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[Display omitted] • On methane dearomatization reaction, two main deactivation modes occurs. • Irreversible damage by zeolite amorphization during the isothermal pre-treatment. • Reversible deactivation by coke deposition ("soft", "hard" and carbide species). • 3 descriptors : coke level, micropore volume loss, monoclinic/orthorhombic change. We report a detailed kinetic study of methane dehydroaromatization on three bifunctional Mo/HZSM-5 catalysts (0.9 wt%, 2.7 wt%, and 17.2 wt% Mo). Two main deactivation modes are present: (i) irreversible damage by zeolite amorphization during the isothermal pre-treatment in an inert atmosphere and (ii) reversible deactivation by coke deposition ("soft", "hard" and carbide species). The former occurs at high Mo loading (>4.0 w%) and provides low activity catalysts. Catalysts with a lower and well-balanced molybdenum loading (<4 w%) suffer mainly from the second deactivation mode. The catalyst decay is modelled by semi-empirical laws including time on stream and coke level. The latter initiates textural and structural catalyst modifications leading to an activity loss. Three deactivation descriptors, 1 : coke level on the spent samples, 2: loss of micropore volume, and 3: monoclinic/orthorhombic phase transition of the zeolite are identified. Further characterization indicates that both molybdenum and carbon species are responsible for the catalytic deactivation of well-balanced catalysts. At least 50% of the initially dispersed molybdenum migrates to the external surface of the zeolite to form large clusters of molybdenum carbide. The coke extracted from the zeolite micropores are confirmed to be mainly unsubstituted polyaromatics. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The SCR activity of zeolite mechanical mixture was investigated for the first time. • The mechanical mixture shows higher SCR activity over a broader temperature range. • The synergistic effect between Cu and Fe in the mixture results in higher activity. • Simple and viable route to prepare highly active catalytic formulations for SCR-NH 3. Abstract SCR-NH 3 activities of Cu-SAPO-34 (Cu-CZC) and Fe-Mordenite (Fe-MOR) and their mechanical mixture (50:50) were investigated in the temperature range 150–450 °C using operando FTIR spectroscopy. Structural and textural studies assessed the quality of the material synthesis, while in situ IR characterisation allowed the quantification of the acidic sites at the surface of the zeolites, as well as the cationic distribution inside the pores. As expected, Cu-CZC showed high NO x activity at lower temperatures (75% of NO x conversion at T < 300 °C), while Fe-MOR was more active (>85%) at higher temperatures (300–450 °C). The co-presence of Cu and Fe in the mechanical mixture catalyzes the undesirable oxidation of ammonia and leads to the formation of NO, especially at high temperatures. However, the mechanical mixture of Cu-CZC and Fe-MOR has been found to efficiently operate in the presence of excess ammonia (NH 3 /NO x = 1.3) in a much broader temperature range comparing to the catalysts modified with only one transition metal (Fe or Cu) and also respect to a sample containing both cations in a single zeolitic framework, thus opening new opportunities in the catalytic reduction of NO x. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of the porous structure of spherical activated carbons obtained from cation-exchange resin beads subjected to ion exchange prior to activation. The study investigated the effects of the type of cation exchange resin, the concentration of potassium cations in the resin beads and the temperature of the activation process on the adsorption properties of the resulting spherical activated carbons. The numerical clustering-based adsorption analysis method and the quenched solid density functional theory were used to analyse the porous structure of spherical activated carbons. Based on original calculations and unique analyses, complex relationships between preparation conditions and the porous structure properties of the obtained spherical activated carbons were demonstrated. The results of the study indicated the need for simultaneous analyses using advanced methods for the analysis of porous structures, i.e., the numerical clustering-based adsorption analysis method and the quenched solid density functional theory. This approach allows a reliable and precise determination of the adsorption properties of the materials analysed, including, among other things, surface heterogeneities, and thus an appropriate selection of production conditions to obtain materials with the expected adsorption properties required for a given industrial process. [ABSTRACT FROM AUTHOR]

Two new complexes [Zn2(pzdc)(L)2(H2O)]2n·2nH2O (1) and [Mn(µ2-O)(H2O)2-(HL)]2n·2nNIPH (2) (H2pzdc = pyrazine-2,3-dicarboxylic acid, HL = 3-(2-Pyridyl) pyrazole, H2NIPH = 5-nitroisophthalic acid) have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectrum, UV spectrum, TG, fluorescence spectrum and single-crystal X-ray diffraction. Complex 1 shows two-dimensional (2D) network, which was stabilized by O–H···O, C–H···O hydrogen bonding and π-π interactions and extended into 3 D supramolecular architecture. Complex 2 is zero-dimensional structure, which was further extended into 3 D supramolecular framework through N–H···O, O–H···O, C–H···O hydrogen bonds and π-π interactions. [ABSTRACT FROM AUTHOR]

SAPO-34 crystals are etched in fluoride medium. The interface between crystalline domains is dissolved and yields a hierarchical material with a system of straight intersecting mesopores that improve the access to micropore space. [ABSTRACT FROM AUTHOR]

The article focuses on nanosize porous solids which have the potential to offer sustainable solutions to global issues including energy demands, resources depletion and health improvement. It discusses the mechanism of zeolite formation in closed systems involving reaction between components of initial gel that leads to nucleation and growth of favorable phase. It also focuses on hydro gel synthesis of zeolite nano crystals from organic template free system under prolonged crystallization.

The present study demonstrated the possibility to form a secondary system of parallel macropores in zeolite crystals. The secondary pore formation was predetermined by the creation of defect zones in ZSM-5 crystals. A high energy 238U ion beam was employed to form latent tracks in zeolite crystals, which were further subjected to attack with diluted HF solution and thus developed to uniformally sized macropores. The selective extraction of material from latent tracks was due to the higher etching velocity of highly agitated zones created by heavy ion bombardment. The combination of complementary methods unambiguously demonstrated the formation of hierarchical zeolite material comprising parallel macropores that extended through the entire crystal. The catalytic tests revealed improved activity at retained selectivity in the reaction of m-xylene conversion. The possibility to control the number ofmacropores per unit of crystal surface and thus the catalytic performance of the material was demonstrated. This model material is expected to bring better understanding to the effect of a secondary pore system in the catalytic performance of hierarchical zeolites obtained by the top-down or bottom-up approach. [ABSTRACT FROM AUTHOR]

