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The catalytic performance of the isomerization of styrene oxide to phenyl acetaldehyde was investigated over different modified beta catalysts under gas-phase atmosphere free of solvents. The physicochemical properties were characterized by a combination of X-ray diffraction (XRD), N adsorption, Fourier transform infrared spectroscopy (FT-IR), Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR), NH-Temperature programmed desorption (NH-TPD) and thermo gravimetric analysis (TGA), etc. Acid sites with stronger strength are responsible for the formation of condensation products and fast deactivation of catalysts. The obtained results also demonstrate that the introduction of boron atoms can create suitable acid strength and acid distribution without significantly destroying its microporous structures. Therefore, BAl-BEA sample is highly active and selective for the rearrangement of styrene oxide as well as very stable to deactivation. Graphical Abstract: [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs) have attracted considerable attention for many potential applications because they have a unique porous structure and excellent thermal and chemical stabilities. In recent years, significant efforts have been made to develop different methods for the controllable synthesis of ZIFs with desirable crystal structure and morphologies, and for decreasing the excessive amounts of organic ligands and solvents used in the synthesis process to reduce the costs and environmental impacts. This paper highlights the strategies recently reported, including the controllable synthesis of ZIFs with desirable morphologies and pore structure using a surfactant and a template in aqueous solution, the synthesis of ZIF particles and nanocrystals in base solution, and the dry gel and mechanochemical syntheses of ZIFs with minimal solvent usage. [ABSTRACT FROM AUTHOR]

The carbonization of a newly reported two-dimensional zeolitic imidazolate framework (ZIF-L) with leaf-like morphology was investigated by TG, SEM, XRD and XPS. ZIF-L flakes were thermally stable at up to 200°C, and completely transformed into an amorphous carbonaceous material after heat treatment in nitrogen at 550°C. A carbon composite membrane was then prepared by deposition of ZIF-L flakes on a porous alumina support and then direct carbonization of ZIF-L film. During the carbonization, the ZIF-L membrane reorganized into a nanoporous carbon composite membrane composed of ZnO nanoparticles and leaf-like carbon flakes. The resulting nanoporous carbon composite membrane exhibited a narrow micropore size distribution, and it had higher BET surface area than the ZIF-L flakes. Gas separation permeation experiments showed that the carbon composite membrane had a high H2 permeance of 3.5×10−6 molm−2 s−1 Pa−1, and moderate H2/N2 and H2/CO2 ideal selectivities of 6.2 and 4.9, respectively. This work presents a simple and effective method for preparing functional nanoporous carbon composite membranes from ZIFs (or MOFs) for many potential applications. [ABSTRACT FROM AUTHOR]

Highlights: [•] ZIF-8 prepared from stoichiometric metal and ligand aqueous solutions. [•] The role of ammonium hydroxide for ZIF-8 preparation was discussed. [•] Concentrated precursor solution was used to prepare ZIF-8. [•] Highly thermally stable ZIF-8 crystals with uniform shapes and high surface areas. [Copyright &y& Elsevier]

Room to breathe: An efficient method for the synthesis of zeolitic imidazolate framework‐7 (ZIF‐7) in ethanol/water at room temperature is reported. The ZIF‐7 undergoes a reverse‐phase transition from large pore (lp)‐phase to narrow pore (np)‐phase under heat treatment and from np‐phase back to lp‐phase in ethanol solution. [ABSTRACT FROM AUTHOR]

Abstract: A new synthesis method was developed to synthesize ZIF-8 membrane by infiltrating precursors into a porous alumina support as a seed-and-nutrient layer, and subsequent solvothermal synthesis. A precursor layer with a thickness of about 10μm was formed inside the porous alumina support and the ZIF-8 membrane grew from both the seeds embedded in the precursor layer and the synthesis solution under solvothermal synthesis conditions. The effects of the solvothermal synthesis temperature and time were investigated, and a continuous and stable ZIF-8 membrane was prepared at 120°C for 8h. Gas permeation tests indicated the membrane synthesized at 120°C for 8h was continuous and compact, and had H2/N2 ideal selectivity of 5.7 with a H2 permeance of 1.7×10−7 molm−2 s−1 Pa−1. [Copyright &y& Elsevier]

Abstract: Zeolitic imidazolate framework-8 (ZIF-8)/chitosan composites were prepared in the chitosan hydrogels. The concentrations of the chitosan and the alkaline solution were varied to the synthesis of the ZIF-8/chitosan composites. In the chitosan hydrogels with the addition of ammonium hydroxide solution, the resulting ZIF-8 crystals exhibited an unusual XRD structure that the XRD peak at about 18o (222) became the strongest. The XRD peak intensity ratio of (222)/(011) increased from 0.68 to 1.5–5.2 in the presence of chitosan hydrogels. ZIF-8/chitosan composites (FC2) were composed of aggregated nanosized particles, and exhibited a higher CO2 adsorption than normal ZIF-8 crystals. After removing chitosan from FC2, XRD pattern of the resulting ZIF-8 crystals returned to the normal state and the morphology kept the same as the composite. [Copyright &y& Elsevier]

