Cobalticenium ions adsorbed on large-pore aluminophosphate VPI-5 studied by X-ray absorption, 13 C solid-state NMR and FTIR spectroscopy

The intercalation compound obtained by solution-phase impregnation of cobaltocene on as-synthesized VPI-5 (sample A) has been investigated. Heating A to 130 °C leads to transformation to AlPO4-8 (sample B). The colours of the samples and the infrared bands show that the guest molecules are present as cobalticenium cations. These samples also contain water and dipropylamine. Solvent pentane molecules were not detected. Thus, it appears that VPI-5 selectively adsorbs cobalticenium from the pentane solution. The Co content in B is significantly larger than in an AlPO4-8 reference system (Sample C) obtained by calcining VPI-5 prior to adsorption. The reference framework has blocked pores due to thermally induced stacking disorders, thereby restricting the guest molecules to the external surface. However, in A and B we suggest that cobalticenium is also attached to the internal surface.