Recent developments in (bio)ethanol conversion to fuels and chemicals over heterogeneous catalysts

Bioethanol is one of the most important bio-resources produced from biomass fermentation and is an environmentally friendly alternative to fossil-based fuels as it is regarded as renewable and clean. Bioethanol and its derivatives are used as feedstocks in petrochemical processes as well as fuel and fuel additives in motor vehicles to compensate for the depletion of fossil fuels. This review chronicles the recent developments in the catalytic conversion of ethanol to diethyl ether, ethylene, propylene, long-chain hydrocarbons, and other important products. Various heterogeneous catalysts, such as zeolites, metal oxides, heteropolyacids, mesoporous materials, and metal-organic frameworks, have been used in the ethanol conversion processes and are discussed extensively. The significance of various reaction parameters such as pressure, temperature, water content in the ethanol feed, and the effect of catalyst modification based on various kinds of literature are critically evaluated. Further, coke formation and coke product analysis using various analytical and spectroscopic techniques during the ethanol conversion are briefly discussed. The review concludes by providing insights into possible research paths pertaining to catalyst design aimed at enhancing the catalytic conversion of (bio)ethanol.

Acceleration of Zeolite Crystallization: Current Status, Mechanisms, and Perspectives

Zeolites are important classes of crystalline materials and possess well-defined channels and cages with molecular dimensions. They have been extensively employed as heterogeneous catalysts and gas adsorbents due to their relatively large specific surface areas, high pore volumes, compositional flexibility, definite acidity, and hydrothermal stability. The zeolite synthesis normally undergoes high-temperature hydrothermal treatments with a relatively long crystallization time, which exhibits low synthesis efficiency and high energy consumption. Various strategies, e.g., modulation of the synthesis gel compositions, employment of special silica/aluminum sources, addition of seeds, fluoride, hydroxyl (·OH) free radical initiators, and organic additives, regulation of the crystallization conditions, development of new approaches, etc., have been developed to overcome these obstacles. And, these achievements make prominent contributions to the topic of acceleration of the zeolite crystallization and promote the fundamental understanding of the zeolite formation mechanism. However, there is a lack of the comprehensive summary and analysis on them. Herein, we provide an overview of the recent achievements, highlight the significant progress in the past decades on the developments of novel and remarkable strategies to accelerate the crystallization of zeolites, and basically divide them into three main types, i.e., chemical methods, physical methods, and the derived new approaches. The principles/acceleration mechanisms, effectiveness, versatility, and degree of reality for the corresponding approaches are thoroughly discussed and summarized. Finally, the rational design of the prospective strategies for the fast synthesis of zeolites is commented on and envisioned. The information gathered here is expected to provide solid guidance for developing a more effective route to improve the zeolite crystallization and obtain the functional zeolite-based materials with more shortened durations and lowered cost and further promote their applications.

Two-Dimensional Zeolites-Potential Catalysts for Biomass Valorization

Valorization of biomass and biomass-derived molecules has become a viable route to get fuels and useful chemicals as fossil feedstocks are dwindling and the demand for renewable feedstocks and sustainable energy sources are rising. Zeolites have been promising catalysts for biomass conversion owing to their structural features and active sites. However, the use of conventional zeolites was limited due to molecular diffusion constraints, which paved the way for the emergence of two-dimensional (2D) zeolites. The high external surface area, bimodal porosity (micropores and mesopores), and 2D structure of these zeolites envisage smooth diffusion of bulky molecules, enhanced accessibility to active sites, and slow deactivation, which are benefits in the valorization of biomass. In this brief review, current advancements in the use of layered 2D zeolites for biomass conversions are discussed. The relationship between the structural features and the catalytic potential of 2D zeolites in some of the major biomass conversion processes like pyrolysis, hydrodeoxygenation, alkylation, acetalization, condensation, and dehydration is discussed and multistep reactions that proceed via a cascade mechanism are highlighted.

