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The high catalytic activity of CO 2 conversion to carbonate on a Cu-MOF observed experimentally is elucidated from DFT calculations. [Display omitted] • The ring opening of PO has a higher energy barrier than the ring closure of PC. • The stabilities of intermediates and transition states are enhanced in NTU-180. • Activation barriers on NTU-180/TBAB are substantially lower than in the gas phase. • Activation barriers are not sensitive to the functional and the basis set. Metal-organic frameworks (MOFs) have emerged as unique catalysts for CO 2 conversion, but the catalytic mechanism remains elusive. In this study, a density functional theory (DFT) study is reported on CO 2 cycloaddition with propylene oxide (PO) to produce propylene carbonate (PC), catalyzed by a Cu-MOF (NTU-180) in the presence of tetrabutylammonium bromide (TBAB). This reaction was experimentally observed to have a remarkably high efficiency. We compute the electronic and Gibbs energies of the reactants, intermediates, transition states and products for two alternative reaction pathways. On NTU-180/TBAB, the three-member ring opening of PO is revealed to possess a higher activation barrier than the five-member ring closure of PC, and thus it is the rate-determining step. Pathway I is kinetically more favorable as its ring opening has a lower barrier than in Pathway II. Moreover, the activation barriers of ring opening and ring closure steps on NTU-180/TBAB are substantially lower than those in the gas phase, and also lower than those on TBAB alone and on a Cu 2 paddle-wheel/TBAB complex. At a molecular level, these results unambiguously highlight the important roles of the Cu sites and the confinement effect of NTU-180 in enhancing the stabilities of reaction intermediates and transition states, and promoting the catalytic cycloaddition of CO 2 with PO. In addition, the sensitivities of the DFT calculation results to the choice of functional and basis set are critically analyzed. While the electronic and Gibbs energies vary substantially with functional, the activation barriers in the rate-determining step are affected only slightly by the functional and marginally by the basis set. This theoretical study provides microscopic and quantitative insights into the high catalytic activity observed experimentally for CO 2 cycloaddition on NTU-180/TBAB, and might facilitate the development of new catalysts for efficient CO 2 conversion. [ABSTRACT FROM AUTHOR]

The evolution of metal-organic frameworks (MOFs) has been one of the most exciting aspects of materials chemistry over the last 20 years. In this Account, we discuss the development during this period in our understanding of the factors that control the crystallization of MOFs from solution. Both classical porous MOFs and dense MOF phases are considered. This is an opportune time at which to examine this complex area because the experimental tools now available to interrogate crystallization processes have matured significantly in the last 5 years, particularly with the use of in situ synchrotron X-ray diffraction. There have also been impressive developments in the use of density functional theory (DFT) to treat not only the energies of very complex structures but also their entropies. This is particularly important in MOF frameworks because of their much greater flexibility compared with inorganic structures such as zeolites. The first section of the Account describes how early empirical observations on the crystallization of dense MOFs pointed to a strong degree of thermodynamic control, with both enthalpic and entropic factors playing important roles. For example, reactions at higher temperatures tend to lead to denser structures with higher degrees of framework connectivity and lower levels of solvation, and polymorphs tend to form according to their thermodynamic stabilities. In the case of metal tartrates, these trends have been validated by calorimetric studies. It has been clear for more than a decade, however, that certain phases crystallize under kinetic control, especially when a change in conformation of the ligand or coordination around a metal center might be necessary to form the thermodynamically preferred product. We describe how this can lead to time-dependent crystallization processes that evolve according to the Ostwald rule of stages and can be observed by in situ methods. We then consider the crystallization of porous MOFs, which presents additional challenges because of solvation effects. In spite of these problems, much has been learned about the energetics of the underlying frameworks, where the relationship between porosity and stability initially seemed to mirror the behavior of zeolites, with more porous structures being less stable. Recently, however, this simple relationship has had to be reconsidered with the emergence of some very flexible structures wherein the open structures are more stable than their denser analogues at finite temperatures because of their large vibrational entropies. In the final section we describe how the concepts developed in the MOF work have been extended into the closely related area of hybrid organic-inorganic perovskites. We describe recent studies on polymorphism in hybrid perovskites, which is amenable to total free energy calculations using a combination of DFT and lattice dynamics methods. [ABSTRACT FROM AUTHOR]

The wide-ranging properties of metal organic frameworks (MOFs) rely in many cases on the presence of defects within their structures and the disorder that is inevitably associated with such defects. In the present work we review several aspects of defects in MOFs, ranging from simple substitutional defects at metal cation or ligand positions, to correlated defects on a larger length scale and the extreme case of disorder associated with amorphous MOFs. We consider both porous and dense MOFs, and focus particularly on the way in which defects and disorder can be used to tune physical properties such as gas adsorption, catalysis, photoluminescence, and electronic and mechanical properties. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs) with non‐blinking applied in bio‐imaging is important for understanding cellular dynamics by monitoring single particles in living cells. Antibunching is once believed to be applied to identify a single QD, which shows a strong dependence on the atom or ion number. However, recent works indicate that the antibunching alone may not be sufficient to demonstrate that the fluorescence comes from a single QD. To some extent, it is neither necessary nor sufficient for a single QD, though it is absolutely right for a single atom because a single QD is composed of thousands of atoms, which in principle are favorable to the formation of multi‐excitonic states. Blinking behavior, almost unobservable in ensembles due to the averaging, is characteristic of the single QD which owns the quantum effect due to its discrete energy levels. Here, a method of transformation of a single graphene quantum dot from non‐blinking to blinking via catalytic reaction to identify a single QD is reported, which can also help with understanding the catalytic dynamics of a single QD, which is a complementary means of confirming a single QD. The reported technique paves the way to understanding a single QD and its catalytic and kinetic behaviors. [ABSTRACT FROM AUTHOR]

