| Autor: |
Rhoda HM; Department of Chemistry, Stanford University, Stanford, California 94305, United States., Plessers D; Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium., Heyer AJ; Department of Chemistry, Stanford University, Stanford, California 94305, United States., Bols ML; Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium., Schoonheydt RA; Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium., Sels BF; Department of Microbial and Molecular Systems, Center for Sustainable Catalysis and Engineering, KU Leuven, Celestijnenlaan 200F, B-3001 Leuven, Belgium., Solomon EI; Department of Chemistry, Stanford University, Stanford, California 94305, United States.; Photon Science, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, California 94025, United States. |
| Abstrakt: |
Using UV-vis and resonance Raman spectroscopy, we identify a [Cu 2 O] 2+ active site in O 2 and N 2 O activated Cu-CHA that reacts with methane to form methanol at low temperature. The Cu-O-Cu angle (120°) is smaller than that for the [Cu 2 O] 2+ core on Cu-MFI (140°), and its coordination geometry to the zeolite lattice is different. Site-selective kinetics obtained by operando UV-vis show that the [Cu 2 O] 2+ core on Cu-CHA is more reactive than the [Cu 2 O] 2+ site in Cu-MFI. From DFT calculations, we find that the increased reactivity of Cu-CHA is a direct reflection of the strong [Cu 2 OH] 2+ bond formed along the H atom abstraction reaction coordinate. A systematic evaluation of these [Cu 2 O] 2+ cores reveals that the higher O-H bond strength in Cu-CHA is due to the relative orientation of the two planes of the coordinating bidentate O-Al-O T-sites that connect the [Cu 2 O] 2+ core to the zeolite lattice. This work along with our earlier study ( J. Am. Chem. Soc , 2018, 140, 9236-9243) elucidates how zeolite lattice constraints can influence active site reactivity. |
