Secondary Metal Ion Research Articles

Secondary metal ion-induced electrochemical reduction of U(VI) to U(IV) solids

Recent studies have shown that aqueous U(VI) ions can be transformed into U(VI) precipitates through electrocatalytic redox reactions for uranium recovery. However, there have been no reports of U(IV) solids, such as UO2, using electrochemical methods under ambient conditions since low-valence states of uranium are typically oxidized to U(VI) by O2 or H2O2. Here we developed a secondary metal ion-induced strategy for electrocatalytic production of U(IV) solids from U(VI) solutions using a catalyst consisting of atomically dispersed gallium on hollow nitrogen-doped carbon capsules (Ga-Nx-C). This method relies on the presence of secondary metal ions, e.g., alkaline earth metals, transition metals, lanthanide metals, and actinide metals, which promote the generation of UO2 or bimetallic U(IV)-containing oxides through a two-electron transfer process. No U(IV) solid products were generated in the presence of alkali metal ions. Mechanistic studies revealed that the strong binding affinity between U(IV) and alkaline earth metals (Ca2+/Mg2+/Sr2+/Ba2+), transition metals (Ni2+/Zn2+/Pb2+/Fe3+, etc.) and lanthanide/actinide metals (Ce4+/Eu3+/Th4+/La3+) suppressed re-oxidation of U(IV) to U(VI), leading to the generation of U(IV)O2 and Mx(M = Ce, Eu, Th, La)U(IV)yO2. This work provides fundamental insights into the electrochemical behavior of uranium in aqueous media, whilst guiding uranyl capture from nuclear waste and contaminated water.

Pathway control in metallosupramolecular polymerization of a monoalkynylplatinum(ii) terpyridine complex through competitive complex formation.

Understanding the pathway complexity of supramolecular polymerization in biomimetic systems has been a challenging issue due to its importance in the development of rationally controlled materials and insight into self-assembly in nature. We herein report a kinetic trapping strategy as a new methodology on how to control the pathway of metallosupramolecular polymerization by employing secondary metal ions and/or ligands which form competitive complex species. For this, we proposed monoalkynylplatinum(ii) metalloligand (Pt-L1) derived from a bis(amideterpyridine) receptor with one unoccupied terpyridyl terminal as a coordination site for the secondary metal ion (Ag+ or Fe2+). The inherent pathway complexity intrinsic to the Pt-L1-anchored supramolecular polymerization has been modulated through the incorporation of Ag+ or Fe2+. During the supramolecular polymerization of Pt-L1 in the presence of Ag+ and Fe2+, the added secondary ligand bpy (4,4'-dimethyl-2,2'-bipyridine) or DA18C6 (1,14-diaza-18-crown-6) form complexes as kinetic species, thereby inhibiting spontaneous polymerizations. The supramolecular polymer (SP-I), with a spherical structure composed of Pt-L1 in the absence of metal ions as a kinetic product, did not transform into the thermodynamic product, namely supramolecular polymer (SP-III) with a left-handed fiber structure, due to a high energy barrier. However, the supramolecular polymer (SP-II) with a left-handed fiber structure, which was formed by Pt-L1 in the presence of AgNO3, converted to SP-III upon the addition of NaCl. Additionally, SP-II transformed into supramolecular polymer (SP-IV) upon the addition of Fe(BF4)2, through an on-pathway process. Both the morphological and emissive characteristics of the resulting supramolecular polymers can be fine-tuned via the Pt⋯Pt or Ag⋯Ag interactions as well as through the changes of the coordination geometry depending on the existing Ag+ or Fe2+ ions. The present results have important implications in expanding the scope of pathway complexity to produce a variety of products via kinetically controlled processes involving secondary metal ions and ligands.

Improving the hydrothermal stability of Al-rich Cu-SSZ-13 zeolite via Pr-ion modification.