The AM-4 Family of Layered Titanosilicates: Single-Crystal-to-Single-Crystal Transformation, Synthesis and Ionic Conductivity

Flexible crystal() structures, which exhibit() single-crystal()-to-single-crystal() (SCSC) transformations(), are attracting attention() in many applied aspects: magnetic() switches, catalysis, ferroelectrics and sorption. Acid treatment() for titanosilicate material() AM-4 and natural() compounds with the same structures led to SCSC transformation() by loss() Na+, Li+ and Zn2+ cations with large structural() changes (20% of the unit()-cell() volume()). The conservation() of crystallinity through complex() transformation() is possible due() to the formation() of a strong hydrogen bonding() system(). The mechanism() of transformation() has been characterized using single-crystal() X-ray() diffraction analysis(), powder() diffraction, Rietvield refinement, Raman spectroscopy and electron microscopy. The low migration() energy() of cations in the considered materials() is confirmed using bond()-valence and density() functional() theory() calculations, and the ion conductivity of the AM-4 family's materials() has been experimentally verified.

Al distribution and structural stability of H-BEA zeolites at different Si/Al ratios and temperatures: a first-principles study

Beta zeolites have been widely used in acid-catalyzed reactions because of their excellent properties. An in-depth study of the position, quantity, and distribution of beta zeolites substituted by Al is significant to understand the catalytic performance of the active site of zeolite catalysts. The distribution of Al in H-BEA and the structure of silanol nests in dealuminated BEA at different Si/Al ratios and synthesis temperatures were studied by the DFT method. T1, T2, T7, and T9 sites were chosen to be simulated. The synthesis temperature can change the distribution of Al and the proportion of T sites at different Si/Al ratios. The proportion of T7 and T9 is more than 70% at different Si/Al ratios of H-BEA and decreases with the synthesis temperature. T1 and T2 sites begin to appear when Si/Al < 20 and the proportion of T1 and T2 sites is less than 20%. When Si/Al < 8, the substitution energy of the AlSiAl structure, which has Si(2Al, 2Si) species, is obviously lower than that of the normal structure, which indicates that the Al-O-Si-O-Al species will appear in H-BEA. The Al(T7)Si(T5)Al(T9)Si(T5)Al(T7) and Al(T1)Si(T1)Al(T9) groups can not only stabilize H-BEA but also play an essential role in the formation of Si(2Al, 2Si) species. For dealuminated BEA zeolites, the silanol nest forms four hydrogen bonds through four silanols. The orientation of silanol groups in the silanol nest formed after dealumination at different T sites is different. The T7 and T9 sites in H-BEA are more likely to undergo dealumination. By contrast, the dealumination of the T1 and T2 sites is a challenge.

Catalytic Performance and Sulfur Dioxide Resistance of One-Pot Synthesized Fe-MCM-22 in Selective Catalytic Reduction of Nitrogen Oxides with Ammonia (NH3-SCR)—The Effect of Iron Content

The catalytic performance of Fe-catalysts in selective catalytic reduction of nitrogen oxides with ammonia (NH₃-SCR) strongly depends on the nature of iron sites. Therefore, we aimed to prepare and investigate the catalytic potential of Fe-MCM-22 with various Si/Fe molar ratios in NH₃-SCR. The samples were prepared by the one-pot synthesis method to provide high dispersion of iron and reduce the number of synthesis steps. We have found that the sample with the lowest concentration of Fe exhibited the highest catalytic activity of ca. 100% at 175 °C, due to the abundance of well-dispersed isolated iron species. The decrease of Si/Fe limited the formation of microporous structure and resulted in partial amorphization, formation of iron oxide clusters, and emission of N₂O during the catalytic reaction. However, an optimal concentration of Fe_xO_y oligomers contributed to the decomposition of nitrous oxide within 250–400 °C. Moreover, the acidic character of the catalysts was not a key factor determining the high conversion of NO. Additionally, we conducted NH₃-SCR catalytic tests over the samples after poisoning with sulfur dioxide (SO₂). We observed that SO₂ affected the catalytic performance mainly in the low-temperature region, due to the deposition of thermally unstable ammonium sulfates.

On route to one-pot synthesis of delaminated Al-SSZ-70 zeolite via partial substitution of OSDA with CTAOH surfactant

Direct synthesis of delaminated layered zeolitic materials aims to synthesize confined catalysts for reactions involving sterically bulky reactants, which are too large to benefit from conventional three-dimensional confinement in micropores.