Upon heating, lithium L-malate undergoes topotactic dehydration to form a phase containing the unsaturated fumarate ligand, in which the original 3-D framework remains intact. Insight into this unusual transformation has been obtained by single crystal X-ray diffraction, MAS-NMR, in situ powder X-ray diffraction and DFT calculations. [ABSTRACT FROM AUTHOR]

Crystallinemetal–organic frameworks (MOFs) are porous frameworkscomprising an infinite array of metal nodes connected by organic linkers.The number of novel MOF structures reported per year is now in excessof 6000, despite significant increases in the complexity of both componentunits and molecular networks. Their regularly repeating structuresgive rise to chemically variable porous architectures, which havebeen studied extensively due to their sorption and separation potential.More recently, catalytic applications have been proposed that makeuse of their chemical tunability, while reports of negative linearcompressibility and negative thermal expansion have further expandedinterest in the field. [ABSTRACT FROM AUTHOR]

We report the phase behaviour of chiral, racemic and meso-lithium tartrate frameworks, which was examined as a function of solvent system, temperature and ligand isomer. Through our comprehensive investigation of this system of 14 diverse phases, we have gained detailed insight into the effect of synthesis conditions on product structure, and elucidated the thermodynamic and kinetic factors involved in phase selection. Reactions in ethanol between lithium acetate and chiral, racemic and meso-tartaric acids give rise to anhydrous kinetic products; polymorphs with higher entropy tend to appear at high temperatures. Reactions at room temperature in water-ethanol mixtures give rise to hydrated kinetic products, including two new crystal structures, [Li2(D,L-tartrate)(H2O)2]n in P̄1 and [Li2(meso-tartrate)(H2O)0.5]n in C2221, whose structures are contrasted with known anhydrous products. Reactions at elevated temperatures in water-ethanol mixtures result in the formation of low enthalpy, anhydrous products and, furthermore, the global minimum energy structure appears at high temperatures in all cases owing to in situ ligand isomerization. [ABSTRACT FROM AUTHOR]

The mechanical properties of hybrid framework materials, including both nanoporous metal–organic frameworks (MOFs) and dense inorganic–organic frameworks, are discussed in this critical review. Although there are relatively few studies of this kind in the literature, major recent advances in this area are beginning to shed light on the fundamental structure–mechanical property relationships. Indeed research into the mechanical behavior of this important new class of solid-state materials is central to the design and optimal performance of a multitude of technological applications envisaged. In this review, we examine the elasticity of hybrid frameworks by considering their Young's modulus, Poisson's ratio, bulk modulus and shear modulus. This is followed by discussions of their hardness, plasticity, yield strength and fracture behavior. Our focus is on both experimental and computational approaches. Experimental work on single crystals and amorphized monoliths involved primarily the application of nanoindentation and atomic force microscopy to determine the elastic moduli and hardness properties. The compressibility and bulk moduli of single crystals and polycrystalline powders were studied by high-pressure X-ray crystallography in the diamond anvil cell, while in one instance spectroscopic ellipsometry has also been used to estimate the elastic moduli of MOF nanoparticles and deposited films. Theoretical studies, on the other hand, encompassed the application of first principles density-functional calculations and finite-temperature molecular dynamics simulations. Finally, by virtue of the diverse mechanical properties achievable in hybrid framework materials, we propose that a new domain be established in the materials selection map to define this emerging class of materials (137 references). [ABSTRACT FROM AUTHOR]

The mechanical properties of hybrid framework materials, including both nanoporous metal–organic frameworks (MOFs) and dense inorganic–organic frameworks, are discussed in this critical review. Although there are relatively few studies of this kind in the literature, major recent advances in this area are beginning to shed light on the fundamental structure–mechanical property relationships. Indeed research into the mechanical behavior of this important new class of solid-state materials is central to the design and optimal performance of a multitude of technological applications envisaged. In this review, we examine the elasticity of hybrid frameworks by considering their Young's modulus, Poisson's ratio, bulk modulus and shear modulus. This is followed by discussions of their hardness, plasticity, yield strength and fracture behavior. Our focus is on both experimental and computational approaches. Experimental work on single crystals and amorphized monoliths involved primarily the application of nanoindentation and atomic force microscopy to determine the elastic moduli and hardness properties. The compressibility and bulk moduli of single crystals and polycrystalline powders were studied by high-pressure X-ray crystallography in the diamond anvil cell, while in one instance spectroscopic ellipsometry has also been used to estimate the elastic moduli of MOF nanoparticles and deposited films. Theoretical studies, on the other hand, encompassed the application of first principles density-functional calculations and finite-temperature molecular dynamics simulations. Finally, by virtue of the diverse mechanical properties achievable in hybrid framework materials, we propose that a new domain be established in the materials selection map to define this emerging class of materials (137 references). [ABSTRACT FROM AUTHOR]

