Coordination state of Cu+ ions in Cu-[Al]MCM-41

A Cu-[Al]MCM-41 sample was studied by FTIR spectroscopy of probe molecules (CO and NO) and methanol conversion test reaction. It was found that the parent MCM-41 material was characterized by the practical absence of strongly acidic hydroxyl groups (typical of zeolites), but possessed some hydroxyls with a moderate acidity. Introduction of copper to the material by a procedure typical of ion-exchange did not affect the OH groups of MCM-41. However, reduction of the deposited Cu2+ ions resulted in formation of Cu+ ions with a high coordinative unsaturation (typical of Cu+ in zeolites): they were able to adsorb up to three CO molecules each. Adsorption of 12C16O–13C18O mixtures was used to prove the polycarbonyl structures. The possible application of Cu-[Al]MCM-41 in environmental catalysis is discussed.

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► Deposition of Cu2+ ions on [Al]MCM-41 proceeds without participation of OH groups.
► Cu+ ions in Cu-[Al]MCM-41 have three coordinative vacancies each.
► FTIR spectra of coadsorbed 12C16O and 13C18O prove polycarbonyl structures.