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  • Transition-state structure for a mixed cobalt-metal oxide on an NU-1000 node abstracting a hydrogen atom from propane; the associated activation (and reaction) enthalpies are very sensitive to the second metal (atom colors are Co, blue; Zr, green; other m
    03/09/18

    Doping effect on C–H bond activation assisted by cobalt-metal oxide clusters supported on metal–organic framework nodes

In a recent edition of ACS Catalysis, University of Minnesota researchers reported computed activities for the oxidative dehydrogenation of propane by cobalt-metal oxide clusters supported on the nodes of the metal–organic framework NU-1000. Different second metals (dopants) had dramatic effects on the turnover-limiting C–H bond activation enthalpy. 

The work, "C–H Bond Activation on Bimetallic Two-Atom Co-M Oxide Clusters Deposited on Zr-Based MOF Nodes: Effects of Doping at the Molecular Level," was a collaborative effort involving several members of the Inorganometallic Catalyst Design Center (ICDC). Electronic structure theory computations elucidated the systematic effects of doping a dicobalt oxide cluster with respect to the energetics associated with activating a methylene C–H bond in propane. Lower activation enthalpies were predicted with (i) increasing radical character and (ii) decreasing negative charge on the O atom abstracting the H atom. This should strongly motivate the synthesis of mixed-metal, or “doped” oxide clusters, as the second metal is predicted to tune the activity of the active site over a very wide range (50 kcal/mol). The ability of computational tools to screen large numbers of potential formulations and determine underlying structure-activity correlations can significantly accelerate the selection of materials targeted for synthesis.

Transition-state structure for a mixed cobalt-metal oxide on an NU-1000 node abstracting a hydrogen atom from propane; the associated activation (and reaction) enthalpies are very sensitive to the second metal (atom colors are Co, blue; Zr, green; other m
Transition-state structure for a mixed cobalt-metal oxide on an NU-1000 node abstracting a hydrogen atom from propane; the associated activation (and reaction) enthalpies are very sensitive to the second metal (atom colors are Co, blue; Zr, green; other metal, garnet; C, gray; O, red; H, white).

The ICDC is an Energy Frontier Research Center based at the University of Minnesota. This work was a collaboration among the groups of Professors Laura Gagliardi, Aditya Bhan, and Christopher Cramer. The study was primarily conducted by graduate student Matthew Simons, working with post-doctoral fellows Manuel Ortuño, Varinia Bernales, and Carlo Alberto Gaggioli. Professor Bhan and Simons are in the Department of Chemical Engineering and Materials Science, and the remaining researchers are in the Department of Chemistry.