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An exact knowledge of the architecture of complex pore networks and the impact on transport processes is critical to understand and optimize their integration in many functional solids. Here, a robust and versatile approach is demonstrated to quantitatively map pore constrictions within hierarchical faujasite-type (Y and USY) zeolites, the most widely applied zeolitic materials in industry. Differential hysteresis scanning measurements by high-resolution argon sorption coupled with an advanced modeling framework enable the derivation of the amount and size of pyramidal, constricted, and occluded mesopores. This yields unprecedented insight into the impact of widely practiced demetallation treatments on the porosity evolution and clearly highlights the interplay between the geometry of mesopores developed by a given treatment and those introduced by previously applied postsynthetic modifications. Based on the findings, the dynamic assessment by positron annihilation spectroscopy confirms the effectiveness of each mesopore type at enhancing the diffusion of ortho-positronium within the crystal. The quantitative descriptors attained by these complementary techniques can revolutionize the design of porous materials for a wide range of applications. [ABSTRACT FROM AUTHOR]

Hierarchical FAU- and LTA-type catalysts are prepared by post-synthetic modifications and evaluated in the base-catalyzed Knoevenagel condensation of benzaldehyde with malononitrile. A novel route to attain mesoporous Al-rich zeolites (A and X) is demonstrated, while mesoporous Y and USY zeolites are prepared using recently developed methods. Base functionality is introduced by alkali ion exchange (Cs, Na) or by high-temperature nitridation in ammonia. A thorough characterization of the zeolites' structure, composition, porosity, morphology, and basicity demonstrates that the presence of a secondary mesopore network enhances the ion-exchange efficiency and the structural incorporation of nitrogen. The modified USY zeolites display twice the conversion, while the hierarchical A, X, and Y are up to 10 times more active based on the enhanced accessibility. These results demonstrate that the Knoevenagel condensation takes place predominately at the external surface, highlighting secondary porosity as a key criterion in the design of basic zeolite catalysts. [ABSTRACT FROM AUTHOR]

On page 5621, J. Kenvin, J. Pérez‐Ramírez, and coworkers demonstrate differential hysteresis scanning by high‐resolution argon sorption and positron annihilation spectroscopy as powerful tools to quantify the complex architecture of pore networks in hierarchical faujasite zeolites and their efficiency in transport processes. The descriptors attained by these complementary techniques further advance the design of porous materials for a wide range of applications. The creatures in the cover, exploring a tortious cave system, exemplify the challenges with pore accessibility and connectivity. [ABSTRACT FROM AUTHOR]

On page 1923 Javier Pérez‐Ramírez and co‐workers establish methods involving acid and optionally base treatments to prepare hierarchical FAU and LTA‐type zeolites. By conquering the latter Al‐rich frameworks, the full compositional and topological flexibility desired in the design of hierarchical zeolites by post‐synthetic strategies is accomplished. Upon functionalization, the mesoporous X, Y, and A zeolites display superior performance as base catalysts. Carolina Flores is acknowledged for perfecting the cover artwork. [ABSTRACT FROM AUTHOR]