Testing of two different samples of Cu/silicalite-1 with CO reveals the exi
stence of Cu+ sites typical of oxide-supported copper. CO adsorbed on these
sites is characterized by a band at 2137 cm(-1). Heating the samples in a
CO atmosphere leads to reduction of particular Cu2+ cations and the Cu+ sit
es formed behave as Cu+ cations exchanged in ZSM-5. Adsorption of CO on the
se sites results in the formation of dicarbonyls ( ns at 2177 cm(-1) and na
s at 2150 cm(-1)) which, after evacuation, are converted into monocarbonyls
(v(CO) at 2157 cm(-1)). In the presence of water, mixed Cu+(H2O)(CO) speci
es are formed (v(CO) at 2130 cm(-1)). NO adsorption on Cu/silicalite-1 resu
lts in the formation of Cu2+(NO) complexes which are characterized by a bro
ad band centered at 1888 cm(-1). Addition of a small amount of oxygen to th
e system results in the formation of surface nitrates typical of supported
copper catalysts (1630, 1608 and 1578 cm(-1)). In addition, weakly bonded N
2O3, N2O4 and NO2 are formed. The reasons for the appearance of Cu+ sites i
n cationic positions are discussed.