Al-rich (Si/Al = 4-6) Cu-SSZ-13 has been recognized as one of the potential catalysts to replace the commercial Cu-SSZ-13 (Si/Al = 10-12) towards ammonia-assisted selective catalytic reduction (NH3-SCR). However, poor hydrothermal stability is a great obstacle for Al-rich zeolites to meet the catalytic applications containing water vapor. Herein, we demonstrate that the hydrothermal stability of Al-rich Cu-SSZ-13 can be dramatically enhanced via Pr-ion modification. Particularly, after high-temperature hydrothermal aging (HTA), CuPr1.2-SSZ-13-HTA with an optimal Pr content of 1.2 wt% exhibits a T80 (temperature window of NO conversion above 80%) window of 225-550 °C and a T90 window of 250-350 °C. These values are superior to those of Cu-SSZ-13-HTA (225-450 °C for T80 and no T90 window). The results of X-ray diffraction Rietveld refinement, electron paramagnetic resonance (EPR) and spectral characterization reveal that Pr ions mainly located in the eight-membered rings (8MRs) in SSZ-13 zeolite can inhibit the generation of inactive CuOx during hydrothermal aging. This finding is further supported by density functional theory (DFT) calculations, which suggest that the presence of Pr ions restrains the transformation from Cu2+ ions in 6MRs into CuOx, resulting in enhanced hydrothermal stability. It is also noted that an excessive amount of Pr ions in Cu-SSZ-13 would result in the production of CuOx that causes the decline of catalytic performance. The present work provides a promising strategy for creating a hydrothermally stable Cu-SSZ-13 zeolite catalyst by adding secondary metal ions.

Liquid Metal Powders Wrapped with Robust Shell by Bimetallic Ions Chelation Strategy for Energy Harvesting and Flexible Electronics

AbstractExcellent electrical and fluidic properties render liquid metal (LM) a promising material for flexible electronics, soft robotics, and stretchable circuits. Although producing LM micro/nano droplets by nanometerization addresses the tricky issue of the processing result from high surface tension, it still remains challenging to obtain stable LM droplets because of their dynamic surfaces. In this study, LM powders wrapped with robust shells are fabricated by bimetallic ions chelation strategy. During sonicating LM (e.g., EGaIn) in an alginate solution, a microgel shell is first formed by the coordination of Ga3+ and carboxyl groups. Subsequently, LM powders are achieved by introducing Ca2+ as secondary metal ions to chelate with redundant carboxyl groups. Besides high chemical stability in water and air, these nonstick LM powders also exhibit superior photothermal effects for energy harvesting, being capable of recovering electrical conductivity by mechanical sintering for flexible electronics. These conductive circuits based on LM powders not only work as electro‐thermal heaters, and electromagnetic interference shielding material but also can be designed as smart actuators. Thus, this bimetallic ions chelation strategy may start a pathway to produce stable, transportable LM powders with multifunctional properties, applicable in stretchable electronics, smart actuators, and electric skins.

Vanadyl as a Spectroscopic Probe of Tunable Ligand Donor Strength in Bimetallic Complexes.

Incorporation of secondary metal ions into heterobimetallic complexes has emerged as an attractive strategy for rational tuning of compounds' properties and reactivity, but direct solution-phase spectroscopic interrogation of tuning effects has received less attention than it deserves. Here, we report the assembly and study of a series of heterobimetallic complexes containing the vanadyl ion, [VO]2+, paired with monovalent cations (Cs+, Rb+, K+, Na+, and Li+) and a divalent cation (Ca2+). These complexes, which can be isolated in pure form or generated in situ from a common monometallic vanadyl-containing precursor, enable experimental spectroscopic and electrochemical quantification of the influence of the incorporated cations on the properties of the vanadyl moiety. The data reveal systematic shifts in the V-O stretching frequency, isotropic hyperfine coupling constant for the vanadium center, and V(V)/V(IV) reduction potential in the complexes. These shifts can be interpreted as charge density effects parametrized through the Lewis acidities of the cations, suggesting broad potential for the vanadyl ion to serve as a spectroscopic probe in multimetallic species.

Spin Crossover Induced by Changing the Identity of the Secondary Metal Ion from PdII to NiII in a Face-Centered FeII 8 MII 6 Cubic Cage.

