National Synchrotron Light Source Seminar

Zeolites are three-dimensional organized microporous systems hosting positively charged cations that balance the negative charge of the framework and act as strong Lewis acid sites. Such materials play a great role in industrial chemistry, as they are very efficient catalysts exhibiting remarkable shape selectivity. The pore dimension and topology select the reactant molecules able to penetrate the framework and to reach the internal active sites. The same holds for the intermediate molecules formed on the catalytic sites and for the final products able to leave the zeolite framework, that actually acts as a nanoreactor of molecular dimension. The understanding of the site reactivity can be achieved by comparing the cations position in the activated catalyst (zeolites subjected to thermal treatments in vacuo conditions, exhibiting no molecules in the channels) with that occupied upon interaction with selected molecules dosed in situ either from the gas or from the liquid phases. The combination of XAFS spectra (collected in situ at ESRF BM8 GILDA or BM29) with high resolution XRPD data (colleted in situ at ESRF ID31) with conventional IR, Raman, UV-Vis, and EPR data is a complete approach to face this complex problem. More recently our group has extended this approach to a novel class of microporous materials: metallorganic frameworks.