Abstract: The control of the inter-particle porosity in polycrystalline zeolite bodies remains a challenge. The present study reports on the preparation of centimeter-sized zeolite bodies (32×2mm pellets) with reduced inter-particle porosity. The bodies were prepared by assembling zeolite colloidal nanocrystals with monomodal particle size distribution and sub-colloidal aluminum hydroxide binder. A secondary growth treatment under hydrothermal conditions was performed in order to fill up the inter-particle voids and obtain polycrystalline zeolite materials with textural characteristics close to those of single zeolite crystals. Initial material, intermediates and ultimate product were studied with a combination of complementary methods revealing a substantial reduction even an elimination of the inter-particle porosity. Particular attention was paid to the chemical evolution of the binder and the migration of aluminum species, employing X-ray powder diffraction, 27Al-MAS, 27Al-3QMAS NMR and X-ray fluorescence spectroscopy analyses. Evidences for insertion of aluminum from the binder into the zeolite framework during secondary growth step were found. Consequently the ultimate pellets comprised aluminum-rich zeolite beta crystals and very low binder content. [ABSTRACT FROM AUTHOR]

Abstract: Zeolite Beta particles with size of 0.1, 0.5 and 1μm were employed as molds for the synthesis of microporous carbon. After infiltration and pyrolysis of propylene at 800°C for 2h, zeolite/carbon composites were obtained and further subjected to acid extraction of the zeolite precursor. The initial zeolite samples, zeolite/carbon composites and carbon replicas were studied by XRD, TG analysis, SEM/TEM, DLS, N2 adsorption measurements and chemical analysis. The experimental data revealed that the carbon replicas faithfully replicate the zeolite morphology and possess higher micropore volume than that of the parent zeolite molds. The use of zeolite molds of different sizes resulted in carbons with fairly different pore structure. Thus, larger (0.5 and 1μm) zeolite crystals provided replicas with a pore structure possessing mainly micropores, whereas the carbon replication of 0.1μm zeolite aggregates built of much smaller crystallites resulted in a material with lower micropore volume and substantial contribution of mesopores to the total pore volume. The different pore structure of the latter carbon was found to be a result of the larger external surface area of the nanosized mold, loss of crystallinity during the preparation procedure and the presence of interparticles porosity. [Copyright &y& Elsevier]

Abstract: The nanoscale events in an organic-template-free gel leading to the formation of a FAU-type zeolite at 90°C were investigated by transmission electron microscopy (TEM). The study was complemented by ex situ X-ray diffraction (XRD), infrared (IR), 23Na 3Q-MAS NMR, N2 adsorption measurements and chemical analyses. It was found that the critical factor that triggers the growth process and mass transformation from amorphous into crystalline zeolite material is the attainment of a specific level of chemical evolution of the system, expressed in homogenization of the starting gel approaching stoichiometric FAU-type zeolite composition. This period was also marked by the formation and development of voids in the gel particles, containing highly hydrated material transformed later on into negative crystals. The evolution of these areas has been found to be an integral and noteworthy part of the chemical transformation of the gel that preceded the nucleation in the system. The observed transformations in the solid part of the system were induced by sodium, which progressively penetrated in the aluminosilicate matrix, breaking its structure and reorganizing the aluminosilicate species. The sodium behaviour was tracked down by a combination of local and bulk chemical analyses complemented by 23Na 3Q-MAS NMR study. During the initial stage of reaction a growth via propagation through the amorphous network co-existed with the typical solution-assisted hydrothermal crystallization. The later stages of development of the system followed the classical for zeolite-yielding systems crystallization that could be described by the autocatalytic nucleation. [Copyright &y& Elsevier]

Abstract: Previous investigations have shown that an all-silica BEA-type (Si-BEA) material is difficult to be nucleated in basic media and that the fluorosilicic precursors formed in near neutral media play an important role in its formation. The present study reports on the synthesis of this microporous material under basic conditions by using TEA2SiF6 as an additional silica source that provides preformed fluorosilicate species. The effect of the amount of TEA2SiF6 on the purity of the final product, crystallization kinetics and morphological features of Si-BEA were systematically studied. The investigation showed that above a certain concentration corresponding to TEA2SiF6/SiO2 =0.07 pure Si-BEA was obtained and further increase in the concentration improved substantially the crystallization kinetics. The increase in TEA2SiF6 content led also to a gradual increase of the size of the pyramidal (h 0l) face coupled with the decrease of pinacoidal (001) one. Thus, the morphology of the zeolite crystals can be varied from well developed truncated bipyramids to plate-like crystals with dominating pinacoidal faces. A consequence of this morphological changes is the number the pore openings of the channel systems running along the a- and c-axes per total external surface. The framework defectness and water content in the synthesized materials were studied by 29Si NMR spectroscopy and TG analysis, respectively. This combined study revealed that materials with a high level of hydrophobicity, due to the specific effect of fluorine anions, have been synthesized under basic conditions. [Copyright &y& Elsevier]

The entire sequence of crystallization events, starting with formation of the initial organic-cation- free gel, proceeding through the zeolite nucleation stage, and finishing with complete transformation into LTA-type zeolite crystals, has been monitored by means of high-resolution transmission electron microscopy. Formation and development of voids, containing highly hydrated material transformed later into negative crystals, has been discovered in the solid part of the system. The evolution of these areas has been found to be an integral and noteworthy part of the chemical transformation of the gel that preceded the nucleation in the system. These void structures and, in particular, their solid-liquid interfaces have been identified as the specific locations where the formation of protozeolite nuclei took place. Further development of the system followed the classical for zeolite-yielding systems of crystallization that could be described by the autocatalytic model. [ABSTRACT FROM AUTHOR]

Abstract: Silicalite-1 was in situ crystallized from clear synthesis solutions onto commercial millipore glass fiber filters. The filters with diameter 2.5cm were soaked in the precursor mixtures and hydrothermally treated at 80°C or 150°C for time up to 150h. After the synthesis, the filters were treated in an ultrasonic bath for 15min with a 0.1M ammonia solution. The disc composites prepared at 80°C swelled during synthesis, were easy to disintegrate upon subsequent manipulations and wrinkled when dried. The calcined materials were brittle with a porcelain-like appearance. The filters synthesized at 150°C, both as synthesized and calcined, seemed identical in shape and mechanical characteristics to the initial glass fiber filters. Prolongation of the treatment at 150°C up to 100h led to densified fiber discs according to the SEM study but without visual changes in their mechanical strength. The difference in crystallization at the two different temperatures was attributed to the slower nucleation process at 80°C, which resulted in greater dissolution of the fiber units and a certain inhibition of the crystallization process caused by the changed chemical environment at the fiber–synthesis solution interface. The silicalite-1/filter composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS), chemical analysis and N2 adsorption measurements. [Copyright &y& Elsevier]

