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Covalent organic frameworks (COFs) have been used in cell imaging, but very rarely for imaging specific cell conditions. Herein, a β-ketoenamine-based fluorescent COF was post-synthetically modified to incorporate a hypoxia-targeting molecule. Fluorescence microscopy imaging shows that the material discriminates between HeLa cells grown under hypoxia and those cultured under normoxia.

A new type of hybrid compound, combining properties of MOFs and borohydrides, was synthesized solvothermally using Mg(BH4)2 and imidazole as precursors. Material in the form of acetonitrile solvate with formula [Mg3{(Im)BH2(Im)}6(ImH)6] ·CH3CN crystallizes in the space group R¯3, having the unit cell parameters a = 15.1942(2)˚A and c = 28.3157(3)˚A as determined by single crystal X-ray diffraction. The structure was further investigated by solid state NMR and DFT quantum chemical calculations. The main feature of the structure, reported here for the first time, is a linear trinuclear complex, where octahedrally nitrogen-coordinated Mg2+ ions are bridged with {(Im)BH2(Im)}– units, forming inside voids of 4.6˚A in diameter between the magnesium ions. Polar intermolecular interactions hold the molecules in a dense 1 Page 1 of 32 ACS Paragon Plus Environment Submitted to Inorganic Chemistry 123456789 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 rhombohedral stacking, where a disordered acetonitrile molecule plays a cohesive role. The compound is stable in air and upon heating to about 160 ◦C. Using an alternative synthesis method from imidazole melt, an imidazole solvate with the formula [Mg3{(Im)BH2(Im)}6(ImH)6] ·ImH and a very similar crystal structure to acetonitrile solvate was prepared. It is stable up to 220 ◦C. Upon further heating, it transformed into a layered structure with the formula Mg(Im3BH)2, space group P¯31c, and unit cell parameters a = 8.7442(4)˚A, c = 17.643(2)˚A determined by synchrotron powder diffraction. Besides its structural novelty, two types of potentially reactive hydrogens, bonded to boron and nitrogen in the same molecule, make the material highly interesting for future investigations in the fields of energy storage applications.

On supercooling a liquid, the viscosity rises rapidly until at the glass transition it vitrifies into an amorphous solid accompanied by a steep drop in the heat capacity. Therefore, a pure homogeneous liquid is not expected to display more than one glass transition. Here we show that a family of homogeneous non-polymeric liquids—titanium tetraalkoxides—do exhibit two calorimetric glass transitions of comparable magnitude, one of which is the conventional glass transition associated with dynamic arrest of the bulk liquid properties, while the other is associated with the freezing out of intramolecular degrees of freedom. Such intramolecular vitrification is likely to be found in molecules in which low-frequency terahertz intramolecular motion is strongly coupled to the surrounding liquid.

Enlarging the quantum coherence times and gaining control over quantum effects in real systems are fundamental for developing of quantum technologies. Molecular electron spin qubits are particularly promising candidates for the realization of quantum information processing due to their modularity and tunability, but there is a constant search for tools to increase their quantum coherence times. Here we present how mechanochemical dilution of active spin qubits in the diamagnetic zirconium-MOF matrix, in synergy with controlled encapsulation of fullerene guest, results in a significant increase in relaxation times and better qubit performances of the moderately porous MOF qubit array candidate. 10% diluted copper(II)-porphyrins as potential molecular spin qubits were incorporated in polymorphic PCN-223 and MOF- 525. Spin properties of this hybrid molecular spin qubit frameworks were studied by continuous-wave and pulse electron spin resonance/electron paramagnetic resonance (ESR/EPR) spectroscopy, showing that both spin-lattice and phase memory electron spin relaxation times, T1 and Tm, respectively, increased by the encapsulation of fullerene molecules into the MOF matrix. Specifically, PCN-223 with a larger filling of fullerene shows better performance in both relaxation times compared with the previously surpassing MOF-525 molecular spin qubit framework.

