Simulação de processos de adsorção molecular em material nanoporoso constituído por tereftalato e zircônio

Abstract

First principle calculations based on Density Functional Theory (DFT) were used to investigate the adsorption of molecules (CO2, CO, H2, CH4, N2, H2S, C4H4S, C2H4O2, C2H4O and H2O) in a porous cavity of Zirconium terephthalate MOF. The MIL-140A was first validated by a very good agreement between the simulation and the experimental spectroscopic (Infra-red and NMR), X-ray diffraction and structural parameters of the selected MOF. The calculations of electronic structure further predicted the preferential adsorption sites, the strength of the host/guest interactions and determine the selectivity for molecules in MIL-140A. The use of the PBE XC functional integrating the DFT-D2 correction was valuable to accurately describe the interaction of those systems. Due relative weak interactions it is expected that the contribution of the zero point energies (ΔEZPE) and thermal energy contributions (ΔETE) are very small in comparison to the dispersion interactions contributions. Thus, the vibrational energies can be neglected and thus ΔH can be approximated to ΔEDFT. A very good agreement between ΔEDFT and the experimental adsorption enthalpy determined for the molecules (CO2, CO, CH4 e N2) confirms this assumption. The water stability of the MIL-140A was explored through the activation barrier associated to the dissociative chemisorption of water. Its high value confirms the very good water stability of this MOF. These results demonstrate that the MIL-140A could act as an ideal adsorvent for the removal of CO2 from a series of gases (e.g. natural gas, syngas, biogas and flue gas). Furthermore the MIL-140A can be able to remove hydrogen sulfide and thiophene from the fuels, act as a platform for reactions with acid acetic and recycle the acetaldehyde ejected from the factories.