Abstract: Aspects of the preparation and features of organized molecular sieve structures are discussed. The account is mainly focused on authors’ contribution to the filed though a short list of recent achievements in the area is also given. The zeolite supported structures considered are zeolite films and coatings grown on various substrates either by a direct synthesis or by preliminary electrostatic adsorption of colloidal zeolite seeds on the support followed by hydrothermal treatment with a fresh synthesis gel or solution. The influence of the support type (composition, shape) as well as the synthesis parameters (synthesis gel or solution, pre-treatment, temperature, etc.) on the product zeolite structures is reviewed. Further, the synthesis of a variety of self-bonded zeolite macrostructures with hierarchical porosity by macrotemplating is described. Silica-containing plants, polystyrene beads and anion exchange resins are the templates used and the resultant self-bonded macrostructures obtained upon template removal have different appearance, porosity and mechanical strength. To cite this article: L. Tosheva et al., C. R. Chimie 8 (2005). [Copyright &y& Elsevier]

The effect of room temperature aging on the crystallization rate and size of MFI-type crystals synthesized under high temperature was investigated. First, synthesis mixtures yielding MFI-type zeolite were aged at room temperature for periods of time between 1 and 60 days. This was followed by a rapid synthesis in a pre-heated at 230 °C conventional oven. The utilization of a pre-aged initial systems and high heating rates allowed very rapid synthesis of zeolite. The effect of aging time, crystallization temperature, duration of synthesis and aluminum content on the crystal size and yield was systematically studied. Zeolite nanoparticles with sizes ranging from 130 to 260 nm and relatively narrow particle size distributions were synthesized employing the pure-silica system. The obtained nanocrystals were characterized by X-ray diffraction, scanning electron microscopy, dynamic light scattering and N2 adsorption measurements. [Copyright &y& Elsevier]

Two new Zn(II)/Co(II) coordination polymers, [Zn1.5(pmda)(OH)(bipy)]2n·2nH2O (1) and [Co(pmda)(bib)]n(2) (H2pmda = 4,4′-[1,2-phenylenebis(methyleneoxy)]dibenzoic acid, bipy = 4,4′-bipyridine, bib = 1,4-bis(imidazol-1-yl)-butane), have been prepared under hydrothermal conditions. Their structure were determined by single-crystal X-ray diffraction analysis, and further characterized by elemental analysis, IR spectra TG, and powder X-ray diffraction analysis. Complexes 1 and 2 both exhibit two-dimensional network structures and the intermolecular hydrogen bonding, π-π stacking interactions extend them into 3D supramolecular architectures, which play an important role in stabilizing them. The solid-state luminescent property of 1 and 2 were characterized and the results revealed that they exhibit fascinating photoluminescence properties. In addition, the sensing property of only 1 has been examined briefly. The quantum-chemical calculations of complex 1 have been performed on 'molecular fragments' extracted from the crystal structure using the PBE0/LANL2DZ method built in Gaussian 16 Program. [ABSTRACT FROM AUTHOR]

• Acid sites in aluminosilicate zeolites are revised. • The in situ and post-synthesis methods of aluminum incorporation are highlighted. • The impact of the framework and extra-framework Al species is discussed. • Acid site distribution within a single zeolite crystal is addressed. • Guidelines for zeolite design in terms of acidity are provided. The exceptional catalytic performance of zeolites is due to the presence of active sites in a shape-selective environment, i.e., in micropores with molecular dimensions. The present review provides a comprehensive analysis of active sites in zeolite frameworks. It is focused on the active sites generated by the Al incorporation in the framework. The inclusion of other heteroatoms in the zeolite framework is also addressed. After the introduction of zeolite-type materials and a discussion of the structure-properties relationship in zeolites the central part of the review is devoted to i) the analytical methods and their complementarity for the evaluation of the number, strength, and position of active sites and ii) the in situ and post-synthesis methods of acid sites assessment and control. The data presented herein provide guidelines for making zeolite materials by design in terms of acidity. [ABSTRACT FROM AUTHOR]

Gas hydrates are non-conventional materials offering great potential in capturing, storage, and sequestration of different gases. The weak van der Waals interactions between a gas molecule and the pore walls stabilize these non-stoichiometric structures. The present article reports an ab initio improved van der Waals density functional (vdW-DF2) study devoted to the interactions associated with H 2 , CH 4 , and CO 2 adsorption in sI clathrate hydrate. The study provides the clathrate stability, diffusion, and energy storage of possible mixed gas occupancy in sI cages in the presence of H 2. The results also provided the hydrogen energy landscapes and the estimated diffusion activation energy barriers to the large and small cage to be 0.181 and 0.685 eV, respectively. In addition, the results showed that the presence of CH 4 or CO 2 could enhance the storage capacity, thermodynamic stability, and hydrogen diffusion in sI clathrates. The volumetric storage, gravimetric storage, and molecular hydrogen content in H 2 –CH 4 binary sI clathrate are calculated to be 2.0 kW h/kg, and 1.8 kW h/L, and 5.0 wt%, respectively. These results are comparable to DOE targets of hydrogen storage. [Display omitted] • CH 4 works as a thermodynamic promoter to stabilize clathrate for hydrogen storage. • Clathrate stability is improved by a double occupancy (H 2 –CO 2) of the large cage. • Double occupancy of the large cages facilitates H 2 diffusion. • H 2 –CH 4 sI clathrate energy storage can reach 2.0 kWh/kg and 1.8 kWh/L. • H 2 –CH 4 sI estimated capacity can meet DOE targets of volumetric and gravimetric energy storage. [ABSTRACT FROM AUTHOR]

The hydrodeoxygenation (HDO) reaction provides a promising catalytic strategy to remove oxygen in biomass‐derived bio‐oil to produce renewable transportation fuels and value‐added chemicals. The development of highly efficient and stable HDO catalysts plays an essential role in biomass valorization. Metal‐zeolite bifunctional catalysts have been well‐developed as the effective HDO catalysts in upgrading lignin‐derived phenolics due to their excellent activity, selectivity, and thermal and hydrothermal stability. However, clarifying the roles of the active sites and their synergistic effect, and establishing effective structure‐performance relationships in the HDO process still face challenges. In this review, we first survey the conventional catalysts applied in the HDO of bio‐oil, followed by thoroughly discussing the roles of metal centers, acid sites, supports, and their impacts on the HDO process of phenolic model compounds or bio‐oil. Finally, a discussion on the stability and deactivation of metal‐zeolite catalysts, especially in the aqueous‐phase HDO reaction, is provided. This critical review offers new insights into the development of state‐of‐the‐art metal‐zeolite bifunctional catalysts with well‐defined porosity and metal‐acid properties for viable biomass valorization. [ABSTRACT FROM AUTHOR]

