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► Commercial metal carbonyls M
x
(CO)
y
are elegant metal-nanoparticle (M-NP) precursors. ► No extra reducing agent is necessary to obtain M-NPs from metal carbonyls. ► Electrostatic ...properties of ionic liquids (ILs) allow for the stabilization of M-NPs. ► Stabilization of M-NPs in ILs without additional capping ligands. ► Easy and rapid microwave induced decomposition of metal carbonyls M
x
(CO)
y
in ILs.
An overview with more than 160 references on the synthesis and stabilization of metal nanoparticles (M-NPs) from metal carbonyls, metal salts in ionic liquids (ILs) and in particular from metal carbonyls in ionic liquids is given. The synthesis of M-NPs can proceed by chemical reduction, thermolysis, photochemical decomposition, electroreduction, microwave and sonochemical irradiation. Commercially available metal carbonyls M
x
(CO)
y
are elegant precursors as they contain the metal atoms already in the zero-valent oxidation state needed for M-NPs. No extra reducing agent is necessary. The side product CO is largely given off to the gas phase and removed from the dispersion. The microwave induced thermal decomposition of metal carbonyls M
x
(CO)
y
in ILs provides an especially rapid and energy-saving access to M-NPs because of the ILs significant absorption efficiency for microwave energy due to their high ionic charge, high polarity and high dielectric constant. The electrostatic and steric properties of ionic liquids allow for the stabilization of M-NPs without the need of additional stabilizers, surfactants or capping ligands and are highlighted by pointing to the DLVO (Derjaugin–Landau–Verwey–Overbeek) and extra-DLVO theory. Examples for the direct use of M-NP/IL dispersions in hydrogenation catalysis of cyclohexene and benzene are given.
A full literature account is given on work describing the transition-metal catalyzed vinyl or addition polymerization to polynorbornene covering the years of 2001 to the beginning of 2008. The ...interest in vinyl polynorbornene is driven by its dielectric and mechanical properties for the technical application in microelectronics applications. Metal catalysts of Ti, Cr, Fe, Co, Ni, Pd and Cu with methylalumoxane (MAO) or perfluorinated borane, e.g. B(C
6F
5)
3, cocatalysts are presented in terms of their activity and ligand effects. Among the ligands Schiff bases, tridentate
N,
N,
N-bis(imino)pyridyl, bidentate
N,
N-anilido-imin,
N,
O-β-ketoiminato,
N,
O-salicylaldiminato (=salicylideneiminato),
O,
O-β-diketonato (=acetylacetonato),
P,
P-bis(phosphino)alkane, multidentate carbon ligands, e.g. allyl, cyclopentadienyl, aryl, and monodentate halo, especially chloro, triphenylphosphane (PPh
3) and phenyl feature prominently.
Confinement of noble nanometals in a zeolite matrix is a promising way to special types of catalysts that show significant advantages in size control, site adjustment, and nano‐architecture design. ...The beauty of zeolite‐confined noble metals lies in their unique confinement effects on a molecular scale, and thus enables spatially confined catalysis akin to enzyme catalysis. In this Minireview, the confined synthesis strategies of zeolite‐confined noble metals will be briefly discussed, showing the processes, advantages, features, and mechanisms. The confined catalysis carried on zeolite‐confined noble metals will be summarized, and great emphasis will be paid to the confinement effects involving size, encapsulation, recognition, and synergy. Great progress of atomic sites in the size effect, supercage stabilization in the encapsulation effect, site adsorption in the recognition effect, and cascade reaction in the synergy effect are highlighted. This Minireview is concluded with challenges and opportunities in terms of the synthesis of zeolite‐confined noble metals and their applications to design multifunctional catalysts with high catalytic activity, selectivity, and stability.
The beauty of zeolite‐confined noble metals lies in their unique confinement effects on a molecular scale, and thus enables spatially confined catalysis akin to enzyme catalysis. This Minireview summarizes synthesis strategies and targeted catalysis applications for multifunctional zeolite‐confined noble metal catalysts.
Mixed‐Matrix Membranes Dechnik, Janina; Gascon, Jorge; Doonan, Christian J. ...
Angewandte Chemie,
August 1, 2017, Volume:
56, Issue:
32
Journal Article
Peer reviewed
Open access
Research into extended porous materials such as metal‐organic frameworks (MOFs) and porous organic frameworks (POFs), as well as the analogous metal‐organic polyhedra (MOPs) and porous organic cages ...(POCs), has blossomed over the last decade. Given their chemical and structural variability and notable porosity, MOFs have been proposed as adsorbents for industrial gas separations and also as promising filler components for high‐performance mixed‐matrix membranes (MMMs). Research in this area has focused on enhancing the chemical compatibility of the MOF and polymer phases by judiciously functionalizing the organic linkers of the MOF, modifying the MOF surface chemistry, and, more recently, exploring how particle size, morphology, and distribution enhance separation performance. Other filler materials, including POFs, MOPs, and POCs, are also being explored as additives for MMMs and have shown remarkable anti‐aging performance and excellent chemical compatibility with commercially available polymers. This Review briefly outlines the state‐of‐the‐art in MOF‐MMM fabrication, and the more recent use of POFs and molecular additives.
Challenging separations: The need for greater energy efficiency and the maximum use of limited resources has focused attention on improved separation technologies. For gas separations, mixed‐matrix membranes can provide enhanced separation performance and lead to more energy‐efficient, sustainable, and cost‐effective commercial applications.
