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Emissions of SO2 from flue gas and marine transport have detrimental impacts on the environment and human health, but SO2 is also an important industrial feedstock if it can be recovered, stored and transported efficiently. Here we report the exceptional adsorption and separation of SO2 in a porous material, [Cu2(L)] (H4L = 4',4‴-(pyridine-3,5-diyl)bis([1,1'-biphenyl]-3,5-dicarboxylic acid)), MFM-170. MFM-170 exhibits fully reversible SO2 uptake of 17.5 mmol g-1 at 298 K and 1.0 bar, and the SO2 binding domains for trapped molecules within MFM-170 have been determined. We report the reversible coordination of SO2 to open Cu(II) sites, which contributes to excellent adsorption thermodynamics and selectivities for SO2 binding and facile regeneration of MFM-170 after desorption. MFM-170 is stable to water, acid and base and shows great promise for the dynamic separation of SO2 from simulated flue gas mixtures, as confirmed by breakthrough experiments.

Magnetic materials are composed of the simple building blocks of magnetic moments on a crystal lattice that interact via magnetic exchange. Yet from this simplicity emerges a remarkable diversity of magnetic states. Some reveal the deep quantum mechanical origins of magnetism, for example, quantum spin liquid (QSL) states in which magnetic moments remain disordered at low temperatures despite being strongly correlated through quantum entanglement. A promising theoretical model of a QSL is the Kitaev model, composed of unusual bond-dependent exchange interactions, but experimentally, this model is challenging to realise. Here we show that the material requirements for the Kitaev QSL survive an extended pseudo-edge-sharing superexchange pathway of Ru3+ octahedra within the honeycomb layers of the inorganic framework solid, RuP3SiO11. We confirm the requisite j eff = 1 2 state of Ru3+ in RuP3SiO11 and resolve the hierarchy of exchange interactions that provide experimental access to an unexplored region of the Kitaev model. Recent theoretical studies indicate that the Kitaev model may be realized in framework materials exhibiting extended superexchange pathways. Here the authors report experimental evidence showing that the material requirements for a Kitaev quantum spin liquid are satisfied in a inorganic framework material. [ABSTRACT FROM AUTHOR]

Calcite and vaterite crystallisation is strongly influenced by the presence of additives during the reaction process, as demonstrated by organic molecules in biogenic calcium carbonate formation. The effect of additives on the lattice parameters of calcite and vaterite in syntheses are frequently reported, but only as discrete studies discussing a single polymorph. The intertwined nature of these polymorphs, due to their shared reaction pathway, is rarely discussed. In this work we report the results of a large scale citizen science project to explore the influence of amino acids and related additives on both polymorphs, highlighting their differences and commonalities in terms of the effect on the lattice parameters and polymorph selectivity. [ABSTRACT FROM AUTHOR]

Formamides are important feedstocks for the manufacture of many fine chemicals. State‐of‐the‐art synthesis of formamides relies on the use of an excess amount of reagents, giving copious waste and thus poor atom‐economy. Here, we report the first example of direct synthesis of N‐formamides by coupling two challenging reactions, namely reductive amination of carbonyl compounds, particularly biomass‐derived aldehydes and ketones, and fixation of CO2 in the presence of H2 over a metal‐organic framework supported ruthenium catalyst, Ru/MFM‐300(Cr). Highly selective production of N‐formamides has been observed for a wide range of carbonyl compounds. Synchrotron X‐ray powder diffraction reveals the presence of strong host‐guest binding interactions via hydrogen bonding and parallel‐displaced π⋅⋅⋅π interactions between the catalyst and adsorbed substrates facilitating the activation of substrates and promoting selectivity to formamides. The use of multifunctional porous catalysts to integrate CO2 utilisation in the synthesis of formamide products will have a significant impact in the sustainable synthesis of feedstock chemicals. [ABSTRACT FROM AUTHOR]

