For several decades olefin metathesis reactions over supported Mo, W, and Re oxides catalysts have attracted remarkable interest owning to their growing industrial applications. Therefore, particular ...attention was devoted to improve the catalytic activity of these catalysts. In the way of exploration of the catalytic performances of these heterogeneous Mo, W, and Re oxides systems, it was found that high dispersion of metal oxide on the support surface and the oxidation state of the metal oxide on the surface of catalyst play crucial factors on the catalysts efficiency. Importantly, these factors have an origin in the preparation methods and the properties of the used supports. In this regard, we have tried to address the various preparation methods of immobilized Mo, W, and Re oxide catalysts as well as properties of supporting material to better understand their impacts on the catalytic performances of these catalysts.
Solar vapor generation is considered a green and practical approach to take advantage of solar energy as a renewable source and provide pure water. However, developing suitable materials with high ...efficiency and long-term stability under one sun illumination is challenging. Consequently, in this paper, we manifested two-dimensional Zn/Co zeolitic imidazolate framework (ZIF)-L as a sacrificial template to prepare carbon nanotube (CNT) through carbonization of the ZIF-L (Z-CNT). This porous Z-CNT as the solar absorber was deposited on a low-cost fiber paper, as a carrier for water transport by the capillary effect. A polystyrene foam was placed under the provided film, which prevents the heat loss to bulk water. By utilizing this solar vapor generator, a high water evaporation rate of 1.44 kg m
2
h
−1
and a photothermal conversion efficiency of 84% was achieved under one sun. Beside the porosity, high light adsorption of carbon nano tubes (CNT) due to having black colour and low thermal conductivity of this material incorporate the high achieved efficiency.
Two-dimensional (2-D) Zn/Co, Zn, and Co zeolitic imidazolium frameworks (ZIF) were synthesized using straightforward ultrasound techniques. Dual metal Zn/Co ZIF-L, Zn ZIF-L and Co ZIF-L with ...leaf-like shape morphologies were prepared in 15 min. Various characterizations have been applied including X-ray diffraction, scanning electron microscopy and energy dispersive X-ray photoelectron spectroscopy to verify that the 2-D structures of these ZIF-L series have been established. The influence of various synthetic conditions such as different metal/ligand ratios as well as different synthesis times on crystal structure, morphology and porosity of Zn/Co ZIF-L were investigated. Cross-leaf morphology was obtained by reducing the metal/ligand ratio. Study of CO
2
adsorption revealed that these ZIF-L series have a considerable CO
2
adsorption capacity. In situ fabrication of TiO
2
nanoparticles within Zn/Co ZIF-L was realized via ultrasonication for 15 min as Zn/Co ZIF-L was created. TiO
2
@Zn/Co ZIF-L was effectively applied as a catalyst in photodegradation of methyl orange under solar irradiation. The results indicate that ultrasound is an efficient way to synthesize high-quality metal matrix frameworks (MOFs) and immobilize nanoparticles in MOF structures with high yield, in a short time.
Catalytic hydrogenation of CO2 into CH4 is an effective method to convert waste CO2 and green hydrogen into clean fuel on a large scale. However, the viability of such process largely relies on the ...development of highly active heterogeneous catalysts. Here, a tailored methanation catalyst, Co nanoparticles immobilized into a highly porous N‐doped carbon matrix, is prepared by the carbonization of a cobalt‐based layered zeolitic imidazolate framework (ZIF−L) material under an argon atmosphere. This catalyst displays a specific activity of 22.3 molCH4/gcat.min at 350 °C, significantly outperforming a similar catalyst derived from the more conventional ZIF‐67 (11.7 molCH4/gcat.min). This is explained by the stabilization of small Co nanoparticles (∼20 nm) and by the presence of abundant medium‐strength basic sites related to the nitrogen doping in the catalyst prepared from ZIF−L. Notably, the new catalyst shows high stability; no deactivation is observed up to 60 hours on stream.
CO2 methanation over cobalt nanoparticles: The carbonization of ZIF−L led to cobalt nanoparticles embedded in a porous nitrogen‐doped carbon material. The catalyst showed high activity in the CO2 methanation reaction; this is explained by the stabilization of small Co nanoparticles and by the abundant N species that act as basic sites for CO2 adsorption.
