Zr-silicate zeolites efficiently catalyze Meerwein-Ponndorf-Verley (MPV) reduction, a key reaction in fine chemical production. However, for substrates such as citronellal, MPV reaction selectivity decreases due to competing Lewis acid-catalyzed reactions, notably carbonyl-ene cyclization, which yields isopulegol as the main product. Reaction selectivity may be determined by site strength as weaker "closed" sites in Zr-beta catalyze MPV reduction, while stronger "open" Zr sites catalyze carbonyl-ene cyclization. But the precise control over acidity strength in Zr-beta catalysts remains an unsolved challenge. This study aims at modulating Al-free Zr-beta zeolite acidity through ion exchange with Li+ , Na+ and Cs+. In citronellal MPV reduction, we increased citronellol selectivity by tuning the Lewis acidity of Zr-beta. As shown by FT-IR spectroscopy of acetone and d3-acetonitrile, ion exchange weakened interactions between carbonyl compounds and "open" Zr Lewis acid sites, converting strong Zr "open" sites into weaker Lewis acid sites and, thus, switching reaction selectivity from isopulegol to MPV reduction. Case in point, ion-exchanged Zr-beta-1-Na+4x provided 77% citronellol selectivity and 23% isopulegol selectivity. In contrast, non-exchanged Zr-beta-1 afforded 26% citronellol selectivity and 73% isopulegol selectivity, at a similar conversion level, without significant changes in the overall rate of citronellal conversion. These findings highlight ion exchange as an effective tool for post-synthesis control of Zr-beta Lewis acidity.

Ammonia is a cornerstone of fertilizers and an emerging carbon-free energy carrier, yet its industrial synthesis via Haber-Bosch consumes similar to 1% of global energy. Photocatalytic nitrogen fixation provides a potential alternative, but conventional processes operate in aqueous media and yield trace concentrations of ammonia that are impractical to collect and use. Here, we introduce a photochemical looping strategy that integrates nitrogen activation, reduction, and solid-state capture in a cyclic process. Using a Pt-heteropolyacid-TiO2 composite, carbon monoxide, either supplied directly or produced in situ from CO2, generates oxygen vacancies on the heteropolyacid that adsorb and activate N-2, while water supplies protons and regenerates the vacancies. The formed ammonia is stored as a stable ammonium salt, which can be released upon calcination to produce aqueous NH3 solutions up to 1.3 wt%, which is significantly higher than the typically reported concentrations in the direct photocatalytic N-2 reduction in aqueous suspensions. By coupling photocatalysis with solid-state storage, this looping approach overcomes long-standing barriers in conversion, selectivity, and product recovery, establishing a scalable framework for solar-driven ammonia production under mild conditions.

Engineering the zeolite dimensionality reveals that 2D MWW layers outperform their 3D analogues by enhancing CO 2 /C 2 H 2 separation efficiency.

Xylene isomerization is a key zeolite-catalyzed petrochemical process for the production of p-xylene, a highly demanded intermediate in the polymer industry. While MFI-type zeolites are widely used in industry as shape-selective catalysts, xylene isomerization also serves as a benchmark reaction for evaluating the shape-selectivity of new zeolite catalysts in relation to their porosity. In this study, IWW zeolite with a three-modal pore network of isolated 8-and 12-ring pores intersected by 10-ring channels was investigated for m-xylene isomerization, with a focus on how both the multidimensional pore system and crystal morphology affect catalytic performance. IWW zeolites were synthesized as germanosilicates with platelet-like and needle-like crystals, functionalized by post-synthetic Ge-to-Al substitution, and tested in gas-phase m-xylene isomerization in comparison with reference zeolite catalysts containing unimodal 8-, 10-, or 12-ring channels. Compared to MFI with a similar concentration of acid sites, Al-IWW catalysts exhibited higher m-xylene conversion across a wide range of WHSV values (4.4-40 h-1), regardless of crystal morphology. Needle-like Al-IWW crystals achieved para-selectivity comparable to that of MFI, while platelet-like Al-IWW outperformed MFI inp-xylene yield at short contact times (WHSV = 40 h-1). STEM analysis confirmed that the 10-ring channels are aligned along the length of the needle-like crystals, promoting shape-selective p-xylene formation. In contrast, the 12-ring channels running along the extended dimension of the platelet-like crystals facilitate the diffusion of reactant and product molecules to and from the active sites. All in all, the integration of multi-sized pores and tunable crystal morphology in IWW zeolites may offer a promising strategy for balancing selectivity and activity in p-xylene synthesis.

