2023
DOI: 10.1021/acs.jpcc.3c01496
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Structural Evolution of Copper-Oxo Sites in Zeolites upon the Reaction with Methane Investigated by Means of Cu K-edge X-ray Absorption Spectroscopy

Abstract: The structure of copper sites formed under an oxidative environment and their evolution in the course of the reaction with methane at elevated temperature was investigated by means of Cu K-edge X-ray absorption spectroscopy for a series of copper-containing MFI, MOR, and FAU zeolites. The pretreatment in oxygen at 723 K leads to the formation of copper(II)-oxo sites, whose nature depends on the framework type. Dimeric species are formed in CuMFI material, dimeric and monomeric sites coexist in CuMOR, and agglo… Show more

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Cited by 7 publications
(6 citation statements)
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“…Its spectroscopic signature is fully consistent with bare Cu I ions coordinated to the MOR framework. 34,70 Overall, the XAS results obtained under CH 4 -TPR well align with the recent report by Artsiusheuski et al, 92 conrming for Cu-MOR the absence of either metallic or oxidic aggregates at the end of the TPR step. Nonetheless, during both C 2 H 6 -and CO-TPR, additional Cu I species were found.…”
Section: Cu II Speciation Aer Pre-treatment In Osupporting
confidence: 90%
“…Its spectroscopic signature is fully consistent with bare Cu I ions coordinated to the MOR framework. 34,70 Overall, the XAS results obtained under CH 4 -TPR well align with the recent report by Artsiusheuski et al, 92 conrming for Cu-MOR the absence of either metallic or oxidic aggregates at the end of the TPR step. Nonetheless, during both C 2 H 6 -and CO-TPR, additional Cu I species were found.…”
Section: Cu II Speciation Aer Pre-treatment In Osupporting
confidence: 90%
“…The spectra of the oxygen-activated CuMOR (dark blue lines) contain a weak peak at 8977 eV due to 1s!3d quadrupole transition and a shoulder at 8986 corresponding to 1s!4p transition typical of copper(II) species in CuMOR. [28,62] Upon reaction of CuMOR with alkanes, the intensity of the aforementioned signals decreases and, simultaneously, a signal at 8983 eV appears and develops. The signal is characteristic of 1s!4p transition in copper(I)-containing zeolites [19,28] indicating the reduction of copper (II) sites.…”
Section: Methodsmentioning
confidence: 99%
“…[28,62] Upon reaction of CuMOR with alkanes, the intensity of the aforementioned signals decreases and, simultaneously, a signal at 8983 eV appears and develops. The signal is characteristic of 1s!4p transition in copper(I)-containing zeolites [19,28] indicating the reduction of copper (II) sites. Figure 4D illustrates the evolution of the Cu II fraction versus temperature from the MCR-ALS analysis (Section 2.7 of the Supporting Information).…”
Section: Methodsmentioning
confidence: 99%
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“…Cu K-edge X-ray absorption spectroscopy is an ideal technique to probe the composition of the Cu cocatalyst. The elemental specificity of X-ray absorption allows for selective probing of Cu in the multicomponent p-GaN/Al 2 O 3 /Au/Cu system. The X-ray absorption near-edge structure (XANES) region of the Cu K-edge absorption spectrum is highly sensitive to both the oxidation state and coordination environment of Cu. , The method can also be applied under operating conditions, for example, under CO 2 and H 2 O vapor atmosphere and under visible light illumination, which is relevant here when characterizing the Cu cocatalyst composition in p-GaN/Al 2 O 3 /Au/Cu.…”
Section: Introductionmentioning
confidence: 99%