In this work, we excited as-spun wet films of PEDOT:PSS by ultrasonic vibration with varying frequency and power. This is a low-cost and facile technique for tailoring the structural and surface ...characteristics of solution-processed thin films and coatings. We deposited the coatings on both rigid and flexible substrates and performed various characterization techniques, such as atomic force microscopy (AFM), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS), attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR), transmittance, electrical conductivity, and contact angle measurements, to understand how the ultrasonic vibration affects the coating properties. We found that as a result of ultrasonic vibration, PEDOT:PSS sheet conductivity increases up to five-fold, contact angle of water on PEDOT:PSS increases up to three-fold, and PEDOT:PSS roughness on glass substrates substantially decreases. Our results affirm that ultrasonic vibration can favor phase separation of PEDOT and PSS and rearrangement of PEDOT-rich charge transferring grains. In addition to providing a systematic study on the effect of ultrasonic frequency and power on the film properties, this work also proves that the ultrasonic vibration is a novel method to manipulate and tailor a wide range of properties of solution-processed thin films, such as compactness, chain length and arrangement of polymer molecules, conductivity, and surface wettability. This ultrasonication method can serve organic, printed and flexible electronics.
Abstract
Catalytic hydrogenation of CO
2
into CH
4
is an effective method to convert waste CO
2
and green hydrogen into clean fuel on a large scale. However, the viability of such process largely ...relies on the development of highly active heterogeneous catalysts. Here, a tailored methanation catalyst, Co nanoparticles immobilized into a highly porous N‐doped carbon matrix, is prepared by the carbonization of a cobalt‐based layered zeolitic imidazolate framework (ZIF−L) material under an argon atmosphere. This catalyst displays a specific activity of 22.3 mol
CH4
/g
cat
.min at 350 °C, significantly outperforming a similar catalyst derived from the more conventional ZIF‐67 (11.7 mol
CH4
/g
cat
.min). This is explained by the stabilization of small Co nanoparticles (∼20 nm) and by the presence of abundant medium‐strength basic sites related to the nitrogen doping in the catalyst prepared from ZIF−L. Notably, the new catalyst shows high stability; no deactivation is observed up to 60 hours on stream.
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•Spray-dry technique was applied to synthesis Pd@ZIF-8.•With this technique Pd@ZIF-8 was prepared without employing any stabilizer or surfactant.•The synthesis procedure is included ...just one step.•Characterization of pd@ZIF-8 demonstrated the presence of Pd nano-particles inside the ZIF-8 structure.•Pd@ZIF-8 as a heterogeneous catalyst showed excellent activity in alkene hydrogenation.
In-situ fabrication of palladium(0) nanoparticles inside zeolitic imidazolate frameworks (ZIF-8) has been established via one-step facile spray-dry technique. Crystal structures and morphologies of the Pd@ZIF-8 samples are investigated by powder XRD, TEM, SAED, STEM, and EDX techniques. High angle annular dark field scanning transmission electron microscopy (HAAD-STEM) and 3D tomographic analysis confirm the presence of palladium nanoparticles inside the ZIF-8 structure. The porosity, surface area and N2 physisorption properties are evaluated for Pd@ZIF-8 with various palladium contents. Furthermore, Pd@ZIF-8 samples are effectively applied as heterogeneous catalysts in alkenes hydrogenation. This straightforward method is able to speed up the synthesis of encapsulation of metal nanoparticles in metal organic frameworks.
In this study, we employed zeolitic imidazolate framework-8 (ZIF-8) as the interlayer between the compact TiO2 and perovskite layers. As a result, enhanced perovskite grain crystallinity, larger ...grains, and considerably improved photovoltaic performance were achieved in the fabricated perovskite solar cells (PSC). It was demonstrated that the ZIF-8 film includes all characteristics suitable for being applied as scaffold in the PSCs with the advantage of easier synthesis process in room temperature in comparison to the mesoporous TiO2 counterpart. Moreover, we replaced the thermal annealing process commonly applied on the perovskite layers with room-temperature ultrasonic vibration post-treatment of wet perovskite films.
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