A 129Xe NMR study of functionalized ordered mesoporous silica

In this publication we report the first application of continuous flow hyperpolarized (HP) Xe-129 techniques to studies of pore structure in ordered mesoporous materials. In particular, we report extensive Xe-129 NMR chemical shift measurements of xenon adsorbed in mesoporous materials of different porosities and surface chemical composition. The use of HP Xe has allowed us to work at very low concentrations of xenon where the contribution of the Xe-Xe interactions is negligible and the observed Xe-129 chemical shift reflects mainly interactions between the xenon atoms and the surface. Variable temperature measurements gave access to information on the adsorption parameters of xenon, and allowed us to follow the changes in these properties due to modification of the mesopore voids. Our Xe-129 NMR data reveal a nonuniform porosity and irregular pore structure in contrast to N-2 adsorption and TEM measurements that indicate regular nanoporous channels.