Showing papers in "Dalton Transactions in 2017"

Chalcogen bonding in synthesis, catalysis and design of materials

Abstract: Chalcogen bonding is a type of noncovalent interaction in which a covalently bonded chalcogen atom (O, S, Se or Te) acts as an electrophilic species towards a nucleophilic (negative) region(s) in another or in the same molecule. In general, this interaction is strengthened by the presence of an electron-withdrawing group on the electron-acceptor chalcogen atom and upon moving down in the periodic table of elements, from O to Te. Following a short discussion of the phenomenon of chalcogen bonding, this Perspective presents some demonstrative experimental observations in which this bonding is crucial for synthetic transformations, crystal engineering, catalysis and design of materials as synthons/tectons.

Two-step hydrothermally synthesized carbon nanodots/WO3 photocatalysts with enhanced photocatalytic performance

Abstract: In this study, carbon nanodots (C-dots)/WO3 photocatalysts were prepared via a two-step hydrothermal method. The morphologies and optical properties of the as-prepared materials were investigated. Compared with the prepared WO3 and C-dots, the C-dots/WO3 possessed stronger photocatalytic capability and excellent recyclability for photocatalytic elimination of Rhodamine B. For example, the achieved first order reaction rate constant of 0.01942 min-1 for C-dots/WO3 was ∼7.7 times higher than that of the prepared WO3. The enhanced photocatalytic activity of C-dots/WO3 was attributed to the enhanced light harvesting ability and efficient spatial separation of photo-excited electron-hole pairs resulting from the synergistic effect of WO3 and C-dots. The high photocatalytic activity of C-dots/WO3 remained unchanged even after 3 cycles of use. Meanwhile, a possible mechanism of C-dots/WO3 for the enhanced photocatalytic activity was proposed.

Luminescent rare-earth-based MOFs as optical sensors

Abstract: Rare-earth-based metal–organic frameworks (ReMOFs) have emerged as an interesting family of compounds, for which new properties are increasingly being found. Based on the potential of ReMOFs, resulting from their optical properties, large numbers of investigations have been carried out during the last decade. Among these investigations, ReMOFs as optical sensors, using their luminescence properties, are increasingly becoming an attractive and useful topic of research. In this study, we have provided the basics of the luminescence behaviour of ReMOFs, various possible sensing mechanisms, and a summary of the uses of ReMOFs for the sensing of nitro explosives, cations, anions, small molecules, pH, and temperature.

Supercapacitor performance of perovskite La1−xSrxMnO3

Abstract: In this study, Sr-doped lanthanum manganite perovskites (La1−xSrxMnO3, LSM) as electrode materials for supercapacitors were prepared via an improved sol–gel method. Among LSM, the x = 0.15 sample shows superior electrochemical performance, delivering the highest specific capacitance of 102 F g−1 at a current density of 1 A g−1 and lower intrinsic resistance in 1 M KOH. The effective charge storage of LSM is due to the redox reaction of the anion intercalation corresponding to the surface redox processes of Mn2+/Mn3+ and Mn3+/Mn4+ occurring within the electroactive materials. The maximum energy density of 3.6 W h kg−1 was achieved at a power density of 120 W kg−1 for the symmetric supercapacitor with a long cycling life after 5000 charging and discharging cycles. With the increase of cycle times, the element leaching phenomenon leads to the decrease of electrochemical performance. Our work indicated that the perovskite manganite La0.85Sr0.15MnO3 shows potential applications in the field of pseudocapacitance electrode materials and is worthy of further investigation.

Multicomponent equiatomic rare earth oxides with a narrow band gap and associated praseodymium multivalency.

