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ITQ-13 is a medium-pore zeolite that can be prepared in all-silica form and as silicogermanate with Si/Ge ratios as low as 3. Usually synthesised in the presence of fluoride, ITQ-13 is among the very few systems containing fluoride anions in two distinct cage types, cube-like d4r units and [4·56] cages. Here, dispersion-corrected density functional theory (DFT) calculations are used to investigate the energetically most favourable Ge distributions for Si/Ge ratios between 55 and 6. The calculations show Ge atoms are incorporated at both the corners of d4r cages and at the basal plane of the [4·56] cages, in accordance with 19F-NMR spectroscopy. Two Ge atoms at adjacent corners of [4·56] cages are stable at the highest Ge content considered (Si/Ge = 6). Such a local environment has not yet been considered in the experimental literature. A calculation of the corresponding 19F-NMR resonance points to overlap with other resonances, which might preclude its clear identification. Additional calculations investigate the variation of the dynamic behaviour of the fluoride anions as a function of the local environment as well as the selective defluorination of the [4·56] cages.

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The cover picture shows the three‐dimensional supramolecular arrangement of 1,10‐phenanthroline (phen) residues in compound (Hphen)6[Ge6(OH)6(hedp)6]·2(phen)·20H2O (where H4hedp stands for etidronic acid). Protonated organic residues, Hphen+, π‐π‐stack along the [101] direction of the unit cell, which leads to the formation of columns that are interconnected through a series of weak C–H···π interactions with neighbouring 1,10‐phenanthrolines. The resulting organic framework is highly porous and contains charge‐balancing centrosymmetric hexameric anionic [Ge6(ν2‐OH)6(C2H4O7P2)6]6– moieties within the channels and a large number of highly disordered water molecules (total available volume of ca. 2462 Å3 per unit cell). Details are discussed in the article by J. Rocha et al. on p. 4741 ff.