A family of coordination polymers with remarkable structural and chemical complexity is produced when Cu and Zn are combined with 5-hydroxyisophthalic acid and 4,4′-bipyridyl. The structures of these four- and five-component phases are fully ordered, with the two metals occupying different sites and the ligands playing distinct bridging roles in each structure. In one five-component phase, oxalate forms as a product of partial ligand decomposition and is incorporated alongside the two original ligands into the resultant solid. The valence of Cu and the Cu/Zn ratios differ between the phases, in spite of similar synthetic conditions. [ABSTRACT FROM AUTHOR]

The protolysis of magnesium sesquicarbide, Mg2C3, with inorganic acids provides an interesting alternative to the more common hydrolysis of ionic carbides for obtaining their respective hydrocarbons. In particular, protolysis reactions with ammonium halides as precursors for hydrogen halides were investigated using in situ methods such as TGA/sDTA/MS and high-temperature XRPD. The protolysis reactions with NH4F and NH4Cl revealed two different reaction mechanisms yielding C3H4 and the respective magnesium halides as expected products. In the case of NH4Cl, intermediate phases that have not been previously observed, specificly (NH4)2MgCl4 (I4/mmm) and two modifications of NH4MgCl3 (P63/mmc), were structurally characterized. [ABSTRACT FROM AUTHOR]

Abstract: Four new magnesium containing metal–organic hybrid compounds have been synthesized in an effort to prepare low-density materials for hydrogen storage. The compounds were prepared hydrothermally and characterized using single crystal X-ray diffraction. Three of these compounds are analogs of known transition metal structures with squarate (I, Pn-3n, a =16.276(5)Å), diglycolate (II, P212121, a =6.860(1)Å, b =9.993(1)Å, c =10.884(1)Å, R 1 =0.0341), and glutarate (III, R-3, a =10.744(2)Å, c =28.677(5)Å, R 1 =0.0554) ligands; the fourth is a novel structure using cyclobutanetetracarboxylate (IV, Pccn, a =9.382(1)Å, b =14.410(2)Å, c =8.725(1)Å, R 1 =0.0465) which contains potassium as well as magnesium cations. [Copyright &y& Elsevier]

The reaction of nickel, cobalt, and manganese with 1,2-ethylenediphosphonic acid or 1,2-ethylenediphosphonic acid and 1,10-phenanthroline under hydrothermal conditions resulted in the pillared layered structures CO2(H2O)2(O3- PC2H4PO3) (I) and Ni2(H2O)2(O3PC2H4PO3) (II), which are isostructural to a zinc phase that has previously been characterized by X-ray powder methods. In addition, a 1 D chain structure, Mn(HO3P(CH2)2PO3H)(H2O)2(C12H8N2) (III), and a pillared layered structure, Mn(HO3P(CH2)2PO3H) (IV), were obtained. The structures of these phases were solved by single-crystal X-ray diffraction methods. The crystallographic data are as follows: compound I P21/n (No. 14), a = 5.6500(11) Å, b = 4.7800(10) Å, c = 15.330(3) Å, β = 98.50(3)°, V 409.47(14) ų, Z 2; compound II P21/n (No. 14), a = 5.5807(11) Å, b = 4.7205(9) Å, c = 15.250(3) Å, β = 98.55(3)° , V = 397.28(13) ų, Z = 2; compound III G2/c (No. 15), a = 12.109(2) Å, b = 15.328(3) Å, c = 9.848(2) Å, β = 108.88(3)°, V = 1729.5(6) ų, Z = 4; compound IV P1 (No. 2), a = 5.498(5) Å, b = 7.71 5(6) Å, c = 8.093(7) Å, α = 82.986(12)°, β = 75.565(12)°, γ = 80.582(12)°, V= 326.7(5) ų, Z = 2. Magnetic measurements show antiferromagnetic behavior below TN = 7 K for I and 13 K for II. [ABSTRACT FROM AUTHOR]

Abstract: We report the synthesis, crystal structures, magnetic properties, and thermal behavior of a family of isostructural transition metal gallate dihydrates containing infinite chains of trans-corner-sharing octahedra. The gallates crystallize in the enantiomorphic space groups and , chirality being imparted by helical motifs in the structure. Ni(C7O5H4)⋅2H2O: , ; Mn(C7O5H4)⋅2H2O: , ; Co(C7O5H4)⋅2H2O: , . The Co(II) and Ni(II) gallates exhibit antiferromagnetic behavior, with and 19 K, respectively, while Mn(II) gallate is paramagnetic down to 5 K. High-temperature X-ray powder diffraction indicates that crystallinity is lost near 200 °C in all of the compounds. Decarboxylation of the gallate moieties is believed to facilitate this thermal decomposition. [Copyright &y& Elsevier]