Abstract: New multicomponent equiatomic rare earth oxides (ME-REOs) containing 3-7 rare earth elements (Ce, Gd, La, Nd, Pr, Sm and Y) in equiatomic proportions are synthesized using nebulized spray pyrolysis. All the systems crystallized as a phase pure fluorite type (Fm3[combining macron]m) structure in spite of the high chemical complexity. A nominal increase in the lattice parameter compared to CeO2 is observed in all ME-REOs. X-ray photoelectron spectroscopy performed on the ME-REOs confirmed that all the constituent rare earth elements are present in the 3+ oxidation state, except for Ce and Pr which are present in 4+ and in a mixed (3+/4+) oxidation state, respectively. The presence of Ce4+ contributes substantially to the observed stability of the single phase structure. These new oxide systems have narrow direct band gaps in the range of 1.95-2.14 eV and indirect band gaps in the range of 1.40-1.64 eV, enabling light absorption over the entire visible spectral range. Furthermore, the oxygen vacancy concentration rapidly increases and then saturates with the number of rare earth elements that are incorporated into the ME-REOs. The lowering of the band gap is found to be closely related to the presence of multivalent Pr. Interestingly, the band gap values are relatively invariant with respect to the composition or thermal treatments. Considering the high level of oxygen vacancies present and the observed low band gap values, these new material systems can be of importance where the presence of oxygen vacancies is essential or in applications where a narrow band gap is desirable.

Boron-doped graphitic carbon nitride nanosheets for enhanced visible light photocatalytic water splitting.

Abstract: A new type of boron-doped graphitic carbon nitride (B-g-C3N4) nanosheets was prepared by a benign one-pot thermal polycondensation process. Systematic studies revealed that a B-doping amount of 1 at% into g-C3N4 (1at%B-g-C3N4) showed the best photocatalytic H2 evolution activity of 1880 μmol h−1 g−1 under visible light irradiation (>400 nm), which is more than 12 times that of the pristine g-C3N4 bulk. Detailed characterizations revealed that the high photocatalytic performance could be attributed to the combination of band structure engineering and morphological control. B-doping not only reduces the band gap to absorb more visible light but also exhibits a higher surface area of B-g-C3N4 (49.47 m2 g−1) as compared to that of g-C3N4 bulk (8.24 m2 g−1), which subsequently improve the photocatalytic performance drastically. This work demonstrates a synergistic strategy to prepare efficient metal-free B-g-C3N4 nanosheets as a promising photocatalyst for H2 evolution under visible light with good stability.

A series of anionic host coordination polymers based on azoxybenzene carboxylate: structures, luminescence and magnetic properties.

Abstract: A series of coordination polymers {[Ln(aobtc)(H2O)4]·Hbipy·H2O}n (H4aobtc = azoxybenzene-2,2′,3,3′-tetracarboxylic acid, bipy = 4,4′-bipyridine, and Ln = Sm(1), Eu(2), Gd(3), Tb(4), Dy(5), Er(6)) have been synthesized and characterized systematically. The cationic Hbipy+ guest incorporated polymers are isostructural sets, featuring a one-dimensional (1D) zigzag double chain edifice composed of binuclear clusters [Ln2(H4aobtc)2], with the Hbipy+ guest being located on two sides. These 1D chains are further interlinked into a 2D layer structure, and further extended into a 3D framework through hydrogen bonding interactions. The luminescence emission spectra of polymers 2 and 3 are based on the H4aobtc acid ligands, while 1 and 4 display the characteristic f–f transitions of Ln(III) ions. Magnetic measurements revealed the presence of ferromagnetic behavior in polymer 3. The magnetic behaviors of 4 and 6 are ascribed to the depopulation of the Stark levels and/or weak antiferromagnetic interactions within MOFs at lower temperature. Slow relaxation is observed through the alternating-current susceptibility measurements for 5 at lower temperature, and the coexistence of weak ferromagnetism corresponding to the spin-canting-like behavior.

Recent development of luminescent rhenium(I) tricarbonyl polypyridine complexes as cellular imaging reagents, anticancer drugs, and antibacterial agents

