5 research outputs found
Efficient Ni<sub>2</sub>P/SiO<sub>2</sub> Catalysts with Enhanced Performance for the Hydrogenation of 4,6-Dimethyldibenzothiophene and Phenanthrene
Highly dispersed Ni2P catalysts (Ni2P/SiO2-DPx) were prepared by reducing
the passivation-free
precursors, which were obtained through the phosphidation of nickel
phyllosilicate with sodium hypophosphite. The strong metal–support
interaction of nickel phyllosilicate and the mild phosphidation conditions
prevented the agglomeration of Ni particles and resulted in a smaller
Ni2P particle size. The superior catalytic performance
of the as-prepared Ni2P/SiO2-DP catalysts was
evaluated in hydrodesulfurization (HDS) of 4,6-dimethyldibenzothiophene
and the hydrogenation of phenanthrene, in comparison with Ni2P/SiO2-IM and CoMoS/γ-Al2O3 prepared from a conventional incipient wetness impregnation method.
The passivation-free Ni-P/SiO2-DPx precursors
showed great storage stability, and Ni2P/SiO2-DP derived from the stored Ni-P/SiO2-DP precursors exhibited
negligible loss of HDS activity. This method provides a potential
preparation strategy for the industrial applications of transition
metal phosphides without the temperature-programmed reduction and
the subsequent passivation process
Highly Reproducible Ag NPs/CNT-Intercalated GO Membranes for Enrichment and SERS Detection of Antibiotics
The increasing pollution of aquatic
environments by antibiotics makes it necessary to develop efficient
enrichment and sensitive detection methods for environmental antibiotics
monitoring. In this work, silver nanoparticles and carbon nanotube-intercalated
graphene oxide laminar membranes (Ag NPs/CNT-GO membranes) were successfully
prepared for enrichment and surface-enhanced Raman scattering (SERS)
detection of antibiotics. The prepared Ag NPs/CNT-GO membranes exhibited
a high enrichment ability because of the π–π stacking
and electrostatic interactions of GO toward antibiotic molecules,
which enhanced the sensitivity of SERS measurements and enabled the
antibiotics to be determined at sub-nM concentrations. In addition,
the nanochannels created by the intercalation of CNTs into GO layers
resulted in an 8-fold enhancement in the water permeance of Ag NPs/CNT-GO
membranes compared to that of pure GO membranes. More importantly,
the Ag NPs/CNT-GO membranes exhibited high reproducibility and long-term
stability. The spot-to-spot variation in SERS intensity was less than
15%, and the SERS performance was maintained for at least 70 days.
The Ag NPs/CNT-GO membranes were also used for SERS detection of antibiotics
in real samples; the results showed that the characteristic peaks
of antibiotics were obviously recognizable. Thus, the sensitive SERS
detection of antibiotics based on Ag NPs/CNT-GO offers great potential
for practical applications in environmental analysis
Bipyridine-Based Nanosized Metal–Organic Framework with Tunable Luminescence by a Postmodification with Eu(III): An Experimental and Theoretical Study
A gallium 2,2′-bipyridine-5,5′-dicarboxylate
metal–organic
framework, GaÂ(OH)Â(bpydc), denoted as COMOC-4 (COMOC = Center for Ordered
Materials, Organometallics and Catalysis, Ghent University) has been
synthesized via solvothermal synthesis procedure. The structure has
the topology of an aluminum 2,2′-bipyridine-5,5′-dicarboxylate
– the so-called MOF-253. TEM and SEM micrographs show the COMOC-4
crystals are formed in nanoplates with uniform size of 30–50
nm. The UV–vis spectra of COMOC-4 in methanol solution show
maximal electronic absorption at 307 nm. This results from linker
to linker transitions as elucidated by time-dependent density functional
theory simulations on the linker and COMOC-4 cluster models. When
excited at 400 nm, COMOC-4 displays an emission band centered at 542
nm. Upon immersion in different solvents, the emission band for the
framework is shifted in the range of 525–548 nm depending on
the solvent. After incorporating Eu<sup>3+</sup> cations, the emission
band of the framework is shifted to even shorter wavelengths (505
nm). By varying the excitation wavelengths from 250 to 400 nm, we