Two new Zn(II) coordination polymers based on bis(imidazol), namely, [Zn(hba)2(bib)]n(1) and [Zn(NAA)(bib)1.5]n·nNO3−·3nH2O (2) (Hhba = 3-hydroxybenzoic acid, HNAA = 1-naphthyl acetic acid, bib = 1,4-bis(imidazol-1-yl)-butane) have been successfully synthesized under hydrothermal conditions. Their structures have been determined by single crystal X-ray diffraction analyses, elemental analyses, IR, TG and fluorescence spectrums. Complex 1 shows a one-dimensional zigzag chain structure. Complex 2 exhibits two-dimensional network structure. The intermolecular hydrogen bonding and π–π stacking interactions extend the complexes 1 and 2 into supramolecular architectures and play an important role in stabilizing complexes 1 and 2. Furthermore, complex 1 exhibits intense blue luminescence and appears to be a good candidate for novel hybrid inorganic–organic photoactive materials, while no photoluminescent response was observed for complex 2. In addition, we analyzed the Natural Bond Orbitals (NBO) of 1 and 2 using the PBE0/LANL2DZ method in the Gaussian 09 Program. The calculations showed the obvious covalent interaction between the coordinated atoms and Zn(II) ion. Two new Zn(II) coordination polymers based on bis(imidazol), namely, [Zn(hba)2(bib)]n(1) and [Zn(NAA)(bib)1.5]n·nNO3−·3nH2O (2) have been successfully synthesized under hydrothermal conditions. Their structures have been determined by single crystal X-ray diffraction analyses, elemental analyses, IR, TG and fluorescence spectrum. Complex 1 shows a one-dimensional zigzag chain structure. Complex 2 exhibits two-dimensional network structure. The intermolecular hydrogen bonding and π–π stacking interactions extend the complex 1 and 2 into supramolecular architectures and play an important role in stabilizing complex 1 and 2. In addition, we analyzed Natural Bond Orbital (NBO) of 1 and 2 in using the PBE0/LANL2DZ method built in Gaussian 09 Program. The calculation results showed the obvious covalent interaction between the coordinated atoms and Zn(II) ion. [ABSTRACT FROM AUTHOR]

Two new complexes [Ni(4-nph)(bix)(H2O)]n(1) and [Zn(4-nph)(mbix)]n·nH2O (2) (4-H2nph = 4-nitrophthalic acid, bix = 1,4-bis(imidazol-1-yl)-benzene, mbix = 1,3-bis(imidazol-1-yl)-benzene) have been hydrothermally synthesized and structurally characterized by elemental analysis, IR spectroscopy, TG, fluorescence spectroscopy, single-crystal and powder X-ray diffraction. Complex 1 exhibits two dimensional (2D) network structure contain 42-number ring and complex 2 shows one-dimensional ribbon, which were further extended into three-dimensional supramolecular structure through hydrogen bonds and π–π stacking interactions. Moreover, we analyzed the natural bond orbital using the PBE0/LANL2DZ method in the Gaussian 03 program of complexes 1 and 2. The calculation results indicated the obvious covalent interactions between the coordinated atoms and the NiII, ZnII ion respectively. [ABSTRACT FROM AUTHOR]

Piezochromic materials with pressure‐dependent photoluminescence tuning properties are important in many fields, such as mechanical sensors, security papers, and storage devices. Covalent organic frameworks (COFs), as an emerging class of crystalline porous materials (CPMs) with structural dynamics and tunable photophysical properties, are suitable for designing piezochromic materials, but there are few related studies. Herein, we report two dynamic three‐dimensional COFs based on aggregation‐induced emission (AIE) or aggregation‐caused quenching (ACQ) chromophores, termed JUC‐635 and JUC‐636 (JUC=Jilin University China), and for the first time, study their piezochromic behavior by diamond anvil cell technique. Due to the various luminescent groups, JUC‐635 has completely different solvatochromism and molecular aggregation behavior in the solvents. More importantly, JUC‐635 with AIE effect exhibits a sustained fluorescence upon pressure increase (≈3 GPa), and reversible sensitivity with high‐contrast emission differences (Δλem=187 nm) up to 12 GPa, superior to other CPMs reported so far. Therefore, this study will open a new gate to expand the potential applications of COFs as exceptional piezochromic materials in pressure sensing, barcoding, and signal switching. [ABSTRACT FROM AUTHOR]

Piezochromic materials with pressure‐dependent photoluminescence tuning properties are important in many fields, such as mechanical sensors, security papers, and storage devices. Covalent organic frameworks (COFs), as an emerging class of crystalline porous materials (CPMs) with structural dynamics and tunable photophysical properties, are suitable for designing piezochromic materials, but there are few related studies. Herein, we report two dynamic three‐dimensional COFs based on aggregation‐induced emission (AIE) or aggregation‐caused quenching (ACQ) chromophores, termed JUC‐635 and JUC‐636 (JUC=Jilin University China), and for the first time, study their piezochromic behavior by diamond anvil cell technique. Due to the various luminescent groups, JUC‐635 has completely different solvatochromism and molecular aggregation behavior in the solvents. More importantly, JUC‐635 with AIE effect exhibits a sustained fluorescence upon pressure increase (≈3 GPa), and reversible sensitivity with high‐contrast emission differences (Δλem=187 nm) up to 12 GPa, superior to other CPMs reported so far. Therefore, this study will open a new gate to expand the potential applications of COFs as exceptional piezochromic materials in pressure sensing, barcoding, and signal switching. [ABSTRACT FROM AUTHOR]

