ITQ-7 is a tri-dimensional twelve-membered ring zeolite which presents double four-membered ring units (D4MR) in its structure. On the basis of theoretical ab initio calculations, which indicate that isomorphic substitution of Ge for Si atoms in the double four-membered ring units stabilizes such small cages, we have carried out the synthesis of ITQ-7 in the presence of Ge. It is found that the incorporation of Ge reduces the crystallization time from 7 days to less than 12 h, while a detailed analysis of the 19F and 29Si MAS NMR leads to the conclusion that Ge selectively occupies positions at the D4MR. An hypothesis has been introduced which assumes that the increase in the crystallization rate is due to the preferential occupancy of D4MR sites by Ge, and this allows relaxation of the constrained T−O−T bonds of these small D4MR cages.

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Ge‐directed zeolites. Forcefield atomic simulations are used to investigate the location of the Ge atoms and the structure‐directing agents (SDAs) in the Ge containing ITQ‐17 zeolite (see picture). The Ge atoms are found to locate preferentially at the T1 sites which form double four‐ring (D4R) units. A combined theoretical and experimental treatment has allowed us to prove the preferential location of Ge atoms in the double four‐member rings of the polymorph C of Beta zeolite, and its corresponding structure‐directing effect to be demonstrated.

The gram-scale synthesis, stabilization, and characterization of well-defined ultrasmall subnanometric catalytic clusters on solids is a challenge. The chemical synthesis and X-ray snapshots of Pt clusters, homogenously distributed and densely packaged within the channels of a metal-organic framework, is presented. This hybrid material catalyzes efficiently, and even more importantly from an economic and environmental viewpoint, at low temperature (25 to 140 °C), energetically costly industrial reactions in the gas phase such as HCN production, CO methanation, and alkene hydrogenations. These results open the way for the design of precisely defined catalytically active ultrasmall metal clusters in solids for technically easier, cheaper, and dramatically less-dangerous industrial reactions.

Controlling the location of acid sites in zeolites can have a great impact on catalysis. In this work we face the objective of directing the location of Al into the 10R channels of ZSM-5 by taking advantage of the structural preference of B to occupy certain positions at the channels intersections, as suggested by theoretical calculations. The synthesis of B-Al-ZSM-5 zeolites with variable Si/Al and Si/B ratio, followed by B removal in a post synthesis treatment, produces ZSM-5 samples enriched in Al occupying positions at 10R channels. The location of the acid sites is determined on the basis of the product distribution of 1-hexene cracking as test reaction. The higher selectivity to propene and lower C4 = /C3 = ratio in the samples synthesized with B and subsequently deboronated can be related to a larger concentration of acid sites in 10R channels, where monomolecular cracking occurs. Finally, several ZSM-5 samples have been tested in the methanol to propene reaction, and those synthesized through the B assisted method show longer catalytic lifetime, higher propene yield and lower yield of alkanes and aromatics.

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ITQ-21 has been synthesized in a wide range of compositions. By rationally modifying the synthesis variables and zeolite composition, it is possible to fine-tune the crystallite size from nanocrystals (<80 nm) up to microns and to avoid the competition of other phases such as CIT-5, SSZ-24, or a laminar phase that can also be synthesized with the same organic structure directing agent. By means of XRD and (19)F MAS NMR, Ge and Si have been localized among the different crystallographic positions, and it is shown that Ge preferentially occupies T1 positions at the D4R cages, avoiding formation of Ge-O-Ge pairs. However, at high Ge loadings (Si/Ge = 1.7), a new (19)F MAS NMR signal at -14 ppm has been observed and assigned to the presence of Ge-O-Ge in Ge-rich D4R cages. Energetic configurations obtained by theoretical calculations fully agree with experimental observations, with the following increasing order in energy for Ge substitution: T1 < T2 < Ge-O-Ge in T1 < T3.