A highly selective catalyst based on mesoporous zeolites for the production of C5–C11 isoparaffins from syngas has been developed. The selectivity to C5–C11 hydrocarbons over Ru/meso‐ZSM‐5 reaches about 80 % with a ratio of isoparaffins to n‐paraffins of 2.7:1. The mesoporous structure and the unique acidity of meso‐ZSM‐5 play key roles in tuning the product selectivity by controlling the secondary hydrocracking reactions.
Rationale:
Endothelial cell–specific molecule 1 (Esm1) is a secreted protein thought to play a role in angiogenesis and inflammation. However, there is currently no direct in vivo evidence supporting a function of Esm1 in either of these processes.
Objective:
To determine the role of Esm1 in vivo and the underlying molecular mechanisms.
Methods and Results:
We generated and analyzed
Esm1
knockout (
Esm1
KO
) mice to study its role in angiogenesis and inflammation.
Esm1
expression is induced by the vascular endothelial growth factor A (VEGF-A) in endothelial tip cells of the mouse retina.
Esm1
KO
mice showed delayed vascular outgrowth and reduced filopodia extension, which are both VEGF-A–dependent processes. Impairment of Esm1 function led to a decrease in phosphorylated Erk1/2 (extracellular-signal regulated kinases 1/2) in sprouting vessels. We also found that
Esm1
KO
mice displayed a 40% decrease in leukocyte transmigration. Moreover, VEGF-induced vascular permeability was decreased by 30% in
Esm1
KO
mice and specifically on stimulation with VEGF-A
165
but not VEGF-A
121
. Accordingly, cerebral edema attributable to ischemic stroke–induced vascular permeability was reduced by 50% in the absence of Esm1. Mechanistically, we show that Esm1 binds directly to fibronectin and thereby displaces fibronectin-bound VEGF-A
165
leading to increased bioavailability of VEGF-A
165
and subsequently enhanced levels of VEGF-A signaling.
Conclusions:
Esm1 is simultaneously a target and modulator of VEGF signaling in endothelial cells, playing a role in angiogenesis, inflammation, and vascular permeability, which might be of potential interest for therapeutic applications.
Selective conversion of methane (CH4) into value-added chemicals represents a grand challenge for the efficient utilization of rising hydrocarbon sources. We report here dimeric copper centers supported on graphitic carbon nitride (denoted as Cu2@C3N4) as advanced catalysts for CH4 partial oxidation. The copper-dimer catalysts demonstrate high selectivity for partial oxidation of methane under both thermo- and photocatalytic reaction conditions, with hydrogen peroxide (H2O2) and oxygen (O2) being used as the oxidizer, respectively. In particular, the photocatalytic oxidation of CH4 with O2 achieves >10% conversion, and >98% selectivity toward methyl oxygenates and a mass-specific activity of 1399.3 mmol g Cu−1h−1. Mechanistic studies reveal that the high reactivity of Cu2@C3N4 can be ascribed to symphonic mechanisms among the bridging oxygen, the two copper sites and the semiconducting C3N4 substrate, which do not only facilitate the heterolytic scission of C-H bond, but also promotes H2O2 and O2 activation in thermo- and photocatalysis, respectively.
Mesoporous beta (meso-beta) zeolites prepared by post-treatment
of H-beta with NaOH aqueous solution were studied as supports of Ru
catalysts for Fischer–Tropsch (FT) synthesis. The size and
volume of the mesopores increased with the concentration of NaOH.
The Brønsted acidity declined because Na+ ions were
exchanged into the meso-beta during the post-treatment, and a further
ion exchange of the meso-beta with NH4
+ followed
by calcination, forming H-meso-beta, could recover the Brønsted
acidity. The use of H-meso-beta or meso-beta instead of H-beta or
Na-beta as the support for FT synthesis decreased the selectivities
to CH4 and heavier hydrocarbons (C12
+) and increased that to C5–C11 hydrocarbons.
The C5–C11 selectivity depended on the
concentration of NaOH used for meso-beta preparation. Under an optimum
NaOH concentration, a C5–C11 selectivity
of 77%, significantly higher than the maximum expected from Anderson–Schulz–Flory
distribution (∼45%), was attained with a ratio of isoparaffins
to n-paraffins being 2.7. The mesoporosity and the
unique acidity of the meso-beta probably contribute to the selective
hydrocracking of the primary heavier hydrocarbons formed on Ru nanoparticles
into gasoline-range liquid fuels.
The HKUST-1@SBA-15 composites with hierarchical pore structure were constructed by in situ self-assembly of metal-organic framework (MOF) with mesoporous silica. The structure directing role of SBA-15 had an obvious impact on the growth of MOF crystals, which in turn affected the morphologies and structural properties of the composites. The pristine HKUST-1 and the composites with different content of SBA-15 were characterized by XRD, N adsorption-desorption, SEM, TEM, FT-IR, TG, XPS, and CO-TPD techniques. It was found that the composites were assembled by oriented growth of MOF nanocrystals on the surfaces of SBA-15 matrix. The interactions between surface silanol groups and metal centers induced structural changes and resulted in the increases in surface areas as well as micropore volumes of hybrid materials. Besides, the additional constraints from SBA-15 also restrained the expansion of HKUST-1, contributing to their smaller crystal sizes in the composites. The adsorption isotherms of CO on the materials were measured and applied to calculate the isosteric heats of adsorption. The HS-1 composite exhibited an increase of 15.9% in CO uptake capacity compared with that of HKUST-1. Moreover, its higher isosteric heats of CO adsorption indicated the stronger interactions between the surfaces and CO molecules. The adsorption rate of the composite was also improved due to the introduction of mesopores. Ten cycles of CO adsorption-desorption experiments implied that the HS-1 had excellent reversibility of CO adsorption. This study was intended to provide the possibility of assembling new composites with tailored properties based on MOF and mesoporous silica to satisfy the requirements of various applications.
Polypyrrole coated hollow MOF composites are synthesized for Li–S battery electrodes, combining the porous structure of ZIF-67 and high conductivity of polypyrrole. The composites obtained a high initial specific capacity and good cycling performance.
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