Abstract: There has been fast-growing interest in the exploitation of the photophysical and photochemical properties of luminescent transition metal complexes in biological applications, with a focus on both diagnostic and therapeutic aspects. In particular, the design of luminescent rhenium(I) tricarbonyl polypyridine complexes as cellular imaging reagents and anticancer drugs has received considerable attention for a number of reasons. First, most rhenium(I) tricarbonyl polypyridine complexes possess diverse photophysical and photochemical properties through the coordination of functionalized ligands. The typical photophysical properties of the complexes such as large Stokes shifts, long emission lifetimes, and high photostability allow them to serve as attractive candidates for optical imaging. Also, the cellular uptake of the complexes can be readily quantified by atomic absorption spectroscopy and inductively coupled plasma-mass spectrometry. Additionally, owing to the characteristic infrared absorption bands and the isostructural relationship between rhenium and technetium-99m, rhenium(I) tricarbonyl complexes have been exploited as multimodal imaging reagents for vibrational and radio-imaging, respectively. Furthermore, the facile photosensitizing properties and the three carbon monoxide (CO) ligands render rhenium(I) tricarbonyl complexes promising candidates as photodynamic therapy reagents and photoactivatable CO-releasing molecules, respectively, for cancer treatment. In this Perspective, we describe the recent development of luminescent rhenium(I) tricarbonyl polypyridine complexes as cellular imaging reagents, anticancer drugs, and antibacterial agents.

A facile hydrothermal synthesis of carbon dots modified g-C3N4 for enhanced photocatalytic H2-evolution performance.

Abstract: Carbon dots (CDs)/g-C3N4 is a promising photocatalyst to split water for H2 production; however, the synthesis of CDs/g-C3N4 is usually rigorous and involves multiple steps, which limits its practical application. In this study, a facile hydrothermal approach was developed to prepare CDs/g-C3N4 photocatalysts using L-ascorbic acid and g-C3N4 as the precursors. Upon in situ thermal polymerization of L-ascorbic acid on the g-C3N4 surface, the carbon dots were homogeneously and solidly modified on the g-C3N4 surface. The CDs/g-C3N4 photocatalysts showed higher photocatalytic performance for H2 production than g-C3N4 under UV light irradiation using lactic acid as the sacrificial agent. The improved photocatalytic performance of CDs/g-C3N4 was mainly attributed to rapid interfacial charge transfer. After a Pt co-catalyst was loaded, the Pt-CDs/g-C3N4 catalyst formed exhibited a further improved photocatalytic performance for H2 production and could even split pure water to produce H2. Considering our present economic and facile synthetic approach for the modification of carbon dots on the surface of g-C3N4 photocatalysts, the as-prepared CDs/g-C3N4 photocatalysts will be promising for practical use in water splitting.

Investigation into the structural features and microwave absorption of doped barium hexaferrites

Abstract: BaFe12−xGaxO19 (x ≤ 1.2) hexaferrites were synthesized via the usual ceramic technology. It has been established that with an increase in x, the unit cell and magnetic parameters monotonically decrease. The frequency of natural ferromagnetic resonance firstly decreases from 49.6 GHz down to 49.1 GHz when x = 0.6, and then it increases up to 50.5 GHz. The line width monotonically increases from 3.5 GHz up to 5 GHz. The peak amplitude of the resonant curve changes slightly with the exception of when x = 0.9, when it reaches −16 dB. The 1.3 GHz kOe−1 frequency shift in the bias field is more intensive for small values, when x = 0.3. The decreasing values of the magnetic parameters are a result of the dilution of Fe3+–O2−–Fe3+ superexchange interactions. The behavior of the amplitude-frequency characteristics is largely determined through the reduction of uniaxial exchange anisotropy. The prospects of Ga-substituted hexaferrites acting as a material that effectively absorbs the high-frequency electromagnetic radiation are shown.

Water-stable Eu-MOF fluorescent sensors for trivalent metal ions and nitrobenzene

Abstract: Two novel Eu metal–organic frameworks (MOFs), namely {[Eu2(pdba)3(H2O)3]·2H2O}n (1) and {[Eu3(pdba)4(H2O)4]·5H2O}n (2), were prepared with 4′-(1H-pyrazol-3-yl)-[1,1′-biphenyl]-3,5-dicarboxylic acid (H2pdba) under hydrothermal conditions. MOF 1 exhibits a 3D supramolecular structure assembled from the π⋯π interactions between the benzene rings of the ligands, whereas 2 comprises a 3D structure through coordination connection between nitrogen atom and Eu3+. It is worth noting that the two MOFs showed good luminescence performance and high-sensitivity fluorescence quenching behavior toward Fe3+ (Cr3+) and nitrobenzene. Furthermore, the experimental results for stability in water and cycle test show that these two MOFs can be used as potential fluorescent probes.