Abstract: Thermochromic VO2 nanorods were prepared via thermal conversion of the metastable VO2–B phase synthesized by hydrothermal methods. We observe an increased thermochromic transition temperature to ∼75–80°C by variable-temperature infrared spectroscopy. Nano- and sub-micron structures of other vanadium oxides (V3O7, (NH4)0.5V2O5, and V2O5) were obtained simply by varying the starting materials in the hydrothermal synthesis. We also obtained nanostructures of the high temperature tetragonal rutile phase of VO2 by thermolysis of single-source vanadium (IV) precursors. [Copyright &y& Elsevier]

Several new forms of transition metal diglycolates (C4H4O5) and iminodiacetates (C4H5O4N) have been synthesized hydrothermally, and their structures solved using single crystal XRD. Isostructural diglycolates of the formula M(H2O)(dga) · H2O (M=Co, Mn) contain 1D cavities occupied by water (Co: [1] P212121, a=6.8220(11) Å, b=9.9700(17) Å, c=10.9102(18) Å, R1=0.0206, Mn: [1] P212121, a=6.8796(18) Å, b=9.856(3) Å, c=11.067 Å, R1=0.0287). In the case the cobalt phase [1], a color change and significant structural changes accompany dehydration at 200 °C, yielding a new phase with reversible water absorption/desorption. A dense, anhydrous phase forms at higher temperatures, Co(dga) [2] (P212121, a=5.8462(12) Å, b=8.1152(17) Å, c=11.223(2) Å, R1=0.0311). Two layered iminodiacetates are also described: Ni(H2O)2(ida) [3] (Pca21, a=13.921(7) Å, b=5.131(3) Å, c=9.595(5) Å, R1=0.0315) and Co(H2O)(ida) [4] (P21/c, a=7.925(3) Å, b=10.628(4) Å, c=7.358(3) Å, β=109.598(7)°, R1=0.0250). These materials further illustrate both the role of higher reaction temperatures in reducing the framework water content and the importance of ligand flexibility in determining the metal–oxygen–metal dimensionality in hybrid systems. [Copyright &y& Elsevier]

Nanoporous hybrid materials, both metal-organic coordination polymers and hybrid metal oxides, have recently developed into an important new class of solid-state compounds. Potential applications in the field of heterogeneous catalysis include acid, shape-selective, chiral, ship-in-a-bottle, and shape-recognition-driven reactions. Here, we summarize the synthesis, structural features, chemical functionality, and catalytic properties of this unique family of materials. [ABSTRACT FROM AUTHOR]

Here, we report curvature‐induced electron spin catalysis by using solid carbon spheres as catalysts, which were synthesized using positive curvature molecular hexabromocyclopentadiene as a precursor molecule, following a radical coupling mechanism. The curvature spin of carbon is regarded as an overlapping state of σ‐ and π‐radical, which is identified by the inverse Laplace transform of pulse‐electron paramagnetic resonance. The growth mechanism of carbon spheres abiding by Kroto's model, is supported by the density functional theory study of thermodynamics and kinetics calculations. The solid carbon spheres present excellent catalytic behaviour of oxidation coupling of amines to form corresponding imines with the conversion of >99 %, selectivity of 98.7 %, and yield of 97.7 %, which is attributed to the predominantly curvature‐induced electron spin catalysis of carbon, supported by the calculation of oxygen adsorption energy. This work proposes a view of curvature‐induced spin catalysis of carbon, which opens up a research direction for curvature‐induced electron spin catalysis. [ABSTRACT FROM AUTHOR]

Presents conformational studies of dihydrobiphenyls. Crystallographic data; Cyclohexadiene ring geometry; Edge-to-face aromatic association.

Presents a study which identified the driving forces of the halocarbon adsorption under equilibrium conditions by probing the influence of various parameters. Information on zeolite/hydrocarbon systems; Discussion of halocarbon behavior in zeolites; Properties of halcarbons/zeolites systems; Methodology used to conduct study.

The author reflects his views on the role of x-ray powder diffraction for studying materials' properties. Topics discussed include the study of phase transitions in ferroelectrics and the location of hydrogen atoms in heavy-metal hydrides, x-ray and time-of-flight neutron data, and the scope of the Rietveld method into organic materials.

