Discovery of Complex Binding and Reaction Mechanisms from Ternary Gases in Rare Earth Metal-Organic Frameworks

Understanding the selectivity of metal-organic frameworks (MOFs) to complex acid gas streams will enable their use in industrial applications. Herein, ab initio molecular dynamic simulations (AIMD) were used to simulate ternary gas mixtures (H₂ O-NO₂ -SO₂ ) in rare earth 2,5-dihydroxyterephthalic acid (RE-DOBDC) MOFs. Stronger H₂ O gas-metal binding arose from thermal vibrations in the MOF sterically hindering access of SO₂ and NO₂ molecules to the metal sites. Gas-gas and gas-linker interactions within the MOF framework resulted in the formation of multiple secondary gas species including HONO, HNO₂ , NOSO, and HNO₃ ^- . Four gas adsorption sites were identified along with a new de-protonation reaction mechanism not observable through experiment. This study not only provides valuable information on competitive gas binding energies in the MOF, it also provides important chemical insights into transient chemical reactions and mechanisms.