Immobilization of Zn4 complex on functionalized Layered HUS-7: Synthesis, Structural Investigation and Catalytic Activity

Tetranuclear Zn (Zn4) complex was selected for the immobilization on novel layered Hiroshima University Silicate (HUS)-7. Modification of HUS-7 was carried out with sulfopropylsilyl agent followed by Zn4 complex incorporation....

Activation and conversion of alkanes in the confined space of zeolite-type materials

Microporous zeolite-type materials, with crystalline porous structures formed by well-defined channels and cages of molecular dimensions, have been widely employed as heterogeneous catalysts since the early 1960s, due to their wide variety of framework topologies, compositional flexibility and hydrothermal stability. The possible selection of the microporous structure and of the elements located in framework and extraframework positions enables the design of highly selective catalysts with well-defined active sites of acidic, basic or redox character, opening the path to their application in a wide range of catalytic processes. This versatility and high catalytic efficiency is the key factor enabling their use in the activation and conversion of different alkanes, ranging from methane to long chain n-paraffins. Alkanes are highly stable molecules, but their abundance and low cost have been two main driving forces for the development of processes directed to their upgrading over the last 50 years. However, the availability of advanced characterization tools combined with molecular modelling has enabled a more fundamental approach to the activation and conversion of alkanes, with most of the recent research being focused on the functionalization of methane and light alkanes, where their selective transformation at reasonable conversions remains, even nowadays, an important challenge. In this review, we will cover the use of microporous zeolite-type materials as components of mono- and bifunctional catalysts in the catalytic activation and conversion of C₁⁺ alkanes under non-oxidative or oxidative conditions. In each case, the alkane activation will be approached from a fundamental perspective, with the aim of understanding, at the molecular level, the role of the active sites involved in the activation and transformation of the different molecules and the contribution of shape-selective or confinement effects imposed by the microporous structure.

Controlled direct synthesis of single- to multiple-layer MWW zeolite

The minimized diffusion limitation and completely exposed strong acid sites of the ultrathin zeolites make it an industrially important catalyst especially for converting bulky molecules. However, the structure-controlled and large-scale synthesis of the material is still a challenge. In this work, the direct synthesis of the single-layer MWW zeolite was demonstrated by using hexamethyleneimine and amphiphilic organosilane as structure-directing agents. Characterization results confirmed the formation of the single-layer MWW zeolite with high crystallinity and excellent thermal/hydrothermal stability. The formation mechanism was rigorously revealed as the balanced rates between the nucleation/growth of the MWW nanocrystals and the incorporation of the organosilane into the MWW unit cell, which is further supported by the formation of MWW nanosheets with tunable thickness via simply changing synthesis conditions. The commercially available reagents, well-controlled structure and the high catalytic stability for the alkylation of benzene with 1-dodecene make it an industrially important catalyst.

Superior Hg0 capture performance and SO2 resistance of Co-Mn binary metal oxide-modified layered MCM-22 zeolite for SO2-containing flue gas

A Co-Mn binary metal oxide-modified layered MCM-22 zeolite was designed to capture gaseous elemental mercury (Hg⁰) from SO₂-containing flue gas. The physicochemical properties of the Co-Mn/MCM-22 zeolite were characterized by XRD, FESEM, TEM, and XPS, and the results showed that MnO₂ was highly dispersed on the surface and in the channel of MCM-22 zeolite. Co₃O₄ was loaded onto the surface of the MCM-22 zeolite via the stepwise ion exchange method to prevent SO₂ poisoning of the MnO₂ active site. The Hg⁰ removal efficiency increased from 54 to 83% at 300 °C with 10% Co loading on the 5% Mn/MCM-22 zeolite when 200 ppm of SO₂ was introduced to the flue gas. The mechanism of Hg⁰ removal was mainly associated with catalytic oxidation and chemisorption. Mn⁴⁺ was the main active site for catalytic oxidation of Hg⁰ to Hg²⁺, and the surface adsorbed oxygen re-oxidized Mn³⁺ and combined with Hg²⁺ to form Hg-O-Mn, in which Mn acted as a bridge. Co³⁺ preferentially reacted with SO₂ to form CoSO₄, thereby protecting the Mn active sites for Hg⁰ capture. Therefore, Co-Mn/MCM-22 zeolite is a promising sorbent for the removal of Hg⁰ and SO₂ resistance from SO₂-containing flue gas.