Epitaxial thin films of BiMnO[sub 3] were deposited on single-crystal substrates of (100)-oriented SrTiO[sub 3] by pulsed-laser deposition. Structural analysis by x-ray diffraction, electron diffraction, and transmission electron microscopy (TEM) indicated that the films were monoclinic and twinned with two dominant orientation relationships. The first is (111) BiMnO[sub 3] ∥ (100) SrTiO[sub 3] and ∼[101] BiMnO[sub 3] ∥ <010> SrTiO[sub 3]; the second is (101) BiMnO[sub 3] ∥ (100) SrTiO[sub 3] and ∼[121] BiMnO[sub 3] ∥ <010> SrTiO[sub 3]. High-resolution TEM images revealed that there is no reaction or appreciable interdiffusion at the substrate/film interface, despite the high temperature of the substrate during deposition (∼1000 K). Magnetic characterization was carried out (both magnetization versus temperature and hysteresis loops) and the results agree with previous reports of a ferromagnetic transition with T[sub C]∼105 K. The actual value of T[sub C] in the films is a few degrees lower than the bulk material, the discrepancy being attributed to strain, nonstoichiometry, or size effects. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Inorganic zeolites have excellent molecular sieving properties, but they are difficult to process into macroscopic structures. In this work, we use metal–organic framework (MOF) glass as substrates to engineer the interface with inorganic zeolites, and then assemble the discrete crystalline zeolite powders into monolithic structures. The zeolites are well dispersed and stabilized within the MOF glass matrix, and the monolith has satisfactory mechanical stabilities for membrane applications. We demonstrate the effective separation performance of the membrane for 1,3‐butadiene (C4H6) from other C4 hydrocarbons, which is a crucial and challenging separation in the chemical industry. The membrane achieves a high permeance of C4H6 (693.00±21.83 GPU) and a high selectivity over n‐butene, n‐butane, isobutene, and isobutane (9.72, 9.94, 10.31, and 11.94, respectively). This strategy opens up new possibilities for developing advanced membrane materials for difficult hydrocarbon separations. [ABSTRACT FROM AUTHOR]

Inorganic zeolites have excellent molecular sieving properties, but they are difficult to process into macroscopic structures. In this work, we use metal–organic framework (MOF) glass as substrates to engineer the interface with inorganic zeolites, and then assemble the discrete crystalline zeolite powders into monolithic structures. The zeolites are well dispersed and stabilized within the MOF glass matrix, and the monolith has satisfactory mechanical stabilities for membrane applications. We demonstrate the effective separation performance of the membrane for 1,3‐butadiene (C4H6) from other C4 hydrocarbons, which is a crucial and challenging separation in the chemical industry. The membrane achieves a high permeance of C4H6 (693.00±21.83 GPU) and a high selectivity over n‐butene, n‐butane, isobutene, and isobutane (9.72, 9.94, 10.31, and 11.94, respectively). This strategy opens up new possibilities for developing advanced membrane materials for difficult hydrocarbon separations. [ABSTRACT FROM AUTHOR]

An interview is presented with the British materials scientist Anthony Cheetham, discussing the China's active development of its scientific research community as of 2015. Questions address topics including the Cheetham's experiences visiting and cooperating with Chinese scientists, which scientific disciplines China is particularly growing in, and the nation's funding application system for ongoing research.

Review: 75 refs. [ABSTRACT FROM AUTHOR]

The article provides information on the research that combines molecular inorganic and organic building blocks to produce open networks. It proves that dense inorganic-organic hybrid materials provide opportunities for creating unusual properties or combinations of properties such as ferromagnetism, metallic conductivity and superconductivity. In addition, dense hybrid frameworks can be more thermally stable than their porous or molecular counterparts. The researchers believed that it is possible to make hybrids with properties that are unique in purely organic or inorganic systems.

Discusses research regarding crystalline porous materials. Domination of these materials by aluminosilicate zeolites; Discovery of new families of porous materials, including amorphous mesoporous materials; Interest in novel porous inorganic and organic solids; Number of elements used in porous materials; Solids with potentially large cavities; Synthesizing a material with large pores; Future research.

Features research on complex inorganic materials. Discovery of superconducting cuprates in 1987; Manipulation of crystallization parameters in substances with complex stoichiometries; Generation of short radiation from optical inorganic materials; Metastability of microporous materials with respect to their condensed polymorphic analogs.

Highlights: Recent advances in the metal–organic framework (MOF)-related catalysts for electrochemical ammonia synthesis protocols under ambient reaction conditions are summarized and discussed. The design and fabrication of efficient electrocatalysts from MOF for the reduction of N2 and NO3− are systematically analyzed. Based on the current advances, the ongoing challenges and promising perspectives are highlighted. Electrocatalytic synthesis under mild conditions has become increasingly important as one of the practical alternatives for industrial applications, especially for the green ammonia (NH3) industry. A properly engineered electrocatalyst plays a vital role in the realization of superior catalytic performance. Among various types of promising nanomaterials, metal–organic frameworks (MOFs) are competitive candidates for developing efficient electrocatalytic NH3 synthesis from simple nitrogen-containing molecules or ions, such as N2 and NO3−. In this review, recent advances in the development of electrocatalysts derived from MOFs for the electrosynthesis of NH3 are collected, categorized, and discussed, including their application in the N2 reduction reaction (NRR) and the NO3− reduction reaction (NO3RR). Firstly, the fundamental principles are illustrated, such as plausible mechanisms of NH3 generation from N2 and NO3−, the apparatus of corresponding electrocatalysis, parameters for evaluation of reaction efficiency, and detection methods of yielding NH3. Then, the electrocatalysts for NRR processes are discussed in detail, including pristine MOFs, MOF-hybrids, MOF-derived N-doped porous carbons, single atomic catalysts from pyrolysis of MOFs, and other MOF-related materials. Subsequently, MOF-related NO3RR processes are also listed and discussed. Finally, the existing challenges and prospects for the rational design and fabrication of electrocatalysts from MOFs for electrochemical NH3 synthesis are presented, such as the evolution of investigation methods with artificial intelligence, innovation in synthetic methods of MOF-related catalysts, advancement of characterization techniques, and extended electrocatalytic reactions. [ABSTRACT FROM AUTHOR]