The stellar optoelectronic properties of metal halide perovskites provide enormous promise for next-generation optical devices with excellent conversion efficiencies and lower manufacturing costs. However, there is a long-standing ambiguity as to whether the perovskite surface/interface (e.g. structure, charge transfer or source of off-target recombination) or bulk properties are the more determining factor in device performance. We fabricated an array of CsPbI3 crystal and hybrid glass composites by sintering and globally visualised the property-performance landscape. Our findings reveal that the interface is the primary determinant of the crystal phases, optoelectronic quality, and stability of CsPbI3. In particular, the presence of a diffusion "alloying" layer is discovered to be critical for passivating surface traps, and beneficially altering the energy landscape of crystal phases. However, high-temperature sintering results in the promotion of a non-stoichiometric perovskite and excess traps at the interface, despite the short-range structure of halide is retained within the alloying layer. By shedding light on functional hetero-interfaces, our research offers the key factors for engineering high-performance perovskite devices.

The catalytic shuttling of functional moieties has emerged as a promising strategy to substitute and diversify traditional hydrofunctionalization technologies. However, these reactions are reversible due to their isodesmic nature, which limits their applicability to a select array of donor and acceptor molecules, and poses significant challenges with regard to atom economy and practicality. Herein we show a new approach that harnesses the shape-selective and catalytic properties of zeolites to drive the shuttling equilibrium to near-completion. This strategy is demonstrated for transfer hydrocyanation and transfer hydroformylation reactions, showing yield increases up to 80% by the addition of a carefully selected zeolite. Clear improvements such as diversification of HCN-donors to e.g. propionitrile and the use of a simple reaction setup with mild conditions are achieved. The use of unstrained and unactivated olefins as HCHO-acceptors is demonstrated for the first time, significantly broadening the scope and utility of the transfer hydroformylation reaction. Mechanistic and spectroscopic studies highlight the unique synergy between the zeolites and the homogeneous transfer catalysts.

At the glass transition, a supercooled liquid vitrifies into an amorphous solid and all viscous relaxation processes cease. The experimental observation of secondary or β relaxations below the glass transition temperature in molecular and metallic glasses suggests that this picture may be somewhat oversimplified but essentially correct. Polymers, on the other hand, are thought of as fundamentally different: on cooling, polymers typically show a cascade of transitions from a viscous liquid, through viscoelastic fluid and viscoelastic solid stages, and finally a brittle glass. Here we show that a family of homogeneous non-polymeric liquids—titanium tetraalkoxides—have double glass transitions giving rise to two distinct steps in the temperature-dependent heat capacities. The double glass transition causes the liquid to transition from viscous to viscoelastic to elastic, like a simple polymer liquid. This result allows us to link the physical behaviour of polymers and small-molecule glass formers in a single universal picture.

NMR spectroscopy is a powerful tool for structural analysis of solids, especially if it is complemented by computations of NMR observables, such as chemical shifts and quadrupole coupling constants...

One of the common features of a glass is the so-called “boson peak”, observed as an excess in the heat capacity over the crystal or as an additional peak in the terahertz vibrational spectrum. The microscopic origins of the boson peak are controversial, albeit the emergence of locally ordered structures inhibiting crystallisation has been put forward as a possible culprit. Unfortunately, the terahertz spectral range is often congested with many other contributions complicating observation of the boson feature. Here, we show that depolarised Raman scattering—obtained using femtosecond optical Kerr-effect spectroscopy in liquids consisting of highly symmetric molecules—can be used to isolate the boson peak, allowing its detailed observation over a wide range of temperatures from the (supercooled) liquid into the glass. The boson peak in the vibrational spectrum matches the excess heat capacity observed in low-temperature heat capacity measurements. As the boson peak intensifies on cooling towards the glass transition, wide-angle x-ray scattering shows the simultaneous appearance of a pre-peak due to molecular clusters consisting of circa 20 molecules. Atomistic molecular dynamics simulations—reproducing both boson and pre peaks—indicate that these clusters are caused by over-coordinated molecules tending towards but prevented from attaining crystalline structural order. These findings represent an essential step toward our understanding of the physics of vitrification.

