Synthesis of Rh6(CO)16 in Supercages of Zeolite HY:Reaction Network and Kinetics of Formation fromMononuclear Rhodium Precursors via Rh4(CO)12Facilitated by the Water Gas Shift Half-Reaction
KAUST DepartmentPhysical Science and Engineering (PSE) Division
Online Publication Date2019-12-18
Print Publication Date2020-01-30
Embargo End Date2020-12-18
Permanent link to this recordhttp://hdl.handle.net/10754/661451
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AbstractRh(I)(CO)2 complexes anchored to zeolite HY were converted into Rh4(CO)12 in the zeolite supercages upon exposure to flowing CO + H2O at 35 °C, and the chemistry and kinetics were characterized with infrared spectroscopy. Rh6(CO)16 formed along with Rh4(CO)12, but only in low yield, although it is more stable than Rh4(CO)12. The formation of Rh6(CO)16 was hindered by trapping of Rh4(CO)12 in the supercages and by the low rate of transport of the mononuclear rhodium species. However, exposure of the sample to wet helium at 80 °C caused the Rh4(CO)12 to fragment, generating anchored Rh(I)(CO)2 and also Rh6(CO)16. IR spectra recorded under various conditions led to elucidation of the reaction network for cluster formation and breakup and a strategy of repetitive treatments that boosted the yield of Rh6(CO)16 to >90%. The reversible formation and breakup of the rhodium carbonyl clusters were facilitated by the half-reactions of the water gas shift reaction, with gas-phase products identified by mass spectrometry. The results show how understanding of the reactions within a zeolite allows control of the nuclearity of encaged metal clusters, an important class of catalyst.
CitationFang, C.-Y., Valecillos, J., Conley, E. T., Chen, C.-Y., Castaño, P., & Gates, B. C. (2019). Synthesis of Rh6(CO)16 in Supercages of Zeolite HY: Reaction Network and Kinetics of Formation from Mononuclear Rhodium Precursors via Rh4(CO)12 Facilitated by the Water Gas Shift Half-Reaction. The Journal of Physical Chemistry C, 124(4), 2513–2520. doi:10.1021/acs.jpcc.9b10291
SponsorsThis work was supported by the U.S. Department of Energy (DOE), Office of Science, Basic Energy Sciences (BES), grant FG02-04ER15513. We acknowledge the support of Ryan Davis and Simon R. Bare and the Co-ACCESS program at beamline 4-1 at the Stanford Synchrotron Radiation Lightsource, supported by DOE, Office of Science, BES, Contract DEAC02-76SF00515.
PublisherAmerican Chemical Society (ACS)
JournalJournal of Physical Chemistry C