Highlights: JUC-610-nanosheet exhibits highly efficient oxygen reduction reaction (ORR) catalytic activity in alkaline electrolyte with half-wave potential of 0.72 V versus reversible hydrogen electrode, which is one of the best covalent organic frameworks (COF)-based ORR electrocatalysts reported so far. It has been confirmed by experiments and density functional theory calculations that the abundant electrophilic structure in Q3CTP-COFs induces a highly density of carbon active sites, and the unique bilayer stacking facilitates the exposure of active carbon sites and accelerates the mass diffusion during ORR. JUC-610-nanosheet can also serve as a promising cathode for Zn-air batteries (power density of 156 mW cm–2 at 300 mA cm–2), which promotes the development of metal-free carbon-based electrocatalysts. Metal-free carbon-based materials are considered as promising oxygen reduction reaction (ORR) electrocatalysts for clean energy conversion, and their highly dense and exposed carbon active sites are crucial for efficient ORR. In this work, two unique quasi-three-dimensional cyclotriphosphazene-based covalent organic frameworks (Q3CTP-COFs) and their nanosheets were successfully synthesized and applied as ORR electrocatalysts. The abundant electrophilic structure in Q3CTP-COFs induces a high density of carbon active sites, and the unique bilayer stacking of [6 + 3] imine-linked backbone facilitates the exposure of active carbon sites and accelerates mass diffusion during ORR. In particular, bulk Q3CTP-COFs can be easily exfoliated into thin COF nanosheets (NSs) due to the weak interlayer π–π interactions. Q3CTP-COF NSs exhibit highly efficient ORR catalytic activity (half-wave potential of 0.72 V vs. RHE in alkaline electrolyte), which is one of the best COF-based ORR electrocatalysts reported so far. Furthermore, Q3CTP-COF NSs can serve as a promising cathode for Zn-air batteries (delivered power density of 156 mW cm–2 at 300 mA cm–2). This judicious design and accurate synthesis of such COFs with highly dense and exposed active sites and their nanosheets will promote the development of metal-free carbon-based electrocatalysts. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) are proposed as promising candidates for engineering advanced molecular sieving membranes due to their precise pore sizes, modifiable pore environment, and superior stability. However, COFs are insoluble in common solvents and do not melt at high temperatures, which presents a great challenge for the fabrication of COF‐based membranes (COFMs). Herein, for the first time, a new synthetic strategy is reported to prepare continuous and intact self‐standing COFMs, including 2D N‐COF membrane and 3D COF‐300 membrane. Both COFMs show excellent selectivity of H2/CO2 mixed gas (13.8 for N‐COF membrane and 11 for COF‐300 membrane), and especially ultrahigh H2 permeance (4319 GPU for N‐COF membrane and 5160 GPU for COF‐300 membrane), which is superior to those of COFMs reported so far. It should be noted that the overall separation performance of self‐standing COFMs exceeds the Robeson upper bound. Furthermore, a theoretical study based on Grand Canonical Monte Carlo (GCMC) simulation is performed to explain the excellent separation of H2/CO2 through COFMs. Thus, this facile preparation method will provide a broad prospect for the development of self‐standing COFMs with highly efficient H2 purification. [ABSTRACT FROM AUTHOR]

Review: 374 refs. [ABSTRACT FROM AUTHOR]

In COP 26, the international community reaffirmed its ambitious targets to reduce carbon emission to mitigate climate change according to Paris Agreement. To achieve that target, a proper combination of energy efficiency and integration of renewables should be applied to ensure a smooth energy transition that balances the increasing demand and environmental commitments. Natural gas can work as a transition fuel between the polluting fossil fuels, and zero-emission renewables such as hydrogen. Carbon capture and sequestration is another important aspect that allows reducing already existing and future carbon emissions that arise from industrial processes. However, the storage and purification of natural gas, CO 2 and H 2 is still challenging and represents an overhead cost that slows down the energy transition process. This review discusses the use of "zeolitic ice" or clathrate hydrates as an environmentally benign material to help the energy transition process. Having structural topologies and properties that are identical to some zeolites and zeolitic clathrasils, those green materials showed unique properties that enable their utilization in different purposes related to the energy transition, such as gas separation, desalination, fuel cells, and others. The review especially focuses on their possible role to purify and safely store gases such as CH 4 , CO 2 , and H 2 , which are in the heart of energy transition. Amongst the objectives of the overview is to present different possible uses of clathrates, their benchmark against existing technologies, and the possibility to integrate them into current technologies with special focus on their application for energy storage and CCS. • Zeolitic ice are eco-friendly materials that can play an important in energy transition. • Gas hydrates possess unique physicochemical properties such as selective adsorption, thermal stability, and ionic conductivity. • Natural gas hydrates offer a unique opportunity for long-term methane storage and utilization of discrete gas resources. • Zeolitic ice can combine carbon capture and sequestration in a single process which can be standalone or combined with exiting technologies. • Clathrate hydrates have a promising potential for safe and cost-effective hydrogen storage. [Display omitted] [ABSTRACT FROM AUTHOR]

Narrowly dispersed ultrafine Cu clusters of sizes smaller than 2.0 nm have been encapsulated in nanosized silicalite-1 zeolite through direct crystallization in the presence of Cu(en)22+ complex ions as the metal precursor. The growing silicalite-1 crystals are rich in vacancy defects and connectivity defects on the grain boundaries, where the terminating silanols promote the decomposition of Cu(en)22+, thus the deposition of ultrafine Cu species. The obtained composite material as a model catalyst is active for CO2 activation and hydrogenation to methanol. The preliminary in situ FTIR study recognizes a series of surface-adsorbed carbonyl, formyl, carbonate, and formate species when the material is exposed to CO2 and H2. Among others, the adsorbed formate decays most rapidly upon cofeeding CO2 and H2, implying that the most probable pathway toward methanol formation over this material is via the formate-mediated mechanism. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: Three‐dimensional (3D) covalent organic frameworks (COFs) are crystalline porous polymers with potential in numerous high‐tech applications, but the linkages involved in their synthesis are still rather limited. Herein, we report novel 3D sp2 carbon‐linked COFs fabricated by the formation reaction of C=C bonds and their application in fluorescence imaging. These new COFs, namely JUC‐580 and JUC‐581, show high stability and excellent light‐emitting properties in solid state and dispersed in various solvents. Furthermore, we investigate the potential application of JUC‐581 as a drug carrier combined with fluorescence imaging. These results indicate that 3D sp2 carbon‐linked COFs are not only potential drug‐loaded and sustained release materials but also promising cell fluorescent stains. This study thus expands the structural categories of 3D COFs based on different linkages, and promotes their prospective applications for biomedicine and fluorescent materials. [ABSTRACT FROM AUTHOR]

This paper deals with the extension of the synthesis field of microporous zeolite-type materials and types of organic structure-directing agents (OSDA) that can be used to promote their crystallization. The highly hydrophilic hexamethylenetetramine (urotropine), with its C/N ratio = 1.5, which is unusual to act as a structure-directing agent in the crystallization of open-framework silica polymorphs, is used to exemplify the novelty of the employed approach. Namely, the protonation of urotropine in an acidic fluorine-containing medium transforms it into a very efficient OSDA that yields dodecasil 3C (MTN-type). This novel synthesis also allows gaining insights into OSDA-framework interactions in the MTN-type structure. The comprehensive 29Si and 19F MAS NMR indicate a small number of point defects of the framework T sites and the multiple bonding of F− ions to Si in a disordered manner. Based on this finding, a unit cell model has been generated using Monte Carlo simulation and validated with Rietveld refinement using experimental powder X-ray diffraction data. In the model, protonated urotropine cations are located in the center of the big hexakaidecahedral [51264] cages at full occupancy with random orientations. The charge balance is provided by the disordered F− ions. [ABSTRACT FROM AUTHOR]

