The performance of zeolite catalysts depends not only on the strength and number of Brønsted acid (or exchange) sites but also on synergistic effects derived from their proximity, in particular, and their distribution, in general. Little is known on the genesis of acid sites and site distributions in hydrothermal zeolite synthesis. By an extensive study of five crystallization systems yielding ZSM-5 (MFI) and SSZ-13 (CHA), with a focus on interzeolite conversion (IZC) methods, several synthesis factors and mechanisms that are key in determining the output acid site distribution have been identified. Key in this study were temporal synthesis profiles while probing the distribution and evolution of proximal acid sites with divalent cation capacity measurements. Over the course of different crystallizations, changing local charge distributions are detected, notably within crystalline materials upon prolonged exposure (maturation). Aluminum is clearly the key driver in IZC syntheses, from charge, dissolution, concentration, and mobility points of view. Quasigeneric principles for IZC syntheses are proposed, distinguishing between Al-loving and Al-averse systems, enabling a new degree of control over the acidity and ion-exchange properties of zeolites, of use to tailoring catalytic activity.

Mixed-matrix membranes (MMMs) have been investigated to render energy-intensive separations more efficiently by combining the selectivity and permeability performance, robustness, and nonaging properties of the filler with the easy processing, handling, and scaling up of the polymer. However, truly combining all in one single material has proven very challenging. In this work, we filled a commercial polyimide with ultrahigh loadings of a high–aspect ratio, CO 2 -philic Na-SSZ-39 zeolite with a three-dimensional channel system that precisely separates gas molecules. By carefully designing both zeolite and MMM synthesis, we created a gas-percolation highway across a flexible and aging-resistant (more than 1 year) membrane. The combination of a CO 2 -CH 4 mixed-gas selectivity of ~423 and a CO 2 permeability of ~8300 Barrer outperformed all existing polymer-based membranes and even most zeolite-only membranes.

Zeolites have long been regarded as difficult to modify during synthesis, as their synthesis is governed by kinetic processes. Recent breakthroughs have made it possible to exert a certain degree of control over zeolite properties with more performant materials as a result. Here, we investigate the effects alkali cations have on high-silica FAU-to-CHA interzeolite conversion (IZC) and on the resulting aluminum distributions. In this way, by using Li-cations in conjunction with an organic structure directing agent, the first route to a "fully paired" (divalent cation capacity, Co 2+ /Al = 0.48) high-silica SSZ-13 zeolite is demonstrated. Lithium shows great potential in steering IZC synthesis as it speeds up crystallization, and evidence was gathered in favor of a more elaborate mechanism of IZC in which dissolved Al-rich oligomers crash out of solution first and possibly spark nucleation. These findings help in gaining insights into a more general theory on zeolite nucleation in heterogeneous environments such as IZC. Furthermore, the "fully paired" sample has great potential for ion-exchanged zeolite catalysis or in adsorbents.

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The search for sustainable polymers requires new ways for accessing monomers from biomass as raw materials. Cis,cis-muconic acid (ccMA), derived from glucose, stands as a potential intermediate to produce valuable monomers, including terephthalic and adipic acids. However, to access terephthalic acid through Diels-Alder cycloaddition, an additional isomerization of ccMA into ttMA (trans,trans-isomer) is required. In this work, we develop a single-atom low-loaded Ru catalyst (0.2 wt.%), supported on *BEA zeolite, that produces tt-muconate in ethanol with total conversion (to equilibrium) and selectivity >95%. We reached productivity rates of 427 mM.h-1 (≈85 g.L-1.h-1), surpassing, by an order of magnitude, the highest values reported for biobased production of 17 mM.h-1 of ccMA, thus making the latter the rate-determining step if both processes were linked. Furthermore, we demonstrate the direct production of terephthalate intermediates with high yields (78%) and selectivity (80%) in a one-pot isomerization/Diels-Alder reaction. This single atom Ru-zeolite isomerizes dienes via a hydride mechanism and could serve the isomerization of other value-added alkenes.