Synthesis and Characterization of a New Aluminosilicate Molecular Sieve from Aluminosilica Perhydrate Hydrogel

A novel structure aluminosilicate molecular sieve, named BUCT-3, was prepared by dynamic hydrothermal synthesis, and the critical factor to obtain the new structure is using an active silicon and aluminum source, aluminosilica perhydrate hydrogel. Meanwhile, only high content of O-O bonds can ensure the pure phase of BUCT-3. Through the characterization of x-ray powder diffraction (XRD), Fourier transform infrared spectra (FTIR), scanning electron microscopy (SEM), and so on, some structure and morphology information of BUCT-3 molecular sieves as well as the special silicon and aluminum source was obtained. It’s worth noticing that the O-O bonds of reactants can be reserved in the products, and thus, help us to get a new structure with cell parameters a = 8.9645 Å, b = 15.2727 Å, c = 11.3907 Å, α = 90°, β = 93.858°, γ = 90°. The crystal system is monoclinic. Though the thermostability of BUCT-3 is not satisfactory, its potential application derived from O-O bonds cannot be neglected.

A Lamellar MWW Zeolite With Silicon and Niobium Oxide Pillars: A Catalyst for the Oxidation of Volatile Organic Compounds

In this work, an MWW-type zeolite with pillars containing silicon and niobium oxide was synthesized to obtain a hierarchical zeolite. The effect of niobium insertion in the pillaring process was determined by combining a controllable acidity and accessibility in the final material. All pillared materials had niobium occupying framework positions in pillars and extra-framework positions. The pillared material, Pil-Nb-4.5 with 4.5 wt % niobium, did not compromise the mesoporosity formed by pillaring, while the increase of niobium in the structure gradually decreased the mesoporosity and ordering of lamellar stacking. The morphology of the pillared zeolites and the niobium content were found to directly affect the catalytic activity. Specifically, we report on the activity of the MWW-type zeolites with niobium catalyzing the gas-phase oxidation of volatile organic compounds (VOCs), which is an important reaction for clean environmental. All produced MWW-type zeolites with niobium were catalytically active, even at low temperatures and low niobium loading, and provided excellent conversion efficiencies.

Combining Soft- and Hard-Templating Approaches in MWW-Type Zeolites

A combination of hard-templating (HT) and soft-templating (ST) approaches was studied to obtain MWW-type materials with intermediate physicochemical properties. The HT methodology involved the introduction of carbon particles as hard templates during gel synthesis to obtain a layered zeolitic precursor (LZP) with particles possessing a microspherical morphology. The LZP obtained was treated with surfactants as soft templates to expand the layers of the LZP, followed by a pillaring procedure. The materials were characterized by X-ray diffraction, transmission and scanning electron microscopy, elemental analysis and N₂ adsorption. The results demonstrate that the obtained material possesses intermediate properties from both approaches, with interparticle mesopores/macropores and pore sizes between 18 and 46 Å. However, the ST procedure causes a partial disruption of some microspheres, forming small crystallite aggregates, and results in a decrease in the number of interparticle mesopores/macropores previously formed by the HT method. All synthesized solids presented catalytic activity, which was evaluated by the cracking of low-density polyethylene (LDPE) as a probe reaction.

