Enhanced Electrochemical O2 -to-H2 O2 Synthesis Via Cu-Pb Synergistic Interplay.

Electrocatalytic reduction of oxygen (O2 ) to produce hydrogen peroxide (H2 O2 ) frequently suffers from the low activity and poor selectivity of catalysts owing to the lack of systematic strategies. The resulting enhancement to enable the further design of a new bimetallic catalyst with the synergistic interplay, as exemplified by Cu-Pb catalyst for two-electron oxygen reduction reaction (2e- ORR), is reported here. Critically, in-depth evidence, including density functional theory (DFT) calculations, electrochemical signals, in-situ Raman, and H2 O2 -proof work, allude to a catalytic favor to the 2e- ORR of Cu-Pb.

Structural Distortion and Bandgap Increase of Two-Dimensional Perovskites Induced by Trifluoromethyl Substitution on Spacer Cations.

In further advancing display technologies, especially for improved blue emitters, to engineer the bandgap of promising semiconductors such as hybrid perovskites is important. Present-day methods for tuning the bandgaps of perovskites, such as the incorporation of mixed halide anions, suffer drawbacks such as phase separation and difficulty in synthesis. Here we report a new 2D lead iodide perovskite that emits in the blue spectral region. We exploit an increased angular distortion of PbI42- octahedra to widen the bandgap of 2D metal halide perovskites. We synthesized 2D lead iodide perovskites based on (4-Y-C6H4CH2NH3)2PbI4 (Y = H, F, Cl, Br, I) and substituted the halogen atoms with a -CF3 group to create (4-CF3-C6H4CH2NH3)2PbI4 compounds. We observed that the CF3-substituted material exhibited a ∼0.16 eV larger bandgap than did the halogen-substituted materials. We used X-ray diffraction and density functional theory simulations and found that the blue shift can be assigned to the angular distortion of the PbI42- lattice, a distortion traceable to repulsive intermolecular interactions between the trifluoromethyl groups on oppositely-arranged spacers. These results add a degree of freedom in tuning 2D perovskites to selected bandgaps for optoelectronic applications.

Nanohybridization of Keggin polyoxometalate clusters and reduced graphene oxide for lithium-ion batteries.

The nanocomposites of reduced graphene oxide (RGO) and polyoxometalates (POMs) have been considered to be effective to boost more Li+ to participate in intercalation/deintercalation process of lithium-ion batteries (LIBs). In this paper, a nanocomposite (PMo12@RGO-AIL) with electrostatic interaction of RGO and Keggin-type [PMo12O40]3- has been fabricated and characterized by XRD, XPS, SEM, and TEM. To prepare PMo12@RGO-AIL, a strategy of covalent modification is developed between amino-based ionic liquid and RGO, helping to achieve the uniform dispersion of [PMo12O40]3-. When the PMo12@RGO-AIL was used as a cathode for LIBs, it could exhibit more excellent reversible capacity, cycle stability, and rate capability than those of samples without modifying by ionic liquids. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s11051-020-05108-x.

Biomolecule-Assisted Synthesis and Electro-Catalytic Hydrogen Evolution of Flowerlike Nickel Sulfide Nanostructures.

In this paper, flowerlike nickel sulfide materials are synthesized using a facile solution-phase biomolecule-assisted approach in the presence of L-cysteine (an ordinary and cheap amino acid), which turned out to serve as both the sulfur source and the directing molecule in the formation of nickel sulfide nanostructures. The morphology, structure, and phase composition of the assynthesized nickel sulfide products are characterized using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and Raman. Moreover, the nickel sulfide materials are investigated as electro catalysts for hydrogen evolution reaction (HER) in strongly alkaline media. The electro catalytic performance of as-prepared nickel sulfide is promising for applications as non-noble-metal HER catalysts with water splitting for hydrogen production.

A bimetallic oxide Fe1.89Mo4.11O7 electrocatalyst with highly efficient hydrogen evolution reaction activity in alkaline and acidic media.

Transition-metal Mo-based materials have been considered to be among the most effective hydrogen evolution reaction (HER) electrocatalysts. Regulating the electronic structure of Mo atoms with guest metal atoms is considered as one of the important strategies to improve their HER activity. However, introduction of guest metal elements in the vicinity of Mo sites with atomic-level hybridization is difficult to realize, resulting in the failure of the modified electronic structure of Mo sites. Herein, an Fe1.89Mo4.11O7/MoO2 material is prepared through the thermal treatment of a ferrimolybdate precursor. It exhibits a Tafel slope of 79 mV dec-1 and an exchange current density of 0.069 mA cm-2 in 1 M KOH medium, as well as a Tafel slope of 47 mV dec-1 and an exchange current density of 0.072 mA cm-2 in 0.5 M H2SO4 medium. Compared to original Mo-based oxides, Fe1.89Mo4.11O7 with the regulated Mo electronic structure shows a more suitable Mo-H bond strength for the fast kinetics of the HER process. Density functional theory (DFT) calculations also indicate that the Mo-H bond strength in Fe1.89Mo4.11O7 is similar to the Pt-H bond strength, resulting in the high kinetic activity of Mo-based HER electrocatalysts in alkaline and acidic media.

