Review: The use of molecular probes for the characterization of nanoporous adsorbents

Molecular probes can be employed in three different ways for the characterization of nanoporous adsorbents. The simplest approach is to use a range of globular nonpolar molecules of different diameter in order to assess the effective size of the pore entrances in a molecular sieve. For this purpose, conventional gas adsorption (static or dynamic measurements) or gas chromatographic techniques can be used. The aim of the second approach is to characterize the nanopore structure with the aid of nitrogen adsorption at 77 K together with isotherm and adsorption energy measurements with a variety of adsorptives of different molecular size, shape and polarity. The third approach is to make use of polar probe molecules (notably water and alcohols) to investigate the surface chemistry and stability of the adsorbent.