Characterization of Cu-exchanged SSZ-13: A comparative FTIR, UV-Vis, and EPR study with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios

作者：Giordanino F.; Vennestrm P.N.R.; Lundegaard L.F.; Stappen F.N.; Mossin S.; Beato P.; Bordiga S.; Lamberti C.^*

来源：Dalton Transactions, 2013, 42(35): 12741-12761.

DOI：10.1039/c3dt50732g

Cu-SSZ-13 has been characterized by different spectroscopic techniques and compared with Cu-ZSM-5 and Cu-β with similar Si/Al and Cu/Al ratios and prepared by the same ion exchange procedure. On vacuum activated samples, low temperature FTIR spectroscopy allowed us to appreciate a high concentration of reduced copper centres, i.e. isolated Cu+ ions located in different environments, able to form Cu+(N2), Cu+(CO) n (n = 1, 2, 3), and Cu+(NO)n (n = 1, 2) upon interaction with N2, CO and NO probe molecules, respectively. Low temperature FTIR, DRUV-Vis and EPR analysis on O2 activated samples revealed the presence of different Cu2+ species. New data and discussion are devoted to (i) [Cu-OH]+ species likely balanced by one framework Al atom; (ii) mono(μ-oxo)dicopper [Cu2(μ-O)] 2+ dimers observed in Cu-ZSM-5 and Cu-β, but not in Cu-SSZ-13. UV-Vis-NIR spectra of O2 activated samples reveal an intense and finely structured d-d quadruplet, unique to Cu-SSZ-13, which is persistent under SCR conditions. This differs from the 22700 cm-1 band of the mono(μ-oxo)dicopper species of the O2 activated Cu-ZSM-5, which disappears under SCR conditions. The EPR signal intensity sets Cu-β apart from the others.