Benefit of Microscopic Diffusion Measurement for the Characterization of Nanoporous Materials

Detailed knowledge of the transport properties of nanoporous materials is a prerequisite for their complete characterization and optimum technological exploitation. One of the best ways to attain this information is provided by the “microscopic” techniques of diffusion measurement, in particular by the pulsed field gradient technique of NMR and by interference microscopy and IR microscopy. Starting with the measuring principles, the various types of evidence as accessible by these techniques are illustrated. A large variety of host‐guest systems with both ordered and random pore networks have been studied, from microporous up to macroporous materials. The information obtained concerns diffusivities in the various pore domains, extra resistances at the interfaces between them and the associated exchange rates. Experimental progress in the pulsed field gradient technique of NMR and introduction of interference microscopy and IR micro‐imaging are used to probe the transport properties of nanoporous materials. The accessible diffusion path lengths are shown to cover the range of particular relevance for the technological applications of these materials in heterogeneous catalysis, adsorption and separation.