Enhanced visible-light photocatalytic H2-generation activity of carbon/g-C3N4 nanocomposites prepared by two-step thermal treatment

Abstract: Photocatalytic hydrogen (H2) production from water by using solar energy and a photocatalyst is a green and sustainable route to tackle the energy issues. Herein, carbon/g-C3N4 nanocomposites were successfully synthesized via a two-step thermal treatment of urea and glucose with different ratios. As confirmed by X-ray photoelectron spectroscopy, a C-O-C bond was formed between carbon and g-C3N4, which leads to a strong interaction between carbon and g-C3N4. The prepared samples were evaluated for photocatalytic H2 generation under visible light irradiation. The experimental results indicate that the carbon/g-C3N4 nanocomposites show great photocatalytic H2 evolution activity, as high as 410.1 μmol g-1 h-1, which is 13.6-fold of pure g-C3N4. The enhanced photocatalytic performance not only originates from the enlarged surface area and extended visible light response range, but also from the effectively separated photo-generated charge carriers. This spatial charge separation greatly suppresses the recombination of photo-generated hole-electron pairs and facilitates efficient H2 production. This work provides a facile way to design highly efficient carbon nitride-based photocatalysts for potential application in photocatalytic reaction by using solar energy.

Tuning the stability of bimetallic Ce(IV)/Zr(IV)-based MOFs with UiO-66 and MOF-808 structures

Abstract: A series of solid solutions of bimetallic Ce/Zr-UiO-66 and -MOF-808 compounds with a varying ratio of Ce4+ to Zr4+ were obtained under mild reaction conditions within 15 min. The lattice parameters of the mixed-metal compounds are in accordance with Vegard's law. Samples with Ce ≤20 at% exhibit an enhanced thermal stability, better resistance against acids and smaller particle sizes.

Formation of hybrid ABX3 perovskite compounds for solar cell application: first-principles calculations of effective ionic radii and determination of tolerance factors

Abstract: The development of hybrid organic-inorganic perovskite solar cells is one of the most rapidly growing fields in the photovoltaic community and is on its way to challenge polycrystalline silicon and thin film technologies. High power conversion efficiencies can be achieved by simple processing with low cost. However, due to the limited long-term stability and environmental toxicity of lead in the prototypic CH3NH3PbI3, there is a need to find alternative ABX3 constitutional combinations in order to promote commercialization. The Goldschmidt tolerance factor and the octahedral factor were found to be necessary geometrical concepts to evaluate which perovskite compounds can be formed. It was figured out that the main challenge lies in estimating an effective ionic radius for the molecular cation. We calculated tolerance factors and octahedral factors for 486 ABX3 monoammonium-metal-halide combinations, where the steric size of the molecular cation in the A-position was estimated concerning the total charge density. A thorough inquiry about existing mixed organic-inorganic perovskites was undertaken. Our results are in excellent agreement with the reported hybrid compounds and indicate the potential existence of 106 ABX3 combinations hitherto not discussed in the literature, giving hints for more intense research on prospective individual candidates.

Novel p–n heterojunction BiOI/CeO2 photocatalyst for wider spectrum visible-light photocatalytic degradation of refractory pollutants

Abstract: Recently, visible-light-driven photocatalysts have been widely used in environmental pollutant remediation. In the present study, BiOI/CeO2 p–n junction photocatalysts were successfully fabricated using a facile in situ chemical bath method. The BiOI/CeO2 p–n junction photocatalysts exhibited excellent photoactivity for the decomposition of the refractory pollutant bisphenol A (BPA) and methylene orange (MO) under visible light illumination. The sample with a 1 : 1 mole ratio of BiOI : CeO2 possessed the highest photocatalytic performance out of all of the as-obtained catalysts. Mott–Schottky plots indicated that p–n junctions were successfully constructed between BiOI and CeO2. The optical and electrical properties of the materials demonstrate that the introduction of BiOI can broaden the visible-light absorption region of CeO2, and the transfer rate of the electron–hole pairs dramatically improves through forming a p–n junction. Furthermore, the BPA degradation efficiency exhibited excellent photostability after four consecutive cycles. These features show that the BiOI/CeO2 p–n junction has great application potential for refractory pollutant removal from wastewater.

