The interaction of Co and No with Co sites in CoZSM-5 zeolite. FTIR, EPR and theoretical studies

What is it about?

The processes occurring during thermal activation of CoZSM-5 were investigated by IR and UV–VIS–NIR methods. Adsorption of CO and NO studied by IR, EPR and complementary DFT techniques was used to probe the status of cobalt ions. Thermal activation of CoZSM-5 involves dehydration, hydrolysis (formation of (Co–OH)+ species) and dehydroxylation steps. The bare Co centers produced above 670 K can readily coordinate diatomic molecules. Their interaction with CO led to formation of three kinds of {2CoCO}7 monocarbonyls at low pressures, and three kinds of {2Co(CO)3}7 tricarbonyl species at higher pressures. Ligation of NO resulted in formation of three kinds of {1CoNO}8 mononitrosyl and only one type of {2Co(NO)2}9 dinitrosyl adduct. An alternative outer–sphere addition of the second NO molecule producing dimeric 1–N2O2 ligand was found by DFT calculations to be less favorable.

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