Heterogeneous catalysts based on metal–organic frameworks (MOFs) have attracted significant attention in the past two decades. The well-defined structure of these molecular materials enables the ...rational design of catalytic centers. While early efforts on MOF catalysis mainly focused on the synthesis of fine chemicals, MOFs have recently been explored for solid–gas phase catalysis to produce commodity chemicals. In this Perspective, we summarize several opportunities in using MOFs for solid–gas phase catalysis and discuss the limitations of MOF catalysts in solid–gas phase reactions. We illustrate the use of MOFs in fundamental mechanistic studies of the industrially relevant catalysts. We attempt to identify specific solid–gas phase reactions that can benefit from MOF catalysis and also point out several scenarios where MOF catalysis is unlikely to replace current technology. We hope that our in-depth discussion and critical assessment of MOF catalysis in the solid–gas phase will promote the development of new MOF-based heterogeneous catalysts for the synthesis of commodity chemicals.
The interfaces of Cu/ZnO and Cu/ZrO2 play vital roles in the hydrogenation of CO2 to methanol by these composite catalysts. Surface structural reorganization and particle growth during catalysis ...deleteriously reduce these active interfaces, diminishing both catalytic activities and MeOH selectivities. Here we report the use of preassembled bpy and Zr6(μ3-O)4(μ3-OH)4 sites in UiO-bpy metal-organic frameworks (MOFs) to anchor ultrasmall Cu/ZnOx nanoparticles, thus preventing the agglomeration of Cu NPs and phase separation between Cu and ZnOx in MOF-cavity-confined Cu/ZnOx nanoparticles. The resultant Cu/ZnOx@MOF catalysts show very high activity with a space-time yield of up to 2.59 gMeOH kgCu-1 h-1, 100% selectivity for CO2 hydrogenation to methanol, and high stability over 100 h. These new types of strong metal-support interactions between metallic nanoparticles and organic chelates/metal-oxo clusters offer new opportunities in fine-tuning catalytic activities and selectivities of metal nanoparticles@MOFs.
ZrZnO x is active in catalyzing carbon dioxide (CO2) hydrogenation to methanol (MeOH) via a synergy between ZnO x and ZrO x . Here we report the construction of Zn2+–O–Zr4+ sites in a metal–organic ...framework (MOF) to reveal insights into the structural requirement for MeOH production. The Zn2+–O–Zr4+ sites are obtained by postsynthetic treatment of Zr6(μ3-O)4(μ3-OH)4 nodes of MOF-808 by ZnEt2 and a mild thermal treatment to remove capping ligands and afford exposed metal sites for catalysis. The resultant MOF-808-Zn catalyst exhibits >99% MeOH selectivity in CO2 hydrogenation at 250 °C and a high space-time yield of up to 190.7 mgMeOH gZn –1 h–1. The catalytic activity is stable for at least 100 h. X-ray absorption spectroscopy (XAS) analyses indicate the presence of Zn2+–O–Zr4+ centers instead of Zn m O n clusters. Temperature-programmed desorption (TPD) of hydrogen and H/D exchange tests show the activation of H2 by Zn2+ centers. Open Zr4+ sites are also critical, as Zn2+ centers supported on Zr-based nodes of other MOFs without open Zr4+ sites fail to produce MeOH. TPD of CO2 reveals the importance of bicarbonate decomposition under reaction conditions in generating open Zr4+ sites for CO2 activation. The well-defined local structures of metal-oxo nodes in MOFs provide a unique opportunity to elucidate structural details of bifunctional catalytic centers.
The η′ meson is associated with the U(1) anomaly. In this paper, a successful effective chiral theory of mesons has been applied to study the anomalous decays of η′→π+π−π+(0)π−(0). Contribution of ...triangle and box diagrams is calculated, which indicates that the box anomaly has a significant contribution to the decay amplitudes. We predict branching ratios of Br(η′→π+π−π+π−)=12Br(η′→π+π−π0π0)=(8.3±1.2)×10−5, which is in good agreement with BESIII measurement.
Microenvironments in enzymes play crucial roles in controlling the activities and selectivities of reaction centers. Herein we report the tuning of the catalytic microenvironments of metal–organic ...layers (MOLs), a two‐dimensional version of metal–organic frameworks (MOFs) with thickness down to a monolayer, to control product selectivities. By modifying the secondary building units (SBUs) of MOLs with monocarboxylic acids, such as gluconic acid, we changed the hydrophobicity/hydrophilicity around the active sites and fine‐tuned the selectivity in photocatalytic oxidation of tetrahydrofuran (THF) to exclusively afford butyrolactone (BTL), likely a result of prolonging the residence time of reaction intermediates in the hydrophilic microenvironment of catalytic centers. Our work highlights new opportunities in using functional MOLs as highly tunable and selective two‐dimensional catalytic materials.
Sheet lightning: Two dimensional metal–organic layers (MOLs) with FeII catalytic centers mimic oxidase enzymes in the aerobic photo‐oxidization of tetrahydrofuran. The product selectivity is fine‐tuned through hydrophilic/hydrophobic modification of the MOLs, for example with gluconic acid (GA), akin to the creation of suitable microenvironments in enzymes for selective catalysis.