Noble-metal-free nickel phosphide modified CdS/C3N4 nanorods for dramatically enhanced photocatalytic hydrogen evolution under visible light irradiation

Abstract: Photocatalytic hydrogen evolution is a promising technology in solving the global energy and environment issues. Therefore, it is urgent to develop highly efficient, nonprecious metal and stable photocatalysts. In this work, we synthesized a highly efficient Ni2P–CdS/g-C3N4 composite based on the concept of combining heterojunction engineering with co-catalyst modification. When employed as a photocatalyst for water splitting, the obtained best composite (5% Ni2P–CdS/g-C3N4) displayed dramatically enhanced hydrogen evolution activity at the rate of 44 450 μmol h−1 g−1, which was about 27 times higher than that of pure CdS (1668 μmol h−1 g−1). The apparent quantum yield at 420 nm reaches 46.3%. The excellent photocatalytic activity and stability can be ascribed to the synergistic effect of the intimate contact between CdS and g-C3N4 and the surface co-catalyst modification. Specifically, the g-C3N4 coated on the CdS nanorods can effectively promote the electron−hole pair separation spatially and Ni2P can lower the overpotential of H+ reduction.

A Perspective – can copper complexes be developed as a novel class of therapeutics?

Abstract: Although copper-ligand complexes appear to be promising as a new class of therapeutics, other than the family of copper(ii) coordination compounds referred to as casiopeinas these compounds have yet to reach the clinic for human use. The pharmaceutical challenges associated with developing copper-based therapeutics will be presented in this article along with a discussion of the potential for high-throughput chemistry, computer-aided drug design, and nanotechnology to address the development of this important class of drug candidates.

Temperature- and vapor-induced reversible single-crystal-to-single-crystal transformations of three 2D/3D GdIII-organic frameworks exhibiting significant magnetocaloric effects.

Abstract: By using Gd2O3, propanedioic acid (H2pda) and oxalic acid (H2ox), a new Gd-based metal–organic framework (MOF) [Gd(pda)(ox)0.5(H2O)2]n (1) has been successfully constructed and structurally characterized. Interestingly, temperature- and vapor-induced reversible single-crystal-to-single-crystal transformations occurred and two new MOFs, namely [Gd(pda)(ox)0.5(H2O)]n (1a) and [Gd(pda)(ox)0.5]n (1b), have been obtained. Complex 1 displays a two-dimensional (2D) layer structure composed of zigzag [Gd(pda)]n chains and it could also be made up of numerous Gd6 macrocycles. Thermal dehydration leads to more complicated three-dimensional (3D) ‘pillar-layer’ structures (1a and 1b) with the same coordination mode of pda2− anions. Magnetic studies suggest the presence of ferromagnetic couplings between the intrachain or intralayer GdIII ions and large magnetocaloric effects (MCEs) with −ΔSmaxm = 45.0 J kg−1 K−1 (1), 46.1 J kg−1 K−1 (1a) and 46.8 J kg−1 K−1 (1b) under a 7 T applied field. Therefore, the interest of ‘robust magnetocaloric MOFs’ is now extended to compounds showing weak ferromagnetic couplings and hence having better magnetocaloric performances for small field changes.

Metal–organic frameworks with 1,4-di(1H-imidazol-4-yl)benzene and varied carboxylate ligands for selectively sensing Fe(III) ions and ketone molecules

Abstract: Four new metal-organic frameworks (MOFs) [Zn(L)(bpdc)]·1.6H2O (1), [Co(L)(bpdc)]·H2O (2), [Ni3(L)2(bptc)2(H2O)10]·2H2O (3) and [Cd2(L)(Hbptc)2] (4) were achieved by reactions of the corresponding metal salt with mixed organic ligands of 1,4-di(1H-imidazol-4-yl)benzene (L) and 4,4'-benzophenonedicarboxylic acid (H2bpdc) or biphenyl-2,4',5-tricarboxylic acid (H3bptc). They exhibit varied structures: MOFs 1 and 4 are porous three-dimensional (3D) frameworks, while 2 is an infinite one-dimensional (1D) chain and 3 is a two-dimensional (2D) network. Remarkably, 1 and 4 can act as potential fluorescent materials for sensing Fe(iii) ions and different ketone molecules with high selectivity and sensitivity. In addition, MOF 1 shows selective adsorption of CO2 over N2.

