(757e) Understanding Structure, Metal Distribution, and Water Adsorption in Mixed-Metal MOF-74

Howe, J. D., Georgia Institute of Technology
Morelock, C. R., Georgia Institute of Technology
Jiao, Y., Georgia Institute of Techonology
Chapman, K. W., Argonne National Laboratory
Walton, K. S., Georgia Institute of Technology
Sholl, D. S., Georgia Institute of Technology
We present a joint computational and experimental study of Mg−Ni-MOF-74 and Mg−Cd-MOF-74 to gain insight into the mixing of metals and understand how metal mixing affects the structure of the undercoordinated open-metal sites that exist in these materials. Our calculations predict that metal mixing is energetically and entropically preferred in these materials. Recent experimental work has demonstrated that Mg−Ni-MOF-74 shows much greater surface area retention in the presence of water than Mg-MOF-74. To probe this effect, we study H2O adsorption in Mg−Ni-MOF-74, finding that the adsorption energetics and electronic structure do not change significantly at the metal sites when compared to Mg-MOF-74 and Ni-MOF-74, respectively. We conclude that the increased stability of Mg−Ni-MOF-74 is a result of a M−O bond length distortion in mixed-metal MOF-74, consistent with recent work on the stability of MOF-74 under water exposure.