Metal-organic frameworks (MOFs) and inorganic fillers are frequently incorporated into mixed-matrix membranes (MMMs) to overcome the traditional trade-off in permeability ( P) and selectivity for pure organic polymer membranes. Therefore, it is of great interest to examine the influence of porous and nonporous fillers in MMMs with respect to the possible role of the polymer-filler interface, that is, the void volume. In this work, we compare the same MOF filler in a porous and nonporous state, so that artifacts from a different polymer-filler interface are excluded. MMMs with the porous MOF aluminum fumarate (Al-fum) and with a nonporous dimethyl sulfoxide solvent-filled aluminum fumarate (Al-fum(DMSO)), both with Matrimid as polymer, were prepared. Filler contents ranged from 4 to 24 wt %. Gas separation performances of both MMMs were studied by mixed gas measurements using a binary mixture of CO/CH with gas permeation following the theoretical prediction by the Maxwell model for both porous and nonporous dispersed phase (filler). MMMs with the porous Al-fum filler showed increased CO and CH permeability with a moderate rise in selectivity upon increasing filler fraction. The MMMs with the nonporous Al-fum(DMSO) filler displayed a reduction in permeability while maintaining the selectivity of the neat polymer. A linear dependence of log P versus the reciprocal specific free fractional volume (sFFV) rules out a significant contribution from a void volume. The sFFV includes the free volume of the polymer and the MOF, but not the polymer-filler interface volume (so-called void volume). The sFFV for the MMM was calculated between 0.23 cm/g for a 24 wt % Al-fum/Matrimid MMM and 0.12 cm/g for a 24 wt % Al-fum(DMSO)/Matrimid MMM. The negligible effect of an interface volume is supported by a good matching of theoretical and experimental density of the Al-fum and Al-fum/(DMSO) MMMs which gave a specific void volume below 0.02 cm/g, often even below 0.01 cm/g.
Covalent triazine frameworks (CTFs) are little investigated, albeit they are promising candidates for electrocatalysis, especially for the oxygen evolution reaction (OER). In this work, nickel nanoparticles (from Ni(COD)2) were supported on CTF-1 materials, which were synthesized from 1,4-dicyanobenzene at 400 °C and 600 °C by the ionothermal method. CTF-1-600 and Ni/CTF-1-600 show high catalytic activity towards OER and a clear activity for the electrochemical oxygen reduction reaction (ORR). Ni/CTF-1-600 requires 374 mV overpotential in OER to reach 10 mA/cm2, which outperforms the benchmark RuO2 catalyst, which requires 403 mV under the same conditions. Ni/CTF-1-600 displays an OER catalytic activity comparable with many nickel-based electrocatalysts and is a potential candidate for OER. The same Ni/CTF-1-600 material shows a half-wave potential of 0.775 V for ORR, which is slightly lower than that of commercial Pt/C (0.890 V). Additionally, after accelerated durability tests of 2000 cycles, the material showed only a slight decrease in activity towards both OER and ORR, demonstrating its superior stability.
A metal–organic
gel (metallogel) based on the new tetracarboxyl ligand N
1,N
4-(diterephthalic acid)terephthalamide
in combination with chromium(III) has been converted into its xero-
and aerogel and demonstrated to have excellent specific sorption properties
for dyes in its metallogel state, where fuchsine is adsorbed faster
than the two other dyes, calcein and disulfine blue, and for water,
sulfur dioxide and carbon dioxide in its xero- and aerogel state.
The metallogel showed very good shape retention and could be extruded
from molds in designed shapes. In a rheology experiment, the storage
modulus was determined to be 1440 Pa, and the metallogel is elastic
up to 3 Hz, breaking at strains higher than 0.3%. Additional metallogels
utilizing the same ligand with a wide range of metal ions (Al(III),
Fe(III), Co(III), In(III), and Hg(II)) have also been synthesized,
and the aluminum and mixed aluminum–chromium derivative were
also converted into its aerogel. The highly porous Cr, Al, and AlCr
metal–organic aerogels proved stable against water vapor in
a physisorption experiment and were used to model breakthrough curves
for SO2/CO2 gas mixtures with the idealized
adsorbed solution theory from their physisorption isotherms. The breakthrough
simulation utilized SO2/CO2 equivalencies from
a real world application and showed effective retention of SO2 from the gas mixture. Furthermore, the materials in this
work exhibit the highest SO2 uptake values for metal–organic
aerogels so far (up to 116.8 cm3 g–1,
or 23.4 wt %).
