Modulação de gap de banda por dopagem e investigação de adsorção molecular em MOF por cálculos DFT

Abstract

Metal-organic networks (MOF) are one of the most studied classes of porous materials due to their versatility and adjustability. Since their discovery, MOFs have proven to be a versatile platform for various applications ranging from gas storage and separation to electronic applications. In the search for the synthesis of new materials, the partial replacement of cations from different species leads to the formation of mixed metal MOFs, which can be applied as electronic conductors, sensors, photoelectronics, and electro/photocatalysis. Within this context, computational simulations prove to be important tools for predicting gas adsorption and providing a better understanding of the structural and electronic properties of MM-MOFs. Thus, the present work aimed to study the modulation of the energy gap of MOF MIP-177 doped with transition metals and the evaluation of MOF as selective adsorbents of sulfur-containing compounds, using calculations based on the Density Functional Theory (DFT). DFT calculations were controlled to systematically explore the doping of the SBU Ti12O15 of the microporous MOF MIP-177(Ti) by a series of transition metals including Fe, Ru, and Zr. A first structural analysis revealed that all dopant metals preferentially substitute at the trimer Ti octahedral sites present in the. It has also been demonstrated how the band gap energy can be highly tunable by the low-concentration metal doping method. Gap values range from 3.18 eV (MIP-177(Ti/RuIV)) to 3.82 eV (MIP-177(Ti/FeIII)) vs 3.92 eV for original MIP-177(Ti). This trend is explained considering a careful analysis of the electronic properties of each doped system. The study of molecular adsorption of sulfur contaminants (2-propanethiol, ethanethiol and DMDS), CO2, H2S and H2O was carried out in six MOFs (MOF-74(Mg), activated MOF-74(Mg), MIL-125(Ti), UiO-66(Zr), UiO-NO2-66(Zr) and MIL-53-TDC(Al)) by DFT calculations. The results of network parameters show that the PBE-D3 method can accurately describe the selected MOF structures and compute reliably satisfactory adsorption. A large part of the adsorption pressures is dictated by hydrogen and long-range bonds associated with van der Waals forces. The MOF UiO-66(Zr) and MIL-125-(Ti) showed the best binding energy results for the capture and retention of sulfur contaminants. In both MOFs, the order of selectivity followed was as follows: organosulfur compounds > H2O + H2S > COS + CO2.