(81e) Structure, Dynamics, and Reactivity for Alkane Oxidation of Fe(II) Sites Situated in the Nodes of a Metal-Organic Framework

Authors: 
Bhan, A., University of Minnesota
Simons, M. C., University of Minnesota
Vitillo, J. G., University of Minnesota
Babucci, M., Koc University
Hoffman, A., Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory
Beauvais, M., Stony Brook University
Chen, Z., Stony Brook University
Cramer, C., University of Minnesota
Chapman, K. W., Argonne National Laboratory
Bare, S. R., Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory
Gates, B., University of California, Davis
Lu, C. C., University of Minnesota
Gagliardi, L., University of Minnesota
Structure, dynamics, and reactivity for alkane oxidation of Fe(II) sites situated in the nodes of a Metal-Organic Framework

Matthew C. Simonsa, Jenny G. Vitillob, Melike Babuccic, Adam Hoffmand, Michelle Beauvaise, Zhihengyu Chene, Christopher J. Cramerb, Karena Chapmane, Simon Bared, Bruce C. Gatesc, Connie Lub, Laura Gagliardib, Aditya Bhan*a

aDepartment of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Avenue SE, Minneapolis, Minnesota 55455, United States

bDepartment of Chemistry, Chemical Theory Center, and Supercomputing Institute, University of Minnesota, 207 Pleasant Street SE, Minneapolis, Minnesota 55455, United States

cDepartment of Chemical Engineering, University of California, Davis, California 95616, United States

dSSRL, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA

eDepartment of Chemistry, Stony Brook University, 100 Nicolls Road, Stony Brook, New York 11794, United States

We demonstrate the ability of mononuclear, high spin (S=2), Fe(II) sites, situated in the nodes of MIL-100(Fe) to convert propane via dehydrogenation, hydroxylation, and overoxidation pathways utilizing an atomic oxidant. Pair distribution function (PDF) analysis, N2 isotherms, X-ray diffraction, and infra-red (IR) and Raman spectroscopy confirm the single-phase crystallinity and stability of MIL-100(Fe) over reaction conditions (523K in vacuo, 378-408 K C3H8+N2O). Density Functional Theory (DFT) calculations suggest that the reaction occurs via a radical rebound mechanism involving the oxidation of Fe(II) species to Fe(III) via a high spin, Fe(IV)=O intermediate, which is supported by X-ray adsorption and Mössbauer spectroscopy. The identity of the Fe(II) active site is confirmed and quantified using in-situ chemical titrations. N2 and C3H6 production rates were calculated to both be first order in N2O pressure and zero order in C3H8 pressure, concurring with DFT cluster calculations that predict the reaction of Fe(II) with N2O to be rate-limiting.