Multiscale Theoretical Study of Sulfur Dioxide (SO₂) Adsorption in Metal-Organic Frameworks

In the present work, we used DFT in order to study the interaction of SO₂ with 41 strategically functionalized benzenes that can be incorporated in MOF linkers. The interaction energy of phenyl phosphonic acid (-PO₃H₂) with SO₂ was determined to be the strongest (-10.1 kcal/mol), which is about 2.5 times greater than the binding energy with unfunctionalized benzene (-4.1 kcal/mol). To better understand the nature of SO₂ interactions with functionalized benzenes, electron redistribution density maps of the relevant complexes with SO₂ were created. In addition, three of the top performing functional groups were selected (-PO₃H₂, -CNH₂NOH, -OSO₃H) to modify the IRMOF-8 organic linker and calculate its SO₂ adsorption capacity with Grand Canonical Monte Carlo (GCMC) simulations. Our results showed a great increase in the absolute volumetric uptake at low pressures, indicating that the suggested functionalization technique can be used to enhance the SO₂ uptake capability not only in MOFs but in a variety of porous materials.