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.

Hybrid systems of hydroxyapatite supported on carbonaceous materials of different nature (activated charcoals, acetylene black, carbon black, graphite flake, synthesized microporous and mesoporous carbons) are investigated as catalysts for vapor-phase Guerbet condensation of butan-1-ol. The structure, morphology, and acid–base characteristics of hydroxyapatite, carbon supports, and the hybrid systems have been characterized by XRD, SEM-EDX, low-temperature (77 K) nitrogen ad(de)sorption, NMR, XPS, EPR, Raman spectroscopy, and TPD-NH3/CO2 techniques. The butan-1-ol conversion and selectivity towards the reaction products are found to be highly dependent on the carbonaceous supports of hybrid catalysts. The important role of acid–base capacity ratio is highlighted to achieve high selectivity in vapor-phase Guerbet condensation of butan-1-ol to 2-ethylhexan-1-ol. In particular, the surface’s strong basic sites are preferable for elongating the carbon chain. The high selectivity towards 2-ethylhexan-1-ol of about 75% is achieved over HAP/graphite flake and up to 57% over HAP/activated coconut charcoal. Compared to the bulk hydroxyapatite, the enhanced performance of the hybrid catalysts (initial activity and target product yield) is associated with the redistribution of active sites over carbon support by strength and location.

We show that the non -canonical nucleobase 2,6-diaminopurine (D) spontaneously base pairs with uracil (U) in water and the solid state without the need to be attached to the ribose -phosphate backbone. Depending on the reaction conditions, D and U assemble in thermodynamically stable hydrated and anhydrated D -U base -paired cocrystals. Under UV irradiation, an aqueous solution of D -U base -pair undergoes photochemical degradation, while a pure aqueous solution of U does not. Our simulations suggest that D may trigger the U photodimerization and show that complementary base -pairing modifies the photochemical properties of nucleobases, which might have implications for prebiotic chemistry.

Exploring hybridization of Bi 2 S 3 nanorods with hard carbon substrate for sodium-ion batteries revealed enhanced performance with MPA modification, elucidating charge storage mechanisms and transformation dynamics, advancing battery electrode design.

Abstract 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.

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 single-component homogeneous molecular liquids, titanium tetraalkoxides, 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 coupled to the surrounding liquid. These results imply that intramolecular barrier-crossing processes, typically associated with chemical reactivity, do not necessarily follow the Arrhenius law but may freeze out at a finite temperature.

Enlarging the quantum coherence times and gaining control over quantum effects in real systems are fundamental for developing quantum technologies. Molecular electron spin qubits are particularly promising candidates for realizing quantum information processing due to their modularity and tunability. Still, there is a constant search for tools to increase their quantum coherence times. Here we present how the mechanochemical introduction of active spin qubits in the form of 10% diluted copper(ii)-porphyrins in the diamagnetic PCN-223 and MOF-525 zirconium-MOF polymorph pair can be achieved. Furthermore, the encapsulation of fullerene during the MOF synthesis directs the process exclusively toward the rare PCN-223 framework with a controllable amount of fullerene in the framework channels. In addition to the templating role, the incorporation of fullerene increases the electron spin-lattice and phase-memory relaxation times, T-1 and T-m. Besides decreasing the amount of nuclear spin-bearing solvent guests in the non-activated qubit frameworks, the observed improved relaxation times can be rationalized by modulating the phonon density of states upon fullerene encapsulation.

Clay minerals, as biofriendly and low-cost materials, are highly essential for the modern industrial applications including the production of clean energy, its storage and conversion. Here, the capabilities of pure and cation exchanged rectorite, a regularly interstratified phyllosilicate from Beatrix Mine (South Africa) were explored and discussed. A comprehensive characterization was performed by means of high resolution solid-state NMR, electrochemical impedance spectroscopy and powder X-ray diffraction. 23Na MAS and 3QMAS NMR spectroscopy was used to characterize accessibility of interlayer space in rectorite for exchangeable cations. Three Na sites attributed to easily exchangeable Na+ on the surface or in large pores, Na+ in dehydrated micaceous interlayers and Na+ in hydrated smectite interlayers were identified. Differences in hydration states in smectitic interlayers depending on the type of intercalation were detected using 1H MAS NMR. A higher amount of hydrating water molecules in pure and Mg-exchanged rectorites was attributed to the higher hydration energy of Ca2+ and Mg2+. The temperature dependences of electrical conductivity in this work were best described using the empirical Vogel-Tammann-Fulcher equation with the temperature-dependent effective activation energy parameter. Significantly stronger change of activation energy in Mg2+ exchanged rectorite in the temperature range of 10 degrees C to 50 degrees C as compared to pure rectorite and its Na+, Li+ and NH4+ modifications was related to an extensive H-bond network in the interlayers, which facilitated an effective proton transfer responsible for electric conductivity. The obtained resutls suggested a greater potential for the use of Mg-exchanged rectorite as ionic conductor at enhanced temperatures.