A stable, pillar-layer metal-organic framework containing uncoordinated carboxyl groups for separation of transition metal ions.

A 3D pillar-layer framework (1) with uncoordinated carboxyl groups exhibits exceptional stability. It can effectively and selectively adsorb Cu(2+) ions and has been applied as a chromatographic column for separating Cu(2+)/Co(2+) ions.

A new type of double-chain based 3D lanthanide(III) metal-organic framework demonstrating proton conduction and tunable emission.

A new type of 3D lanthanide(III) metal-organic framework directly constructed by double-chain motifs was synthesized. It shows a proton conductivity of 1.6 × 10(-5) S cm(-1) at 75 °C at 97% RH, and tunable emission including white light.

A multifunctional proton-conducting and sensing pillar-layer framework based on [24-MC-6] heterometallic crown clusters.

3D pillar-layer framework with [24-MC-6] heterometallic crown clusters exhibits proton conductivity and selective sensing of acetone as well as Cu(2+) ions.

Employing tripodal carboxylate ligand to construct Co(II) coordination networks modulated by N-donor ligands: syntheses, structures and magnetic properties.

Hydrothermal reaction of a tripodal bridging ligand, 5-(4-carboxyphenoxy)isophthalic acid (H3cpia) with cobalt salts modulated by N-donor neutral ligands leads to the formation of six novel coordination networks formulated as {[Co(1.5)(cpia)(o-bix)](H2O)(1.5)}n (1), {[Co2(cpia)(µ-OH)(m-bix)]H2O}n (2), {[Co(1.5)(cpia)(m-bix)]}n (3), {[Co(1.5)(cpia)(p-bix)(0.5)(H2O)]H2O}n (4), {[Co(2.5)(cpia)(Hcpia)(4,4'-bpy)(2.5)](H2O)3}n (5), and {[Co3(cpia)2(bpp)2]H2O}n (6). Compound 1 exhibits a two-dimensional, (3,8)-connected layered architecture composed of trinuclear cobalt clusters. Compound 2 possesses a three-dimensional dense framework with (3,8)-connected tfz-d topology built from butterfly-shaped tetranuclear Co4(µ3-OH)2(6+) clusters. Similar to compound 1, trinuclear Co clusters act as secondary building units to construct the final 2D layered structure modulated by m-bix and bpp ligands in compounds 3 and 6. In compound 4, trinuclear Co clusters connected by cpia(3-) anions give rise to two-dimensional layers, which are further pillared by p-bix ligands to the three-dimensional framework. Compound 5 features a 2D, (3,4,6)-connected molecular network assembled from alternate binuclear and mononuclear Co building blocks. The magnetic investigation indicates that strong antiferromagnetic interactions between cobalt ions are dominant in compounds 2 and 6.

Two high-connected metal-organic frameworks based on d10-metal clusters: syntheses, structural topologies and luminescent properties.

The d(10)-metal-oxo clusters connected by the asymmetric tricarboxylate and linear neutral ligands give rise to two novel high-connected MOFs. They feature the highest (3,16)- and (3,8)-connected three-dimensional frameworks based on cube-like octanuclear [Zn8(µ2-OH)4(CO2)12] clusters and butterfly-like tetranuclear [Cd4(µ3-OH)2(CO2)6] clusters as the secondary building units, respectively.

Supramolecular isomerism, single-crystal to single-crystal transformation induced by release of in situ generated I2 between two supramolecular frameworks.

Two supramolecular isomers, [H2tpim·H4betc]·I (1) and [H2tpim·H4betc]·I3·2H2O (2), have been synthesized by one-pot reactions. Single-crystal to single-crystal transformations are observed between the two supramolecular isomers which are induced by release of in situ generated I2.

Spin canting magnetization in a 3D Cu(II) complex based on molybdate oxide cluster and 5-triazole isophthalic acid.

A unique 3D Cu(II) complex based on a molybdate oxide cluster and 5-triazole isophthalic acid was synthesized under hydrothermal condition: {Cu(2)(HL)(2)[Mo(4)O(13)]}·2H(2)O (H(2)L = 5-triazole isophthalic acid) (1). Compound 1 shows a spin canting magnetization behavior, and a definite hysteresis loop with a large coercive field of 6.85 kOe.

Syntheses, structures and physical properties of transition metal-organic frameworks assembled from trigonal heterofunctional ligands.

