Controlled architecture of solids with micro- and meso-porosity obtained by pillaring of montmorillonite with an LaNiO x binary oxide

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Abstract
High-surface-area solids containing both micropores and mesopores have been synthesized by intercalation of the heterobinuclear cation of the complex NiLa(fsaen)NO3 between the layers of montmorillonite clay and calcination at 500 °C. The adsorption mechanism of the complex follows an exchange reaction involving up to 2 mmol of complex cations per g of clay. Further amounts of complex are adsorbed in sites other than exchange ones as shown by zeta-potential experiments. The IR spectra of the intercalated complex showed no major alterations of the complex during adsorption and a stabilization effect and enhancement of the parallel orientation of the clay plates. X-Ray diffraction (XRD) measurements at low angles showed that the pillared clay possesses an inter-layer distance of 13.4 Å at 500 °C. Its BET surface area reaches a maximum of 220 m2 g–1 at this temperature. The as plots showed a maximum microporosity at ⩽2 mmol g–1. Additional loading results in transformation to a mesoporous delaminated structure. X-Ray photoelectron spectra (XPS) of the composite materials showed that the ratios La/Si and Ni/Si are lower than those determined by chemical analysis, owing to the shielded environment of the LaNiOx pillars in the clay. The same method indicated that for a high degree of loading the aggregates seem to be of perovskite origin.

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