Herein, we uncover structural dimensionality as a key factor governing CO2/C2H2 separation in MWW zeolites. Exfoliated MWW monolayers outperform 3D frameworks by extended breakthrough interval with higher selectivity. Combined experimental and DFT analyses reveal site-specific adsorption and reduced transport barriers, establishing dimensionality as a new design axis for molecular sieving.

The conversion of methane to valuable products is one of the main challenges of modern chemistry. Acetic acid (AcOH) is a key chemical reagent in industry, produced nowadays by the carbonylation of methanol over homogeneous Rh and Ir catalysts. Here, we propose a stepwise chemical looping approach for the highly selective stoichiometric synthesis of AcOH by carbonylation of methane with CO using single-site Pt over isolated phosphotungstic anions on a titania support (Pt-HPW-TiO2). The reaction proceeds by methane activation, which coincides with the reduction of initially oxidized Pt species in the presence of CO at 423 K and results in surface acetates attached to TiO2. Subsequent hydrolysis by water at ambient temperature results in the synthesis of AcOH in a stoichiometric amount corresponding to 1.5 Pt. Spent Pt-HPW-TiO2 is restored to the initial state by subsequent calcination in air. This approach provides an opportunity for the selective synthesis of AcOH (>99% in liquid phase) from methane, carbon monoxide, and air. A high concentration of AcOH (1.1 wt %) in an aqueous solution can be obtained at a high conversion of methane (4.5%).

Zeolites, known for their crystallinity and porosity, exhibit versatile acid functionalities, making them valuable industrial catalysts. This chapter discusses the acidity of zeolites, including Brønsted and Lewis acids, and their variations. It focuses on the principal methodologies for adjusting zeolite acidity, including isomorphous substitution, steaming, and the impact of extraframework species. The engineering of acid site accessibility and its applications in catalysis, adsorption, and environmental remediation are also discussed. Future perspectives and viewpoints are briefly mentioned.

The conversion of renewable compounds to versatile platform molecules over environmentally friendly heterogeneous catalysts is a major challenge. Zeolites stand as active, selective, and reusable solid catalysts for various acid-catalyzed reactions involved in the one-pot cascade transformation of polysaccharides to 5-hydroxymethylfurfural (HMF), a platform molecule opening the way to various valuable chemicals. However, the acidity-performance relationships of zeolite catalysts in HMF synthesis have not been fully elucidated. Here, we have addressed the effect of acid site nature in zeolite catalysts for sucrose-to-HMF transformation by comparing the performance of conventional Al-substituted IWW zeolite with that of Sn-, Zr-, and Ge-containing zeolite catalysts of the same structure. Ge-associated acid sites were found to exhibit superior HMF selectivity compared to Sn, Zr, and Al acid centers, while experiencing evolution into Br & oslash;nsted acid centers during the catalytic run. The conversion of sucrose over germanosilicate zeolites enhances with increasing catalyst pore diameter or decreasing crystal size. Specifically, the extra-large pore Ge-UTL catalyst, featuring intersecting 14- and 12-ring pores (crystal size 10 x 20 x <1 mu m), and large-pore Ge-IWW with 12-, 10- and 8-ring pores (crystal sizes of 1 mu m) showed a yield of targeted HMF comparable to or even exceeding the values previously reported for homogeneous or heterogeneous catalysis (54 % after 3 h at 120 degrees C). Ge-IWW catalyst demonstrated reusability across a minimum of 3 catalytic runs, while in situ structural transformation precluded stable performance of Ge-UTL catalyst in the repetitive catalytic cycles. The results of this study highlight zeolites with uncharacteristic chemical compositions as active, selective, and reusable catalysts for highly demanding applications in biomass valorization.

Conversion of renewable compounds to versatile platform molecules over environmentally friendly heteroge-neous catalysts is of increasing demand. Bifunctional Zr,Al-containing large-pore zeolites stand as active, se-lective and reusable solid catalysts for a one-pot cascade transformation of biomass-derived furfural to gamma-valerolactone, a platform molecule opening the way to various valuable chemicals. However, the influence of zeolite structure type and the ratio between Al-and Zr-associated acid sites on the outcome of this catalytic reaction has not been fully elucidated. Here we have compared the performance of the most efficient large-pore zeolites USY and Beta with systematically varied Al/Zr ratios for the one-pot synthesis of gamma-valerolactone from furfural using 2-propanol or 2-pentanol as reacting solvents. The optimization of the catalyst structure (USY) and chemical composition (Al/Zr = 0.6) enables to achieve the yield of targeted gamma-valerolactone comparable to or even exceeding the values previously reported for homogeneous or heterogeneous catalysis (88% after 24 h at 120 degree celsius). The remarkable catalytic performance of the optimized Zr-Al-USY catalyst was related to the balanced ratio between Zr-and Al-associated acid sites catalyzing different steps of the studied cascade reaction.