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 substantial challenges with regard to atom economy and practicality. Here we show an approach that harnesses the shape-selective and catalytic properties of zeolites to drive the shuttling equilibrium of transfer hydrocyanation and transfer hydroformylation reactions to near-completion. The zeolites irreversibly convert the transfer reaction co-products in an exergonic tandem reaction while excluding the substrates via pore size restrictions. Through fine-tuning of the zeolite’s properties, yield increases of up to 80% can be achieved, enabling diversification of nitrile donors to propionitrile and aldehyde acceptors to unactivated olefins. Mechanistic and spectroscopic studies highlight the unique synergy between the zeolites and the homogeneous transfer catalysts.

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 common feature of glasses is the “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 this peak are not well understood; the emergence of locally ordered structures has been put forward as a possible candidate. Here, we show that depolarised Raman scattering in liquids consisting of highly symmetric molecules can be used to isolate the boson peak, allowing its detailed observation from the liquid into the glass. The boson peak in the vibrational spectrum matches the excess heat capacity. As the boson peak intensifies on cooling, 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 indicate that these are caused by over-coordinated molecules. These findings represent an essential step toward our understanding of the physics of vitrification.

A gamma-aluminasupport functionalized with transition metalsis one of the most widely used industrial catalysts for the totaloxidation of volatile organic compounds (VOCs) as air pollutants athigher temperatures (280-450 degrees C). By rational design ofa bimetal CuFe-gamma-alumina catalyst, synthesized from a dawsonitealumina precursor, the activity in total oxidation of toluene as amodel VOC at a lower temperature (200-380 degrees C) is achieved.A fundamental understanding of the catalyst and the reaction mechanismis elucidated by advanced microscopic and spectroscopic characterizationsas well as by temperature-programmed surface techniques. The natureof the metal-support bonding and the optimal abundance betweenCu-O-Al and Fe-O-Al species in the catalystsleads to synergistic catalytic activity promoted by small amountsof iron (Fe/Al = 0.005). The change in the metal oxide-clusteralumina interface is related to the nature of the surfaces to whichthe Cu atoms attach. In the most active catalyst, the CuO6 octahedra are attached to 4 Al atoms, while in the less active catalyst,they are attached to only 3 Al atoms. The oxidation of toluene occursvia the Langmuir-Hinshelwood mechanism. The presented materialintroduces a prospective family of low-cost and scalable oxidationcatalysts with superior efficiency at lower temperatures.

: 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, T 1 and T m , 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 fast adsorption kinetics of zeolitic imidazolate frameworks (ZIFs) enable a wide range of sorption applications. The most commonly used framework, ZIF-8, is relatively non-polar. Increasing the polarity of ZIF-8 through the encapsulation of different polar species shows promise for enhancing the sorption performance for pure CO2. Recently, the outlook has re-focused on gas mixtures, mostly in the context of post-combustion CO2 capture from wet flue gasses. While water is known to sometimes have a synergistic effect on CO2 sorption, we still face the potential problem of preferential water vapor adsorption. Herein, we report the preparation of three ZIF-8/organic dye (OD) composites using Congo red, Xylenol orange, and Bromothymol blue, and their impact on the sorption properties for CO2, water, and a model wet CO2 system at 50% RH. The results show that the preparation of OD composites can be a promising way to optimize adsorbents for single gasses, but further work is needed to find superior ZIF@OD for the selective sorption of CO2 from wet gas mixtures.

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. Here we fabricate an array of CsPbI3 crystal and hybrid glass composites by sintering and globally visualise 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. MOF glass nanocomposites allow researchers to study lead halide perovskites' bulk and interfacial regions in relation to their optoelectronic properties. Here authors provide insights for the advancement of stable and efficient perovskite optoelectronic devices design.

Selective catalytic reduction of CO 2 to methanol has tremendous importance in the chemical industry. It mitigates two critical issues in 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 break-through in the controllable synthesis of bimetallic MOF-74 materials by ball milling,

The present work deals with the study of water adsorption on acid-modified zeolites A. Commercial zeolites 4A (Na form) and 5A (Ca form) were subjected to EDTA dealumination, and their structure, textural properties and stability were checked by XRD, EDX, NMR and N2 physisorption analyses. The water adsorption isotherms of the parent zeolites and their modified forms were measured at a temperature of 25 °C and up to a relative pressure of 0.9. The results show that the treatment with EDTA drastically changes the structural properties of the zeolites and increases the water adsorption capacity by up to 10%. The changes depend on the type of extra-framework cations (Na+ and Ca2+) and the EDTA concentration.

Invited for the cover of this issue is the collaborative research team coordinated by Arie van der Lee at the University of Montpellier. The image depicts chiral channels with highly mobile water molecules resulting from the robust self-organization of a simple achiral acetamide. Fully reversible release and re-uptake of water molecules takes place near ambient conditions, with efficient water transport and a good selectivity against NaCl suggesting it to be an efficient candidate for desalination processes. Read the full text of the article at 10.1002/chem.20200383.

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.