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Na[Al(CH3NHBH3)4] and an intermediate Na[AlH(CH3NHBH3)3] were synthesized by ball milling. Na[Al(CH3NHBH3)4] + 12NaH/6NaNH2 released pure hydrogen at moderate temperatures, making this and similar systems interesting candidates for H-storage.

A highly complicated structure of Mg(en)1.2(BH4)2 was solved from single crystal synchrotron X-ray diffraction, the new Mg(en)2(BH4)2 was shown to be its decomposition intermediate. The role of less reactive amorphous Mg(BH4)2 was demonstrated.

The first mesoporous bimetallic Ti

The dinuclear compound [Co2(Hatzc)2(H2O)6](NO3)2·4H2O containing the polytopic ligand Hatzc‒ = 3-amino-4H-1,2,4-triazole-5-carboxylate was synthesized and characterized. Single-crystal X-ray diffraction showed that two monoanionic N,O-chelating Hatzc‒ ligands bridge two Co(II) ions in a µ-N1,N2 fashion. Both Co(II) centers are further coordinated by three H2O ligands making up an octahedral coordination. A complex network of intra- and intermolecular O‒H···O and N‒H···O hydrogen bonding interactions characterize the structure. Hirshfeld surface analysis, ATR–FTIR, and FT-Raman spectroscopy in combination with density functional theory (DFT) calculation of vibrational modes confirm this multitude of H bonds. Thermogravimetric and differential thermal analysis experiments under an argon atmosphere in the temperature range of 25–900 °C showed thermal stability till about 100 °C and multi-step decomposition yielding Co2O3 at about 280 °C. The octahedral environment of Co(II) was confirmed by UV–vis absorption spectroscopy, which shows weak absorption bands at around 520 nm assignable to electronic d‒d transitions alongside with π‒π* transitions dominating the 250–350 nm range. Time-dependent DFT calculated excited states agree very well in terms of energy match with the observed transitions. The direct and indirect optical band gap values were determined using the Tauc plot method to 3.33 eV and 2.75 eV, respectively, indicating semiconducting properties.

MIL 100(Al) and MIL 101(Al) are two related and particularly interesting mesoporous aluminium-based metal-organic frameworks (MOFs) that are able to adsorb and encapsulate a large panel of molecules and catalyse a wide range of reactions. Furthermore, they can be functionalized in many ways, or transformed into oxide or carbonaceous materials with interesting properties. In this review, we first cover various synthetic methods used for selectively obtaining those MOFs in a pristine state, including formation mechanisms and thermodynamic considerations. Then, the main applications of those materials, including catalysis, gas storage and adsorption of various chemical species, are addressed. Post-functionalization and encapsulation strategies to obtain MOF materials with improved properties are also discussed, as well as the advantages of such hybrid materials over the pristine MOFs. Furthermore, we describe synthetic methods for obtaining (doped) aluminium oxides and carbon materials from MIL 100(Al) and MIL 101(Al), together with their applications. By summarizing the main findings concerning those two particular MOFs and their derivatives, together with some pitfalls to avoid when characterizing them, we highlight unaddressed challenges and provide directions for future research.

Recently metal organic frameworks (MOFs), already known as adsorbent materials, have gained increasing research interest in thermal energy storage and conversion. MOF-water working pairs have been envisaged to provide the next revolutionary advancement in the existing sorption-based thermal energy storage and conversion systems. Herein, a promising MOF for high water sorption, MIL–100(Fe), and its transition metal-doped (Ni2+ and Co2+) derivatives are produced following a green synthesis procedure. The synthesized materials were tested in water sorption measurements using a thermogravimetric technique. The experimentally obtained adsorption data were correlated with the Sun-Chakraborty adsorption isotherm model. As an example of thermal energy conversion, an adsorption chiller is considered, and hence cooling cycles were drawn using the sorption data. The cooling cycles revealed that the nickel-doped MIL–100(Fe) demonstrates the highest value of the specific cooling effect (450.79 kJ kg−1) among the studied MOFs. Inverse gas chromatography technique was employed to investigate the surface free energy of the parent and doped MIL–100(Fe) MOFs. It was found that nickel-doped MIL–100(Fe) had the highest total surface free energy of 105.41 mJ m−2. Surfaces’ Lewis acid-base activities and the work of cohesion and adhesion (towards water molecules) were investigated. The surfaces’ properties were correlated with the water adsorption isotherms, which can provide crucial information for developing optimal adsorbents targeting water as the adsorbate for an efficient and effective thermal energy storage and conversion system.