Dihydroxybenzenes, including catechol, resorcinol and hydroquinone, have significant commercial value for a variety of applications such as adhesives, resins, pharmaceuticals, coatings etc. However, selective production of required isomers by phenol hydroxylation represents a considerable challenge. Here, we report a new approach for the synthesis of dihydroxybenzenes by their isomerization using a bifunctional Pt/ZSM-5 catalyst. The catalyst successfully facilitates the transformation of catechol and hydroquinone to each other with a selectivity of up to 74 % and yields up to 50 %. The investigation of the mechanism suggests that isomerization proceeds via a carbonaceous deposit (coke) formed by intermediate quinone condensation with subsequent hydrogenolysis to isomers. The proposed mechanism shows the way for the design of the efficient process for isomerization of dihydroxybenzenes.

Lewis acid zeolites containing tetravalent metals, such as Sn or Zr, are of great interest as catalysts for various reactions owing to their tunability, activity, and reusability. In the context of emerging trends in biomass-related substrates processing, the synthesis of Lewis acid zeolites with extra-large pores presents a key step by addressing diffusion restriction associated with these molecules. In this paper, we report on the incorporation of Sn and Zr into extra-large pore zeolites UTL and *CTH through a four-step approach, including synthesis of parent germanosilicate zeolites, followed by their post-synthesis stabilization, degermanation, and metal incorporation. The resulting zeolites were examined in Meerwein-Ponndorf-Verley (MPV) reduction of furfural in batch and flow reactors. In a batch, the designed Lewis acid extra-large pore zeolites exhibited similar yields to the MPV reduction product as the respective Sn- and Zr-substituted zeolite *BEA known as the optimum catalysts for this reaction. On the other hand, a better mass balance was observed for the MPV reduction of furfural over UTL/Sn (91%) vs. *BEA/Sn zeolite catalysts (73 – 91%) in a batch mode, suggesting the hindered formation of insoluble furfural transformation products in the extra-large pore system of UTL zeolite. Showing stable performance in MPV reduction in a flow reactor (50% selectivity to MPV reduction product at 20 – 25% furfural conversion), the extra-large pore Sn-UTL zeolite designed in this study was verified as a promising solid Lewis acid catalyst under industrially relevant conditions.

Lewis acid catalysts convert biomass compounds to green chemicals and fuels. Among these catalysts, stannosilicate zeolites display high thermal stability and reusability. However, only a few Sn-zeolites can be prepared using conventional synthesis methods, preventing us from developing shape-selective stannosilicate catalysts. Here, we propose a synthetic approach toward shape-selective Sn-zeolite catalysts, leveraging the Assembly, Disassembly, Organization, Reassembly (ADOR) strategy. By combining isomorphous Sn incorporation (i) into germanosilicate zeolites UOV, IWW, and IWR in the A step with structural modification in the DOR steps, we targeted new Sn-zeolite structures with either parallel or intersecting 12- and 8-ring pores predominantly containing Lewis acid centers with hydrolyzed Sn-O-Si bonds. The shape-selective performance of the designed Sn-zeolite catalysts was experimentally assessed and theoretically rationalized in transformations of citronellal into citronellol by Meerwein-Ponndorf-Verley reduction and into isopulegol isomers via intramolecular cyclization. Therefore, iADOR paves the way toward new zeolite catalysts with engineered Sn active sites for green chemistry.

Addressing the synthesis–property relations in the Assembly step of ADOR enabled to design previously unknown IPC-17 zeolite by optimization of the chemical composition and crystallite dimensions in the parent IWR germanosilicate.

Hierarchical zeolite catalysts containing additional meso- or macropores have attracted significant interest due to their beneficial performance in various reactions involving bulky molecules. A surfactant-templated post-synthesis of zeolites in basic medium (NaOH) advances from the uniform mesopore size distribution and easy regulation of micro-to-mesopore volume ratio in thus prepared hierarchical zeolites, although their synthesis-acidity-performance relationships remain elusive. In this study, we tackled this problem by designing a series of surfactant-templated hierarchical FAU catalysts with systematically varied textural and acidic characteristics, while assessing their catalytic performance in two model reactions: (1) acid-site-strength insensitive O-alkylation of bulky alcohols (1-octadecanol and 1-adamatylmethanol) and (2) acid-site-strength sensitive Friedel-Crafts benzoylation of p-xylene. A systematic increase in the NaOH/Si molar ratio in the synthesis from 0.075 to 0.25 decreased the number of strong Bronsted acid sites in hierarchical FAU zeolites, while it increased the concentration of Bronsted acid sites accessible for bulky molecules (up to 67% in hierarchical zeolites vs. 21% in the parent FAU zeolite). The development of transport mesopores was shown to positively affect the outcome of the studied reactions independently of the required acid site strength. Although, the optimal interplay between the concentration of strong Bronsted acid sites and their 'accessibility' (i.e., fraction of acid sites accessible to molecules with a kinetic diameter larger than the micropore opening in zeolites) was found to differ for O-alkylation of bulky alcohols or Friedel-Crafts benzoylation of p-xylene, the possibility of balancing these characteristics in the hierarchical surfactant-templated zeolites was shown by adjusting the NaOH/Si ratio used for their preparation. The results of this study contribute to the understanding of the synthesis-property-performance relationships of surfactant-templated hierarchical zeolite catalysts and provide a guide to tailor the best catalyst for a given reaction. A surfactant-templated synthesis results in hierarchical zeolites with controllable micropore-to-mesopore volume ratio. However, the relationships between the synthesis conditions, acidity and catalytic performance of thus prepared zeolites are not fully understood and require further investigation.

