-a and Z) on conversion degree (alpha), the mechanisms of degradation were discussed. In this way it was shown that second and third steps of degradation of coordination polymer are complex involving more than one elementary step. The second step corresponds to the loss of two C6H5CH2O- fragments in two parallel steps. The third step of degradation, ascribed to the loss of two -C(=O)NHCH2- fragments, is complicated by changing kinetically to diffusion control. (C) 2011 Elsevier B.V. All rights reserved.