V,Al]-ITQ-6: Novel porous material and the effect of delamination conditions on V sites and their distribution

Abstract

This paper reports on the delamination of the layered [V,Al]-PREFER to originate the [V,Al]-ITQ-6. The swollen material was prepared under alkaline conditions; the delaminated solids were obtained directly from the basic medium after sonication and after acid addition. Vanadium and aluminum atoms are part of the lattice sites as confirmed by 27Al-MAS–NMR, 51V-MAS–NMR and UV–Vis spectroscopy. The extent of delamination was monitored by X-ray diffraction, N 2 adsorption–desorption isotherms and 29Si-MAS–NMR. The presence of bands in the double rings region, as verified by FTIR, shows that in the delaminated materials, the structural unit of the initial lamellar precursor is still preserved. The material obtained after acid addition contains extraframework octahedral V 5+ and V 5+ in a tetrahedral sites, the first ones are easily exchanged by sodium ions. On the opposite, the material prepared only under basic conditions presents only framework tetrahedral V 5+. The presence of the V 4+ was confirmed in the lamellar precursor by EPR but the vanadium oxidation state and localization change throughout the delamination procedure.