Two-Dimensional Zeolite Materials: Structural and Acidity Properties

Zeolites are generally defined as three-dimensional (3D) crystalline microporous aluminosilicates in which silicon (Si⁴⁺) and aluminum (Al³⁺) are coordinated tetrahedrally with oxygen to form large negative lattices and consequent Brønsted acidity. Two-dimensional (2D) zeolite nanosheets with single-unit-cell or near single-unit-cell thickness (~2-3 nm) represent an emerging type of zeolite material. The extremely thin slices of crystals in 2D zeolites produce high external surface areas (up to 50% of total surface area compared to ~2% in micron-sized 3D zeolite) and expose most of their active sites on external surfaces, enabling beneficial effects for the adsorption and reaction performance for processing bulky molecules. This review summarizes the structural properties of 2D layered precursors and 2D zeolite derivatives, as well as the acidity properties of 2D zeolite derivative structures, especially in connection to their 3D conventional zeolite analogues' structural and compositional properties. The timeline of the synthesis and recognition of 2D zeolites, as well as the structure and composition properties of each 2D zeolite, are discussed initially. The qualitative and quantitative measurements on the acid site type, strength, and accessibility of 2D zeolites are then presented. Future research and development directions to advance understanding of 2D zeolite materials are also discussed.

Bridging the Gap between Structurally Distinct 2D Lamellar Zeolitic Precursors through a 3D Germanosilicate Intermediate

There is broad scientific interest in lamellar zeolitic materials for a large variety of technological applications. The traditional synthetic methods towards two-dimensional (2D) zeolitic precursors have made a great impact in the construction of families of related zeolites; however, the connection between structurally distinct 2D zeolitic precursors is much less investigated in comparison, thereby resulting in a synthetic obstacle that theoretically limits the types of zeolites that can be constructed from each layer. Herein, we report a Ge-recycling strategy for the topotactic conversion between different 2D zeolitic precursors through a three-dimensional (3D) germanosilicate. Specifically, the intermediate germanosilicate can be constructed within 150 min by taking advantage of its structural similarity with the parent lamellar precursor. This process enables the conversion of one 2D zeolite structure into another distinct structure, thus overcoming the synthetic obstacle between two families of zeolitic materials.

Expandable Layered Hybrid Materials Based on Individual 1D Metalorganic Nanoribbons

Different metalorganic lamellar hybrid materials based on associated nanoribbons were synthesized by the use of alkyl-benzyl monocarboxylate spacers, containing alkyl tails with variable lengths, which acted like structural growing inhibitors. These molecular agents were perpendicularly located and coordinated to aluminium nodes in the interlayer space, controlling the separation between individual structure sub-units. The hybrid materials were studied by X-ray diffraction (XRD), chemical and thermogravimetrical analysis (TGA), nuclear magnetic resonance (NMR) and infrared spectroscopy (IR), and field emission scanning electron microscopy (FESEM)/transmission electron microscopy (TEM), showing their physicochemical properties. The specific capacity of the metalorganic materials to be exfoliated through post-synthesis treatments, using several solvents due to the presence of 1D structure sub-units and a marked hydrophobic nature, was also evidenced.

Layered Zn2[Co(CN)6](CH3COO) double metal cyanide: a two-dimensional DMC phase with excellent catalytic performance

A new, layered double metal cyanide phase proved to be a reusable, stable and highly active catalyst in two important DMC applications.

Double metal cyanides (DMCs) are well known, industrially applied catalysts for ring opening polymerization reactions. In recent years, they have been studied for a variety of catalytic reactions, as well as other applications, such as energy storage and Cs sorption. Herein, a new, layered DMC phase (L-DMC), Zn₂[Co(CN)₆](CH₃COO)·4H₂O, was synthesized. The structure, which crystallizes in the monoclinic space group P2₁/m, consists of positively charged {Zn₂Co(CN)₆}⁺ DMC layers linked through acetate groups and presents a new layered structure to the family of double metal cyanides. L-DMC proved to be a reusable and stable catalyst that exhibited a higher activity than the benchmark DMC catalyst in two important applications: hydroamination of phenylacetylene with 4-isopropylaniline and polymerization of 1,2-epoxyhexane.

Carboxylic acid-protruding zincophosphate sheets exhibiting surface mechanochemical reactivity and intriguing nano-morphological reversibility

A hybrid zincophosphate with surface-active and interior –COOH exhibits remarkable characteristics of high thermal stability, modifiable wettability and nano-morphological reversibility.

