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Новости Nature

Nitrogen-doped mesoporous SiC materials with catalytically active cobalt nanoparticles for the efficient and selective hydrogenation of nitroarenes

Solid catalysts under the spotlight

A general soft-enveloping strategy in the templating synthesis of mesoporous metal nanostructures

Facile storage and release of white phosphorus and yellow arsenic

In situ quantitative single-molecule study of dynamic catalytic processes in nanoconfinement

Three-dimensional bicontinuous nanoporous materials by vapor phase dealloying

MXene molecular sieving membranes for highly efficient gas separation

Solid-state synthesis

Publisher Correction: Hierarchical self-entangled carbon nanotube tube networks

Three-Dimensional Bi-Continuous Nanoporous Gold/Nickel Foam Supported MnO2 for High Performance Supercapacitors

Ultrathin graphene oxide-based hollow fiber membranes with brush-like CO2-philic agent for highly efficient CO2 capture

Redox-switchable breathing behavior in tetrathiafulvalene-based metal–organic frameworks

Лента новостей (Journal of Porous Materials)

Study on coordination structure of Re adsorbed on Mg–Al layered double hydroxide using X-ray absorption fine structure

Abstract

Porous materials of hydrotalcite-like layered double hydroxides (LDHs) have been used for removal of anionic contaminants from solution. However, local coordination structures of anions adsorbed on LDHs are not fully understood because of the lack of spectroscopic studies. In this study, we utilized X-ray absorption fine structure spectroscopy to clarify the coordination structure of Re in Mg–Al LDH as a surrogate of Tc. Adsorption experiments of ReO4 on calcined and uncalcined Mg–Al LDHs were conducted in aqueous solutions with different concentrations of NaCl, NaNO3, and Na2SO4. The tested calcined and uncalcined Mg–Al LDHs were characterized by chemical composition analysis, scanning electron microscopy (SEM), and BET surface area. Calcined Mg–Al LDH showed much higher adsorption than uncalcined one. The adsorption of ReO4 was reversible, and decreased with increasing concentration of competing anions like Cl, NO3, or SO42−. Rhenium LIII-edge X-ray absorption near edge structure suggested that neither redox reaction nor change of coordination structure occurred during intercalation of Re into Mg–Al LDH. Analysis of Re LIII-edge extended X-ray absorption fine structure indicated that ReO4 was adsorbed as an outer-sphere complex on Mg–Al LDH. The observed Re adsorption–desorption behavior, which was sensitive to the presence of competing anions, was consistent with the formation of outer sphere-complex.

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Hybrid material based on clay and calixarenic derivatives

Abstract

Hybrid nanocomposites were obtained in this study by solid–solid reaction based on calixarenic derivatives and natural Tunisian clay: clay-calixarene. For this purpose, two calixarenic derivatives were synthesized and their properties were studied. Results show their affinity towards bivalent mercury and lithium by complexation in a homogeneous medium and vis-a-vis the rubidium by extraction of water to dichloromethane. The clay was purified and characterized by means of X-ray diffraction, X-ray fluorescence, cation exchange capacity and BET techniques. Intercalation of the calixarenes in the interfoliar space of the clay has been demonstrated by the spacing of the basal space after reaction and the comparison of infrared spectra confirms that the reaction has taken place. In addition, these hybrids have developed important specific surfaces area. Both nanocomposites prepared are among the first synthesis of clay-calixarenic hybrids in solid state. According to the calixarenic structures, it is assumed that these materials were of class II hybrids.

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The use of covalent organic frameworks as template for conductive polymer synthesis and their sensor applications

Abstract

In this study, the synthesis of a mesoporous crystalline covalent organic framework (COF) based on melamine and 1,4-dibromo butane as COF-1,4 and its use as a template for in situ synthesis of conductive polymers such as poly(Aniline) (PANi) and poly(Pyrrole) (PPy) within the pores were reported. The synthesized COF-1,4/conductive polymer semi-Interpenetrating Network (semi-IPN) composites were characterized via FT-IR spectroscopy and thermogravimetric analyzer (TGA), and the conductivities of the prepared composites were determined with an electrometer. It was found that upon the in situ synthesis of the conductive polymers such as PANi and PPy within COF-1,4, the conductivity of bare COF-1,4 was increased 3 million-fold for COF-1,4/PANi, and 500 thousand-fold for COF-1,4/PPy, respectively. Furthermore, the potential sensor applications of these COF-1,4/conductive polymer semi-IPN composites were investigated against HCl and NH3, and methyl orange (MO), and methylene blue (MB) dyes in aqueous solutions. The sensor studies revealed that the conductivity of bare COF-1,4 increased 20 and 7K-folds upon 15 min exposure to HCl and NH3 gases, respectively. Interestingly, an eightfold decrease in the conductivity of COF-1,4/PANi was observed upon 15 min exposure to NH3 gas vapor at ambient conditions. Also, the conductivities of prepared COF-1,4 and its conductive polymer composites changed after treatment with MO and MB dyes suggesting other potential sensor applications of these porous materials.