Discrete spin crossover (SCO) heteronuclear cages are a rare class of materials which have potential use in next-generation molecular transport and catalysis. Previous investigations of cubic cage [Fe8 Pd6 L8 ]28+ constructed using semi-rigid metalloligands, found that FeII centers of the cage did not undergo spin transition. In this work, substitution of the secondary metal center at the face of the cage resulted in SCO behavior, evidenced by magnetic susceptibility, Mössbauer spectroscopy and single crystal X-ray diffraction. Structural comparisons of these two cages shed light on the possible interplay of inter- and intramolecular interactions associated with SCO in the NiII analogue, 1 ([Fe8 Ni6 L8 (CH3 CN)12 ]28+ ). The distorted octahedral coordination environment, as well as the occupation of the CH3 CN in the NiII axial positions of 1, prevented close packing of cages observed in the PdII analogue. This led to offset, distant packing arrangements whereby important areas within the cage underwent dramatic structural changes with the exhibition of SCO.

Synergetic effects of the co-doping transition metal ions and the silica-shell coating for enhancing the photoluminescence and stability of Mn: CsPbCl3 nanocrystals and their application

Doping Mn2+ ions into cesium lead halide CsPbX3 (X = Cl, Br, I) perovskite nanocrystals (PNCs) has been proven to be an effective strategy to reduce the Pb2+ content. However, excessive Mn2+ ions may form the Mn–Mn dimers in PNCs, leading to concentration quenching effects and low photoluminescence quantum yields (PLQYs). Herein, secondary metal ions (Ni2+, Cu2+, Zn2+) were introduced to substitute Pb2+ ions as co-doped (Mn, M):CsPbCl3 PNCs (M = Ni, Cu, Zn), which were prepared by a facile method under ambient conditions, aiming for positively passivating the surface defects and improving the Mn2+ emission. Also, to protect the co-doped (Mn, M):CsPbCl3 PNCs from moisture damage, we performed silica encapsulation, which further passivated surface defects due to the effective hydrolysis of silane. The evolution of optical properties and stabilities of three series of (Mn, M):CsPbCl3 PNCs was compared. The PLQYs of co-doped (Mn, M):CsPbCl3 PNCs were larger than those of single-doped Mn: CsPbCl3 PNCs, especially for (Mn, Ni):CsPbCl3 and (Mn, Cu):CsPbCl3, which can reach nearly 30%. The PLQYs of (Mn, Ni):CsPbCl3 and (Mn, Zn):CsPbCl3 PNCs decreased dramatically during the encapsulation process, while the PLQY values of (Mn, Cu):CsPbCl3 remained 30% even after the same treatment process. Consequently, the prototypes of white light-emitting devices (WLEDs) were successfully fabricated based on orange-red (Mn, Ni):CsPbCl3@SiO2 and (Mn, Zn):CsPbCl3@SiO2 composites. The synergetic effects of co-doping transition metal ions and silica-shell coating on improving optical properties and stabilities were investigated. It has potential for a wide range of applications in the field of solid-state light emission.

Robust bimetallic metal-organic framework cathode catalyst to boost oxygen reduction reaction in microbial fuel cell

Metal-organic frameworks (MOFs) have emerged as versatile materials for widespread energy and environmental applications due to their intrinsic physical and chemical properties. To this extent, this research is focused on the synthesis of novel amine-functionalized single (Zr) and bimetallic (Zr, Ni) MOF viz. NH2-UiO-66(Zr) and NH2-UiO-66(Zr/Ni), followed by their testing as cathode catalysts to improve oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) for bioenergy recovery from organic wastes. The physical and chemical characterization techniques depicted the successful synthesis of octahedral-shaped MOF nanoparticles with similar structural integrity despite the incorporation of the secondary metal ion. However, electrochemical analyses demonstrated NH2-UiO-66(Zr/Ni) as a better catalyst, achieving a high ORR peak current, low charge transfer resistance, and high diffusion coefficient as compared to both NH2-UiO-66(Zr) and 10% Pt-C catalyzed cathodes. MFC performance evaluation further confirmed the high catalytic activity of NH2-UiO-66(Zr/Ni), allowing to recover a power density (PD) of 0.8 W/m2 at a coulombic efficiency (CE) of 75.4%, outperforming the MFC using 10 % Pt-C catalysed cathode. This study suggests that the NH2-UiO-66(Zr/Ni) can be used as an efficient ORR catalyst for application in large-scale MFCs.