This feature article highlights recent developments in nanosized zeolites and addresses the question: what will be next? Until recently the limiting step to practical applications was determined by the challenging synthesis of nanosized zeolites in high yield and adequate form. The advances in the synthesis of nanozeolites that provide the basis for future developments and for diverse practical applications are reviewed. The main trends and challenges in processing, characterization and applications of nanosized zeolites are summarized. Particular attention is paid to the processing of nanosized zeolites in terms of their further use. The extending applications of nanosized zeolites in nanotechnology, medicine, pharmaceutical, and food industry, are discussed. [ABSTRACT FROM AUTHOR]

This review highlights recent developments in the synthesis and unconventional applications of nanosized microporous crystals including framework (zeolites) and layered (clays) type materials. Owing to their microporous nature nanosized zeolites and clays exhibit novel properties, different from those of bulk materials. The factors controlling the formation of nanosized microporous crystals are first revised. The most promising approaches from the viewpoint of large-scale production of nanosized zeolites and clays are discussed in depth. The preparation and advanced applications of nanosized zeolites and clays in free (suspension and powder forms) and fixed (films) forms are summarized. Further the review emphasises the non-conventional applications of new porous materials. A comprehensive analysis of the emerging applications of microporous nanosized crystals in the field of semiconductor industry, optical materials, chemical sensors, medicine, cosmetics, and food industry is presented. Finally, the future needs and perspectives of nanosized microporous materials (zeolites and clays) are addressed. [ABSTRACT FROM AUTHOR]

Water extraction from air is a promising strategy for alleviating the current water crisis since it provides inexhaustible water resources to the places where surface and groundwater are scarce. This study systematically assesses 12 selected microporous materials out of zeolites, aluminophosphate zeotypes (AlPOs), and metal-organic frameworks (MOFs), the most promising adsorbents to meet the stringy criteria for economic water harvesting. Through a comparative study of water adsorption isotherms, desorption enthalpies, regeneration temperatures, water capacity, and kinetics at the same condition, the zeotype aluminophosphate with AEI framework topology (AlPO-18) stands out. Using AlPO-18, 0.29 g/g water uptake is achieved in a narrow relative humidity range before 13%. The adsorbent regeneration is almost completed below 70 °C. Moreover, AlPO-18 is non-toxic and the synthesis is low-cost. Therefore, AlPO-18 is a good candidate for adsorbent in developing energy-saving atmospheric water harvest (AWH) technology to extract water from "dry" air. [Display omitted] • Nanoporous materials were studied as atmospheric water harvesting (AWH) sorbents. • Micropoous AlPOs demonstrate high capacity and low-temperature water desorption. • AlPO-18 is potential candidate for developing an energy-saving AWH system. [ABSTRACT FROM AUTHOR]

The development of novel zeolite‐like materials with large channel windows and high stability is of importance but remains a tremendous challenge. Herein, we report the first example of a 3D covalent organic framework with zeolitic network, namely the zeolitic organic framework (ZOF). By combining two kinds of tetrahedral building blocks with fixed or relatively free bond angles, ZOF‐1 with the zeolitic crb net has been successfully synthesized. Its structure was determined by the single‐crystal 3D electron diffraction technique. Remarkably, ZOF‐1 shows high chemical stability, large pore size (up to 16 Å), and excellent specific surface area (≈2785 m2 g−1), which is superior to its analogues with the same network, including traditional aluminosilicate zeolites and zeolitic imidazole frameworks. This study thus opens a new avenue to construct zeolite‐like materials with pure organic frameworks and will promote their potential applications in adsorption and catalysis for macromolecules. [ABSTRACT FROM AUTHOR]

The development of novel zeolite‐like materials with large channel windows and high stability is of importance but remains a tremendous challenge. Herein, we report the first example of a 3D covalent organic framework with zeolitic network, namely the zeolitic organic framework (ZOF). By combining two kinds of tetrahedral building blocks with fixed or relatively free bond angles, ZOF‐1 with the zeolitic crb net has been successfully synthesized. Its structure was determined by the single‐crystal 3D electron diffraction technique. Remarkably, ZOF‐1 shows high chemical stability, large pore size (up to 16 Å), and excellent specific surface area (≈2785 m2 g−1), which is superior to its analogues with the same network, including traditional aluminosilicate zeolites and zeolitic imidazole frameworks. This study thus opens a new avenue to construct zeolite‐like materials with pure organic frameworks and will promote their potential applications in adsorption and catalysis for macromolecules. [ABSTRACT FROM AUTHOR]

The development of bioinspired nano/subnano‐sized (<2 nm) ion channels is still considered a great challenge due to the difficulty in precisely controlling pore's internal structure and chemistry. Herein, for the first time, we report that three‐dimensional functionalized covalent organic frameworks (COFs) can act as an effective nanofluidic platform for intelligent modulation of the ion transport. By strategic attachment of 12‐crown‐4 groups to the monomers as ion‐driver door locks, we demonstrate that gating effects of functionalized COFs can be activated by lithium ions. The obtained materials exhibit an outstanding selective ion transmission performance with a high gating ratio (up to 23.6 for JUC‐590), which is among the highest values in metal ion‐activated solid‐state nanochannels reported so far. Furthermore, JUC‐590 offers high tunability, selectivity, and recyclability of ion transport proved by the experimental and simulated studies. [ABSTRACT FROM AUTHOR]

Owing to the finite building blocks and difficulty in structural identification, it remains a tremendous challenge to elaborately design and synthesize three‐dimensional covalent organic frameworks (3D COFs) with predetermined topologies. Herein, we report the first two cases of 3D COFs with the non‐interpenetrated hea net, termed JUC‐596 and JUC‐597, by using the combination of tetrahedral and triangular prism building units. Due to the presence of triptycene functional groups and fluorine atoms, JUC‐596 exhibits an exceptional performance in the H2 adsorption up to 305 cm3 g−1 (or 2.72 wt%) at 77 K and 1 bar, which is higher than previous benchmarks from porous organic materials reported so far. Furthermore, the strong interaction between H2 and COF materials is verified through the DFT theoretical calculations. This work represents a captivating example of rational design of functional COFs based on a reticular chemistry guide and demonstrates its promising application in clean energy storage. [ABSTRACT FROM AUTHOR]

