The utilization of in situ DRIFT spectroscopy combined with advanced thermo
analytical techniques (temperature programmed decomposition, TPDE; temperat
ure programmed oxidative decomposition, TPOD) allows the characterization o
f redox behavior of copper ions inside ZSM-5 zeolites. The oxidation of car
bonaceous impurities inside the solid matrix to CO and CO2 is demonstrated
to be responsible for Cu(ii)--> Cu(i) reduction, since the formation of oth
er oxidation products, namely O-2, H2O2 or O-2(-) ions, was not detected by
mass spectrometry and DRIFT. The unusual kinetics of CO evolution in therm
oanalytical experiments was attributed to the formation of a relatively sta
ble Cu+... CO adduct characterized by a typical IR band at 2157 cm(-1), whi
ch acts as a specific active site of a chromatographic adsorbent material.