The zeolite frameworks(FER,TON,CHA,and IFR)with a large diversity of the IR band shapes in the OH stretching region were investigated by combined use of FT-IR spectroscopy and DFT calculations.The analysis of various isolated Br0nsted acid sites was performed with a model based on Boltzmann weighted relative energies and OH frequencies obtained by the ω/r correlation method.This approach has recently been used to reveal the non-statistical incorporation of aluminum into the H-MOR framework.The model correctly predicts the band shapes of H-FER and H-TON zeolites in the free OH region of the FT-IR spectra.For H-CHA and H-IFR,however,the mutual BAS interactions cannot be ignored even for high Si/Al ratios,which renders the concept of isolated BAS inadequate.Thus,the periodic calculations of adsorption and catalytic properties of zeotype frameworks should always be carried out with extended models mimicking real heteroatom distribution in these materials.
Acidic zeolitesAb initio calculationsIR spectra
Miroslav Rubes、Michal Trachta、Jan Vaculik
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Institute of Organic Chemistry and Biochemistry,Academy of Sciences of the Czech Republic,Flemingovo nam.2,162 10,Prague,Czech Republic
Department of Physical Chemistry,Faculty of Chemical Technology,University of Pardubice,Studentska 573,532 10,Pardubice,Czech Republic
NSTL
