This review of 53 references deals with the uses of zeolites and zeolite-based materials for developing gas sensors. The potential of these materials is highlighted and avenues for further research are suggested.

Thermal analyses were used to study the sorbate/framework and sorbate/sorbate interaction on siliceous MFI type zeolite. Alkanes, aromatics, alkyl alcohols, multivalue hydroxyl alcohols, alkylamines, organic acids, acetaldehyde, ethyl ether, acetone, and ethyl acetate were investigated as the adsorbate. The adsorption and desorption behavior of high silica MFI type zeolite is greatly influenced by the presence of framework aluminum, cations, and silanol defects. There is a perfect Si−O−Si micropore surface without cations and silanol defects in the high hydrophobic zeolite silicalite. The essential host/guest interaction can be clearly studied by the thermal desorption behavior from silicalite. A general hydrophobic/organophilic property of 27 organic compounds with different functional groups on silicalite has been compared in terms of the affinity index A T determined by DTG. The physical meaning of the A T value, and the nature of the host/guest interaction are discussed. Silicalite has a strong affinity for some organic compounds with high polarity and is usually phobic to organics with hydroxyl groups. The special sorbate/framework and sorbate/sorbate interactions for certain organics can be identified from the double peaks in the DTG curves and thermal effects in the DTA curves. The formation of the double-molecule complexes of p-xylene, toluene, phenol, ethylene glycol, and ethylamine in silicalite is revealed.

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The generation of magic number silica clusters [(SiO 2 ) n O 2 H 3 ]with n ) 4 and 8 by XeCl laser (308 nm) ablation of porous siliceous materials is reported. The production of magic cluster [(SiO 2 ) 4 O 2 H 3 ]can be enhanced by sample selection and experimental optimization so that it becomes the most prominent species in silica clusters. To study the structure of the magic cluster [(SiO 2 ) 4 O 2 H 3 ] -, we performed structural optimization for the neutral bare cluster (SiO 2 ) 4 , the neutral complex cluster (SiO 2 ) 4 O 2 H 4 , and the anionic cluster [(SiO 2 ) 4 O 2 H 3 ]at the HF/6-31G** level. It was found that the ground state of the bare silica tetramer has a linear chain structure whereas a pseudotetrahedral cage-like structural isomer of S 4 symmetry is most stable for the complex cluster (SiO 2 ) 4 O 2 H 4 . The stabilization of the three-dimensional (3D) structure can be attributed to the active participation of the O 2 H 4 group in chemical bonding during cluster formation. Our theoretical calculation and bonding analysis indicate that the magic number anionic cluster [(SiO 2 ) 4 O 2 H 3 ]might also take a pseudotetrahedral structure similar to (but with a different symmetry) that of the neutral precursor (SiO 2 ) 4 O 2 H 4 as the ground state in which the valence, coordination, and bonding characteristics of all the constituent atoms are nearly fully satisfied.