Actinide ion extraction using room temperature ionic liquids: opportunities and challenges for nuclear fuel cycle applications

Abstract: Studies on the extraction of actinide ions from radioactive feeds have great relevance in nuclear fuel cycle activities, mainly in the back end processes focused on reprocessing and waste management. Room temperature ionic liquid (RTIL) based diluents are becoming increasingly popular due to factors such as more efficient extraction vis-a-vis molecular diluents, higher metal loading, higher radiation resistance, etc. The fascinating chemistry of the actinide ions in RTIL based solvent systems due to complex extraction mechanisms makes it a challenging area of research. By the suitable tuning of the cationic and anionic parts of the ionic liquids, their physical properties such as density, dielectric constant and viscosity can be changed which are considered key parameters in metal ion extraction. Aqueous solubility of the RTILs, which can lead to significant loss in the solvent inventory, can be avoided by appending the extractant moieties onto the ionic liquid. While the low vapour pressure and non-flammability of the ionic liquids make them appear as ‘green’ diluents, their aqueous solubility raises concerns of environmental hazards. The present article gives a summary of studies carried out on actinide ion extraction and presents perspectives of its applications in the nuclear fuel cycle. The article discusses various extractants used for actinide ion extraction and at many places, comparison is made vis-a-vis molecular diluents which includes the nature of the extracted species and the mechanism of extraction. Results of studies on rare earth elements are also included in view of their similarities with the trivalent minor actinides.

Nickel–cobalt-layered double hydroxide nanosheet arrays on Ni foam as a bifunctional electrocatalyst for overall water splitting

Abstract: Bifunctional electrocatalysts, which are active both for the oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), can increase the efficiency of overall water splitting, which is considered an attractive technology for hydrogen production. In this study, we report NiCo-LDH ultrathin nanosheets grown on nickel foam as a bifunctional electrocatalyst for overall water splitting. When used as OER and HER electrodes, NiCo-LDH/NF demonstrated excellent water splitting performance, achieving a current density of 10 mA cm−2 at 1.66 V. Thus, the synthesis of hierarchical 3D porous structure composed of 2D ultrathin nanosheets in NiCo-LDH/NF demonstrated the significance of structural features for achieving a high electrocatalytic activity in overall water splitting.

Markedly enhanced visible-light photocatalytic H2 generation over g-C3N4 nanosheets decorated by robust nickel phosphide (Ni12P5) cocatalysts

Abstract: In the present work, nickel phosphide (Ni12P5) modified graphitic carbon nitride (g-C3N4) nanosheets were synthesized by a simple grinding method. The structural characterization clearly proved that Ni12P5 nanoparticles were well loaded on the surface of g-C3N4 nanosheets. The photocatalytic activity of the composites was tested by catalyzing the reduction of water to hydrogen under visible light irradiation. The results demonstrate that Ni12P5 is an efficient co-catalyst for photocatalytic H2 production of g-C3N4 nanosheets. The maximum photocatalytic H2-production rate of 126.61 μmol g−1 h−1 could be obtained by loading 2.0% Ni12P5 nanoparticles on the surface of g-C3N4, which is about 269.4 times higher than that of pure g-C3N4. It is believed that Ni12P5 nanoparticles on the surface of g-C3N4 could act as significant active sites to boost separation of photoexcited electrons and holes and accelerate the H2-evolution kinetics, thus achieving greatly enhanced hydrogen generation. It is expected that this work could contribute to further experimental investigation for exploiting the low cost, high-efficiency, and environmentally friendly g-C3N4-based nanocomposites for photocatalytic H2 production.