The selective activation of inert C–H bonds has emerged as a promising tool for avoiding the use of wasteful traditional coupling reactions. Oxidative coupling of simple aromatics allows for a cost-effective synthesis of biaryls. However, utilization of this technology is severely hampered by poor regioselectivity and by the limited stability of state-of-the-art homogeneous Pd catalysts. Here, we show that confinement of cationic Pd in the pores of a zeolite allows for the shape-selective C–H activation of simple aromatics without a functional handle or electronic bias. For instance, out of six possible isomers, 4,4′-bitolyl is produced with high shape selectivity (80%) in oxidative toluene coupling on Pd-Beta. Not only is a robust, heterogeneous catalytic system obtained, but this concept is also set to control the selectivity in transition-metal-catalysed arene C–H activation through spatial confinement in zeolite pores. Controlling the regioselectivity in the coupling of simple aromatics is challenging. Now, para–para selectivity is achieved during the aerobic dehydrogenative homocoupling of arenes through a shape-selective catalyst based on molecular palladium confined within the framework of zeolite materials.

Two types of preformed alginate wet gels, one with a low (30–35%) and the other with a high (65–75%) content of glucuronic acid, were reacted with an aliphatic triisocyanate that was priorly allowe...

Strong concerns about the toxicity and endocrine disrupting properties of widespread phthalate plasticizers stimulate the demand for safe and preferably biobased alternatives. Citric acid forms in this respect an excellent and abundant platform chemical for the production of valuable plasticizers. Here, we report a new and direct synthesis route for propane-1,2,3-tricarboxylic acid (PTA) from citric acid via a sequential one pot dehydration–hydrogenation process. This saturated triacid can serve as a basis for the production of tricarballylate esters via esterification, which have been shown to possess excellent plasticizing properties in vinyl resins. In the presence of a solid acid H-Beta zeolite and Pd/C hydrogenation catalyst, yields up to 85% of PTA were obtained under mild reaction conditions and in water as a green solvent. Partial dealumination of the H-Beta zeolite by citric acid could be counteracted by reincorporating aluminium into the framework of the recycled H-Beta zeolite through realumination, regenerating a significant fraction of the initial activity of the catalytic system. The success of the realumination procedure was verified via MAS NMR spectroscopy.

The catalytic activity of UiO-66 type Zr metal–organic frameworks can be tuned by the linker employed, e.g. nitro- or aminoterephthalic acid. Here we study composition–activity relations for the UiO-66 catalyzed dehydration of fructose into hydroxymethylfurfural, a carbon-neutral feedstock for chemicals and fuels. Variation of the substituents on the NO2/NH2 functionalized solids has a clear influence on the number of missing linkers around the Zr oxo clusters, on the hydrophobicity/hydrophilicity of the eventual metal–organic framework and on the Bronsted acidity. The thermally modulated UiO-66-NH2 is able to yield 25 molecules of HMF per defective Zr site after 1 h at 100 °C, maintaining its activity in 4 consecutive runs.

In this study, a water-stable microcrystalline bioMOF was synthesized, characterized, and loaded with silver ions or highly emissive rare earth (RE) metals such as Eu3+/Tb3+. The obtained materials were used as active layers in a proof-of-concept sustainable light-emitting device, highlighting the potential of bioMOFs in optoelectronic applications. ispartof: CHEMICAL COMMUNICATIONS vol:58 issue:5 pages:677-680 ispartof: location:England status: published

A systematic structural study of Ni in the Ni/ZSM-5 materials is presented, which is beneficial for any further investigation of the catalytic activities of Ni/ZSM-5 and other metal-modified bifunctional catalysts.

Inorganic chemistry 61(45), 18181 - 18192 (2022). doi:10.1021/acs.inorgchem.2c02898, MOF-74 is an archetypal magnetic metal–organic framework (MOF) family, with metal nodes bridged by 2,5-dioxido-1,4-benzenedicarboxylic acid (H$_4$dobdc) 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., Published by American Chemical Society, Washington, DC