MoO3 on zeolites MCM-22, MCM-56 and 2D-MFI as catalysts for 1-octene metathesis

Highly active olefin metathesis catalysts were prepared by thermal spreading MoO₃ and/or MoO₂(acac)₂ on MWW zeolites (MCM-22, delaminated MCM-56) and on two-dimensional MFI (all in NH₄⁺ form). The catalysts‘ activities were tested in the metathesis of neat 1-octene (as an example of a longer chain olefin) at 40 °C. Catalysts with 6 wt % or 5 wt % of Mo were used. The acidic character of the supports had an important effect on both the catalyst activity and selectivity. The catalyst activity increases in the order 6MoO₃/HZSM-5(25) (Si/Al = 25) << 6MoO₂(acac)₂/MCM-22(70) < 6MoO₃/2D-MFI(26) < 6MoO₃/MCM-56(13) < 6MoO₃/MCM-22(28) reflecting both the enhancing effect of the supports‘ acidity and accessibility of the catalytic species on the surface. On the other hand the supports‘ acidity decreases the selectivity to the main metathesis product C14 due to an acid-catalyzed double bond isomerization (followed by cross metathesis) and oligomerization. 6MoO₃/2D-MFI(26) with a lower concentration of the acidic centres resulting in catalysts of moderate activity but with the highest selectivity.

From 3D to 2D zeolite catalytic materials

Research activities and recent developments in the area of three-dimensional zeolites and their two-dimensional analogues are reviewed. Zeolites are the most important industrial heterogeneous catalysts with numerous applications. However, they suffer from limited pore sizes not allowing penetration of sterically demanding molecules to their channel systems and to active sites. We briefly highlight here the synthesis, properties and catalytic potential of three-dimensional zeolites followed by a discussion of hierarchical zeolites combining micro- and mesoporosity. The final part is devoted to two-dimensional analogues developed recently. Novel bottom-up and top-down synthetic approaches for two-dimensional zeolites, their properties, and catalytic performances are thoroughly discussed in this review.

Lamellar MWW-Type Zeolites: Toward Elegant Nanoporous Materials

This article provides an overview of nanoporous materials with MWW (Mobil twenty two) topology. It covers aspects of the synthesis of the MWW precursor and the tridimensional zeolite MCM-22 (Mobil Composition of Matter number 22) as well as their physicochemical properties, such as the Si/Al molar ratio, acidity, and morphology. In addition, it discusses the use of directing agents (SDAs) to obtain the different MWW-type materials reported so far. The traditional post-synthesis modifications to obtain MWW-type materials with hierarchical architectures, such as expanded, swelling, pillaring, and delaminating structures, are shown together with recent routes to obtain materials with more open structures. New routes for the direct synthesis of MWW-type materials with hierarchical pore architecture are also covered.

Dandelion-Like Microspherical MCM-22 Zeolite Using BP 2000 as a Hard Template

The chemistry between layered MWW zeolite and carbon black pearls (BP 2000) as an inexpensive hard template was investigated to develop a rational one-pot synthesis of MCM-22 microspheres. The characterization results showed that the insertion of BP 2000 in the gel synthesis did not substantially compromise the crystallinity and microporosity, and the microscopic analyses showed that BP 2000 played a key role in controlling the final morphology of the MCM-22 zeolite, creating beautiful dandelion-like microspherical particles. The morphology obtained is due to the tortuous shape of the hard template, the particular MWW particle crystals, the interaction with the external surface of the MWW zeolitic precursor, and the synthesis conditions. The stacking of MWW crystals with edge-to-face orientations generates meso-/macrovoids, allowing access to the interiors of the microspheres. The microspheres were homogeneous with sizes ranging from 6 to 8 μm with an increase of the external surface and a macroporous size distribution centered at 200 nm, which is two times that of the traditional MCM-22 zeolite.

Toward a New Era of Designed Synthesis of Nanoporous Zeolitic Materials

Due to their nanoporous framework structures, zeolites have been widely used as catalysts, adsorbents, and ion exchangers in many industrial fields. Discovering zeolitic materials with new structures and desired functions is one of the most important tasks in the zeolite community. Traditional zeolite discovery relies primarily on low-efficiency trial-and-error processes. So far, many computational and experimental efforts have been devoted to the designed synthesis of zeolitic materials, representing a promising highway toward function-led discovery of nanoporous materials. In particular, the design of structure-directing agents, the design of target zeolites via structure enumeration, and the reorganization of disassembled building layers have led to the discovery of dozens of unprecedented zeolitic structures in the past 5 years. In this Perspective, we briefly discuss these advances and describe the research efforts that are needed in the coming era of function-led zeolite discovery.

