Synthesis of plasmonic Fe/Al nanoparticles in ionic liquids.

Bottom-up and top-down approaches are described for the challenging synthesis of Fe/Al nanoparticles (NPs) in ionic liquids (ILs) under mild conditions. The crystalline phase and morphology of the metal nanoparticles synthesized in three different ionic liquids were identified by powder X-ray diffractometry (PXRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), selected-area electron diffraction (SAED) and fast Fourier transform (FFT) of high-resolution TEM images. Characterization was completed by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) for the analysis of the element composition of the whole sample consisting of the NPs and the amorphous background. The bottom-up approaches resulted in crystalline FeAl NPs on an amorphous background. The top-down approach revealed small NPs and could be identified as Fe4Al13 NPs which in the IL [OPy][NTf2] yield two absorption bands in the green-blue to green spectral region at 475 and 520 nm which give rise to a complementary red color, akin to appropriate Au NPs.

Acetylenedicarboxylate and In Situ Generated Chlorofumarate-Based Hafnium(IV)-Metal-Organic Frameworks: Synthesis, Structure, and Sorption Properties.

New acetylenedicarboxylate (ADC) and chlorofumarate (Fum-Cl) based hafnium-metal-organic frameworks have been synthesized by alternatively reacting acetylenedicarboxylic acid in DMF or water with appropriate hafnium salt, in the presence of acetic acid modulator. The two materials of respective ideal formulas [Hf6O4(OH)4(ADC)6] (Hf-HHU-1) and [Hf6O4(OH)4(Fum-Cl)6] (Hf-HHU-2) have been structurally characterized by powder X-ray diffraction to be UiO-66 isostructural, consisting of octahedral [Hf6O4(OH)4]12+ secondary building units each connected to other units by 12 ADC or Fum-Cl linkers into a microporous network with fcu topology. This structure was confirmed by Rietveld refinement. Hf-HHU-2 is formed by in situ hydrochlorination of acetylenedicarboxylic acid to chlorofumarate. Its presence has been determined by combined Raman spectroscopy, solid-state NMR, scanning electron microscopy, energy dispersive X-ray and X-ray photoelectron spectroscopies. Hf-HHU-1 and Hf-HHU-2 exhibit very high hydrophilicity as revealed by their water sorption profiles, meanwhile Hf-HHU-2 adsorbs CO2 with an isosteric heat of 39 kJ mol-1. Hf-HHU-2 also adsorbs molecular iodine vapor exclusively as polyiodide anions due to grafted chloro-functions on the pores surface. It has been observed that defective nanodomains with reo tolopology can be introduced in the structure of Hf-HHU-2 by variation of the linker to metal-salt molar ratio.

Aggregation control of Ru and Ir nanoparticles by tunable aryl alkyl imidazolium ionic liquids.

Metal-nanoparticles (M-NPs) were synthesized in a wet-chemical synthesis route in tunable aryl alkyl ionic liquids (TAAILs) based on the 1-aryl-3-alkyl-substituted imidazolium motif from Ru3(CO)12 and Ir4(CO)12 by microwave-heating induced thermal decomposition. The size and size dispersion of the NPs were determined by transmission electron microscopy (TEM) to an average diameter of 2.2(±0.1) to 3.9(±0.3) nm for Ru-NPs and to an average diameter of 1.4(±0.1) to 2.4(±0.1) nm for Ir-NPs. The TAAILs used contain the same bis(trifluoromethylsulfonyl)imide anion but differ in the substituents on the 1-aryl ring, e.g. 2-methyl-, 4-methoxy- and 2,4-dimethyl groups and in the 3-alkyl chain lengths (C4H9, C5H11, C8H17, C9H19, C11H23). All used TAAILs are suitable for the stabilization of Ru- and Ir-NPs over months in the IL dispersion. Different from all other investigations on M-NP/IL systems which we are aware of the particle separation properties of the TAAILs vary strongly as a function of the aryl substituent. Good NP separation can be achieved with the 4-methoxyphenyl- and 2,4-dimethylphenyl-substituted ILs, irrespective of the 3-alkyl chain lengths. Significant aggregation can be observed for 2-methylphenyl-substituted ILs. The good NP separation can be correlated with a negative electrostatic potential at the 4-methoxyphenyl or 4-methylphenyl substituent that is in the para-position of the aryl ring, whereas the 2-(ortho-)methylphenyl group assumes no negative potential. ε-ePC-SAFT calculations were used to validate that the interactions between ILs and the washing agents (required for TEM analyses) do not cause the observed aggregation/separation behaviour of the M-NPs. Ru-NPs were investigated as catalysts for the solvent-free hydrogenation of benzene to cyclohexane under mild conditions (70 °C, 10 bar) with activities up to 760 (mol cyclohexane) (mol Ru)-1 h-1 and over 95% conversion in ten consecutive runs for Ru-NPs. No significant loss of catalytic activity could be observed.

Synthesis of rare-earth metal and rare-earth metal-fluoride nanoparticles in ionic liquids and propylene carbonate.

Decomposition of rare-earth tris(N,N'-diisopropyl-2-methylamidinato)metal(III) complexes [RE{MeC(N(iPr)2)}3] (RE(amd)3; RE = Pr(III), Gd(III), Er(III)) and tris(2,2,6,6-tetramethyl-3,5-heptanedionato)europium(III) (Eu(dpm)3) induced by microwave heating in the ionic liquids (ILs) 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]), 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIm][NTf2]) and in propylene carbonate (PC) yield oxide-free rare-earth metal nanoparticles (RE-NPs) in [BMIm][NTf2] and PC for RE = Pr, Gd and Er or rare-earth metal-fluoride nanoparticles (REF3-NPs) in the fluoride-donating IL [BMIm][BF4] for RE = Pr, Eu, Gd and Er. The crystalline phases and the absence of significant oxide impurities in RE-NPs and REF3-NPs were verified by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED) and high-resolution X-ray photoelectron spectroscopy (XPS). The size distributions of the nanoparticles were determined by transmission electron microscopy (TEM) and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) to an average diameter of (11 ± 6) to (38 ± 17) nm for the REF3-NPs from [BMIm][BF4]. The RE-NPs from [BMIm][NTf2] or PC showed diameters of (1.5 ± 0.5) to (5 ± 1) nm. The characterization was completed by energy-dispersive X-ray spectroscopy (EDX).

Realizing the Potential of Acetylenedicarboxylate by Functionalization to Halofumarate in ZrIV Metal-Organic Frameworks.

A strategy was developed to obtain from acetylenedicarboxylic acid either an acetylenedicarboxylate-based ZrIV metal-organic framework (MOF) with fcu topology or a halo-functionalized-MOF-801 through in situ ligand hydrohalogenation. The new materials feature exceptionally high hydrophilicity and CO2 /H2 adsorption energetics. The acetylenedicarboxylate linker and its functionalizable triple-bond discloses its potential in the engineering of microporous materials with targeted properties.