Low-Dimensional Magnetism in Multivariate Copper/Zinc MOF-74 Materials Formed via Different Mechanochemical Methods

MOF-74 is an archetypal magnetic metal−organic framework (MOF) family, with metal nodes bridged by 2, 5-dioxido-1, 4-benzenedicarboxylic acid (H4dobdc) and arranged into one of the simplest representations of the 1D Ising magnetic model. Recently, a novel mechano-synthetic approach opened a pathway toward a series of bimetallic multivariate (1:1) M1M2-MOF-74 materials, with the uniform distribution of metal cations in the oxometallic chains, offering a unique opportunity to investigate low-dimensional magnetism in these heterometallic MOFs. We explore here how different mechanochemical procedures affect the interaction between the metal nodes of the model system of three multivariate copper(II)/zinc(II)-MOF-74 materials, two of which were obtained through a template-controlled procedure, and the third one was obtained by recently developed mechanical MOF-alloying combined with subsequent accelerated aging. While the three Cu/Zn-MOF-74 products have almost identical powder X-ray diffraction (PXRD) diffractograms and Fourier transform infrared spectra, they differ significantly in their magnetic properties, as revealed through detailed magnetization and X-band and multifrequency high-field electron spin resonance measurements. The magnetic results of the three multivariate Cu/Zn-MOF-74s were compared to the properties of the monometallic Cu-MOF-74, which shows antiferromagnetic intrachain and weaker ferromagnetic interchain interactions. Energy-dispersive X-ray spectroscopy/scanning electron microscopy and solid-state nuclear magnetic resonance spectroscopy helped rationalize the observed differences in magnetization, and in situ synchrotron PXRD monitoring of template-controlled MOF formation revealed different reaction pathways when using the zinc or copper intermediates, involving even the fleeting occurrence of a rare MOF-74 polymorph

Tuning size and properties of zinc ascorbate metal-organic framework via acid modulation

One of the biggest advantages of MOFs is the possibility of modifying their properties and tuning their inherent activity (i.e., sorption, storage, catalytic activity etc.). Textural properties can be tuned by manipulating process and compositional parameters, among which, the effect of additives can be even further distinguished among them based on the way they affect these properties. Beyond the effect that additives have on the size and morphology of nanoMOFs, there is also an effect on properties via creating point defects—missing linker and missing node defects. In this study, we investigated the effect of four monotopic acid modulators—formic, acetic, dichloroacetic and propionic acid, their concentration and the heating type (conventional and microwave—MW) on the size, morphology and textural properties of a recently discovered bioNICS1. It was confirmed that the proposed seesaw model for the controlled size of nanoMOF crystals is less applicable in the case of MW-assisted synthesis, in comparison to conventional heating. In the case of formic acid- and propionic acid-modified materials, we demonstrated that the type of additive plays a different role in crystal growth and generation of defects, implying high tunability being crucial for a material’s structure–property performance optimization

Unraveling the arrangement of Al and Fe within the framework explains the magnetism of mixed-metal MIL-100(Al,Fe)

Properties of mixed-metal MOFs depend on the distribution of different metals within their frameworks. Determination of this distribution is often very challenging. Using an example of aluminum- and iron-containing MIL-100, we demonstrate that 27Al NMR spectroscopy, when combined with first-principles calculations and magnetic, X-band electron paramagnetic resonance, Fe K-edge extended X-ray absorption fine structure, and Mössbauer measurements, enables one to accurately determine the arrangement of Al and Fe within the metal trimers, which are the basic building units of MIL-100. In this particular material, the incorporation of Fe and Al on the framework metal sites is random. Crucial for deciphering the arrangement is detecting NMR signals, shifted because of the strong hyperfine interaction between the 27Al nuclei and the unpaired electronic spins of Fe3+ ions, assigning the shifted signals aided by first-principles calculations of hyperfine couplings, and quantitatively evaluating the NMR intensities and the measured effective magnetic moment