The structure and vibrational spectroscopy of centrohexaindane, 1, was investigated. This unusual molecule has a quaternary carbon atom that is coordinated to four further such quaternary carbon atoms as its core, each pair of which is bonded to an ortho‐phenylene unit. Previous NMR studies have shown that the molecule has tetrahedral (Td) symmetry in solution. The infrared and Raman spectra of chloroform and deuterochloroform solutions of 1 are completely in agreement with this conclusion, as the only modes that are visible are those allowed for Td symmetry. This is not the case in the solid state: X‐ray powder diffraction indicates that the unit cell is triclinic or monoclinic with a volume in excess of 4000 Å3. The vibrational spectroscopy is consistent with C1 site symmetry and the presence of at least two molecules in the primitive cell. It is likely that the space group is centrosymmetric. [ABSTRACT FROM AUTHOR]

The interactions between adsorbed gas molecules within porous metal-organic frameworks are crucial to gas selectivity but remain poorly explored. Here, we report the modulation of packing geometries of CO2 and C2H2 clusters within the ultramicroporous CUK-1 material as a function of temperature. In-situ synchrotron X-ray diffraction reveals a unique temperature-dependent reversal of CO2 and C2H2 adsorption affinities on CUK-1, which is validated by gas sorption and dynamic breakthrough experiments, affording high-purity C2H2 (99.95%) from the equimolar mixture of C2H2/CO2 via a one-step purification process. At low temperatures (<253 K), CUK-1 preferentially adsorbs CO2 with both high selectivity (>10) and capacity (170 cm3 g−1) owing to the formation of CO2 tetramers that simultaneously maximize the guest-guest and host-guest interactions. At room temperature, conventionally selective adsorption of C2H2 is observed. The selectivity reversal, structural robustness, and facile regeneration of CUK-1 suggest its potential for producing high-purity C2H2 by temperature-swing sorption. Guest clusters within confined nanospaces have a significant impact on molecular recognition. Here authors highlight the potential to systematically control gas-cluster rearrangement, leading to tunable sorption and separation behaviour in a MOF. [ABSTRACT FROM AUTHOR]

Tungsten bronze (TB) structured materials have attracted attention as possible thermoelectrics because of their complex crystal structure. In this work, a new thermoelectric ceramic with a tetragonal tungsten bronze (TB) structure, Ba6Ti2Nb8O30 (BTN), was prepared by the conventional mixed oxide route with some samples processed by Spark Plasma Sintering (SPS). The addition of MnO enabled the fabrication of high density BTN ceramics at a low sintering temperature of 1580 K in air and by SPS. All samples were annealed in a reducing atmosphere after sintering. X-ray diffraction showed that Ba6Ti2Nb8O30 crystallizes with tetragonal symmetry (P4bm space group). High angle annular dark field-electron energy loss spectroscopy analysis confirmed the proposed crystal structure and provided exact elemental distributions in the lattice, showing higher concentrations of Ti in the 2b lattice sites compared to the 8d lattice sites. XPS showed the presence of two spin-orbit double peaks at 207.7 eV in the reduced BTN samples, confirming the presence of Nb4+ ions. By the use of a sintering aid and optimization of the processing parameters, the ceramics achieved a high power factor of 280 μW/m K2 at 873 K. The BTN ceramics showed phonon-glass-type thermal conduction behavior with a low thermal conductivity of 1.7–1.65 W/m K at 300–873 K. A thermoelectric figure of merit (ZT) of 0.14 was achieved at 873 K. This ZT value is comparable with results for many TB thermoelectrics. However, BTN has the advantage of much easier processing. [ABSTRACT FROM AUTHOR]

We present the results of the high-temperature neutron and x-ray diffraction experiments on the Ca3–xSrxTi2O7 (x = 0.5, 0.8, 0.85, 0.9) compounds. The ferro- to paraelectric transition in these hybrid improper ferroelectric materials arises from the so-called trilinear coupling. Depending on the strontium content, various structures and phase transitions, different from theoretical predictions, emerge. The in situ x-ray powder diffraction indicates a direct ferro- to paraelectric transition between the orthorhombic A21am and the tetragonal undistorted I4/mmm phase for x ≤ 0.6. We identified a reduction in the trilinear coupling robustness by increasing the Sr-doping level to lead to the emergence of the intermediate tetragonal P42/mnm phase and the gradual suppression of the orthorhombic phase. The observed character of the structure transitions and the Ca3–xSrxTi2O7 phase diagram are discussed in the framework of theoretical models of other related hybrid improper ferroelectric systems. [ABSTRACT FROM AUTHOR]