Synergistic effect of Co/Ni bimetallic metal–organic nanostructures for enhanced electrochemical energy storage

Introducing a secondary metal ion is an effective strategy to significantly enhance the electrochemical performance of monometallic metal–organic frameworks (MOFs). Herein, we synthesize a series of cobalt–nickel bimetallic MOFs (Co/Ni-MOFs) by the Co2+ substitution into Ni-MOF ({Ni3(OH)2(tdc)2(H2O)4}n, H2tdc = 2,5-thiophenedicarboxylic acid). The Co/Ni-MOF-2:1 with optimal Co/Ni ratio possesses improved electrical conductivity, intrinsic reactivity, and stability. Compared with the monometallic Ni-MOF, the bimetallic Co/Ni-MOF-2:1 with nanowire morphology achieves a higher specific capacitance (610 F g−1 at a current density of 0.5 A g−1), a better rate capacity (88 % capacitance retention at 5 A g−1) and cycling performance (72 % retention after 5000 cycles). Moreover, the asymmetric supercapacitor constructed with Co/Ni-MOF-2:1 and activated carbon exhibits a high specific capacitance (228 F g−1 at 0.5 A g−1) and excellent cycling stability (95.5 % of capacitance retention after 5000 circulations at 5 A g−1).

Unveiling Secondary-Ion-Promoted Catalytic Properties of Cu-SSZ-13 Zeolites for Selective Catalytic Reduction of NOx.

The incorporation of secondary metal ions into Cu-exchanged SSZ-13 zeolites could improve their catalytic properties in selective catalytic reduction of NOx with ammonia (NH3-SCR), but their essential roles remain unclear at the molecular level. Herein, a series of Cu-Sm-SSZ-13 zeolites have been prepared by ion-exchanging Sm ions followed by Cu ions, which exhibit superior NH3-SCR performance. The NO conversion of Cu-Sm-SSZ-13 is nearly 10% higher than that of conventional Cu-SSZ-13 (175-250 °C) after hydrothermal ageing, showing an enhanced low-temperature activity. The Sm ions are found to occupy the six-membered rings (6MRs) of SSZ-13 by X-ray diffraction Rietveld refinement and aberration-corrected scanning transmission electron microscopy. The Sm ions at 6MRs can facilitate the formation of more active [ZCu2+(OH)]+ ions at 8MRs, as revealed by temperature-programmed reduction of hydrogen. X-ray photoelectron spectroscopy and density functional theory (DFT) calculations indicate that there exists electron transfer from Sm3+ to [ZCu2+(OH)]+ ions, which promotes the activity of [ZCu2+(OH)]+ ions by decreasing the activation energy of the formation of intermediates (NH4NO2 and H2NNO). Meanwhile, the electrostatic interaction between Sm3+ and [ZCu2+(OH)]+ results in a high-reaction energy barrier for transforming [ZCu2+(OH)]+ ions into inactive CuOx species, thus enhancing the stability of [ZCu2+(OH)]+ ions. The influence of the ion-exchanging sequence of Sm and Cu ions into SSZ-13 is further investigated by combining both experiments and theoretical calculations. This work provides a mechanistic insight of secondary ions in regulating the distribution, activity, and stability of Cu active sites, which is helpful for the design of high-performance Cu-SSZ-13 catalysts for the NH3-SCR reaction.

