The effect of framework organic moieties on the acidity of zeolites: A DFT study

Acidic properties of H-CHA, H-ZOL-C, and H-ZOL-N have been investigated using periodic density functional calculations to understand the effect of organic moiety incorporation on their acidities. Results from NH3 adsorption energy, deprotonation energy, and relative nucleophilicity calculations are consistent and show that the relative Bronsted acid site strength decreases in the order H-CHA > H-ZOL-C > H-ZOL-N. The geometrical parameters of the optimized structures indicate the easier incorporation of NH rather than CH2 in the chabazite framework. Moreover, the basicity of the lattice O, N, and C atoms increases in the order C < O < N. (c) 2006 Elsevier B.V. All rights reserved.