Germanosilicate zeolites are attractive adsorbents and catalysts, thanks to their diverse structures and versatile textural properties. However, hydrolytic instability of such zeolites, even under ambient conditions, restricts their practical applications. In this study, we report dynamic changes in the state of the zeolite framework atoms due to Ge de-intercalation and Si re-insertion in aqueous medium and propose a strategy for stabilizing zeolites with planar and orthogonal locations of Ge-rich domains by managing both processes. Adjusting the acidity or temperature of the aqueous environment enabled Ge and Si atoms to reach balanced mobility, allowing Ge atoms to be leached and Si atoms to be inserted into the released positions, thereby stabilizing the zeolite framework. The developed approach offers a practical and controllable method for structural stabilization of any labile germanosilicate material, with potential applications in catalysis, as demonstrated after the incorporation of Al-associated acid centers.

The morphology of zeolite crystals strongly affects their textural, catalytic, and mechanical attributes. However, controlling zeolite crystal morphology without using modifiers or structure-directing agents remains a challenging task because of our limited understanding of the relationships between zeolite crystal shape, crystallization mechanism, and composition of the starting synthesis mixture. In this study, we aimed at developing a general method for controlling the morphology of zeolites by assessing the impact of the Si/T molar ratio of the synthesis gel on the growth rate of zeolite crystals in various crystallographic directions and on the final crystal morphology of the UTL germanosilicate with a 2D system of intersecting 14- and 12-ring pores. Our results showed that flat UTL crystals progressively thicken with the Si/Ge molar ratio, demonstrating that Ge concentration controls the relative rate of crystal growth in the perpendicular direction to the pore system. The morphology of other zeolites and zeotypes with an anisotropic structure, including AFI (12R), IFR (12R), MWW (10-10R), and IWW (12-10-8R), can also be predicted based on their Si/T ratio, suggesting a systematic pattern across zeolite structures and in a wide range of zeolite framework elements. Combined, these findings introduce a facile and cost-efficient method for directly controlling crystal morphology of zeolites with anisotropic structures with a high potential for scale-up while providing further insights into the role of elemental composition in zeolite crystal growth.

Methanol-to-hydrocarbons (MTH) process has been considered one of the most practical approaches for producing value-added products from methanol. However, the commonly used zeolite catalysts suffer from rapid deactivation due to coke deposition and require regular regeneration treatments. We demonstrate that low-melting-point metals, such as Ga, can effectively promote more stable methanol conversion in the MTH process by slowing coke deposition and facilitating the desorption of carbonaceous species from the zeolite. The ZSM-5 zeolite physically mixed with liquid gallium exhibited an enhanced lifetime in the MTH reaction, which increased by a factor of up to ~14 as compared to the parent ZSM-5. These results suggest an alternative route to the design and preparation of deactivation-resistant zeolite catalysts.

Zeolites are key materials in both basic research and industrial applications. However, their synthesis is neither diverse nor applicable to labile frameworks because classical procedures require harsh hydrothermal conditions, whereas post-synthesis methods are limited to a few suitable parent materials. Remaining frameworks can fail due to amorphization, dissolution, and other decomposition processes. Nevertheless, stopping degradation at intermediate structures could yield new zeolites. Here, by optimizing the design and synthesis parameters of the parent zeolite IWV, we "caught" a new, highly crystalline, and siliceous zeolite during its degradation. IWV seed-assisted crystallization followed by gentle transformation into the water-alcohol system yielded the highly crystalline daughter zeolite IPC-20, whose structure was solved by precession-assisted three-dimensional electron diffraction. Without additional requirements, as in conventional (direct or post-synthesis) strategies, our approach may be applied to any chemically labile material with a staged structure.