Tuning the interaction strength and the adsorption of CO2 in metal organic frameworks by functionalization of the organic linkers

• Phenyl hydrogen sulfate (OSO3H) had the highest binding energy (–5.4 kcal/mol) among the functional groups examined.
• CO2 acts both as a Lewis acid and a Lewis base through its C and O atoms leading to increased binding energy.
• Electron density redistribution plots shows that higher binding energies correspond to larger redistribution on CO2.
• The IRMOF-8 modified with the-OSO3H and-CNH2NOH functional groups showed enhanced CO2 storage capacity.

The interaction strength of CO2 with a set of fourteen, strategically selected, functional groups was investigated by performing MP2 calculations. These functional groups potentially can be incorporated in MOF linkers. Initially, the energetically most favorable intermolecular structures for each of the CO2–functional group complexes were found, starting from several different initial configurations of CO2 over the functional groups. Among the functional groups that were considered, the highest interaction energy (−5.4 kcal/mol) with CO2 was found for phenyl hydrogen sulfate (OSO3H), which is almost 2 times larger than the corresponding binding energy for benzene (−2.9 kcal/mol). Electrostatic potential maps of the functionalized benzenes and electron redistribution density plots of the corresponding complexes with CO2 were generated to understand the nature of the interaction of CO2 with the functionalized benzenes. Additionally, we tried to find any correlations between the obtained binding energies and the geometrical parameters of the CO2–functional group complexes. The best functional groups were tested for their ability to capture CO2 at 298 K for a wide pressure range by performing GCMC simulations.

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