Proposição de estrutura e parâmetros de interação molecular em adsorventes e catalisadores à base de hidroxissais, carboxilatos e MOF de Zn2+ usando cálculos de estrutura eletrônica

Abstract

The zinc element presents various applications and advantages due to its low toxicity and its biocompatibility. Some compounds, such as the hydroxide salts (LSH) and the double hydroxide salts (LDH), the layered carboxylates and the MOFs, are excelent materials with many potentials. Some of these applications are the intercalation processes, adsorption and catalysis. In this work, the catalysis of the biodiesel production with zinc acetate (a layered carboxylate) as the catalyst, the intercalation of surfactants and anionic iron(III) porphyrins in LDH and LHS, the adsorption properties of ZIF-9 and the exfoliation of a series of layered zinc carboxylates and the surfactants intercalated in LDH and LHS were investigated. In order to conduct all this study and these investigations, electronic structure calculations based on DFT by the Quantum Espresso package were performed. In the case of the exfoliation of the zinc carboxylates and the intercalation/exfoliation of the surfactants, a comparison of the exchange-correlation functionals (PBE and vdW-DF) and the semiempiric method DFT-D2 was made to capture the van der Waals forces of these systems. This same methodological study was made for the properties of ZIF-9. For the study of the intercalation of the anionic iron(III) porphyrins, the effect of the spin polarization and the Hubbard correction were investigated for the structural and electronic properties. Certain aspects could be predicted such as the exfoliation energies of the studied family of layered zinc carboxylates and also for the surfactants intercalated in LDH and LHS. The adsorption energies of the molecules involved in the esterification/transesterification reactions and the energy barrier of the alkoxide formation favored the comprehension of these processes at an atomistic scale. A structural elucidation was also achieved for the intercalation of the dehydrated and hydrated surfactants, and the anionic iron(III) porphyrins. The adsorption properties of ZIF-9 were also studied, in order to predict the selectivity of the studied molecules (CO2, H2S, methanol e ethanol).