An iron-based metal-organic framework (large structure) can catalyze a reaction that transforms ethane (gray and light blue molecules) into pure ethanol (light blue, red and gray). Scientists think the framework could help reveal ways to mimic other biological functions. Credit: NIST. Click to enlarge.

This iron-based MOF was built in the lab of Jeffrey Long, a professor of chemistry at the University of California Berkeley, who also has patented it. Having learned two years ago that Fe-MOF-74 could effectively separate closely related components of natural gas from one another, this time Long’s collaborators at the NIST Center for Neutron Research (NCNR) looked at its power to catalyze reaction. In this case, they turned ethane into ethanol.

While the MOF was great at catalyzing the reaction, the team wasn’t sure why. The search for understanding led to two discoveries at the NCNR: the importance of the MOF’s iron for catalysis, and the reason the oxidizer worked so well.

Iron being able to change its number of electrons is the key to creating a high-yield catalytic process. When the team substituted magnesium for 10% of the iron in the MOF, the reaction produced 40% less ethanol than before. The NCNR’s neutron diffractometer helped clarify why, and they also showed that the oxidizer—nitrous oxide, a lopsided molecule with oxygen at one end and two nitrogen atoms at the other—must connect its oxygen end to the iron in the MOF for catalysis to occur.

Brown says exploring the catalytic behavior in this material may reveal other ways to use MOFs to mimic what biology can do.

Resources

D.J. Xiao, E.D. Bloch, J.A. Mason, W.L. Queen, M.R. Hudson, N. Planas, J. Borycz, A.L. Dzubak, P. Verma, K. Lee, F. Bonino, V. Crocellá, J. Yano, S. Bordiga, D.G. Truhlar, L. Gagliardi, C.M. Brown, J.R. Long. (2014) “Oxidation of ethane to ethanol by N₂O in a metal–organic framework with coordinatively unsaturated iron(II) sites.” Nature Chemistry doi: 10.1038/nchem.1956