Thermal stability of copper-based MOF under different atmospheres

MIL-53(Cu), belonging to the group of metal-organic frameworks (MOFs) with terephthalate as a ligand, was prepared. The success of the synthesis was confirmed by XRD, FTIR, SEM and chemical analysis. The MOF thermal behavior was studied by thermogravimetry, in situ and ex situ XRD and mass spectrometry, using different atmospheres (inert, oxidizing and reducing). This MOF had a higher stability when the inert atmosphere was used (622 K), and this was lower (559 K) under an oxidizing atmosphere. The integrated intensities of the main peak of each phase in the X-ray diffractograms showed that under inert or reducing atmospheres (CO or H-2) the decomposition generated metallic copper. Under oxidizing atmosphere, a mixture of copper oxides (Cu2O and CuO) was obtained, in which Cu2O was an intermediate, with only traces observed at 773 K. The FWHM calculation at the main peak of each phase indicated the formation of larger crystallites under hydrogen atmosphere and smaller ones under CO. There was a tendency of the formed copper oxides to sinter in the presence of air. The main volatile compounds formed during the thermal treatment of the MOF (decomposition of terephthalate) were CO2 and benzene. Thus, this study contributes to the development of new copper-based catalysts by the thermal treatment of MOF, which allows greater control of the phases formed (metallic Cu or CuO).

Automated summary

The synthesis of MIL-53(Cu), a metal-organic framework (MOF) with terephthalate as a ligand, was confirmed by XRD, FTIR, SEM, and chemical analysis. The MOF exhibited higher stability under inert atmosphere and generated metallic copper under reducing atmosphere. Under oxidizing atmosphere, a mixture of copper oxides (Cu2O and CuO) was obtained, with Cu2O as an intermediate. The thermal treatment of the MOF produced CO2 and benzene as the main volatile compounds and allowed for the control of the phases formed (metallic Cu or CuO).