Abstract
Cu-zeolites are able to directly convert methane to methanol via a three-step process using O2 as oxidant. Among the different zeolite topologies, Cu-exchanged mordenite (MOR) shows the highest methanol yields, attributed to a preferential formation of active Cu-oxo species in its 8-MR pores. The presence of extra-framework or partially detached Al species entrained in the micropores of MOR leads to the formation of nearly homotopic redox active Cu-Al-oxo nanoclusters with the ability to activate CH4. Studies of the activity of these sites together with characterization by 27Al NMR and IR spectroscopy leads to the conclusion that the active species are located in the 8-MR side pockets of MOR, and it consists of two Cu ions and one Al linked by O. This Cu-Al-oxo cluster shows an activity per Cu in methane oxidation significantly higher than of any previously reported active Cu-oxo species. In order to determine unambiguously the structure of the active Cu-Al-oxo cluster, we combine experimental XANES of Cu K- and L-edges, Cu K-edge HERFD-XANES, and Cu K-edge EXAFS with TDDFT and AIMD-assisted simulations. Our results provide evidence of a [Cu2AlO3]2+ cluster exchanged on MOR Al pairs that is able to oxidize up to two methane molecules per cluster at ambient pressure.
| Original language | English |
|---|---|
| Pages (from-to) | 1412-1421 |
| Number of pages | 10 |
| Journal | JACS Au |
| Volume | 1 |
| Issue number | 9 |
| DOIs | |
| State | Published - Sep 27 2021 |
| Externally published | Yes |
Funding
I.L., T.I., L.T., M.S.-S., and J.A.L. are thankful to the Deutsche Forschungsgemeinschaft (DFG, Project Number 326562156) and the TUM International Graduate School of Science and Engineering (IGSSE) for financial support. M.-S.L., O.Y.G., J.L.F., J.Z.H., V.-A.G., R.R., and J.A.L. were supported by the U.S. Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences (Transdisciplinary Approaches to Realize Novel Catalytic Pathways to Energy Carriers, FWP 47319). Computational work was performed using the Molecular Sciences Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a U.S. Department of Energy (DOE) national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located and the Pacific Northwest National Laboratory (PNNL) and the National Energy Research Scientific Computing Center (NERSC) located at Lawrence Berkley National Laboratory provided by a user proposal. PNNL is operated by Battelle for DOE. We acknowledge DESY beamlines P-64 and P-65 (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities for X-ray experiments. The used infrastructure of the von Hamos spectrometer at the beamline P64 was realized in the frame of Projects FKZ 05K13UK1 and FKZ 05K14PP1. A.J. and R.K. were supported by BMBF under Project MatDynamics (Verbundprojekt 05K13W03). We acknowledge the Paul Scherrer Institut, Villigen, Switzerland, for the provision of synchrotron beamtime at beamline PHOENIX of the SLS. The authors thank Matthias Bauer for his assistance. I.L., T.I. L.T., M.S.-S., and J.A.L. are thankful to the Deutsche Forschungsgemeinschaft (DFG, Project Number 326562156) and the TUM International Graduate School of Science and Engineering (IGSSE) for financial support. M.-S.L., O.Y.G., J.L.F., J.Z.H., V.-A.G. R.R., and J.A.L. were supported by the U.S. Department of Energy (DOE) Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences (Transdisciplinary Approaches to Realize Novel Catalytic Pathways to Energy Carriers, FWP 47319). Computational work was performed using the Molecular Sciences Computing Facility (MSCF) in the William R. Wiley Environmental Molecular Sciences Laboratory, a U.S. Department of Energy (DOE) national scientific user facility sponsored by the DOE’s Office of Biological and Environmental Research and located and the Pacific Northwest National Laboratory (PNNL) and the National Energy Research Scientific Computing Center (NERSC) located at Lawrence Berkley National Laboratory provided by a user proposal. PNNL is operated by Battelle for DOE. We acknowledge DESY beamlines P-64 and P-65 (Hamburg, Germany), a member of the Helmholtz Association HGF, for the provision of experimental facilities for X-ray experiments. The used infrastructure of the von Hamos spectrometer at the beamline P64 was realized in the frame of Projects FKZ 05K13UK1 and FKZ 05K14PP1. A.J. and R.K. were supported by BMBF under Project MatDynamics (Verbundprojekt 05K13W03). We acknowledge the Paul Scherrer Institut, Villigen, Switzerland, for the provision of synchrotron beamtime at beamline PHOENIX of the SLS. The authors thank Matthias Bauer for his assistance.
Keywords
- AIMD
- Cu L-edge XANES
- HERFD
- Methane oxidation
- TDDFT
- zeolite