Zeolite materials are extremely porous aluminosilicate materials extensively used as heterogeneous catalysts, separation substrates, and ion exchange materials. They are composed of SiO₄^4- and AlO₄^5- tetrahedra joined by shared oxygen atoms at the corners.

M_x/n(AlO₂)_x(SiO₂)_y · mH₂0

where M = charge compensating cations, x>y, and n = cation charge.

Although the cations are required to maintain electro-neutrality, they are not rigorously bonded to the structure and consequently retain considerable mobility. Although the kinetic and mechanistic details of cation mobility are poorly understood, this phenomenon is currently thought to play a fundamental role in:

• dictating catalytic activity where cations have been observed to relocate in order to maximize selective interaction with sorbates

• contributing to catalyst deactivation and contamination from binding materials

• facilitating solid state cation exchange in the synthesis of new catalytic materials

We are interested in the sorbate promoted migration of cations in zeolite materials which has recently been suggested to play a fundamental role in dictating adsorption selectivity, catalytic reactivity, and catalyst deactivation and contamination.

We are interested in the catalytic activity of zeolites with heteroatoms in the framework. The titanium substituted zeolites are of particular interest because of their utility in selective oxidation reactions. However, the structural details of the titanium catalytic center remains a subject of continued debate. In spite of numerous spectroscopic and structural studies, there are virtually none that conclusively place titanium in the framework. We are utilizing a number of spectroscopic techniques and catalytic reactions in an attempt to characterize the catalytic centers in these important materials.

Zeolite materials are known to be excellent sorption media. They are often referred to as molecular sieves. The ability of zeolite materials to selectively adsorb different ions and compounds from aqueous and organic solvents is a function of the Si/Al ratio, pore size and geometry, and specific cations present. We are interested in developing a fundamental understanding of sorption selectivity under competitive conditions ( when more than one component is present). We are particularly interested in halogenated compounds and the role that the cation plays in exhibited sorption selectivity. We utilize a number of spectroscopic and chromatographic techniques to examine this phenomenon.