Role of Hydrogen Bonding on Transport of Coadsorbed Gases in Metal-Organic Frameworks Materials

Coadsorption of multicomponents in metal-organic framework (MOF) materials can lead to a number of cooperative effects, such as modification of adsorption sites or during transport. In this work, we explore the incorporation of NH₃ and H₂O into MOFs preloaded with small molecules such as CO, CO₂, and SO₂. We find that NH₃ (or H₂O) first displaces a certain amount of preadsorbed molecules in the outer portion of MOF crystallites, and then substantially hinders diffusion. Combining in situ spectroscopy with first-principles calculations, we show that hydrogen bonding between NH₃ (or H₂O) is responsible for an increase of a factor of 7 and 8 in diffusion barrier of CO and CO₂ through the MOF channels. Understanding such cooperative effects is important for designing new strategies to enhance adsorption in nanoporous materials.