The development of bioinspired nano/subnano‐sized (<2 nm) ion channels is still considered a great challenge due to the difficulty in precisely controlling pore's internal structure and chemistry. Herein, for the first time, we report that three‐dimensional functionalized covalent organic frameworks (COFs) can act as an effective nanofluidic platform for intelligent modulation of the ion transport. By strategic attachment of 12‐crown‐4 groups to the monomers as ion‐driver door locks, we demonstrate that gating effects of functionalized COFs can be activated by lithium ions. The obtained materials exhibit an outstanding selective ion transmission performance with a high gating ratio (up to 23.6 for JUC‐590), which is among the highest values in metal ion‐activated solid‐state nanochannels reported so far. Furthermore, JUC‐590 offers high tunability, selectivity, and recyclability of ion transport proved by the experimental and simulated studies. [ABSTRACT FROM AUTHOR]

Owing to the finite building blocks and difficulty in structural identification, it remains a tremendous challenge to elaborately design and synthesize three‐dimensional covalent organic frameworks (3D COFs) with predetermined topologies. Herein, we report the first two cases of 3D COFs with the non‐interpenetrated hea net, termed JUC‐596 and JUC‐597, by using the combination of tetrahedral and triangular prism building units. Due to the presence of triptycene functional groups and fluorine atoms, JUC‐596 exhibits an exceptional performance in the H2 adsorption up to 305 cm3 g−1 (or 2.72 wt%) at 77 K and 1 bar, which is higher than previous benchmarks from porous organic materials reported so far. Furthermore, the strong interaction between H2 and COF materials is verified through the DFT theoretical calculations. This work represents a captivating example of rational design of functional COFs based on a reticular chemistry guide and demonstrates its promising application in clean energy storage. [ABSTRACT FROM AUTHOR]

The mesopores formation in zeolite crystals has long been considered to occur through the stochastic hydrolysis and removal of framework atoms. Here, we investigate the NH4F etching of representative small, medium, and large pore zeolites and show that the zeolite dissolution behavior, therefore the mesopore formation probability, is dominated by zeolite architecture at both nano‐ and sub‐nano scales. At the nano‐scale, the hidden mosaics of zeolite structure predetermine the spatio‐temporal dissolution of the framework, hence the size, shape, location, and orientation of the mesopores. At the sub‐nano scale, the intrinsic micropore size and connectivity jointly determine the diffusivity of reactant and dissolved products. As a result, the dissolution propensity varies from removing small framework fragments to consuming nanodomains and up to full digestion of the outmost part of zeolite crystals. The new knowledge will lead to new understanding of zeolite dissolution behavior and new adapted strategies for tailoring hierarchical zeolites. [ABSTRACT FROM AUTHOR]

This paper deals with the synthesis conditions–defect formation relationship in zeolites. Silicalite‐1 (MFI‐type) is used as a model material. Samples synthesized from a system with high basicity (at 100 °C), a system with moderate basicity (at 150 °C), and a fluoride‐containing system in neutral medium (at 170 °C) are compared. Well‐crystallized materials with sizes ≈0.1, 1–10, and 30–40 µm are obtained. The samples are analyzed by complementary methods providing information on the short‐ and long‐range order in the zeolite framework. A strong correlation between the number of point defects in the zeolite framework and preparation conditions is established. Silicalite‐1 synthesized under mild synthesis conditions from a highly basic system exhibits a larger number of framework defects and thus low hydrophobicity. Further, the calcined samples are subjected to aluminum and silicon incorporation by postsynthesis treatment. The Al/Si incorporation in the zeolite framework and its impact on the physicochemical properties is studied by XRD, TEM/SEM, solid‐state NMR, FTIR, and thermogravimetric analyses. The defects healing as a function of the number of point defects in the initial material and zeolite crystal size is evaluated. The results of this study will serve for fine‐tuning zeolite properties by in situ and postsynthesis methods. [ABSTRACT FROM AUTHOR]

This paper deals with the synthesis conditions–defect formation relationship in zeolites. Silicalite‐1 (MFI‐type) is used as a model material. Samples synthesized from a system with high basicity (at 100 °C), a system with moderate basicity (at 150 °C), and a fluoride‐containing system in neutral medium (at 170 °C) are compared. Well‐crystallized materials with sizes ≈0.1, 1–10, and 30–40 µm are obtained. The samples are analyzed by complementary methods providing information on the short‐ and long‐range order in the zeolite framework. A strong correlation between the number of point defects in the zeolite framework and preparation conditions is established. Silicalite‐1 synthesized under mild synthesis conditions from a highly basic system exhibits a larger number of framework defects and thus low hydrophobicity. Further, the calcined samples are subjected to aluminum and silicon incorporation by postsynthesis treatment. The Al/Si incorporation in the zeolite framework and its impact on the physicochemical properties is studied by XRD, TEM/SEM, solid‐state NMR, FTIR, and thermogravimetric analyses. The defects healing as a function of the number of point defects in the initial material and zeolite crystal size is evaluated. The results of this study will serve for fine‐tuning zeolite properties by in situ and postsynthesis methods. [ABSTRACT FROM AUTHOR]

This paper deals with the synthesis conditions–defect formation relationship in zeolites. Silicalite‐1 (MFI‐type) is used as a model material. Samples synthesized from a system with high basicity (at 100 °C), a system with moderate basicity (at 150 °C), and a fluoride‐containing system in neutral medium (at 170 °C) are compared. Well‐crystallized materials with sizes ≈0.1, 1–10, and 30–40 µm are obtained. The samples are analyzed by complementary methods providing information on the short‐ and long‐range order in the zeolite framework. A strong correlation between the number of point defects in the zeolite framework and preparation conditions is established. Silicalite‐1 synthesized under mild synthesis conditions from a highly basic system exhibits a larger number of framework defects and thus low hydrophobicity. Further, the calcined samples are subjected to aluminum and silicon incorporation by postsynthesis treatment. The Al/Si incorporation in the zeolite framework and its impact on the physicochemical properties is studied by XRD, TEM/SEM, solid‐state NMR, FTIR, and thermogravimetric analyses. The defects healing as a function of the number of point defects in the initial material and zeolite crystal size is evaluated. The results of this study will serve for fine‐tuning zeolite properties by in situ and postsynthesis methods. [ABSTRACT FROM AUTHOR]

