Thermal decomposition kinetics of M−BTC (M = Cu, Co, Zn, and Ce) and M−BTC/Pt composites under oxidative and reductive environments

Abstract

Metal-organic frameworks (MOFs) have been utilized as an important precursor/template to prepare diverse metal or metal oxide nanomaterials. Herein, we studied the thermal decomposition behaviors of M−BTC (M = Cu, Co, Zn, and Ce; BTC = benzene-1, 3, 5-tricarboxylate) and the Pt-supported M−BTC nanocomposites (M−BTC/Pt) in different atmospheres by using thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), in-situ X-ray diffractometer (in-situ XRD), and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). The results indicated that the presence of Pt promoted the decomposition of the Cu-BTC, Co-BTC, and Zn-BTC under air atmosphere with lower activation energies. For instance, the Ea values of the decomposition process of Cu-BTC and Cu-BTC/Pt were 231 and 133 kJ/mol, respectively, which can be attributed to the enhanced ligand-to-metal charge transfer effect and higher oxygen adsorption capacity after the immobilization of Pt. However, the thermal decomposition of Ce-BTC showed a different trend with a larger Ea value in the presence of Pt (167 vs 105 kJ/mol). In-situ DRIFTS showed that the introduction of Pt would change the thermal decomposition modes of MOFs by the strong hydrogen overflow effect. However, the improved thermostability of Cu-BTC, Co-BTC, and Zn-BTC in the hydrogen atmosphere is owing to the hydrogenation of the carboxylate on the organic linkers. For instance, the Ea values of the decomposition process of Co-BTC and Co-BTC/Pt were 197 and 237 kJ/mol, respectively. Such findings could provide reference and guidance for further understanding of the effects of metal nanoparticles on the thermal decomposition of MOFs for controlling the physicochemical properties of the MOF-derived metal oxide nanomaterials.