Halide double perovskites [A2MIMIIIX6] are an important class of materials that have garnered substantial interest as non‐toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs2NaLnI6 (Ln=Ce, Nd, Gd, Tb, Dy). The complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported. [ABSTRACT FROM AUTHOR]

Halide double perovskites [A2MIMIIIX6] are an important class of materials that have garnered substantial interest as non‐toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs2NaLnI6 (Ln=Ce, Nd, Gd, Tb, Dy). The complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported. [ABSTRACT FROM AUTHOR]

Here, we report kinetic studies using electron spin resonance spectroscopy on spin catalysis reactions caused by using graphene belts which were synthesized by a radical coupling method. The results show that σ‐type free radical species provide the dominant sites for catalytic activity through the spin‐spin interaction, although there are some other influencing factors. The spin catalysis mechanism can be applied both in the oxygen reduction reaction (ORR) and in organic synthesis. The graphene belt spin catalyst shows excellent performance with a high ORR half‐wave potential of 0.81 V and long‐term stability with almost no loss of activity after 50 000 cycles in alkaline media. It also shows excellent performance in a benzylamine coupling with molecular oxygen to generate the corresponding imine at an average conversion of ≈97.7 % and an average yield of ≈97.9 %. This work opens up a new research direction for understanding aerobic processes in the field of spin catalysis. [ABSTRACT FROM AUTHOR]

Here, we report kinetic studies using electron spin resonance spectroscopy on spin catalysis reactions caused by using graphene belts which were synthesized by a radical coupling method. The results show that σ‐type free radical species provide the dominant sites for catalytic activity through the spin‐spin interaction, although there are some other influencing factors. The spin catalysis mechanism can be applied both in the oxygen reduction reaction (ORR) and in organic synthesis. The graphene belt spin catalyst shows excellent performance with a high ORR half‐wave potential of 0.81 V and long‐term stability with almost no loss of activity after 50 000 cycles in alkaline media. It also shows excellent performance in a benzylamine coupling with molecular oxygen to generate the corresponding imine at an average conversion of ≈97.7 % and an average yield of ≈97.9 %. This work opens up a new research direction for understanding aerobic processes in the field of spin catalysis. [ABSTRACT FROM AUTHOR]

Perovskite-related materials show very promising properties in many fields. Pb-free perovskites are particularly interesting, because of the toxicity of Pb. In this study, hybrid double perovskite MA2KBiCl6 (MA = methylammonium cation) was found to have interesting variable temperature behaviours. Both variable temperature single crystal X-ray diffraction, synchrotron powder diffraction, and Raman spectroscopy were conducted to reveal a rhombohedral to cubic phase transition at around 330 K and an order to disorder transition for inorganic cage below 210 K. [ABSTRACT FROM AUTHOR]

The article presents materials science research study on how Aluminum formate, an earth-abundant material for CO2 capture. Topics include combination of gas adsorption and gas breakthrough measurements show that the metal-organic framework, Al(HCOO)3 (ALF), which can be made inexpensively from commodity chemicals; and preferential adsorption of CO2 is a size-selective separation that depends on the subtle difference between the kinetic diameters of CO2 and nitrogen gas (N2).

First principles calculations on the hybrid perovskite CH3NH3PbI3 predict strong hydrogen-bonding which influences the structure and dynamics of the methylammonium cation and reveal its interaction with the tilting of the PbI6 octahedra. The calculated atomic coordinates are in excellent agreement with neutron diffraction results. [ABSTRACT FROM AUTHOR]

Chiral hybrid metal halides with a high dissymmetry factor (glum) and a superior photoluminescence quantum yield (PLQY) are promising candidates for circularly polarized luminescence (CPL) light sources. Here, we report eight new chiral hybrid manganese halides, crystallizing in the non‐centrosymmetric space group P212121 and showing intense CPL emissions. Oppositely‐signed circular dichroism (CD) and CPL signals are detected according to the R‐ and S‐configurations of the chiral alkanolammonium cations. Time‐resolved PL spectra show long averaged decay lifetimes up to 1 ms for (R‐3‐quinuclidinol)MnBr3 (R‐1). The glum of polycrystalline samples for coordinated structures (23×10−3) is more than doubled compared with the non‐coordinated ones (8.5×10−3), due to the structural variations. R‐1 exhibit both a high glum and a high PLQY (50.2 %). The effective chirality transfer mechanism through coordination bonds, with strongly emissive MnII centers, enables a new class of high‐performance CPL materials. [ABSTRACT FROM AUTHOR]

