Article ID Journal Published Year Pages File Type
9617715 Microporous and Mesoporous Materials 2005 6 Pages PDF
Abstract
We have examined the adsorption of the phosphine stabilized cluster Cu6(TePh)6(PPh2Et)5 as well as the free ligands ethyldiphenylphosphine (EDPP) and ethyldiphenylphosphine oxide (EDPPO) in several MCM-41 types of mesoporous materials by 31P solid-state NMR spectroscopy. The results indicate that upon loading into siliceous MCM-41 (Si-MCM-41), the phosphine shell of the copper cluster dissociates from the metal core. After dissociation, some EDPP molecules exist as physisorbed species and a significant amount of phosphine is oxidized to the corresponding phosphine oxide, occluded in the channels of Si-MCM-41. The reaction seems to be catalyzed by the Cu(I) species since direct loading of EDPP under the same conditions does not yield any phosphine oxide in the framework of Si-MCM-41. The 31P NMR spectra of EDPP and EDPPO adsorbed in Si-MCM-41 suggest that neither Brønsted nor Lewis acid sites exist on the channel surface of Si-MCM-41. The adsorption of EDPP and EDPPO in the acidic form of aluminium-containing MCM-41 (Al-MCM-41), however, does indicate the interactions between the guest species and three Brønsted acid sites with different strengths. No Lewis acid site was observed in Al-MCM-41.
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Physical Sciences and Engineering Chemical Engineering Catalysis
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