A survey of the different roles of polyoxometalates in their interaction with amino acids, peptides and proteins

Abstract: One of the most attractive areas in inorganic chemistry is the synthesis of polyoxometalates (POMs) exhibiting new properties and applications. Since the impact of POMs in biochemistry and related fields of research has increased in the last few years, there has been a special interest in this topic. Significant progress in biological applications has been made where the interaction of POMs with amino acids, peptides and proteins is relevant. Versatile POMs play a series of different roles in the interaction with these biomolecules as described in this review. Various types of interactions are established, depending on the POM shape and charge, the amino acid side chain, peptide sequence or protein structure. Experimental conditions such as temperature, acidity, solvent, etc. are also important factors that influence the binding/reactivity of POM with biomolecules, as described herein. This understanding allows the adequate design of the POM-biomolecule couple for tailoring and controlling mechanisms of action such as catalysis, inhibition, and aggregation, or the crystallising agent.

pH-Stable Eu- and Tb-organic-frameworks mediated by an ionic liquid for the aqueous-phase detection of 2,4,6-trinitrophenol (TNP).

Abstract: Two pH-stable luminescent metal-organic frameworks (LMOFs), {[Ln2(L)2(OH)(HCOO)]·[H2O]}n (Ln = Eu 1, Tb 2), based on a new π-conjugated organic building block involving both carboxylate and terpyridine groups were rationally synthesized under a combination of hydro/solvothermal and ionothermal conditions (H2L = 4'-(4-(3,5-dicarboxylphenoxy)phenyl)-4,2':6',4''-terpyridine). 1 and 2 are isostructural and feature noninterpenetrated open 3D condensed frameworks constructed by rod-shaped lanthanide-carboxylate building units. Their excellent water-stability and pH-stability allow them to be used in aquatic systems. 1 and 2 both exhibit selective and sensitive aqueous phase detection of the well-known nitroaromatic explosive environmental pollutant 2,4,6-trinitrophenol (TNP), which is highly desirable for practical applications. The presence of a free pyridine group on the LMOF particle surface was strategically utilized for the purpose of exclusive TNP-sensing.

A binder-free wet chemical synthesis approach to decorate nanoflowers of bismuth oxide on Ni-foam for fabricating laboratory scale potential pencil-type asymmetric supercapacitor device.

Abstract: The present study involves the synthesis of a bismuth oxide (Bi2O3) electrode consisting of an arranged nano-platelets for evolving a flower-type surface appearance on nickel-foam (Bi2O3-Ni-F) by a simple, inexpensive, binder-free and one-step chemical bath deposition (CBD) method, popularly known as a wet chemical method. The as-prepared Bi2O3 on Ni-foam, as an electrode material, demonstrates 557 F g-1 specific capacitance (SC, at 1 mA cm-2), of which 85% is retained even after 2000 cycles. With specific power density of 500 kW kg-1, the Bi2O3-Ni-F electrode documents a specific energy density of 80 Wh kg-1. Furthermore, a portable asymmetric supercapacitor device, i.e. a pencil-type cell consisting of Bi2O3-Ni-F as an anode and graphite as a cathode in 6 M KOH aqueous electrolyte solution, confirms 11 Wh kg-1 and 720 kW kg-1 specific energy and specific power densities, respectively. An easy and a simple synthesis approach for manufacturing a portable laboratory scale pencil-type supercapacitor device is a major outcome of this study, which can also be applied for ternary and quaternary metal oxides for recording an enhanced performance. In addition, we presented a demonstration of lighting a light emitting diode (LED) using a home-made pencil-type supercapacitor device which, finally, has confirmed the scaling and technical potentiality of Bi2O3-Ni-F in energy storage devices.

Recent advances using [Cp*Co(CO)I2] catalysts as a powerful tool for C–H functionalisation

Abstract: Expansion of the synthetic chemists' toolbox is currently a topic of great interest, with successes providing access to novel compounds and more efficient routes towards new and known pharmaceuticals and agrochemicals. In this context, the development and application of first-row transition metal-catalysed C-H functionalisation protocols is seen as a key opportunity. This perspective provides a brief background of the discovery and application of high-valent cobalt-catalysis in C-H functionalisation, before detailing examples of recent advances in this field using the powerful [Cp*Co(CO)I2] catalysts for both terminal couplings and heterocycle formation. Finally, a discussion on the detection and isolation of elusive reactive intermediates in high-valent cobalt-catalysed C-H functionalisation, shedding light on how these catalyst systems operate, will be provided.

