Gas Adsorption Enhancement in Partially Amorphized Metal- Organic Frameworks

Abstract

Amorphous metal-organic frameworks (MOFs) have the potential for applications such as controlled drug delivery and hazardous material encapsulation. Moreover, their distinct mechanical properties may facilitate fabrication of industrial-scale adsorbents for gas uptake applications. However, the dense amorphous phase has less capacity for gas adsorption compared to its parent crystalline structure because for the majority of MOFs, amorphization drops their accessible porosity and negatively affects their gas adsorption capability. In the present computational study, we show that for some MOFs with nonaccessible regions, the deformed (partially amorphized) structure can compete with its crystalline counterpart for the surface area available for gas uptake. Our reactive molecular dynamics simulations show that more than 40% increase in the accessible surface area can be attained upon shear deformation for some of the MOFs that were investigated. Overall, we demonstrate that for some MOFs, amorphization can bring favorable features and improve their surface area characteristics by opening up the nonaccessible regions during the amorphization process.