2D 1H DQ-SQ NMR spectra of zeolites TPA-OH-ZSM-5 and TEA-OH-ZSM-5 clearly demonstrate the specific spatial correlations between the SiO–··HOSi hydrogen bonds within the framework and the alkyl chains of TPA+ and TEA+. For zeolite TPA-OH-ZSM-5,the 2D 1H DQ-SQ NMR spectrum shows that the SiO–··HOSi hydrogen bonds within the framework are spatially close to the methyl groups of TPA+ cations. For zeolite TEA-OH-ZSM-5, the 2D 1H DQ-SQ NMR spectrum shows that the SiO–··HOSi hydrogen bonds within the framework are spatially close to both the methyl and methylene groups of TEA+ cations. These observations imply that the position and distribution of the negative charge centers such as F anions, SiO–··HOSi hydrogen bonds and T3+ atoms in the MFI framework are influenced by TPA+ or TEA+ cations for the strong electrostatic interactions. By analyzing the variable contact time 1H–13C CP/MAS NMR experimental results, the 13C signal with δ = 10.6 ppm can be assigned to the methyl groups of TPA+ cations located in zigzag channels and the 13C signal with δ = 11.6 ppm can be assigned to the methyl groups of TPA+ cations located in straight channels. Both 2D 1H DQ-SQ NMR spectrum and 1H–13C CP/MAS NMR spectra of TEA-OH-Beta show that the SiO–··HOSi hydrogen bonds within the framework are spatially further from the alkyl chains of TEA+ in Beta than those in ZSM-5, which indicates that van der Waals interactions play the dominant roles during the crystallization process of zeolite Beta. According to our NMR observations, it can be inferred that the nature of structure direction of OSDAs roots in the complex relationship between van der Waals interactions and electrostatic interactions in the inorganic–organic composites formed in the induction period.

Multinuclear solid state NMR techniques have been applied to study the structural characteristics of extra-large-pore zeolite ITQ-33. Through analysis of 2D 29Si{19F} HETCOR NMR spectra, the configurations of Ge-D4R units in ITQ-33 can be confirmed to have the most separation between Si and Ge atoms. Because F anions are not in the center of D4R units for shorter Ge–F bond lengths and Ge-D4R units with Ge–F bonds in the crystals are related by mirror symmetries, 29Si NMR signals of D4R units are magnetically inequivalent, therefore two 29Si peaks are observed in 19F–29Si CP/MAS and 19F–29Si HETCOR spectra. The formation of specific D4R configurations proves that Ge atoms and F– anions play important structural directing roles in the formation process of zeolite ITQ-33. 27Al 5QMAS experimental results confirm that a major amount of Al atoms is incorporated into the 3-ring in the framework. 1D 13C–27Al S-RESPDOR experimental results show that Al atoms in the framework are spatially close to the methyl groups of HM2+ cations in the 18-ring channels. Therefore, it can be suggested that the delicate electrostatic balances between the negative charge centers such as F– anions in Ge-D4R units and Al atoms in 3-ring in the zeolite framework and the HM2+ cations orient the formation of ultralarge pores (18R) in zeolite ITQ-33. Our observations could be helpful in the design and synthesis of new extra-large-pore zeolites.

Crystallization of AlPO4-5 with AFI structure under solvent-free conditions has been investigated. Attention was mainly focused on the characterization of the intermediate phases formed at the early stages during the crystallization. The development in the long-range ordering of the solid phases as a function of crystallization time was monitored by XRD, SEM, IR, UV-Raman, and MAS NMR techniques. Particularly, the UV-Raman spectroscopy was employed to obtain the information on the formation process of the framework. J-HMQC 27Al/31P double-resonance NMR experiments were used to identify the P–O–Al bonded species in the intermediate phases. For the first time the P–O–Al bonded species in the intermediate phases can be correctly described through using this advanced NMR technique. The crystallization under solvent-free conditions appears to follow the pathway: The initial amorphous raw material is converted to an intermediate phase which has four-/six-membered ring species, then gradually transformed into crystalline AlPO4-5. This observation is not consistent with the common idea that the intermediate phase is the semicrystalline intermediates with a three-dimensional structure.