Assembly of three sulfonylcalix[4]arene-based multinuclear complexes: Tunable structures and guest encapsulation properties

Understanding and controlling the structure of polymetallic clusters plays a fundamental role in supramolecular chemistry. Herein we describe the preparation of three sulfonylcalix[4]arenebased multinuclear cluster complexes, namely, [Fe4(TBSC)2(DMF)4(µ3-H2O)2(H2O)2·2MeCN] (1), [Fe2Na4(TBSC)2(DMF)4(µ6-H2O)(H2O)2] (2), and [Fe4(TBSC)(Py)4(µ4-H2O)] (3) from trivalent iron ions and p-tert-butylsulfonylcalix[4]arene ligands by the metal-directed assembly. These complexes exhibit interesting tunable core structures, exo cavities, supramolecular packing characteristics in the solid state. As a result, the three multinuclear complexes exhibit selective molecular recognition toward the dye molecules.

Transcriptomic and physiological analyses of Miscanthus lutarioriparius in response to plumbum stress

Soil plumbum (Pb) contamination has become a global environmental issue, which threaten soil quality, food security and human health. Miscanthus species have exhibited high tolerance and restoration capacity to heavy metals stress. However, the mechanisms of Pb resistance in Miscanthus species have not been fully elucidated. In the current report, transcriptome changes of Miscanthus lutarioriparius response to different Pb treatment time were analyzed to investigate the key genes and pathways involved in Pb uptake patterns. Based on the assembled transcriptome data, totally 19332 differentially expressed genes (DEGs), in which 200–11313 DEGs in each comparison group were identified respectively. Gene ontology and pathway enrichment analysis found that different expression genes under Pb stress are predominantly involved in the pathways of phenylpropanoid biosynthesis and metabolism, biosynthesis of secondary metabolites, photosynthesis and metal ion transporters. The results in the current study could serve as a ground work for future studies to determine the exact expression of genes in plants under heavy metal stress, the processes involved and how they can be efficiently utilized to improve plant tolerance to toxic metals and facilitate the remediation process.

Microwave-assisted in-situ isomorphism via introduction of Mn into CoCo2O4 for battery-supercapacitor hybrid electrode material

Introducing secondary metal ions into host electrode materials may result in extra redox sites and regulating the electronic structure to increase electrochemical properties. With the assistance of microwave, Mn cation was in-situ isomorphism doped into porous CoCo2O4 nanowires during a hydrothermal process. Ex-situ characterizations reveal that the doped Mn2+ and Mn3+ in CoCo2O4 provides additional redox reaction by forming reversible Mn4+, which effectively improved electrochemical storage capacity. The added redox reaction of Mn cations is also helpful to effectively suppress the water-splitting, which expanded the operating voltage window. As a result, the as-obtained Mn-doped CoCo2O4 nanowire array electrodes exhibited an enlarged specific capacity (1528.0C g−1/424.4 mA h g−1 at 1 A g−1) with a widened operating voltage window of 1.1 V and superior cycling stability (91.5 % retention after 5000cycles). Correspondingly, the battery-supercapacitor hybrid device constructed by Mn2CoCo2O4 porous nanowire array electrode and biomass-derived N doped porous carbon delivered a stable working voltage of 1.9 V and superior energy density of 58.6 Wh kg−1 at power density of 950 W kg−1 as well as excellent stability (83.7 % specific capacity retained at 10 A g−1 for 8000cycles). This work provides a feasible route for the construction of energy storage devices with high energy density and high power density.

Supramolecular Chirality from Hierarchical Self-Assembly of Atomically Precise Silver Nanoclusters Induced by Secondary Metal Coordination.

Chiral assembly of metal nanoparticles (NPs) into complex superstructures has been widely studied, but their formation mechanisms still remain mysterious due to the lack of precise structural information from the metal-organic interface to metallic kernel. As "molecular models" of metal NPs, atomically precise metal nanoclusters (NCs) used in the assembly of a macroscale superstructure will provide details of microscopic structure for deep understanding of such highly sophisticated assemblies; however, chiral superstructures have not been realized starting from achiral metal NCs with atomic precision. Herein, we report the supramolecular assembly of a water-soluble silver NC ((NH4)9[Ag9(mba)9], H2mba = 2-mercaptobenzoic acid, abbreviated as Ag9-NCs hereafter) into chiral hydrogels induced by the coordination of secondary metal ions. Single crystal X-ray diffraction reveals the triskelion-like structure of Ag9-NCs with a pseudochiral conformation caused by special arrangement of the peripheral mba2- ligands. The enantioselective orientation of the peripheral carboxyl group facilitates the assembly of Ag9-NCs into nanotubes with a chiral cubic (I*) lattice when coordinating to Ba2+. The nanotubes can further intertwine into one-dimensional chiral nanobraids with a preferred left-handed arrangement. These multiple levels of chirality can be tuned by drying, during which the I* phase is missing but the chiral entanglement of the nanotubes is enhanced. Through the gelation of atomically precise, achiral NCs coordination of secondary metal ions, chiral amplification of superstructures was realized. The origination of the chirality at different length scales was also discussed.