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Enhanced cracking of bulky hydrocarbons over hierarchical ZSM-5 materials: a comparative study

Abstract

A comparative study of hierarchical ZSM-5 materials including nanosized ZSM-5 (Nano-ZSM-5), nanosized ZSM-5/SBA-15 composite (Com-ZSM-5) and mesoporous ZSM-5 (Meso-ZSM-5) for the enhanced cracking of bulky hydrocarbons is reported. The studied materials were thoroughly characterized by XRD, SEM, TEM, N2-sorption, AAS, ICP-AES, NH3-TPD, FTIR of adsorbed pyridine before being tested in the cracking of 1,3,5 tri-isopropyl-benzene (TIPB) as a representative of bulky hydrocarbons. It was found that all synthesized hierarchical ZSM-5 materials exhibit the preservation of intrinsic, strong Brønsted acidity of ZSM-5 along with the enlarged external/mesoporous surface. The catalytic test results show that these hierarchical ZSM-5 materials indeed promote successive cracking reactions, leading to the enhanced TIPB conversion and selectivity to the deep cracking products, i.e. cumene and benzene compared to those of bulk, commercial ZSM-5. However, the development of mesoporosity by reducing the crystal size of ZSM-5 appears limited (Smeso = 134 m2 g−1). As a result, Nano-ZSM-5 affords only the moderate TIPB conversion and selectivity to deep cracking products (ca. 70% and ca. 20% respectively). Remarkably, the introduction of either intercrystalline mesopores by dispersion of Nano-ZSM-5 in the mesoporous SBA-15 analog matrix (Com-ZSM-5) or intracrystalline mesopores by the alkaline-acid treatments (Meso-ZSM-5) significantly improves the external/mesoporous surface (Smeso = 233–297 m2 g−1), giving rise to both the high TIPB conversion and selectivity to the deep cracking products (ca. 90% and ca. 25% respectively).

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Facile synthesis of hollow structured mesoporous silica nanoreactors with confined ultra-small Pd NPs for efficient hydrogenation reactions

Abstract

A facile method has been developed for the synthesis of hollow structured mesoporous silica nanoreactors with confined ultra-small metal nanoparticles through a one-pot sol–gel process in ethanol–water/ammonia medium. As examples, Pd nanoparticles protected with PVP [poly(N-vinyl-2-pyrrolidone)] or dendrimer [hydroxyl-terminated poly(amidoamine) (PAMAM)] molecules were successfully encapsulated, and the small particle size could be well maintained (< 2 nm). Such nanoreactors exhibited excellent catalytic activity towards nitrobenzene hydrogenation under 1 MPa H2 pressure at room temperature, which could also be stably recycled without deterioration on the activity. The efficient strategy might be adapted onto other nanostructures for catalysis applications.

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Preparation of hierarchically porous carbon spheres derived from waste resins and its application in water purification

Abstract

In this research, ultrafine CeO2 nanoparticles modified porous carbon spheres were developed from waste resins and their efficiency in removing Cr(VI) from aqueous solutions was tested, which exhibited excellent adsorptive activities. Furthermore, various characterization methods were employed to prove that the CeO2 nanoparticles and raw carbons were closely bonded with one-step impregnation. Results showed that carbon spheres decorated with ultrafine CeO2 nanoparticles improves the removal efficiency by nearly six times compared with the raw carbons, reaching 90% for 100 mg/L Cr(VI). The kinetics and adsorption isotherm tests confirmed that the process was pseudo-second-order and controlled by both external transfer and intra-particle diffusion. Regeneration experiments verified long stability of the adsorbents, suggesting KSAC-CeO2 is a type of promising absorbent for the Cr(VI) removal from wastewater.

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Fe 3 O 4 @FSM-16-SO 3 H as a novel magnetically recoverable nanostructured catalyst: preparation, characterization and catalytic application

Abstract

Fe3O4@FSM-16-SO3H was prepared as new magnetically recoverable catalyst and characterized by SEM, BET, XRD, EDS, VSM and FT-IR techniques. The catalytic activity was investigated in the reaction of various aldehydes, ethyl cyanoacetate, dimedone and ammonium acetate for the preparation of Polyhydroquinolines in one pot. This protocol suggests benefits in terms of higher yields and short reaction time. In addition, the catalyst could be separated using an external magnet and is reusable many times without significant loss of activity.

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Mesoporous silica supported samarium as recyclable heterogeneous catalyst for synthesis of 5-substituted tetrazole and 2-substituted benzothiazole

Abstract

Synthesis of nitrogen-containing heterocycles such as tetrazoles and benzothiazoles gains immense importance as they are omnipresent structural modules often utilized in pharmaceuticals. In the present study, well ordered MCM-41 type mesoporous silica with large pore (l-MSN) was synthesized and impregnated with samarium nitrate (Sm@l-MSN). Due to high abundance of samarium relative to many catalytically active transition metals (e.g. Ru, Ir, Pt), it may offer an opportunity to develop sustainable catalysts for organic conversions. The synthesized materials were characterized using nitrogen sorption, scanning electron microscopy, energy-dispersive X-ray, elemental mapping and transmission electron microscopy. The catalytic efficiency of the materials was explored for the synthesis of tetrazoles and benzothiazoles, two very important heterocyclic moieties in medicinal chemistry and biology. The catalyst was readily recovered and recycled up to five consecutive runs without noteworthy loss of activity or leaching.

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