Iron(III) carboxylate based metal organic frameworks (MOFs)/porous coordination polymers (PCPs) have sparked great interest owing to their high structural diversity and tunable porosity, excellent stability, tailored functionality and their scalability as well as green synthesis associated with their biocompatible and biodegradable character. Herein, we present a new robust Fe(III) based PCP (labelled MIL-178(Fe)) built up from chains of corner sharing Fe octahedra interconnected by 1,2,4-benzene tricarboxylic acid, delimiting one dimensional narrow pore channels (pore diameter < 4.5 Å) decorated with polar groups (μ2-OH and –CO2H functions). These structural and chemical features are suitable for the selective adsorption of CO2. MIL-178(Fe) was synthesized following a simple and green protocol in water under near ambient conditions using non-toxic reactants, allowing the production of sub-micrometer sized MIL-178(Fe) particles in a large amount (30 g). As shown by single-gas isotherms and CO2/N2 co-adsorption experiments as well as molecular simulations, this material exhibits a moderate CO2 capacity at low pressure but a high CO2/N2 selectivity. This is fully consistent with the presence of μ2-OH groups acting as CO2 adsorption sites, as revealed from both molecular simulations and in situ PXRD experiments. Finally, the good compatibility of this MOF with the elastomer block copolymer Pebax®-3533 allowed the processing of homogeneous and defect-free mixed matrix membranes with a MIL-178(Fe) loading of up to 25 wt% that outperformed pure Pebax®-3533 membranes for CO2/N2 separation., We acknowledge the European Community Seventh Framework Program (FP7/2007-2013) for funding the research presented in this article under Grant Agreement No. 608490 (Project M4CO2). The computational work was performed using HPC resources from GENCI-CINES (Grant A0100907613).

The first mesoporous bimetallic TiIII/Al metal-organic framework (MOF) containing amine functionalities on its linkers has been selectively obtained by converting the cheap commercially available (TiCl3)3AlCl3 into Ti3-xAlxCl3(THF)3 and reacting this complex with 2-aminoterephthalic acid in DMF under soft solvothermal conditions. This compound is structurally related to the previously described NH2-MIL-101(M) (M = Cr, Al and Fe) MOFs. Thermal gravimetric analyses and in situ PXRD measurements demonstrated that this highly air-sensitive TiIII-containing MOF is structurally stable up to 200°C. Nuclear magnetic resonance (NMR) spectroscopy, elemental and inductively-coupled plasma (ICP) analyses revealed that NH2-MIL-101(TiIII) contains trinuclear Ti3(μ3-O)Cl(DMF)2(RCOO)6 clusters with strongly bound DMF molecules, and a small amount of aluminum. Sorption experiments reveal a higher affinity of this MOF for hydrogen compared to the previously described monometallic unfunctionalized MIL-101(TiIII) MOF.

The metal sites of MIL-100(Fe), MIL-100(Fe,Al), and MIL-100(Al) metal-organic frameworks (MOFs) were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierarchized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule in each trimeric Al

The metal sites of MIL-100(Fe), MIL-100(Fe,Al) and MIL-100(Al) MOFs were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierachized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule by trimeric Al3O cluster unit, whereas the two other aluminium sites are occupied by an hydroxyl and a water molecule. The -NH2 sites of the grafted ethylenediamine can be used for further post-functionalization through amine chemistry and is responsible for basicity of the functionalized material. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity and for a unique carbon dioxide sorption mecanism, that distinguishes this material from its iron and chromium counterparts.

The metal sites of MIL-100(Fe), MIL-100(Fe,Al), and MIL-100(Al) metal-organic frameworks (MOFs) were decorated with ethylenediamine (EN). Interestingly, the Al-containing MOFs presented hierarchized porosity, and their structural integrity was maintained upon functionalization. Solution and solid-state NMR confirmed the grafting efficiency in the case of MIL-100(Al) and the presence of a free amine group. It was shown that MIL-100(Al) can be functionalized by only one EN molecule in each trimeric Al3O cluster unit, whereas the other two aluminum sites are occupied by a hydroxyl and a water molecule. The -NH2 sites of the grafted ethylenediamine can be used for further postfunctionalization through amine chemistry and are responsible for the basicity of the functionalized material as well as increased affinity for CO2. Furthermore, the presence of coordinated water molecules on the Al-MOF is responsible for simultaneous Brønsted acidity. Finally, the Al-containing MOFs show an unusual carbon dioxide sorption mechanism at high pressures that distinguishes those materials from their iron and chromium counterparts and is suspected to be due to the presence of polarized Al-OH bonds.

Metal–organic frameworks (MOFs) are recognized as ideal candidates for many applications such as gas sorption and catalysis. For a long time the properties of these materials were thought to essentially arise from their well-defined crystal structures. It is only recently that the importance of structural defects for the properties of MOFs has been evidenced. In this work, salt-assisted and liquid-assisted grinding were used to introduce defects in a copper-based MOF, namely HKUST-1. Different milling times and post-synthetic treatments with alcohols allow introduction of defects in the form of free carboxylic acid groups or reduced copper(I) sites. The nature and the amount of defects were evaluated by spectroscopic methods (FTIR, XPS) as well as TGA and NH3 temperature-programmed desorption experiments. The negative impact of free –COOH groups on the catalytic cyclopropanation reaction of ethyl diazoacetate with styrene, as well as on the gravimetric CO2 sorption capacities of the materials, was demonstrated. The improvement of the catalytic activity of carboxylic acid containing materials by the presence of CuI sites was also evidenced.