Various factors affect the process of zeolite formation and thus the characteristics of the ultimate material. The present study is devoted to the influence of the density of the starting aluminosilicate hydrogels, i.e. the amount of the solid phase in the system, on the characteristics of the final product. Different density (viscosity) of the five alumosiliate gels was obtained by changing the ratio SiO2/H2O, while the ratios Na2O/H2O and SiO2/Al2O3 remained constant. The freshly prepared hydrogels were hydrothermally treated at 80 °C under static conditions. The reaction course was followed by a set of complementary analyses including XRD, chemical analysis, microscopy and thermogravimetry. The linear rate of crystal growth was calculated according to Zhdanov and Samulevich's method. The crystal size distribution curves of the end products were measured and the corresponding curves of nuclei distribution within gel matrix and specific number of crystals were calculated. The observed effect of “local ordered structure” (potential nuclei) formation was commented on from the viewpoint of the autocatalytic nucleation theory. [ABSTRACT FROM AUTHOR]

The synthesis of zeolites in a strongly acidic medium is a new and nearly unexplored chemistry field. In addition to the previously reported silicalite-1 and the several clathrasils, this paper elaborates that one more material of unique properties could be successfully crystallized in the strongly acidic fluoride medium. A pure-silica zeolite ZSM-8 has been obtained using tetraethylammonium ion as a structure-directing agent. Rietveld refinement proves that ZSM-8 is of the MFI topology, i.e., it is another silicalite-1 but different in framework distortions. Moreover, the discrete and uniform crystals of the acidic-medium synthesized pure-silica ZSM-8 possess a substantially perfect framework structure and thus hydrophobic surfaces. This remarkable character renders the material an ideal adsorbent for discriminating molecules on the polarity basis, which is desired in developing green separation processes. C 3 H 8 , CH 4, and CO 2 are chosen as examples respecting their different polarities and tested for the adsorptive parameters. Acidic-medium synthesized pure-silica ZSM-8 zeolite has perfect framework connectivity, thus extremly hydrophobic surface, which makes it an ideal adsorbent for separations of polar and apolar molecules. [Display omitted] • Pure-silica ZSM-8 crystallizes at pH = 2.9∼4.8 using TEABr as the SDA. • Pure-silica ZSM-8 has MFI framework. Other than TPA+, TEA+ interacts stronger with the framework, leading to distortions. • Acidic-medium synthesized ZSM-8 possesses unprecedently perfect framework, thus extremely hydrophobic surface. • The adsorption energies of CH 4 , C 3 H 8 are obviously different from that of CO 2. [ABSTRACT FROM AUTHOR]

Zeolite Y and its ultra‐stabilized hierarchical derivative (USY) are the most widely used zeolite‐based heterogeneous catalysts in oil refining, petrochemisty, and other chemicals manufacturing. After almost 60 years of academic and industrial research, their resilience is unique as no other catalyst displaced them from key processes such as FCC and hydrocracking. The present study highlights the key difference leading to the exceptional catalytic performance of USY versus the parent zeolite Y in a multi‐technique study combining advanced spectroscopies (IR and solid‐state NMR) and molecular modeling. The results highlight a hitherto unreported proton transfer involving inaccessible active sites in sodalite cages that contributes to the exceptional catalytic performance of USY. [ABSTRACT FROM AUTHOR]

Zeolite Y and its ultra‐stabilized hierarchical derivative (USY) are the most widely used zeolite‐based heterogeneous catalysts in oil refining, petrochemisty, and other chemicals manufacturing. After almost 60 years of academic and industrial research, their resilience is unique as no other catalyst displaced them from key processes such as FCC and hydrocracking. The present study highlights the key difference leading to the exceptional catalytic performance of USY versus the parent zeolite Y in a multi‐technique study combining advanced spectroscopies (IR and solid‐state NMR) and molecular modeling. The results highlight a hitherto unreported proton transfer involving inaccessible active sites in sodalite cages that contributes to the exceptional catalytic performance of USY. [ABSTRACT FROM AUTHOR]

With excellent designability, large accessible inner surface, and high chemical stability, covalent organic frameworks (COFs) are promising candidates as metal‐free heterogeneous catalysts. Here, we report two 3D radical‐based COFs (JUC‐565 and JUC‐566) in which radical moieties (TEMPO) are uniformly decorated on the channel walls via a bottom‐up approach. Based on grafted functional groups and suitable regular channels, these materials open up the application of COFs as highly efficient and selective metal‐free redox catalysts in aerobic oxidation of alcohols to relevant aldehydes or ketones with outstanding turn over frequency (TOF) up to 132 h−1, which has exceeded other TEMPO‐modified catalytic materials tested under similar conditions. These stable COF‐based catalysts could be easily recovered and reused for multiple runs. This study promotes potential applications of 3D functional COFs anchored with stable radicals in organic synthesis and material science. [ABSTRACT FROM AUTHOR]

With excellent designability, large accessible inner surface, and high chemical stability, covalent organic frameworks (COFs) are promising candidates as metal‐free heterogeneous catalysts. Here, we report two 3D radical‐based COFs (JUC‐565 and JUC‐566) in which radical moieties (TEMPO) are uniformly decorated on the channel walls via a bottom‐up approach. Based on grafted functional groups and suitable regular channels, these materials open up the application of COFs as highly efficient and selective metal‐free redox catalysts in aerobic oxidation of alcohols to relevant aldehydes or ketones with outstanding turn over frequency (TOF) up to 132 h−1, which has exceeded other TEMPO‐modified catalytic materials tested under similar conditions. These stable COF‐based catalysts could be easily recovered and reused for multiple runs. This study promotes potential applications of 3D functional COFs anchored with stable radicals in organic synthesis and material science. [ABSTRACT FROM AUTHOR]

Abstract: The present work deals with the removal of organic template, tetraethylammonium (TEA) and activation of Beta zeolite nanocrystals using cold plasma (nonthermal) treatment as efficient and environmentally benign approach. The entire process of nonthermal plasma activation of the nanosized zeolite is monitored in a reactor using real time in situ FTIR. The influence of the environmentally friendly cold plasma treatment in comparison to conventional activation (heating at high temperature in the presence of reducing gases) on the physicochemical properties of Beta zeolite nanocrystals is investigated. It is shown that the cold plasma treatment removes the organic template from the nanosized Beta crystals within several minutes, without carbon deposition and thus eliminating the high temperature treatment and the use of hazardous chemicals. The acidic properties of the nanosized Beta zeolite after calcination and cold plasma treatment using pyridine adsorption and temperature programmed desorption are studied by in situ IR spectroscopy. In addition, the Beta nanocrystals treated by the two methods are characterized by X-ray diffraction, 29Si NMR spectroscopy and nitrogen sorption. It is shown that the cold plasma treatment is an environmental solution for removal of unwanted products (organic templates) in very short time resulting in energy saving and reduction of hazardous solvents and gases. [Copyright &y& Elsevier]