International audience; Achiral 2-hydroxy-N-(diphenylmethyl)acetamide (HNDPA) crystallizes in the P61 chiral space group as a hydrate, building up permeable chiral crystalline helical water channels. The crystallization driven chiral self-resolution process is highly robust, with the same air stable crystalline form readily obtained from a variety of conditions. Interestingly, the HNDPA supramolecular helix inner pore is filled by a helical water wire. The whole edifice is mainly stabilized by robust hydrogen bonds involving the HNDPA amide bonds and CH…π interactions between the HNDPA phenyl groups. The crystalline structure shows a breathing behavior, with completely reversible release and reuptake of water inside the chiral channel, under ambient conditions. Importantly, the HNDPA channel is able to transport water very efficiently and selectively in biomimetic conditions. With a permeability per channel of 3.3 million water molecules per second in large unilamellar vesicles (LUV) and a total selectivity against NaCl, the HNDPA channel is a very promising functional nanomaterial for future applications.

The melting behaviour of metal-organic frameworks (MOFs) has aroused significant research interest in the areas of materials science, condensed matter physics and chemical engineering. This work first introduces a novel method to fabricate a bimetallic MOF glass, through melt-quenching of the cobalt-based zeolitic imidazolate framework (ZIF) [ZIF-62(Co)] with an adsorbed ferric coordination complex. The high-temperature chemically reactive ZIF-62(Co) liquid facilitates the formation of coordinative bonds between Fe and imidazolate ligands, incorporating Fe nodes into the framework after quenching. The resultant Co-Fe bimetallic MOF glass therefore shows a significantly enhanced oxygen evolution reaction performance. The novel bimetallic MOF glass, when combined with the facile and scalable mechanochemical synthesis technique for both discrete powders and surface coatings on flexible substrates, enables significant opportunities for catalytic device assembly.

Lead halide perovskite (LHP) semiconductors show exceptional optoelectronic properties. Barriers for their applications, however, lie in their polymorphism, instability to polar solvents, phase segregation, and susceptibility to the leaching of lead ions. We report a family of scalable composites fabricated through liquid-phase sintering of LHPs and metal-organic framework glasses. The glass acts as a matrix for LHPs, effectively stabilizing nonequilibrium perovskite phases through interfacial interactions. These interactions also passivate LHP surface defects and impart bright, narrow-band photoluminescence with a wide gamut for creating white light-emitting diodes (LEDs). The processable composites show high stability against immersion in water and organic solvents as well as exposure to heat, light, air, and ambient humidity. These properties, together with their lead self-sequestration capability, can enable breakthrough applications for LHPs.

The majority of research into metal-organic frameworks (MOFs) focuses on their crystalline nature. Recent research has revealed solid-liquid transitions within the family, which we use here to create a class of functional, stable and porous composite materials. Described herein is the design, synthesis, and characterisation of MOF crystal-glass composites, formed by dispersing crystalline MOFs within a MOF-glass matrix. The coordinative bonding and chemical structure of a MIL-53 crystalline phase are preserved within the ZIF-62 glass matrix. Whilst separated phases, the interfacial interactions between the closely contacted microdomains improve the mechanical properties of the composite glass. More significantly, the high temperature open pore phase of MIL-53, which spontaneously transforms to a narrow pore upon cooling in the presence of water, is stabilised at room temperature in the crystal-glass composite. This leads to a significant improvement of CO2 adsorption capacity., The formation of composite materials has been widely exploited to alter the chemical and physical properties of their components. Here the authors form metal–organic framework (MOF) crystal–glass composites in which a MOF glass matrix stabilises the open pore structure of MIL-53, leading to enhanced CO2 adsorption.

Angewandte Chemie / International edition International edition 58(27), 9160 - 9165 (2019). doi:10.1002/anie.201904347, While titanium‐based metal–organic frameworks (MOFs) have been widely studied for their (photo)catalytic potential, only a few TiIV MOFs have been reported owing to the high reactivity of the employed titanium precursors. The synthesis of COK‐47 is now presented, the first Ti carboxylate MOF based on sheets of TiIVO6 octahedra, which can be synthesized with a range of different linkers. COK‐47 can be synthesized as an inherently defective nanoparticulate material, rendering it a highly efficient catalyst for the oxidation of thiophenes. Its structure was determined by continuous rotation electron diffraction and studied in depth by X‐ray total scattering, EXAFS, and solid‐state NMR. Furthermore, its photoactivity was investigated by electron paramagnetic resonance and demonstrated by catalytic photodegradation of rhodamine 6G., Published by Wiley-VCH, Weinheim

