Discovering the Theoretical Limits of Oxygen Storage within Nanoporous Materials

Discovering the Theoretical Limits of Oxygen Storage within Nanoporous Materials

Blake Dube (bwd9@pitt.edu), Alec Kaija (a.r.kaija@gmail.com), Chris Wilmer (wilmer@pitt.edu)

The use of nanoporous materials as means of gas storage has been a topic of significant study over the past decade.  Certain classes of these materials, such as metal-organic frameworks (MOFs), have received attention do to their predictable structure-property relationships and experimental viability.  Recent efforts to improve gas storage have focused on these types of materials, and how they store gases like carbon dioxide, methane, and hydrogen.  Oxygen, a gas with uses in medicine, energy, and space exploration, has been largely neglected by researchers working to discover new materials for gas storage.  Studies that have focused on oxygen storage have done so without a theoretical limit to define how much oxygen can be stored, even with the best materials.  A limit for oxygen storage would expedite the search for new materials by providing narrowed bounds by which scientists can frame their research.  This paper is aimed at defining a theoretical limit for the storage of oxygen within nanoporous materials at 298 K and 30 bar.  High-throughput methods were used to generate and simulate libraries of 10000 hypothetical materials for oxygen adsorption at 30 bar and 298 K.  These hypothetical materials were randomly generated by an algorithm that assigns values (within a reasonable range) for the following parameters: partial charges, Lennard Jones (LJ) radii, potential well depths, coordinates (within unit cell), as well as unit cell dimensions and number density of the material. In the simulations, atoms are represented as points that interact via LJ and Coulombic interactions. LJ interactions depend on the radii and potential well depths assigned to each atom in the model, while Coulombic interactions depend on the atomic partial charges.  Grand canonical Monte Carlo simulations were used to model adsorption of oxygen at 30 bar and 298 K.  Surface area and void fraction simulations were also conducted simultaneously.  Preliminary data has been collected analysis is ongoing.  Further simulations are needed to determine a robust theoretical limit for oxygen storage within nanoporous materials at 140 bar and 298 K.