A new strategy for the development of efficient impedimetric tobramycin aptasensors with metallo-covalent organic frameworks (MCOFs)

Two bimetallic CoNi-based metallo-covalent organic frameworks (MCOFs) were prepared and explored as the sensitive platforms of impedimetric aptasensors for efficient detection of tobramycin (TOB). The two CoNi-MCOFs were constructed using metallophthalocyanine tetra-amine (MPc-TA, M = Co2+ or Ni2+) and 4,4ʹ-(1,10-phen-anthroline-2,9-diyl) dibenzaldehyde (PTD) as building units and further coordinating to the secondary metal ions (Ni2+ or Co2+) by phenanthroline. Interestingly, the immobilization ability of CoPc-TA-PTD(Ni) to TOB-targeted aptamer is higher than that of NiPc-TA-PTD(Co) due to its stronger binding interactions to aptamer. As a result, the CoPc-TA-PTD(Ni)-based aptasensor shows the superior TOB detection ability, giving a low detection limit of 0.07 fg mL−1 and satisfied sensing performances, such as high selectivity, good reproducibility, and excellent stability. Also, the aptasensor shows the acceptable applicability for detecting TOB in milk or chicken egg. This MCOFs-based sensing strategy could be extensively applied to detect other analytes by anchoring the corresponding probes.

Promotion and Tuning of the Electrochemical Reduction of Hetero‐ and Homobimetallic Zinc Complexes**

AbstractCompounds containing multiple metals attract significant interest due to the useful redox and reactivity properties of such species. Here, the electrochemical properties of a family of macrocyclic complexes that feature a zinc(II) center paired with a secondary redox‐inactive metal cation in heterobimetallic (Na+, Ca2+, Nd3+, Y3+) motifs or homobimetallic (Zn2+) motifs have been investigated. The new complexes were prepared via a divergent strategy, isolated, and structurally characterized with single‐crystal X‐ray diffraction (XRD) analysis. XRD results show that the structures of the complexes are modulated by the identity of the incorporated secondary metal ions. Cyclic voltammetry data reveal that ligand‐centered reduction is promoted in the bimetallic complexes and that the paired metal ions synergistically influence the redox properties of the complexes. Similar to prior work from our group and others, the bimetallic complexes containing stronger Lewis acids undergo more significant reduction potential shifts; contrasting with prior work on complexes containing redox‐active metals, however, the zinc(II) complexes studied here display faster electron transfer (as judged by lower reorganization energies, λ) when incorporating di‐ or tri‐valent Lewis acids in contrast to monovalent (and more weakly acidic) sodium. The quantified trends in these data offer insights that could help distinguish metal‐ versus ligand‐centered reduction of bimetallic complexes.

An efficient synthetic approach toward a sporadic heterocyclic scaffold: 1,3-Oxathiol-2-ylidenes; alkaline phosphatase inhibition and molecular docking studies