Supramolecular Organization in Confined Nanospaces

Empty spaces are abhorred by nature, which immediately rushes in to fill the void. Humans have learnt pretty well how to make ordered empty nanocontainers, and to get useful products out of them. When such an order is imparted to molecules, new properties may appear, often yielding advanced applications. This review illustrates how the organized void space inherently present in various materials: zeolites, clathrates, mesoporous silica/organosilica, and metal organic frameworks (MOF), for example, can be exploited to create confined, organized, and self-assembled supramolecular structures of low dimensionality. Features of the confining matrices relevant to organization are presented with special focus on molecular-level aspects. Selected examples of confined supramolecular assemblies - from small molecules to quantum dots or luminescent species - are aimed to show the complexity and potential of this approach. Natural confinement (minerals) and hyperconfinement (high pressure) provide further opportunities to understand and master the atomistic-level interactions governing supramolecular organization under nanospace restrictions.

Pillaring of layered zeolite precursors with ferrierite topology leading to unusual molecular sieves on the micro/mesoporous border

Layered zeolite materials with FER layer topology can produce various condensed and expanded structures including zeolite frameworks, FER and CDO, their interlayer expanded forms (IEZ), and organic-intercalated and pillared derivatives. This work concerns pillaring of the surfactant-swollen derivative with a gallery height of ca. 2.5 nm between layers by treatment with tetraethylorthosilicate (TEOS) at room and elevated temperatures. The materials obtained at 100 °C and higher showed unusual properties including 2 nm pores on the micro/mesoporous border and disordered layer packing indicated by the absence of distinct low angle interlayer peaks at d-spacing >3 nm (∼3° 2θ Cu Kα radiation) in the X-ray diffraction pattern (XRD). TEOS treatment at room temperature produced a pillared molecular sieve with the expected mesoporous characteristics, namely a pore size of around 3 nm and a high intensity low angle (001) peak at 2.3° 2θ, and a d-spacing of 3.8 nm, in the XRD. The characterization aiming to elucidate the nature of the obtained unusual products included gas adsorption isotherms, aberration corrected (C_s-corrected) Scanning Transmission Electron Microscopy (STEM) studies and ²⁹Si solid state NMR. BET surface area values decreased with the temperature of TEOS treatment from approximately 1200 m² g^-1 to ∼900 and 600 m² g^-1, at room temperature, 100 °C, and 120 °C, respectively. The ²⁹Si solid state NMR revealed the presence of both Q³ ((SiO)₃SiOX, X = H or minus charge) and Q⁴ ((SiO)₄Si) centers giving separated signals up to the pillaring step. After pillaring at 100 °C and calcination, the nominal intensity ratios Q⁴ : Q³ were 2.17 and 2.61 but the signals were merged into one broad peak indicating the structural heterogeneity of Si-O coordination. The microscopy showed the presence of FER layers in the samples but the overall structure and composition were not well-defined. The observed unusual disorganization and possible partial degradation of layers during pillaring may result from the combination of high temperature, alkalinity (surfactant hydroxide) and siliceous composition of the layers. The obtained pillared products are of interest for the preparation of larger pore catalysts and sorbents or controlled drug delivery.

Effect of template removal using plasma treatment on the structure and catalytic performance of MCM-22

Template removal from MCM-22 using dielectric-barrier discharge (DBD) plasma could decrease the formation of extra-framework aluminum (EFAl) and increase the concentration of the acidic sites and external surface area of MCM-22.

α-Pinene oxide isomerization: role of zeolite structure and acidity in the selective synthesis of campholenic aldehyde

The highest campholenic aldehyde yield (83%) achieved over MCM-22 is a result which rivals the best ones published so far.

Cooperative structure direction of organosilanes and tetrapropylammonium hydroxide to generate hierarchical ZSM-5 zeolite with controlled porous structure

Hierarchical ZSM-5 zeolites of controlled porous structure were realized by the cooperative direction of organosilanes and tetrapropylammonium hydroxide.