Molecular dynamics simulations of metal-organic framework-5 and its interactions with water

I&EC 104

Jeffery A. Greathouse, jagreat@sandia.gov, Geochemistry Dept, Sandia National Laboratories, Albuquerque, NM 87185 and Mark D. Allendorf, mdallen@sandia.gov, Microfluidics Dept, Sandia National Laboratories, Mail Stop 9291, Livermore, CA 94551-0969.
Metal-organic framework-5 (MOF-5) consists of Zn4O centers with 1,4-benzenedicarboxylate linkers. MOF-5 has an extremely large surface area and therefore represents a promising medium for gas storage. We have included framework (and adsorbate) flexibility by combining a general force field for organic molecules with parameters that accurately model zincite (ZnO). Our molecular dynamics simulations of pure MOF-5 reproduce the experimental lattice parameter to within 0.2 Å. MOF-5 is stable with water contents as high as 2.3 % by mass, although the lattice parameter decreases with added water. Above 3.9 % water, the framework is not stable due to replacement of MOF O atoms by water O atoms in the ZnO4 tetrahedra. Results will also be presented for other Zn-based MOFs, demonstrating the potential of this method to serve as a screening tool to identify new MOFs that are less susceptible to decomposition in water.