In this study we present the crystal structure, spectroscopic and thermal behavior, Hirshfeld surface analysis, and DFT calculations of a new organic-inorganic hybrid compound (C7H8N3)2[CoCl4]. This compound crystallizes in the centrosymmetric space group P 1 ¯ . Single-crystal X-ray diffraction analysis indicates that structure consists of a succession of mixed layers formed by organic cations and inorganic anions parallel to the (001) plane and propagate according to the c-axis. Layers further are assembled into a 3D supramolecular architecture through N-H…Cl hydrogen bonds and π…π interactions. The peak positions of the experimental PXRD pattern are in agreement with the simulated ones from the crystal structure, indicating phase purity of the title compound. The presence of the different functional groups and the nature of their vibrations were identified by ATR-FTIR and FT-Raman spectroscopies. The tetrahedral environment of Co2+ was confirmed by UV–visible spectroscopy, where the spectrum shows three weak absorption bands in the visible range due to d-d electronic transitions 4A2(F) → 4T2(F), 4A2(F) → 4T1(F) and 4A2(F) → 4T1(P) typical of Co(II) coordination compounds. The direct and indirect optical band gap values were determined by Tauc method. The optimized structure and calculated vibrational frequencies were obtained by density functional theory (DFT) using B3LYP functional. TGA and DSC coupled to mass spectrometry (MS) experiments under argon atmosphere in the temperature range (25–950 °C) were carried out in order to determine the thermal stability of the title compound.

Here we present a scalable and green methodology to synthesize a large variety of MIL-100(Fe,M), metal-doped iron-based MOFs with high thermal stability and surface areas. Our synthesis is performed at room temperature in aqueous media and can be applied to doping with p-, d- and f-elements in oxidation states from +I to +V, therefore being highly general. The influence of the doping metal nature on the thermal and textural properties is systematically investigated. We show that large differences between the ionic radius of the doping and the templating metals does not lead to phase segregation. The incorporation of Cu(I) drastically lowers the thermal stability of MIL-100(Fe,Cu), while the incorporation of V, Al and Ti induces the formation of mesopores. Finally, we developed a PXRD-based method that can be combined with TGA to easily access the metal ratios in complex mixed-metal MOFs.

The most common methods to evaluate hydrogen sorption (volumetric and gravimetric) require significant experience and expensive equipment for providing reproducible results. Both methods allow one to measure excess uptake values which are used to calculate the total amount of hydrogen stored inside of a tank as required for applications. Here we propose an easy to use and inexpensive alternative approach which allows one to evaluate directly the weight of hydrogen inside a material-filled test tank. The weight of the same tank filled with compressed hydrogen in the absence of loaded material is used as a reference. We argue that the only parameter which is of importance for hydrogen storage applications is by how much the material improves the total weight of hydrogen inside of the given volume compared to compressed gas. This parameter which we propose to name Gain includes both volumetric and gravimetric characterization of the material; it can be determined directly without knowing the skeletal volume of the material or excess sorption. The feasibility of the Gravimetric Tank (GT) method was tested using several common carbon and Metal Organic Framework (MOF) materials. The best Gain value of ∼12% was found for the Cu-BTC MOF which means that the tank completely filled with this material stores a 12% higher amount of hydrogen compared to H2 gas at the same P-T conditions. The advantages of the GT method are its inexpensive design, extremely simple procedures and direct results in terms of tank capacity as required for industrial applications. The GT method could be proposed as a standard check for verification of the high hydrogen storage capacity of new materials. The GT method is expected to provide even better accuracy for evaluation of a material's performance for storage of denser gases like e.g. CO2 and CH4.

Polyamidoamine (PAMAM) dendrimers were covalently immobilized on multi-walled carbon nanotubes (MWNT) by two "grafting to" strategies. We demonstrate the existence of non-covalent interactions between the two components but outline the superiority of our two grafting approaches, namely xanthate and click chemistry. MWNT surfaces were functionalized with activated ester and propargylic moieties prior to their reaction with PAMAM or azido-PAMAM dendrimers, respectively. The grafting of PAMAM generations 0 to 3 was evaluated with X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). The versatility of our hybrids was demonstrated by post-functionalization sequences involving copper alkyne-azide cycloaddition (CuAAC). We synthesized homogeneous supported iridium complexes at the extremities of the dendrimers. In addition, our materials were used as templates for the encapsulation of Pd nanoparticles (NPs), validating our nanocomposites for catalytic applications. The palladium-based catalyst was active for carbonylative coupling over five consecutive runs without loss of activity.