We developed a simple and robust method for synthesis of 1,3-oxathiol-2-ylidene benzamides (4a–m) a sporadic class of heterocycles, by reacting freshly prepared aroyl isothiocyanates, with ethyl 2-chloroacetoacetate in presence of N-methylimidazole in dry acetonitrile. The synthesized compounds were explored for their inhibition against alkaline phosphatases and HeLa cancer cell lines. The results suggest that almost all the compounds possess good % inhibition against both enzymes, with compound 4m showing dual inhibition while 4g and 4i as potent and selective inhibitors of TNAP and c-IAP respectively. Structure activity relationship for the active members of series has been carried out based on molecular docking studies. The result of SAR shows the involvement of active inhibitors in H-bonding at various sites with different amino acid residues in addition to secondary metal ion interactions with Zn ions inside the active pocket of the enzyme. The π-π interactions between the 1,3-oxathiole ring and imidazole ring of His321 and His 317 further defines the dual mode of inhibition by compound 4m. These compounds also possess inhibition potential against cervical cell lines in the range of 2.42–69.03% with the maximum inhibition shown by the unsubstituted member 4a compared to the reference drug cisplatin.

Template-Free Self-Assembly of Molecular Trefoil Knots and Double Trefoil Knots Featuring Cp*Rh Building Blocks.

Understanding and controlling the topology of self-assembled structures plays a fundamental role in supramolecular chemistry. Herein, the preparation of a series of tetranuclear metallarectangles and hexanuclear trefoil knots featuring Cp*Rh building blocks by template-free self-assembly with four different rigid and flexible ligands is described. Transformations between the trefoil knots and the corresponding macrocycles can be induced by using concentration effects. Remarkably, the hexanuclear trefoil knot 5 was shown to assemble further to provide rare examples of [12+1] heteronuclear double trefoil knots (5 a/5 b/5 c/5 d) through coordination of the amide oxygen atoms to the secondary metal ions Na+ /K+ /Ca2+ /Cd2+ . The synthetic results are supported by single-crystal XRD.

MxOy-ZrO2 (M = Zn, Co, Cu) Solid Solutions Derived from Schiff Base-Bridged UiO-66 Composites as High-Performance Catalysts for CO2 Hydrogenation.

Metal-organic frameworks have been exploited as excellent solid precursors and templates for the preparation integrated nanocatalysts with multicomponent and hierarchical structures. Herein, a novel synthetic protocol has been developed to fabricate versatile Zr-based solid solutions (such as ZnO-ZrO2, Co3O4-ZrO2, and CuO-ZrO2) via pyrolysis of Schiff base-modified UiO-66 octahedrons (size <100 nm), which were then utilized as efficient catalysts for CO2 hydrogenation. The Schiff base serves as an effective bridge to dope secondary metal ions into UiO-66 frameworks with controlled amounts of 0.13-8.8 wt %, which are initially hard to achieve. Interestingly, by simply changing the loading metal ions, the selectivity of C1 hydrogenation products can be facilely tuned. For instance, the maximum CO2 conversion of ZnO-ZrO2, Co3O4-ZrO2, and CuO-ZrO2 solid solutions were 5.8, 11.4, and 22.5%, with the main product selectivity of 70% CH3OH, 92.5% CH4, and 86.7% CO, respectively. Moreover, in situ diffuse reflectance infrared Fourier transform spectra characterization reveals that the significant difference in C1 product selectivity is mainly determined by the balance of *HCOO, *CH3O, and *CO intermediate species over the Zr-based solid solutions.

Comparative Study of Ethylene Carbonate-Based Electrolyte Decomposition at Li, Ca, and Al Anode Interfaces

One of the major bottlenecks to the development of alternatives to existing Li ion battery technology, such as Li metal or multivalent ion (Mg, Ca, Zn, or Al) batteries, has to do with the layer of inorganic and organic compounds that forms at the interface between the metallic anode and electrolyte via solvent and salt decomposition (the solid–electrolyte interphase or SEI). In Li metal batteries the growth of dendrites causes continual formation of new SEI, while in multivalent ion batteries the SEI does not allow for the diffusion of the ions. Finding appropriate electrolytes for such systems and gaining an understanding of SEI formation is therefore critical to the development of secondary Li metal and multivalent ion cells. In this work, we use ab initio molecular dynamics simulations to investigate the initial stages of decomposition of organic electrolytes based on ethylene carbonate (EC) and formation of the SEI on Li, Ca, and Al metal surfaces. We first find that pure EC only decomposes to CO and...