can fine-tune the emission from red to yellowish green in the CIE
diagram. The luminescence behavior of Eu<sup>3+</sup> cations is well
preserved and the solid-state luminescence lifetimes of τ<sub>1</sub> = 45 μs (35.4%) and τ<sub>2</sub> = 162 μs
(64.6%) are observed
New Functionalized Metal–Organic Frameworks MIL-47‑X (X = −Cl, −Br, −CH<sub>3</sub>, −CF<sub>3</sub>, −OH, −OCH<sub>3</sub>): Synthesis, Characterization, and CO<sub>2</sub> Adsorption Properties
Six new functionalized vanadium hydroxo
terephthalates [V<sup>III</sup>(OH)Â(BDC-X)]·nÂ(guests) (MIL-47Â(V<sup>III</sup>)-X-AS) (BDC =
1,4-benzeneÂdiÂcarboxylate; X = −Cl, −Br,
−CH<sub>3</sub>, −CF<sub>3</sub>, −OH, −OCH<sub>3</sub>; AS = as-synthesized) along with the parent MIL-47 were synthesized
under rapid microwave-assisted hydrothermal conditions (170 °C,
30 min, 150 W). The unreacted H<sub>2</sub>BDC-X and/or occluded solvent
molecules can be removed by thermal activation under vacuum, leading
to the empty-pore forms of the title compounds (MIL-47Â(V<sup>IV</sup>)-X). Except pristine MIL-47 (+III oxidation state), the vanadium
atoms in all the evacuated functionalized solids stayed in the +IV
oxidation state. The phase purity of the compounds was ascertained
by X-ray powder diffraction (XRPD), diffuse reflectance infrared Fourier
transform (DRIFT) spectroscopy, Raman, thermogravimetric (TG), and
elemental analysis. The structural similarity of the filled and empty-pore
forms of the functionalized compounds with the respective forms of
parent MIL-47 was verified by cell parameter determination from XRPD
data. TGA and temperature-dependent XRPD (TDXRPD) experiments in an
air atmosphere indicate high thermal stability in the 330–385
°C range. All the thermally activated compounds exhibit significant
microporosity (<i>S</i><sub>BET</sub> in the 305–897
m<sup>2</sup> g<sup>–1</sup> range), as verified by the N<sub>2</sub> and CO<sub>2</sub> sorption analysis. Among the six functionalized
compounds, MIL-47Â(V<sup>IV</sup>)-OCH<sub>3</sub> shows the highest
CO<sub>2</sub> uptake, demonstrating the determining role of functional
groups on the CO<sub>2</sub> sorption behavior. For this compound
and pristine MIL-47Â(V<sup>IV</sup>), Widom particle insertion simulations
were performed based on ab initio calculated crystal structures. The
theoretical Henry coefficients show a good agreement with the experimental
values, and calculated isosurfaces for the local excess chemical potential
indicate the enhanced CO<sub>2</sub> affinity is due to two effects:
(i) the interaction between the methoxy group and CO<sub>2</sub> and
(ii) the collapse of the MIL-47Â(V<sup>IV</sup>)-OCH<sub>3</sub> framework
New V<sup>IV</sup>-Based Metal–Organic Framework Having Framework Flexibility and High CO<sub>2</sub> Adsorption Capacity
A vanadium based metal–organic framework (MOF),
VOÂ(BPDC)
(BPDC<sup>2–</sup> = biphenyl-4,4′-dicarboxylate), adopting
an expanded MIL-47 structure type, has been synthesized via solvothermal
and microwave methods. Its structural and gas/vapor sorption properties
have been studied. This compound displays a distinct breathing effect
toward certain adsorptives at workable temperatures. The sorption
isotherms of CO<sub>2</sub> and CH<sub>4</sub> indicate a different
sorption behavior at specific temperatures. In situ synchrotron X-ray
powder diffraction measurements and molecular simulations have been
utilized to characterize the structural transition. The experimental
measurements clearly suggest the existence of both narrow pore and
large pore forms. A free energy profile along the pore angle was computationally
determined for the empty host framework. Apart from a regular large
pore and a regular narrow pore form, an overstretched narrow pore
form has also been found. Additionally, a variety of spectroscopic
techniques combined with N<sub>2</sub> adsorption/desorption isotherms
measured at 77 K demonstrate that the existence of the mixed oxidation
states V<sup>III</sup>/V<sup>IV</sup> in the titled MOF structure
compared to pure V<sup>IV</sup> increases the difficulty in triggering
the flexibility of the framework