Chiral hybrid metal halides with a high dissymmetry factor (glum) and a superior photoluminescence quantum yield (PLQY) are promising candidates for circularly polarized luminescence (CPL) light sources. Here, we report eight new chiral hybrid manganese halides, crystallizing in the non‐centrosymmetric space group P212121 and showing intense CPL emissions. Oppositely‐signed circular dichroism (CD) and CPL signals are detected according to the R‐ and S‐configurations of the chiral alkanolammonium cations. Time‐resolved PL spectra show long averaged decay lifetimes up to 1 ms for (R‐3‐quinuclidinol)MnBr3 (R‐1). The glum of polycrystalline samples for coordinated structures (23×10−3) is more than doubled compared with the non‐coordinated ones (8.5×10−3), due to the structural variations. R‐1 exhibit both a high glum and a high PLQY (50.2 %). The effective chirality transfer mechanism through coordination bonds, with strongly emissive MnII centers, enables a new class of high‐performance CPL materials. [ABSTRACT FROM AUTHOR]

Yellow-emitting phosphors activatedby Ce3+are keycomponents of white light-emitting diodes (LEDs) based on the blue(Ga,In)N LED. In these phosphors, the electronic environment aroundCe3+determines its photoluminescence wavelengths. PlacingCe3+in octahedral sites in oxides can potentially leadto yellow or orange phosphors that can compete with the importantcommercial phosphor, Y3Al5O12:Ce.However, there are very few examples of such materials. In this article,we explore the photoluminescent behavior of Ce3+in oxideswith the olivine structure, whereby two distorted octahedral dopingsites exist. We demonstrate that the promising new yellow phosphorγ-Ca2SiO4:Ce requires a second dopant,Al3+, to avoid the formation of the undesired β polymorph.Our results indicate that the yellow emission is indirectly causedby the complex polymorphism of Ca2SiO4, particularlythe low temperature formation of the γ-phase. The dramatic shiftin emission from yellow to light-blue when this phosphor is heatedto 800 °C is explained in terms of the redistributionof Ce3+in the lattice. A similar effect is observed whenSi4+is substituted by Ge4+. The light-blueemission of Ca2GeO4:Ce,Al is reported as wellas the photoluminescent properties of the Ca2(Ge,Si)O4:Ce,Al solid solution. [ABSTRACT FROM AUTHOR]

Six novel crystalline coordination polymers composed of alkali metal ions and trithiocyanurate anions (C3N3S3H2− = ttcH2−) were synthesized. Single crystals were used both for structure determinations by X-ray diffraction and ionic conductivity measurements by AC impedance methods. The structures are: (i) sodium trithiocyanurate trihydrate, Na(ttcH2)(H2O)3 in space group P21; (ii) potassium trithiocyanurate hydrate, K(ttcH2)(H2O) in P1̅; (iii) rubidium trithiocyanurate hydrate, Rb(ttcH2)(H2O) in P1̅; (iv) rubidium trithiocyanurate hydrate, Rb3(ttcH2)2(ttcH3)2(H2O)5(OH) in P1̅; and (v, vi) two anhydrous polymorphs of caesium trithiocyanurates, Cs(ttcH2) in P1̅ and Cc. With the exception of the sodium phase, which is layered, all of these compounds consist of three dimensional coordination networks. In all systems, the inorganic regions are interleaved by arrays of ttcH2− anions. The most interesting feature of this system is the thiol-rich environment formed between the trithiocyanurate layers, where alkali metal ions are located. Water molecules, where present, are always coordinated to a cation. Among these crystals, K(ttcH2)(H2O) exhibited proton conductivity under atmospheric conditions (25 ± 0.2 °C): 1.1 × 10−5 S cm−1 in the direction perpendicular to the bc plane and 3.1 × 10−6 S cm−1 along the c axis. [ABSTRACT FROM AUTHOR]

Sparse aperture masking interferometry (SAM) is a high-resolution observing technique that allows for imaging at and beyond a telescope’s diffraction limit. The technique is ideal for searching for stellar companions at small separations from their host star; however, previous analyses of SAM observations of young stars surrounded by dusty disks have had difficulties disentangling planet and extended disk emission. We analyze VLT/SPHERE-IRDIS SAM observations of the transition disk LkCa 15, model the extended disk emission, probe for planets at small separations, and improve contrast limits for planets. We fit geometrical models directly to the interferometric observables and recover previously observed extended disk emission. We use dynamic nested sampling to estimate uncertainties on our model parameters and to calculate evidences to perform model comparison. We compare our extended disk emission models against point-source models to robustly conclude that the system is dominated by extended emission within 50 au. We report detections of two previously observed asymmetric rings at ∼17 and ∼45 au. The peak brightness location of each model ring is consistent with the previous observations. We also, for the first time with imaging, robustly recover an elliptical Gaussian inner disk, previously inferred via SED fitting. This inner disk has an FWHM of 5 au and a similar inclination and orientation to the outer rings. Finally, we recover no clear evidence for candidate planets. By modeling the extended disk emission, we are able to place a lower limit on the near-infrared companion contrast of at least 1000. [ABSTRACT FROM AUTHOR]