Six novel metal-organic frameworks (MOFs), {Mn(bpydb)(bpyHdbH)}(n) (1) {[Co(2)(bpydb)(2)](H(2)O)(0.5)}(n) (2), {[Ni(0.5)(bpydbH)(H(2)O)](DMF)(2)}(n) (3), {[Cu(2)(bpydb)(2)](H(2)O)(0.5)}(n) (4), {Zn(bpyHdb)(2)}(n) (5) and {[Cd(0.5)(bpydb)(0.5)(DMF)](H(2)O)}(n) (6), were successfully synthesized by assembling transition metal salts with trigonal heterofunctional ligand 4,4'-(4,4'-bipyridine-2,6-diyl) dibenzoic acid (bpydbH(2)) under hydrothermal and/or solvothermal conditions. Compound 1 features a rare 4-fold interpenetrating (3,5)-connected framework with hms-type topology. Isostructural compounds 2 and 4, constructed by M(2)(COO)(4) secondary building units, exhibit a robust 3D framework with alb topological type in 2-fold interpenetrating mode. Compound 3 consists of 2D (4,4) networks, which are further assembled into the new topological framework with the symbol (5(3)·6(2)·8)(5(3)·6(3))(2) through O-HO interactions. Compound 5 manifests a novel 4-connected interpenetrating framework, constructed by 2D (4,4) layers and interbedded N-HO interactions. Non-interpenetrating honeycomb networks are observed in compound 6, and further packed into a 3D framework featuring 1D channels. The magnetic susceptibility of compound 2 indicates antiferromagnetic interactions between cobalt ions. The photoluminescent properties of 5 and 6 were investigated in the solid state at room temperature.

Syntheses, structures, photoluminescence, and magnetic properties of (3,6)- and 4-connected lanthanide metal-organic frameworks with a semirigid tricarboxylate ligand.

Lanthanide coordination polymers [LnL(DMF)(2)]·0.25H(2)O [Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8), Dy (9), Ho (10), Er (11), and Tm (12)], and [GdL(H(2)O)(3)] (7') (H(3)L = 5-(4-carboxy-2-nitrophenoxy)-isophthalic acid), have been synthesized under hydro- and solvothermal conditions, respectively. Compounds 1-12 exhibit the same three-dimensional (3D) architecture, which is built up from binuclear paddle-wheel building blocks, and their resulting frameworks can be rationalized as rarely reported flu-3,6-C2/c topology. Compound 7' crystallizes in the monoclinic system, space group P2(1)/c. The ligands (L) bridge the Gd(III) centers to form 3D frameworks featuring a zeolite BCT topology, which have been unreported based on rare earth metals until now. Moreover, compound 6 exhibits characteristic red luminescent properties of Eu(III) complexes. The magnetic susceptibilities, over a temperature range of 2.0-300 K, of 7 and 7' have also been investigated.

New class of Preyssler-lanthanide complexes with modified and extended structures tuned by the lanthanide contraction effect.

A family of polyoxometalate compounds based on Preyssler anions and lanthanide cations, K(5)Na(5)[{Pr(4)(H(2)O)(12)(pydc)(4)}{Na(H(2)O)P(5)W(30)O(110)}]·46H(2)O (1, H(2)pydc = pyridine-2,6-dicarboxylic acid), Na(7)[{Pr(4)(H(2)O)(20)(pydc)(2)(Ac)}{Na(H(2)O)P(5)W(30)O(110)}]·23H(2)O (2), and Na(10)H(2) [{Ln(2)(H(2)O)(10)(pydc)(2)}{Na(H(2)O)P(5)W(30)O(110)}]·XH(2)O (Ln = Sm 3, Eu 4, Gd 5; X = 11 for 3 and 5, 13 for 4), have been synthesized and characterized by elemental analysis and single crystal X-ray diffraction. Compound 1 exhibits a two-dimensional honeycomb layer which is built up from unique {Pr(4)} metallacycles and Preyssler anions. Remarkably, the strong involvement of the sodium countercations leads to the formation of a unique three-dimensional open architecture with one-dimensional channels. The 2D grid layer of compound 2 is constructed by the longest currently known rare-earth metal clusters {Pr(8)} and Preyssler anions. Isostructural compounds 3, 4, and 5, obtained by introduction of the intermediate lanthanide ions into the above reaction system, exhibit bisupporting [{Ln(2)(H(2)O)(10)(pydc)(2)}{Na(H(2)O)P(5)W(30)O(110)}](12-) polyoxometalate cluster structures. The magnetic properties of compounds 1 and 2 and the luminescent properties of compounds 3 and 4 are discussed in this paper.

Controlling the synthesis of novel chiral polyoxometalate-based compounds and racemic compounds from the same system.

A pair of enantiomers and one racemic compound have been constructed in the absence of any outside chiral influence. The enantiomers represent the first chiral configuration based on s-block cation linked 1D chain. Meanwhile, the racemic compound comprised of two chiral units shows centrosymmetric structure due to spatial structural symmetry.