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ITQ-1, a microporous pure-silica polymorph isomorphous to zeolite MCM-22, forms upon calcination of a layered precursor obtained by hydrothermal synthesis. Calcined ITQ-1 contains a remarkably small concentration of connectivity defects (≅7 Si(OSi)3OH mol %) in contrast to uncalcined ITQ-1 (≅30%). 29Si NMR spectra, which are in good agreement with the structure proposed for MCM-22, demonstrate the defects are not randomly distributed in the layered precursor but arise mostly from unconnected T1−O−T1 and T2−O−T3 bonds.
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Camblor et al. (1996) studied this question.
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