In this study, an economical way for SSZ-13 preparation with the essentially cheap choline chloride as template has been attempted. The as-synthesized SSZ-13 zeolite after ion exchange by copper ...nitrate solution exhibited a superior SCR performance (over 95% NOx conversion across a broad range from 150 to 400 °C) to the traditional zeolite-based catalysts of Cu-Beta and Cu-ZSM-5. Furthermore, the opportune size of pore opening (∼3.8 Å) made Cu-SSZ-13 exhibiting the best selectivity to N2 as well as satisfactory tolerance toward SO2 and C3H6 poisonings. The characterization (XRD, XPS, XRF, and H2-TPR) of samples confirmed that Cu-SSZ-13 possessed the most abundant Cu cations among three investigated Cu-zeolites; furthermore, either on the surface or in the bulk the ratio of Cu(+)/Cu(2+) ions for Cu-SSZ-13 is also the highest. New finding was announced that CHA-type topology is in favor of the formation of copper cations, especially generating much more Cu(+) ions than the others, rather than CuO. The activity test of Cu(CuCl)-ZSM-5 (prepared by a solid-state ion-exchange method) clearly indicated that Cu(+) ions could make a major contribution to the low-temperature deNOx activity. The activity of protonic zeolites (H-SSZ-13, H-Beta, H-ZSM-5) revealed the topology effect on SCR performances.
Bio-based platform chemical 5-hydroxymethylfurfural (5-HMF) can be converted into large-scale, high value-added compounds generally obtained from petroleum. Hence, developing an efficient catalytic ...system to transform glucose (a cheap and abundant branch of biomass) into 5-HMF has drawn significant attention. Earlier reports have concentrated on a two-step conversion of glucose to 5-HMF involving glucose isomerization into fructose and subsequent dehydration. In this work, efficient heterogeneous niobium-loaded montmorillonite (Nb-MMT) catalysts containing Lewis and Brønsted acid sites have been synthesized by a readily cation-exchanged synthetic method and were used to convert glucose and showed high selectivity and conversion. An optimum 5-HMF yield of 70.52% with a 99% conversion of glucose was achieved in a biphasic solvent of methyl isobutyl ketone (MIBK)/water at 170 °C for 3 h. The catalytic system also exhibited an excellent activity in the conversion of disaccharides and polysaccharides to 5-HMF with satisfactory yields. In addition, Nb-MMT was effectively reused four times without significant loss of activity. Nb-MMT also featured good catalytic activity and selectivity towards carbohydrate conversion in water. Furthermore, the reaction mechanism for the transformation of glucose to 5-HMF over Nb-MMT was investigated by density functional theory (DFT) calculations, and the results showed that niobium oxyhydroxide species of Nb-MMT played an essential role in glucose conversion, and the catalytic mechanism was a synergetic proton transfer process
via
hydrogen bonding. This study paves the way for improvements in Nb-containing solid acid catalysts for conversion of carbohydrates.
Niobium-loaded montmorillonite was employed as a highly efficient catalyst for the catalytic conversion of glucose to 5-HMF in a biphasic solvent.
Hierarchical MIL-88B-on-MOF-5 octapods were synthesized
via
a mechanism involving phase-competition-driven growth (PCDG). Dramatically different morphologies (nanocubes, octapods, flowers) were also ...produced by controlling the phase competition between MIL-88B and MOF-5. The octapod MOFs showed a high catalytic performance for the reverse water-gas shift (RWGS) reaction.
An approach involving phase-competition-driven growth (PCDG) was developed and used to synthesize a series of MOF-on-MOF structures.
A mixed metal–ion metal–organic framework (MOF(Fe/Co)) was synthesized by a hydrothermal process using ferric and cobalt salts as the metal–ion precursors and trimesic acid as the organic ligand. The ...structure of the as-prepared MOF(Fe/Co) was characterized by X-ray diffraction (XRD), N2 adsorption–desorption, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and thermogravimetry/differential thermogravimetry (TG/DTG). The bifunctional catalytic activities of MOF(Fe/Co) toward the oxygen evolution reaction (OER) and the oxygen reduction reaction (ORR) in alkaline electrolyte were investigated by cyclic voltammetry (CV) and linear sweep voltammetry (LSV). The results demonstrate that the as-prepared MOF(Fe/Co) has a good crystalline structure with abundant micropores, a high specific surface area and a high thermal stability. The MOF(Fe/Co) exhibits excellent bifunctional catalytic activities for OER and ORR. The high specific surface area and abundant micropores are beneficial for oxygen diffusion and catalytic sites utilization in the catalyst, which is favorable for the OER and ORR. The RDE results for MOF(Fe/Co)-catalyzed ORR indicate that the two-electron pathway was preferred at relatively positive potentials, whereas the four-electron pathway gradually dominated at more negative potentials.
•A mixed metal–ion MOF(Fe/Co) was synthesized by a hydrothermal process.•The MOF(Fe/Co) exhibits excellent bifunctional catalytic activities for OER and ORR.•The high specific surface area and abundant micropores are favorable for OER and ORR.
The development of energy storage and conversion systems, such as the unitized regenerative fuel cells and the rechargeable metal-air batteries, heavily relies on the effective bifunctional ...electrocatalysts for oxygen reduction/evolution reactions (ORR/OER). We herein report a Co metal-organic framework (MOF, denoted as Co-BTC-IMI), which was synthesized from Co ions, 1,3,5-benzenetricarboxylic acids and imidazoles through a hydrothermal reaction. The MOF was studied as an unpyrolyzed bifunctional electrocatalyst in an alkaline half-cell, where it delivered an ORR half-wave potential of 0.80 V
vs.
the reversible hydrogen electrode (RHE) and an OER potential of 1.59 V
vs.
