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Nests of three silanol groups are located on the internal pore surface of calcined zeolite SSZ-70. 2D 1 H double/triple-quantum single-quantum correlation NMR experiments enable a rigorous identification of these silanol triad nests. They reveal a close proximity to the structure directing agent (SDA), that is, N,N'-diisobutyl imidazolium cations, in the as-synthesized material, in which the defects are negatively charged (silanol dyad plus one charged SiO- siloxy group) for charge balance. It is inferred that ring strain prevents the condensation of silanol groups upon calcination and removal of the SDA to avoid energetically unfavorable three-rings. In contrast, tetrad nests, created by boron extraction from B-SSZ-70 at various other locations, are not stable and silanol condensation occurs. Infrared spectroscopic investigations of adsorbed pyridine indicate an enhanced acidity of the silanol triads, suggesting important implications in catalysis.

Force field calculations, solid-state NMR and impedance spectroscopy are used to investigate the motion of sodium cations in sodalite and cancrinite under the influence of anions. The results show that sodium migration can be boosted in open channel systems by anion interactions, but a dynamics coupling between anion reorientation and cations mobility was not seen.

A study of defect sites in zeolites using multiple-quantum (super 1)H MAS nuclear magnetic resonance spectroscopy is discussed. The analysis of these siliceous as-made ZSM-12 zeolites provides significant information on the nucleation mechanism.

A study of as-made all-silica zeolites has shown the presence of strong Coulombic forces between cationic structure-directing agents and charge-compensating defect sites. The findings are consistent with a model where the framework aluminium is directly linked with the charge centre of the structure-directing agent.

The zeolite catalyst SSZ‐42 shows a remarkable high abundance (≈80 %) of hydrogen‐bonded Brønsted acid sites (BAS), which are deshielded from the 1H chemical shift of unperturbed BAS at typically 4 ppm. This is due to their interaction with neighboring oxygen atoms in the zeolite framework when oxygen alignments are suitable. The classification and diversity of hydrogen bonding is assessed by DFT calculations, showing that oval‐shaped 6‐rings and 5‐rings allow for a stronger hydrogen bond to oxygen atoms on the opposite ring side, yielding higher experimental chemical shifts (δ (1H)=6.4 ppm), than circular 6‐rings (δ(1H)=5.2 ppm). Cage‐like structures and intra‐tetrahedral interactions can also form hydrogen bonds. The alignment of oxygen atoms is expected to impact their role in the stabilization of intermediates in catalytic reactions, such as surface alkoxy groups and possibly transition states. [ABSTRACT FROM AUTHOR]

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The motion of B(OH)(sub 4)(super -) anions and the surrounding sodium cations in the sodalite cages is discussed by solid-state NMR techniques. The described NMR methods provide a great deal of structural details for which traditional X-ray diffraction methods are largely insensitive.