Abstract
Metal-organic frameworks (MOFs) constitute a class of three-dimensional porous materials that have shown applicability for carbon dioxide capture at low pressures, which is particularly advantageous in dealing with the well-known environmental problem related to the carbon dioxide emissions into the atmosphere. In this work, the effect of changing the metallic center in the inorganic counterpart of MIL-53 (X), where X = Fe3+, Al3+, and Cu2+, has been assessed over the ability of the porous material to adsorb carbon dioxide by means of first-principles theory. In general, the non-spin polarized computational method has led to adsorption energies in fair agreement with the experimental outcomes, where the carbon dioxide stabilizes at the pore center through long-range interactions via oxygen atoms with the axial hydroxyl groups in the inorganic counterpart. However, spin-polarization effects in connection with the Hubbard corrections, on Fe 3d and Cu 3d states, were needed to properly describe the metal orbital occupancy in the open-shell systems (Fe- and Cu-based MOFs). This methodology gave rise to a coherent high-spin configuration, with five unpaired electrons, for Fe atoms leading to a better agreement with the experimental results. Within the GGA+U level of theory, the binding energy for the Cu-based MOF is found to be Eb = -35.85 kJ/mol, which is within the desirable values for gas capture applications. Moreover, it has been verified that the adsorption energetics is dominated by the gas-framework and internal weak interactions.
Highlights
The World Meteorological Organization (WMO) has pointed out an expected average temperature of 1.5 ○C higher than the preindustrial levels in less than 35 years, as the most abundant greenhouse gas, carbon dioxide, has reached an increase in 3.3 ppm (0.83%) in one year of analysis, which corresponds to an overall increase of about 145% compared to the pre-industrial levels.1 In this context, great efforts are necessary from different sectors of our society for a further change in the current scenario.2,3 The carbon capture and storage (CCS) program4–6 has different technologies to partially deal with the carbon emissions, finding applications in several industrial installations that include thermodynamic power plants and steel production
In order to evaluate how the metallic center affects the ability of a non-functionalized metal–organic framework to capture carbon dioxide, we have considered the bulk structure from MIL-53 (Fe3+) with a diamond-shape pore, called the narrow pore form
In MIL-53 (Fe3+), the inorganic counterpart formed by the iron metallic center is linked to the benzene dicarboxylate (BDC) ligands via oxygen atoms that are located in equatorial positions
Summary
The World Meteorological Organization (WMO) has pointed out an expected average temperature of 1.5 ○C higher than the preindustrial levels in less than 35 years, as the most abundant greenhouse gas, carbon dioxide, has reached an increase in 3.3 ppm (0.83%) in one year of analysis, which corresponds to an overall increase of about 145% compared to the pre-industrial levels. In this context, great efforts are necessary from different sectors of our society for a further change in the current scenario. The carbon capture and storage (CCS) program has different technologies to partially deal with the carbon emissions, finding applications in several industrial installations that include thermodynamic power plants and steel production. The World Meteorological Organization (WMO) has pointed out an expected average temperature of 1.5 ○C higher than the preindustrial levels in less than 35 years, as the most abundant greenhouse gas, carbon dioxide, has reached an increase in 3.3 ppm (0.83%) in one year of analysis, which corresponds to an overall increase of about 145% compared to the pre-industrial levels.. The World Meteorological Organization (WMO) has pointed out an expected average temperature of 1.5 ○C higher than the preindustrial levels in less than 35 years, as the most abundant greenhouse gas, carbon dioxide, has reached an increase in 3.3 ppm (0.83%) in one year of analysis, which corresponds to an overall increase of about 145% compared to the pre-industrial levels.1 In this context, great efforts are necessary from different sectors of our society for a further change in the current scenario..
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