Reactive aluminum alkoxide (ASB, aluminium sec-butoxide) was chelated using β-diketone (EAA, ethyl acetoacetate) in order to gain control over rapid hydrolysis in the course of the sol-gel process. Derived chelates were analysed using several NMR spectroscopic techniques: one-dimensional 1H, 13C, 27Al NMR and two-dimensional COSY, HSQC and DOSY. The NMR analysis enabled identification of the formed chelate species, as well as determination of their quantitative relationships. Several complexation products were observed: tris-chelated monomer, Al(EAA)3, bis-chelated dimmer, Al2(OnBu)4(EAA) 2, tris-chelated dimmer, Al2(OnBu)3(EAA)3, tetra-chelated dimmer, Al2(OnBu)2(EAA)4, and monochelated trimer, Al3(OnBu)8(EAA). Of the formed oligomer compounds, this is the first evidence of Al2(OR)3L3 in any alkoxide and β-ketoester or β-diketone combination. Aluminium sec-butoxide and ethyl acetoacetate complexes Al2(OnBu)4(EAA) 2 and Al2(OnBu)2(EAA)4 were also observed for the first time. With the increase of the EAA/ASB ratio the coordination of aluminium shifts towards six, whereas above the EAA/ASB ratio of 2.5 solely six-coordinated aluminium exists. This work is licensed under a Creative Commons Attribution 4.0 International License.

Metal-doped polyurea-crosslinked alginate aerogel beads (X–M–alginate; M: Ca, Co, Ni, Cu) were prepared via the reaction of an aromatic triisocyanate (Desmodur RE) with the –OH groups on the surface of pre-formed M–alginate wet gels, and with adsorbed gelation water. The X–M–alginate aerogels consisted of 49–63% polyurea and contained 2–7% metal ions; they were fibrous macro/meso/microporous materials with porosities up to 94% v/v, and BET surface areas 245–486 m2 g−1, comparable to those of native M–alginate aerogels (258–542 m2 g−1). The pyrolysis of X–M–alginate aerogels (M: Co, Ni, Cu) at 800 °C yielded carbon aerogels (X–M–C; 33–37% yield) doped with the corresponding metal (as well as with Cu2O in the case of X–Cu–C), with crystallite sizes of around 22 nm. The X–M–C aerogels retained the general fibrous morphology of their precursor (X–M–alginate) aerogels, and while X–Co–C and X–Ni–C appeared similar, the fibrous morphology of X–Cu–C was distinctly different, indicating an effect of the metal on the nanostructure of the corresponding carbon. The porosities of all X–M–C aerogels were in the range of 88–92% v/v, including macro-, meso- and micropores. Their BET surface areas were in the range of 426–541 m2 g−1, of which 208–319 m2 g−1 was allocated to micropores. In addition to the metals, XPS, Raman and FTIR analyses showed the presence of oxygen and nitrogen functionalities. Carbon in the X–M–C aerogels showed signs of stacking of graphene oxide sheets (14–15 nm), but also a low degree of graphitization and a large number of defects. This work provides a direct, inexpensive method for the preparation of fibrous metal-, oxygen- and nitrogen-doped carbon aerogels with potential for catalytic and electrochemical applications.