This review summarizes the use of metallocene complexes and related compounds as catalysts in the dimerization or oligomerization of olefins (alkenes) or terminal acetylenes (alkynes) and in the ...dehydrocoupling/dehydrooligomerization of silanes. Metallocene complexes of group-III metals (scandocenes, yttrocenes, lanthanocenes), lanthanoids (neodymocenes) and group-IV metals (titanocenes, zirconocenes, hafnocenes) have been utilized in the selective (co-/hydro-)oligomerization of ethene, of the α-olefins propene, 1-butene, 1-pentene, 1-hexene, 1-heptene, and 1-octene, of branched olefins, e.g. methyl-butenes, methyl-pentenes and styrene, of cycloolefins, e.g. cyclopentene and norbornene and of α, ω-dienes, e.g. 1,5-hexadiene and 1,7-octadiene. Group-III metallocenes are often active in the C–C coupling without a cocatalyst; group-IV metallocenes require the help of a cocatalyst, such as methylalumoxane, MAO, aluminum alkyls, e.g. Al
i
Bu
3, or perfluorated boranes, e.g. B(C
6F
5)
3. The actinoid metallocenes (C
5M
5)
2AnMe
2 with An
=
thorium, uranium allow for the dimerization and oligomerization of terminal acetylenes. The dehydrooligomerization of (hydro)silanes is typically achieved by group-IV metallocene chlorides together with
n-butyl lithium. Also included in this review are related sandwich and half-sandwich (mono-cyclopentadienyl) complexes used for olefin oligomerization. The related sandwich complexes feature phospholyl, boratabenzene or carboranate ligands. Methods of oligo–olefin analyses by gel permeation chromatography (GPC),
1H NMR spectroscopy, gas chromatography (GC) or viscosity measurements for molecular weight determinations and by
1H and
13C NMR spectroscopy or MALDI–TOF mass spectrometry for end group structure determinations are summarized. Possible applications of olefin oligomers, in particular oligopropenes are presented. The functionality of a double bond at the end of each chain (for further modifications) together with the product homogeneity are the advantages of oligomers from metallocene catalysis. In addition, olefin oligomerization is used to study mechanistic aspects and to obtain a better insight into the reaction mechanism of metallocene polymerization catalysis because of the homogeneity of the reaction mixture and because certain mechanistic aspects are easier to investigate in oligomeric products than in high-molar-mass polymers.
The adsorption of water vapor in the highly porous metal‐organic framework (MOF) of 3D‐Cr3F(H2O)2O(bdc)3·~25H2O (MIL‐101) (bdc = benzene‐1,4‐dicarboxylate, terephthalate) of up to 1 g of water per ...gram of sorbent material (between 140 °C and 40 °C under a water vapor pressure of 5.6 kPa) together with the stability over several cycles makes MIL‐101 the most promising material, so far, for heat transformation applications like thermally driven heat pumps or adsorption chillers.
A new application for MOFs – heat transformation and adsorption chilling: MIL‐101 is one of the most promising water sorbent materials for heat‐transformation applications known so far, as 1 g adsorbs up to 1 g of water and is stable even over several cycles.
MOFs for Use in Adsorption Heat Pump Processes Henninger, Stefan K.; Jeremias, Felix; Kummer, Harry ...
European journal of inorganic chemistry,
June 2012, Volume:
2012, Issue:
16
Journal Article
Peer reviewed
Thermally driven heat pumps can significantly help to minimize primary energy consumption and greenhouse gas emissions generated by industrial or domestic heating and cooling processes. This is ...achieved by using solar or waste heat as the operating energy rather than electricity or fossil fuels. One of the most promising technologies in this context is based on the evaporation and consecutive adsorption of coolant liquids, preferably water, under specific conditions. The efficiency of this process is first and foremost governed by the microporosity, hydrophilicity, and hydrothermal stability of the sorption material employed. Traditionally, inorganic porous substances like silica gel, aluminophosphates, or zeolites have been investigated for this purpose. However, metal–organic frameworks (MOFs) are emerging as the newest and by far the most capable class of microporous materials in terms of internal surface area and micropore volume as well as structural and chemical variability. With further exploration of hydrothermally stable MOFs, a large step forward in the field of sorption heat pumps is anticipated. In this work, an overview of the current investigations, developments, and possibilities of MOFs for use in heat pumps is given.
This review introduces metal–organic frameworks (MOFs) as a promising new class of microporous materials for use in adsorption heat transformation applications. The water adsorption characteristics of several MOFs are summarized, including heat of adsorption and cycle stability, which show the tremendous potential of MOFs in thermally driven heat pumps.
Herein, we report a pre‐synthetic pore environment design strategy to achieve stable methyl‐functionalized metal–organic frameworks (MOFs) for preferential SO2 binding and thus enhanced low (partial) ...pressure SO2 adsorption and SO2/CO2 separation. The enhanced sorption performance is for the first time attributed to an optimal pore size by increasing methyl group densities at the benzenedicarboxylate linker in Ni2(BDC‐X)2DABCO (BDC‐X=mono‐, di‐, and tetramethyl‐1,4‐benzenedicarboxylate/terephthalate; DABCO=1,4‐diazabicyclo2,2,2octane). Monte Carlo simulations and first‐principles density functional theory (DFT) calculations demonstrate the key role of methyl groups within the pore surface on the preferential SO2 affinity over the parent MOF. The SO2 separation potential by methyl‐functionalized MOFs has been validated by gas sorption isotherms, ideal adsorbed solution theory calculations, simulated and experimental breakthrough curves, and DFT calculations.
A pre‐synthetic pore environment tailoring strategy has been applied to improve low‐pressure SO2 affinity on stable isostructural methyl‐functionalized MOFs by controlling methyl groups density. Enhanced low‐pressure SO2 uptake and SO2 separation was achieved. This work provides a facile strategy to obtain tailor‐made MOF adsorbents for challenging gas purification applications.
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