Bifunctional Imidazolium/Amine Polymer Foams: One-pot Synthesis and Synergistic Promotion of CO2 Sorption

peer reviewedAmines and imidazolium are well-known functional groups in carbon dioxide capture applications because of their excellent interactions with CO2, but their combination and possible synergistic effects when combined in polymer foams have not yet been considered. This work reports an innovative one-pot water-mediated synthesis of bifunctional imidazolium/amine microcellular polymer foams containing tunable ratios of these functions by combining the Radziszewski multicomponent reaction and high internal phase emulsion (HIPE) polymerization in a one-pot manner. The resulting polymer foams have unique textural and structural properties exhibiting rapid CO2 sorption kinetics with good capacities and excellent ability to selectively capture CO2 from the gas mixture in spite of their low specific surface. The bifunctional amine/imidazolium foams showed superior CO2 capture performances compared to their monofunctional counterparts, indicating the synergy between the functional groups. Comparison with the corresponding non-porous bulk materials also proved that the imidazolium/amine bifunctionality must be incorporated in a highly porous morphology to beneficiate from efficient and fast CO2 uptake. The marked influence of both the amine/imidazolium ratio and the nature of the imidazolium counteranion on CO2 capture capacity under dry and humid conditions is demonstrated, as well as the outstanding multicyclic capture performance

On the mechanism of visible-light accelerated methane dry reforming reaction over Ni/CeO[sub](2-x) catalysts

The methane dry reforming reaction (DRM) converts methane and CO2 into syngas, a mixture of H2 and CO. When illuminated by 790 mW cm−2 of white light, the 2Ni/CeO2−x catalyst converts CH4 and CO2 beyond thermodynamic equilibrium, while the energy efficiency reaches 33%. The DRM reaction is sustained in a purely photocatalytic mode without external heating, yielding CH4 and CO2 rates of 0.21 and 0.75 mmol (gcat • min)−1, respectively. Theoretical analysis of Ni/CeO2−x optical properties agrees with in-situ UV-Vis DRS results and reveals partly reduced Ce3+ sites crucial for extending the optical absorption of Ni/CeO2−x into the visible light range. Two photocatalytic mechanisms are postulated to occur: the hot charge-carrier driven photocatalytic mechanism and the near-field induced resonant energy transfer, depending on the energy of photons used to stimulate the catalyst. This work identifies sub-stoichiometric Ni/CeO2−x as highly efficient for boosting methane activation by visible light under mild conditions

Réactions multicomposants en emulsion : synthèse de poly(liquide ionique)s macroporeux pour la catalyse et la capture de CO2

The abstract is provided as supporting informatio

New insights into manganese local environment in MnS-1 nanocrystals

Manganese plays an important role in redox catalysis using zeolites as inorganic support materials, but the formation of the preferred redox manganese species (framework or extraframework) is still not well understood. Herein, the influence of the amount of manganese together with conventional and microwave-assisted hydrothermal synthesis paths on the formation of manganese species within the zeolite silicalite-1 (S-1) with MFI structure was investigated. It was found out that both synthesis procedures led to the formation of frameworkand extraframework manganese species, but in different molar ratios. However, theconventional synthesis procedure with all Mn/Si molar ratios generates moreframework Mn in comparison to the microwave procedure. Additionally, thediminution of the zeolite crystals to nanoscale from 100 to 200 nm was achievedvia the conventional procedure for the first time. UV−vis, Raman, and X-rayabsorption spectroscopic analyses revealed different local environments ofmanganese: Mn$^{3+}$ incorporated into the silicalite-1 framework as “frameworkmanganese” and Mn$^{2+/3+}$ present as “extraframework manganese” (Mn$_2$O$_3$, Mn$_3$O$_4$). TEM reveals the presence of Mn$_3$O$_4$nanorods. Both framework manganese and extraframework manganese exhibit good catalytic activity for styrene epoxidation.Catalytic results suggest that, in oxidation reactions of hydrocarbons, framework manganese is more active at lower Mn contents(Mn/Si 0.015)