Selective catalytic reduction of CO

Selective catalytic reduction of CO2 to methanol has tremendous importance in the chemical industry. It mitigates two critical issues in the modern society, the overwhelming climate change and the dependence on fossil fuels. The most used catalysts are currently based on mixed copper and zinc phases, where the high surface of active copper species is a critical factor for the catalyst performance. Motivated by the recent breakthrough in the controllable synthesis of bimetallic MOF-74 materials by ball milling, we targeted to study the potential of ZnCu-MOF-74 for catalytic CO2 reduction. Here, we tested whether the nanosized channels decorated with readily accessible and homogeneously distributed Zn and Cu metal sites would be advantageous for the catalytic CO2 reduction. Unlike the inactive monometallic Cu- MOF-74, ZnCu-MOF-74 shows moderate catalytic activity and selectivity for the methanol synthesis. Interestingly, the postsynthetic mechanochemical treatment of desolvated ZnCu-MOF-74 resulted in amorphization and a significant increase in both the activity and selectivity of the catalyst despite the destruction of the well-ordered and porous MOF-74 architecture. The results emphasize the importance of defects for the MOF catalytic activity and the potential of amorphous MOFs to be considered as heterogeneous catalysts. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and 13C magic angle-spinning nuclear magnetic resonance (MAS NMR) were applied to establish quantitative structure− reactivity relationships. The apparent activation energy of rate reaction kinetics has indicated different pathway mechanisms, primarily through reverse water−gas shift (RWGS). Prolonged time on stream productivity, stability and deactivation were assessed, analysing the robustness or degradation of metal−organic framework nanomaterials. Scalable MOF production processes are making the latter more appealing within emerging industrial decarbonisation, in particular for carbon capture and utilisation (CCU) or hydrogen carrier storage. Acknowledging scale, the costs of fabrication are paramount.

The novel high-temperature polymorph of sodium imidazolate reported in this paper was discovered in the mechanochemical reaction of NaIm with NaBH4 and later prepared directly by thermal treatment of the room-temperature polymorph of NaIm. Solid- state NMR was used for initial elucidation of structural features ; the crystal structure was determined by single-crystal X-ray diffraction, while the in situ HT-XRPD experiments utilizing synchrotron radiation have been performed in order to gain the insight into the structural evolution and thermal stability, in addition to differential thermal analysis and hot-stage microscopy measurements. Contrary to the RT polymorph that forms a dense and hypercoordinated structure without pores, the high-temperature polymorph of NaIm exhibits pores of 50 Å3 that suggest possible application for gas sorption/separation. It is important to highlight that, once formed, the high-temperature polymorph of NaIm retains its structure and remains stable at room temperature.

We report the synthesis and detailed structural and chemical characterization including electrochemical properties of a lithium vanadium oxy/fluoro-phosphate material. To the best of our knowledge,...

The diagenetic modifications of archaeological bones from the Celtic site of Radovesice (Czech Republic) were described combining histological and instrumental analysis with infrared (FT-IR) and nuclear magnetic resonance (NMR) spectroscopy. The post-mortem changes in microstructure, mineral and organic fraction of human bones were related to seasonal fluctuations in water saturation and temperature, reflecting the Atlantic influence on the continental climate system of this transitional area of Eastern-Central Europe. The effects of a burial environment characterised by a well-oxygenated soil with good hydraulic conductivity, which evolved from the Quaternary loess deposits of the Bohemian massif, led to a common diagenetic pathway, which comprised micro-fissuring, mineral dissolution and degradation of collagen by microbial activity, followed by secondary calcite deposition under mildly alkaline conditions. Observed intra-site variations reflected changes in the early taphonomic history or in microenvironmental conditions, such as prolonged acidic conditions hindering apatite reprecipitation, as well as secondary calcite crystallisation. Diffuse effects of surface abrasion by sediments and absence of brown staining did not support the hypothesis of extensive use of wooden coffins. New indexes obtained from 31P and 1H NMR, respectively, were employed to describe diagenesis. They were found to correlate with FT-IR indexes, although reflecting distinct structural characteristics of bone which are not accessible to FT-IR.