Abstract: This paper presents the synthesis of zeolitic imidazolate framework (ZIF)-8 membranes on the outer surface of alumina hollow fibers using a concentrated synthesis gel. The resulting membranes were characterized by X-ray diffraction, scanning electron microscopy, focused ion beam/scanning electron microscopy and high-resolution transmission electron microscopy. The results showed that the crystalline ZIF-8 membranes were compact and continuous, and contained micro-cavities. Single gas permeances of H2, N2, CH4 and CO2 were determined as a function of permeation time at 25°C. H2, N2 and CH4 permeances almost did not change with the permeation time. However, CO2 permeance decreased from 9.8×10−8 to 1.7×10−8 mol/sm2 Pa within 12h, and CO2 permeation led to an unrecoverable reduction in gas permeation rates in the further permeation experiments. After the first round tests, H2, N2, CH4 and CO2 permeances in the second round permeation tests dropped by 40%, 24%, 11%, and 6%, and remained constant in the further repeated measurements; the equilibrium ideal selectivities of H2/CO2, N2/CO2 and CH4/CO2 were 32.2, 12.9, and 11.9, respectively; the H2/CO2 separation factor was 7.1 for a H2/CO2 binary mixture (45% H2). The small CO2 permeance should arise from the strong CO2 adsorption in ZIF-8 membranes with micro-cavities, and the adsorbed CO2 partially blocked the gas permeation. [Copyright &y& Elsevier]

Abstract: Glycerol was introduced as the cosolvent in the synthesis of zeolite A. The molar ratio of glycerol to Al2O3 in the synthesis solution, and the aging time were examined. The association of glycerol with water affected the nuclei formation during aging and resulted in different particle sizes. The sizes of zeolite A were controlled in the range of 0.4–1.5μm when the glycerol to Al2O3 molar ratios were of 0–6. However, too much glycerol in the synthesis solution (molar ratio of glycerol/Al2O3 >4) produced zeolite A with a small amount of sodalite. A long aging time (16h) was necessary to make the product have a pure zeolite A structure and a small particle size. [Copyright &y& Elsevier]

Abstract: Magnetic ZSM-5/Ni/fly-ash hollow microspheres are prepared by using fly-ash cenospheres as the template. The preparation procedure mainly includes two steps, i.e., preparation of magnetic nickel/fly-ash composites by electroless plating and growth of the ZSM-5 layers on the nickel/fly-ash composites by a secondary growth method. The samples are characterized by scanning electron microscope, X-ray diffraction, nitrogen adsorption and vibrating sample magnetometer. The resulting ZSM-5/Ni/fly-ash hollow microspheres show integral hollow structure and magnetic property. They are floatable on water surface when the electroless plating time is 10 min and the hydrothermal synthesis time is 12 h at 180 °C. The floatability of these hollow microspheres can further be adjusted by changing the electroless plating and hydrothermal synthesis times. Furthermore, their magnetic property can also be managed by controlling the synthesis conditions. [Copyright &y& Elsevier]

Abstract: Adsorption isotherms and kinetics of methylene blue (MB) onto mesoporous carbons prepared by using acid- and alkaline-treated zeolite X as the template and furfuryl alcohol as carbon source through vapor-deposition polymerization method were determined. Adsorption isotherm models, Langmuir and Freundlich were used to simulate the equilibrium data of MB. It was found that equilibrium adsorption capacities of MB at 20°C onto the carbons prepared using acid- and alkaline-treated zeolite X as the template were 223 and 380mg/g, respectively. Adsorption isotherm data could be better described by Langmuir model than Freundlich model. Water treatment of the carbon for 2h resulted in the increase of adsorption velocity without changing the equilibrium adsorption capacity. The adsorption capacity increased with temperature increased in the range of 20–40°C. The adsorption kinetics of MB on mesoporous carbons could be well depicted by using pseudo-second-order kinetic model. [Copyright &y& Elsevier]

Zeolite ZIF‐8 has been etched with acid to form microporous ZIF‐8‐E crystals. These were then introduced into a polyethersulfone (PES) membrane matrix to enhance its CO2/N2 separation performance. Open through pores of size about 100 nm formed in the ZIF‐8 crystals allow the ingrowth of polyethersulfone chains, ensuring a reduction in the number of nonselective voids, thereby achieving better interaction between ZIF‐8‐E and PES. As a result, the CO2/N2 separation performance of the ZIF‐8‐E/PES membrane increased significantly, showing a CO2 permeability of 15.7 Barrer and a CO2/N2 ideal selectivity of 6.5. [ABSTRACT FROM AUTHOR]

Sodalite/NaTaO 3 composite was prepared by a one-pot hydrothermal synthesis method. Sodalite and NaTaO 3 grow interpenetrated, and the resulting composites have similar morphology as the pure sodalite. The sodalite/NaTaO 3 composite has a lower band gap of 3.35 eV due to the heterogeneous doping effect, and exhibits an enhanced photodegradation of methyl orange under UV irradiation as compared to the pure NaTaO 3 . A slight structure distortion is found for NaTaO 3 after removing sodalite by acid washing the sodalite/NaTaO 3 composite, and such result further confirms the co-growth of the two crystals. This one-pot hydrothermal method opens up new avenues for the preparation of photocatalytic composites. [ABSTRACT FROM AUTHOR]

Abstract: Hollow sodalite spheres with a hole on the shell were synthesized in a first-closed then-open system from the synthesis gels aged under ultrahigh N2 pressures. The effect of the synthesis time and the aging pressure was examined. The formation process was characterized by scanning electronic microscopy and X-ray diffraction. The results indicated that high pressure aging and synthesis in the open system were crucial for forming the hollow structure. By changing the synthesis time in the closed system, the size of the hollow sodalite spheres and the diameter of the hole as well as the fine structure of the sodalites could be adjusted. The formation process of the hollow sodalites was observed to follow a surface-to-core crystallization mechanism, i.e., formation of cubic zeolite A crystals in the closed system, growth of small sodalite spheres on the zeolite A crystal, wrap of the zeolite A by sodalite sphere aggregate and dissolution of zeolite A in the open system. Compared with those methods for synthesis of hollow zeolite crystals, this method is simple, effective and without using any template or additives. [Copyright &y& Elsevier]