A Ni-based MOF for selective detection and removal of Hg2+ in aqueous medium: a facile strategy

Abstract: The uncoordinated sulfur atom of the thiocyanato ligand of a 3D metallo-organic framework (MOF), [Ni(3-bpd)2(NCS)2]n (1), where 3-bpd is 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene, has been explored for selective visual detection and effective removal of Hg2+ in aqueous medium. [Ni(3-bpd)2(NCS)2]n has been synthesized under ambient conditions and characterized by elemental analysis, FT-IR spectroscopy, UV-vis spectroscopy, FE-SEM and EDX, XPS and X-ray single crystal diffraction analysis. 1 shows two thiocyanato moieties bound to the hexacoordinated metal center with N atoms whereas the sulfur end remains uncoordinated. The strategy for binding and removal of Hg2+ is very simple. Hg2+ is known for its affinity for strong bond formation with the soft center, S. The sulfur atoms form bonds with this heavy metal ion. The color of 1 changes from green to grey as Hg atoms form coordinate bonds with S atoms of the SCN− group. It has been found that Hg is present in grey materials in a 2 : 1 ratio (Hg/Ni). 1 is selective for Hg as other metals/metalloids, including heavy metal ions, present in water are unable to change the color of 1 as they do not form any bond with it. Binding of Hg with the S end of the thiocyanato moiety has been confirmed by a number of techniques, e.g. IR and UV-vis spectra, FESEM, EDX, and XPS. Simple filtration is done to separate grey materials for the removal of Hg2+ ion from the water medium. A theoretical calculation has been performed to rationalize the fact.

Advances in the preparation of highly selective nanocatalysts for the semi-hydrogenation of alkynes using colloidal approaches.

Abstract: In the last decade, the semi-hydrogenation of alkynes has experienced significant advances in terms of fine control of alkene selectivity and prevention of the over-hydrogenation reaction. Such advances have been possible to a large extent through the progress in colloidal methods for the preparation of metallic nanoparticles. The present review describes the contributions in the field of the selective hydrogenation of alkynes involving the utilization of colloidal methodologies. These approaches permit the fine modulation of several parameters affecting the catalytic performance of the active phase such as the particle size, the bulk and the surface structure and composition. For the transformation of liquid substrates, the nature of the stabilizers, the reducing agents and the metal precursors employed for the synthesis of the catalysts can be tuned to enhance the alkene selectivity. In contrast, in catalytic transformations of gaseous substrates, the presence of adsorbed species at the metal surface usually gives detrimental results while the interplay between the support and the active phase appears to be a more convincing alternative for catalyst tuning.

Ligand modification of UiO-66 with an unusual visible light photocatalytic behavior for RhB degradation.

Abstract: A series of isostructural UiO-66-X (X = H, NH2, Br, (OH)2, (SH)2) catalysts have been successfully synthesized by modifying different functional groups on the ligand. The effects of the ligand modification of UiO-66 were investigated for their photocatalytic activity of Rhodamine B degradation under visible light. Surprisingly, UiO-66-NH2 and UiO-66-(OH)2 which have narrow bandgaps and excellent visible light absorption do not show outstanding photocatalytic performances compared to UiO-66 and UiO-66-Br. Electrochemical test results indicated that the conduction band potential of UiO-66-X and the separation efficiency of electrons were quite important in these photocatalytic reactions, other than the electronic effect as reported. Similar photocatalytic degradation behaviors were found for Congo red and methyl orange. Herein, we firstly reported different mechanisms of selective degradation in the case of UiO-66, which subverted the previous understanding of photodegradation behavior.

A unified ligand electronic parameter based on 13C NMR spectroscopy of N-heterocyclic carbene complexes

Abstract: The properties and reactivities of transition metal complexes are rooted in the stereoelectronic properties of their ligands. While the bulk of a ligand can be easily evaluated and compared by the drawing of its Lewis structure, prediction on the electronic contributions is often less straightforward. Thus, several electronic parameters have been developed for the experimental evaluation of ligands throughout the years. This article accounts for the most recent one developed by the Huynh group, which employs 13C NMR spectroscopy to determine ligand donor strengths using N-heterocyclic carbene complexes. This parameter not only proves to be safer, more convenient and accurate in comparison to existing methodologies, but it also provides, in certain cases, more intuitive and reliable results. Furthermore, it is currently the only one that allows the direct comparison of various Werner-type and organometallic ligands on a unified scale.