International audience; ZnLaZrSi oxide systems prepared with a silica component of the different nature have been studied in 1,3-butadiene production from aqueous ethanol. The following silica materials were used: KSKG, A-175, A-380, SBA-15, MCM-41, MCM-48, MCF, and dealuminated BEA zeolites. The characteristics of the porous structure of the silica support, such as porosity, pore size distribution, and specific and external surface areas, were found not to be critical parameters for achieving a high 1,3-butadiene yield during the EtOH–H2O mixture conversion in the presence of ZnLaZrSi oxide catalysts. On the contrary, the quantity and strength of Lewis acid sites, which in turn differ depending on the choice of silica material, have a significant impact on 1,3-butadiene selectivity and yield. The highest values of the selectivity of 1,3-butadiene formation (up to 68%) and yield as well as stability toward deactivation in the presence of H2O were achieved over ZnLaZr–KSKG, ZnLaZr–SBA-15, and ZnLa–Zr1SiBEA (with mononuclear isolated tetrahedral Zr(IV) species). The productivity of ZnLa–Zr1SiBEA catalyst accounts for 0.324 g1,3-BD·gcat–1·h–1 (T = 648 K, WHSV = 2.88 h–1, 80 vol % EtOH in water as an EtOH source). The main reason for the decrease in 1,3-butadiene yield in the presence of H2O in the reaction mixture was shown to be a deactivation of acetaldehyde condensation sites on the catalyst surface, while the rate of acetaldehyde formation decreases slightly. According to 1H–13C CP/MAS NMR spectroscopic results, the use of aqueous ethanol as the feed for the ethanol-to-butadiene process is very advantageous to prevent the carburization of the catalysts.

The identification of markers of the modifications occurring in human bones after death and of the sedimentary and post-sedimentary processes affecting their state of preservation, is of interest for several scientific disciplines. A new index, obtained from spectral deconvolution of the

Perfluorinated alkylated substances (PFASs) are widely used in industrial and commercial applications, leading to a widespread occurrence of these persistent and harmful contaminants in our environment. Removal of these compounds from surface and waste waters is being mandated by European and U.S. governments. Currently, there are no treatment techniques available that lower the concentrations of these compounds for large water bodies in a cost- and energy-efficient way. We hereby propose a hydrophobic, all-silica zeolite Beta material that is a highly selective and high-capacity adsorbent for PFASs, even in the presence of organic competitors. Advanced characterization data demonstrate that the adsorption process is driven by a very negative adsorption enthalpy and favorable steric factors. ispartof: ANGEWANDTE CHEMIE-INTERNATIONAL EDITION vol:59 issue:33 pages:14086-14090 ispartof: location:Germany status: published

Mechanically responsive metal–organic frameworks (MOFs) came very recently into the spotlight of material science for their unique properties and potential new fields of application. We present here a clarification of the magnetic properties of prototypical magnetic MOF-74 material, Ni(II)-MOF-74, using magnetization measurements, X-band electron spin resonance (ESR), multi-frequency high-field ESR (HF-ESR), and theoretical model. It was established that the guests populating the honeycomb channels have little influence on the magnetism of Ni-MOF-74, whereas magnetic properties change significantly upon mechanical amorphization. Amorphous material (am-Ni-MOF-74), which can be readily prepared by the mechanochemical treatment of dehydrated Ni-MOF-74 (deh-Ni-MOF-74), as shown by in situ monitoring methods, displays significantly lower bulk magnetization compared to Ni-MOF-74 and deh-Ni-MOF-74. This decline in magnetization is established to be a consequence of the spin-crossover from high-spin to a low-spin state of nickel(II) ions. The observed spin-crossover was rationalized by an insight into the changes of the nickel coordination sphere during the amorphization, which was provided by solid-state nuclear magnetic resonance (NMR) and infrared (IR) spectroscopy. Additionally, it was found that am-Ni-MOF-74 behaves differently than its zinc analogue when exposed to vapors or liquid-additives in the milling process, indicating that the nature of the metal node plays a substantial role in the mechanical properties of this modular family of MOF materials.

The synthesis of four novel crystalline zeolitic imidazolate framework (ZIF) structures using a mixed-ligand approach is reported. The inclusion of both imidazolate and halogenated benzimidazolate-derived linkers leads to glass-forming behavior by all four structures. Melting temperatures are observed to depend on both electronic and steric effects. Solid-state NMR and terahertz (THz)/far-IR demonstrate the presence of a Zn-F bond for fluorinated ZIF glasses. In situ THz/far-IR spectroscopic techniques reveal the dynamic structural properties of crystal, glass, and liquid phases of the halogenated ZIFs, linking the melting behavior of ZIFs to the propensity of the ZnN4 tetrahedra to undergo thermally induced deformation. The inclusion of halogenated ligands within metal-organic framework (MOF) glasses improves their gas-uptake properties.