FTIR Study of Cobalt Containing Aluminophosphates with Chabasite Like Structure by Using CO and NO as Molecular Probes

FTIR spectroscopy of adsorbed molecules such as CO and NO was used to monitor the nature of cobalt centres in Co-containing aluminophosphates (AlPOs) and silicoaluminophosphates (SAPOs) with chabasite-like structures. The samples were synthesized by following a facile route during which the cobalt ions were directly inserted in the synthesis gels. These studies show that Co²⁺ ions are located in framework positions in CoAPO-34, where they substitute for some Al³⁺ ions, whilst in CoAPSO-34, where Si⁴⁺ ions replacing for some phosphorous lead to negative charges in the aluminophosphate framework, are contemporarily present both in framework and extra-framework positions. It is likely that, in the latter case, some cobalt ions act as counter ions compensating the negative structure.