In the present work, a direct Z-scheme composite photocatalyst, NH2-MIL-101(Cr)@CuS, with high photodegradation efficiency of Rhodamine B (RhB) degradation in the visible light spectrum, is fabricated through a solvothermal method. It was found that the NH2-MIL-101(Cr)@CuS composite with an appropriate amount of NH2-MIL-101(Cr) exhibited high catalytic performance in the RhB photodegradation. The photocur-rent density and results from the electrochemical impedance spectroscopy (EIS) analysis confirm the promoted photocatalytic activity of the NH2-MIL-101(Cr)@CuS composite compared to the pristine MIL-101(Cr) and CuS nanoparticles, which were supported by the electron lifetime (τn) calculations for the samples. The trapping ex-periments and Mott-Schottky analysis revealed that the superoxide radicals (•O − 2) played an essential role in the photodegradation of RhB and the promoted photocatalytic activity contributed to a direct Z-scheme mechanism between CuS and NH2-MIL-101(Cr). Stability study also shows acceptable results during photocatalytic reaction. Furthermore, Density Functional Theory (DFT) calculations were performed to gain a better understanding of the electronic properties of the NH2-MIL-101(Cr)@CuS nanocomposite. The calculated band structures showed that the nanocomposite has a higher photocatalytic efficiency in the visible region compared to the pristine MIL-101 (Cr) and CuS. The calculated band gap of both the semiconductors and the hybrid nanocomposite confirms the experimental results.
Here we report, room temperature heterogeneous catalysis of the Suzuki‐Miyaura cross‐coupling reaction by a Pd0 nanoparticle‐immobilized porous organic polymer (TPU‐Pd), providing excellent yields (up to 99%) using low catalyst loading. High nitrogen‐ and oxygen‐donor content of triazine‐based porous polyurethane (TPU) makes it an efficient porous polymer for Pd‐immobilization and subsequent heterogeneous catalysis of C–C cross‐coupling reactions. X‐ray photoelectron spectroscopy of TPU‐Pd showed characteristic binding energy peaks of Pd0. Atomic absorption spectroscopy revealed 10.4 wt% of Pd0 in TPU‐Pd, and transmission electron microscopy images showed well‐dispersed and facetted Pd0 nanoparticles of size 5–20 nm. Catalysis of Suzuki‐Miyaura reaction was observed to be completed in 3 h at 25 °C for a wide range of aryl halide substrates with phenylboronic acid, whereas increasing the reaction temperature to 80 °C largely allows decreasing the reaction time to 0.5‐1 h. The porosity and surface area of the catalyst was not affected after catalysis, and the catalyst has been reused for five consecutive runs.
Metal-organic framework/polymer (MOF-polymer) mixed-matrix membranes (MMMs) have been prepared by embedding the luminescent lanthanide (Ln) MOFs 3 ∞ [Sr 0.9 Eu 0.1 Im 2 ] and 2 ∞ [Tb 2 Cl 6 (bipy) 3 ]·2bipy (Im -= imidazolate, bipy = 4,4′-bipyridine) into polysulfone (PSF, Ultrason® S) and Matrimid® polymer films. The successful embedding of the Sr and Eu MOFs has been achieved for both matrixes, and the original MOF luminescence is maintained. The defect-free nature of the membranes was proven by the slightly lower gas permeation of the MMMs with the dense filler particles. For the Tb-bipy MOF, successful embedding is possible for polysulfone only. For the preparation of the MOF polymer membranes, the influence of [a]
Well-defined spherical Pd-NPs (~6-12 nm size , 4-17 %wt content) were efficiently deposited on nano- or micro- (~100-2500 nm) crystals of zeolite imidazolate frameworks (ZIFs) from different ionic liquids (ILs,...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.