Mono(phosphine)–M (M–PR3; M = Rh and Ir) complexes selectively prepared by postsynthetic metalation of a porous triarylphosphine-based metal–organic framework (MOF) exhibited excellent activity in ...the hydrosilylation of ketones and alkenes, the hydrogenation of alkenes, and the C–H borylation of arenes. The recyclable and reusable MOF catalysts significantly outperformed their homogeneous counterparts, presumably via stabilizing M–PR3 intermediates by preventing deleterious disproportionation reactions/ligand exchanges in the catalytic cycles.
Potassium-selenium (K-Se) batteries are a promising electrical energy storage candidate because of the cost-effectiveness and material sustainability, yet they suffer from shuttle effect, volume ...expansion and low powder density. The development of Se-based cathode is an effective way to overcome the above issues. Here we designed a hollow nano-spherical Co-Fe bi-metallic selenide coated with N-doped carbon (denoted as CFS@N-C) as cathode for K-Se batteries. Bimetallic selenide is benefit to improve the conductivity of composite materials; N-doped carbon layer encapsulation effectively inhibits the dissolution of poly-selenides and relieves the volume expansion. The as-prepared K-Se battery exhibits excellent rate performance (300 mAh·g
–1
at 1000 mA·g
–1
) and slow-charge/ultrafast-discharge capability (discharge at 5000 mA·g
–1
and charge at 100 mA·g
–1
with ultrahigh capacity of 227 mAh·g
–1
) with Coulombic efficiency nearly 100%. In addition, the ex-situ high-resolution transmission electron microscopy (HRTEM) images reveal that the charge–discharge mechanism of CFS@N-C is K
+
replaces the bimetal and forms K
2
Se. The unique design in this work may provide certain directions on researching for high power density K-storage materials.
Emerging evidences have indicated that the composition of gut microbiota was significantly influenced by central nervous system diseases. The digestion and metabolism disturbances of patients with ...amyotrophic lateral sclerosis (ALS) might be strongly associated with ALS; however, this has rarely been evaluated in these populations. This study was to evaluate bacterial and archaeal composition of gut flora and the corresponding metabolism performance of these micro-organisms in fecal samples of patients with ALS.
A comparative study was performed on the intestinal microbiota from eight patients with ALS and eight healthy individuals at Huadong Hospital during November 2017 to April 2018; meanwhile, the metabolite concentrations of human endotoxin, short-chain fatty acids (SCFA), NO2-N/NO3-N, and γ-aminobutyric acid were also evaluated by spectrophotometry methods. The correlations between intestinal microbiota and metabolite concentration were compared between the two groups using one-way analysis of variance; the relative abundance of beneficial and harmful micro-organisms in fecal samples was also analyzed.
In general, the richness and evenness of bacterial and archaeal communities of healthy individuals were healthier than that of patients with ALS. The phylum Firmicutes/Bacteroidetes ratio, genus Methanobrevibacter showed an enhancive tendency in patients with ALS, whereas the relative abundance of beneficial micro-organisms (genera Faecalibacterium and Bacteroides) presented a significant decrease tendency in patients with ALS. In addition, the average concentrations of human endotoxin, SCFA, NO2-N/NO3-N, and γ-aminobutyric acid in patients with ALS and healthy individuals were 64.2 vs. 65.3 EU/mL, 57.5 vs. 55.3 μg/mL, 5.7 vs. 5.3 ng/mL, and 6.1 vs. 5.4 μmol/L, respectively, indicating that the digestion and metabolism functions of gastrointestinal tract of patients might decline with this disease.
The relative abundance of beneficial and harmful micro-organisms respectively showed decrease and increase tendency in patients with ALS.
Molecularly imprinted polymers are synthetic polymers possessing specific cavities designed for target molecules. They are prepared by copolymerization of a cross-linking agent with the complex ...formed from a template and monomers that have functional groups specifically interacting with the template through covalent or noncovalent bonds. Subsequent removal of the imprint template leaves specific cavities whose shape, size, and functional groups are complementary to the template molecule. Because of their predetermined selectivity, molecularly imprinted polymers (MIPs) can be used as ideal materials in wastewater treatment. Especially, MIP-based composites offer a wide range of potentialities in wastewater treatment. This paper reviews the latest applications of MIPs in wastewater treatment, highlights the development of MIP-based composites in wastewater, and offers suggestions for future success in the field of MIPs.
Hydrogen sulfide (H
S) has been recognized as an important endogenous gasotransmitter associated with biological signaling transduction. However, recent biological studies implied that the H
...S-related cellular signaling might actually be mediated by hydrogen polysulfides (H
S
,
> 1), not H
S itself. Unraveling such a mystery strongly demanded the quantification of endogenous H
S
in living systems. However, endogenous H
S
has been undetectable thus far, due to its extremely low concentration within cells. Herein, we demonstrated a strategy to detect ultra-trace endogenous H
S
a fluorescent
-probe, through changes of fluorescence lifetime instead of fluorescence intensity. This
-probe exhibited an ultrasensitive response to H
S
, bringing about the lowest value of the detection limit (2 nM) and a lower limit of quantification (10 nM) to date. With such merits, we quantified and mapped endogenous H
S
within cells and zebrafish. The quantitative information about endogenous H
S
in cells and
may have a significant implication for future research on the role of H
S
in biology. The methodology of the
-probe established here might provide a general insight into the design and application of any fluorescent probes, beyond the limit of utilizing fluorescence intensity.
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