Crystalline porous materials such as zeolites are widely used in separations,
catalysis, and ion-exchange. Emerging applications of these materials include
molecular sieving membranes, nanostructured hosts, chemical sensors,
ion-conducting films and low-k dielectrics. These applications will be
enabled by the synthesis of materials with new functionalities, as well as the of
fabrication of existing materials into thin films, membranes, and nanocomposites.
Recent results in the synthesis and characterization of zeolite
and layered silicate materials and membranes are presented.
We have recently discovered and characterized the first layered silicate
with three-dimensional nanopores, which may enable the fabrication of molecular
sieving polymer/silicate nanocomposite membranes for gas separations.
Inelastic neutron scattering has been used to study the host-guest interactions
in zeolite-organic systems, using organic probe molecules. In particular, we
have measured methyl rotational tunneling spectra from p-xylene molecules embedded
in a crystalline zeolite host. The interpretation of these tunneling spectra can
yield specific information regarding host-guest interactions, which are not easily
obtained by vibrational or NMR spectroscopy.
Polycrystalline zeolite molecular sieving membranes have also attracted
attention recently. We are developing quantitative infrared reflectance techniques
for characterizing these membranes and for studying adsorption and mass transport
through them. Preliminary results on the quantitative interpretation of
infrared reflectometric data for characterizing zeolite films, are presented.