The first thermochemical analysis by room-temperature aqueous solution calorimetry of a series of zeolite imidazolate frameworks (ZIFs) has been completed. The enthalpies of formation of the evacuated ZIFs—ZIF-zni, ZIF-1, ZIF-4, CoZIF-4, ZIF-7, and ZIF-8—along with as-synthesized ZIF-4 (ZIF-4·DMF) and ball-milling amorphized ZIF-4 (amZIF-4) were measured with respect to dense components: metal oxide (ZnO or CoO), the corresponding imidazole linker, and N,N dimethylformamide (DMF) in the case of ZIF-4·DMF. Enthalpies of formation of ZIFs from these components at 298 K are exothermic, but the ZIFs are metastable energetically with respect to hypothetical dense components in which zinc is bonded to nitrogen rather than oxygen. These enthalpic destabilizations increase with increasing porosity and span a narrow range from 13.0 to 27.1 kJ/mol, while the molar volumes extend from 135.9 to 248.8 cm3/mol; thus, almost doubling the molar volume results in only a modest energetic destabilization. The experimental results are supported by DFT calculations. The series of ZIFs studied tie in with previously studied MOF-5, creating a broader trend that mirrors a similar pattern by porous inorganic oxides, zeolites, zeotypes, and mesoporous silicas. These findings suggest that no immediate thermodynamic barrier precludes the further development of highly porous materials. [ABSTRACT FROM AUTHOR]

Abstract: Hybridizing carbon nanotubes with complex inorganic nanostructures provides a new route to designing next-generation photocatalysts. These hybrids utilize charge transfer processes through the interface, which reduce the electron–hole recombination rate in the photocatalyst. This work presents the first complex CNT hybrid, using titanium-silicate (TS-1), with dramatically improved photocatalytic activity for the degradation of organic compounds compared with the corresponding nanocomposite and the individual components. [ABSTRACT FROM AUTHOR]

The mechanical properties of seven zeolitic imidazolate frameworks (ZIFs) based on five unique network topologies have been systematically characterized by single-crystal nanoindentation studies. We demonstrate that the elastic properties of ZIF crystal structures are strongly correlated to the framework density and the underlying porosity. For the systems considered here, the elastic modulus was found to range from 3 to 10 GPa, whereas the hardness property lies between 300 MPa and 1.1 GPa. Notably, these properties are superior to those of other metal-organic frameworks (MOFs), such as MOF-5. In substituted imidazolate frameworks, our results show that their mechanical properties are mainly governed by the rigidity and bulkiness of the substituted organic linkages. The framework topology and the intricate pore morphology can also influence the degree of mechanical anisotropy. Our findings present the previously undescribed structuremechanical property relationships pertaining to hybrid open frameworks that are important for the design and application of new MOF materials. [ABSTRACT FROM AUTHOR]

Two isostructural hybrid inorganic-organic frameworks, M2(4,4′-bpy)(tfhba)2·4,4′-bpy, (M = Co (1), Zn (2); 4,4′-bpy = 4,4′-bipyridine; tfhba = 2,3,5,6-tetrafluoro-4-hydroxybenzoate) have been synthesized and their structures elucidated using single crystal X-ray diffraction. These materials are the first hybrid structures synthesized using the tfhba ligand. They contain a one-dimensional chain of corner-sharing MO4N trigonal bipyramids that has not been observed to date for Co2+ units. The magnetic properties of 1 have been investigated and indicate ferromagnetic ordering along the chains, with weak antiferromagnetic interactions between them. Overall the system is antiferromagnetic with a Nel temperature of 3 K, but undergoes a field-induced magnetic phase transition at 3 kOe. [ABSTRACT FROM AUTHOR]

Four three-dimensional (3D) inorganic−organic heterometallic Na−Bi benzenedicarboxylate (BDC) frameworks, [NaBi(1,4-BDC)2(DMF)2], 1, [NaBi(1,4-BDC)2(DMF)(H2O)]·(DMF), 2, [NaBi(1,3-BDC)2(DMF)], 3, and [NaBi(1,3-BDC)2(EtOH)], 4, have been synthesized under solvothermal conditions and their structures were determined by single crystal X-ray diffraction. Compounds 1 and 2 have very similar channel structures in which infinite Na−O−Bi chains of one-dimensional inorganic connectivity are linked by the 1,4-BDC anions into 3D structures (I1O2). Compound 2 was obtained from 1 when it was exposed to moisture; it becomes amorphous when the solvent is removed from the channels on heating, but the activated phase has a reasonably high surface area of 71 m2/g from nitrogen porosimetry measurements. Compounds 3 and 4 are isostructural except for the solvents; they contain Na−O−Bi layers that are linked into 3D structures (I2O1) by 1,3-BDC anions. They are robust owing to their two-dimensional inorganic connectivity and retain their framework structures even after the removal of the solvent molecules from the channels. However, the surface area of an activated sample of 3 is only 8 m2/g due to the narrow apertures into the cavities. Tb3+- and Eu3+-doped 2 and 3 emit characteristic ligand-sensitized green and red luminescence, respectively. Four hybrid inorganic−organic heterometallic Na−Bi benzenedicarboxylate frameworks with channel structures have been synthesized and their properties were investigated. [ABSTRACT FROM AUTHOR]