RHE at 10 mA cm
−2
. Co-BTC-IMI possessed good structural stability against hydroxide corrosion and great π-π stacking and hydrogen bonding interactions and, therefore, excellent bifunctional catalytic durability. Structure characterizations demonstrated that one of the Co(
ii
) ions in Co-BTC-IMI was connected by two O atoms from two different deprotonated 1,3,5-benzenecarboxylic acids, leaving the coordination of Co(
ii
) largely unsaturated. Further modeling simulations shed light on the advantage of the unsaturated coordination by significantly promoting the interactions with molecular water and oxygen and improving the electronic conductivity, leading to enhanced mass and charge transfer properties. The moderate affinity of oxygen and higher valent Co after water adsorption contributed to the enhanced bifunctional catalytic activity of Co-BTC-IMI as compared to Co-BTC. The overall bifunctional activity of Co-BTC-IMI is promising as compared to the recently reported unpyrolyzed MOFs, as well as the commercial platinum-group metals.
A coordinately unsaturated MOF for bifunctional oxygen electrocatalysis with a potential gap Δ
E
(OER
j
=10
-ORR
1/2
) as small as 0.79 V.
Next‐generation desalination technologies are needed to meet the increasing demand for clean water. Capacitive deionization (CDI) is a thermodynamically efficient technique to treat non‐potable water ...with relatively low salinity. The salt removal capacity and rate of CDI are highly dependent on the electrode materials, which are preferentially porous to store ions through electrosorption and/or redox reactions. Metal–organic frameworks (MOFs) with “infinite” combinations of transition metals and organic linkers simplify the production of carbonaceous materials often with redox‐active components after pyrolysis. MOFs‐derived materials show great tunability in both compositions and structures but require further refinement to improve CDI performance. This review article summarizes recent progress in derivatives of MOFs and MOF‐like materials used as CDI electrodes, focusing on the structural and compositional material considerations as well as the processing parameters and electrode architectures of the device. Furthermore, the challenges and opportunities associated with this research area are also discussed.
The rational design of precursory metal–organic frameworks (MOFs) is a new approach to improve the non‐Faradaic and Faradaic characteristics of electrode materials and increase the energy efficiency and reduce costs of capacitive deionization (CDI). The key compositional and structural considerations for the pyrolyzed MOF approach and their correlations with CDI performance are comprehensively discussed in this article.
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•CuO-CeO2 catalyst is more active than pure CuO and CeO2 for N2O decomposition.•The co-existence of CuO and CeO2 exhibited a synergetic effect.•The synergetic effect contributes to ...the formation of Cu+ and Ce3+ active sites.•The desorption of surface adsorbed oxygen is promoted over CuO-CeO2 catalyst.
The catalytic decomposition of N2O was investigated over a series of CuO-CeO2 mixed oxide catalysts prepared by the hydrothermal method. It was found that CuO-CeO2 mixed oxide catalyst exhibited higher activity than pure CuO and CeO2. The co-existence of CuO and CeO2 exhibited a synergetic effect, which inhibited the crystallization of the CuO phase, leading to the high surface area. Moreover, the two redox couples (Ce4+/Ce3+ and Cu2+/Cu+) formed over CuO-CeO2 mixed oxide contribute to the desorption of surface adsorbed oxygen species and thus the regeneration the active sites, which is favorable for the catalytic N2O decomposition to proceed.
Direct oxidation of methane to methanol (DMTM) is a big challenge in C1 chemistry. We present a continuous N2O‐DMTM investigation by simultaneously introducing 10 vol % H2O into the reaction system ...over Cu‐BEA zeolites. Combining a D2O isotopic tracer technique and ab initio molecular dynamics (AIMD) simulation, we for the first time demonstrate that the H2O molecules can participate in the reaction through a proton transfer route, wherein the H2O molecules can build a high‐speed proton transfer bridge between the generated moieties of CH3− and OH− over the evolved mono(μ‐oxo) dicopper (Cu‐O‐Cu2+) active site, thereby pronouncedly boosting the CH3OH selectivity (3.1→71.6 %), productivity (16.8→242.9 μmol gcat−1 h−1) and long‐term reaction stability (10→70 h) relative to the scenario of absence of H2O. Unravelling the proton transfer of H2O over the dicopper Cu‐O‐Cu2+ site would substantially contribute to highly efficient catalyst designs for the continuous DMTM.
H2O can directly participate in the continuous N2O‐DMTM reaction through a proton‐transfer‐bridge over the dicopper Cu‐O‐Cu site of Cu‐BEA zeolite. This can significantly boost CH3OH production rate and enhance long‐term reaction stability.
The UNIFAC model has recently become very popular for ionic liquids (ILs) because of its applicability for prediction of thermodynamic properties. This work is a continuation of our studies on the ...extension of group parameters of the UNIFAC model to systems with ILs. The new IL groups for 33 main groups and 53 subgroups were added into the current UNIFAC parameter matrix. The parameters of group surface area and volume for ILs were obtained by the COSMO calculation, while the group binary interaction parameters, a nm and a mn, were obtained by means of correlating the activity coefficients of solutes at infinite dilution in ILs at different temperatures exhaustively collected from literature by the end of 2011. The predicted results of UNIFAC model are more accurate than those of the COSMO-RS model so that it can be used for identifying the general relationship between molecular structure of ILs and separation performance for the separation of liquid mixtures with ILs.
A facile one-step strategy has been developed for preparing monodisperse CeO2 mesoporous spheres with high surface areas, uniform size distributions, and well-defined pore topologies. These ...mesoporous spheres have been demonstrated to be catalytically stable and active for CO oxidation.
