Growing Crystalline Chalcogenidoarsenates in Surfactants: From Zero-Dimensional Cluster to Three-Dimensional Framework

M6[Cd2(CO3)2(B12O18)(OH)6] (M = K, Rb): Borate-Carbonates with Two CdCO3 Embedded in a Cyclic Oxoboron Anion

Two metal borate-carbonates, M6[Cd2(CO3)2(B12O18)(OH)6] [M = K (1), Rb (2)], were obtained under surfactant-thermal conditions. In 1 and 2, each cyclic [(B12O18)(OH)6]6- anion captures two CdCO3 in two sides of the rings and finally forms the unusual (CdCO3)2@[(B12O18)(OH)6] cluster. Both 1 and 2 show moderate birefringence. Density functional theory calculations indicate that carbonate groups have a major contribution to electron-related optical transition.

Hydrazine-Assisted Synthesis, Structures, Photoelectricity, and Photocatalysis of Ternary Mercury-Tellurostannate Hybrids with Transition-Metal Complexes

Tellurostannates are traditionally prepared by multistep reactions using the tellurides SnTe, SnTe2, K4SnTe4, or A6SnTe6 (A = K, Rb, or Cs) as precursors, which are usually prepared by the molten reaction of alkali metals Sn and Te under harsh synthetic conditions. Differently, ternary Hg-tellurostannate hybrids [Mn(en)3]HgSnTe3(Te2) (1) (en = ethylenediamine), [Mn(dien)2]HgSnTe3(Te2) (2), and [Fe(dien)2]HgSnTe3(Te2) (3) (dien = diethylenetriamine) were synthesized by one-pot reactions using Sn and Te powders as starting materials in the presence of hydrazine under mild solvothermal conditions. In 1, HgTe3 and SnTe4 units are joined via Te-sharing to form a 1-D polymeric chain [HgSnTe3(Te2)]n2n-, while the [HgSnTe3(Te2)]n2n- chains in 2 and 3 are composed of HgTe4 and SnTe4 units. The common feature of the [HgSnTe3(Te2)2-]n chains in 1-3 is that they are constructed by both the telluride anion Te2- and the polytelluride anion Te22-. 1-3 exhibited strong photocurrent responses with current densities of 5.26, 3.38, and 3.94 μA cm-2, respectively. They showed effective photocatalytic activities for methylene blue degradation with degradation ratios in the range of 85.3-94.6% after light irradiation for 80 min. Investigation of the photocatalytic mechanism showed that •O2- radicals and h+ holes were the main active substances in the photodegradation.

Two Electrocatalytic Selenoarsenates with Manganese Complex Cations as Counterions

The discovery of new organic hybrid chalcogenidometalates is of great importance for structural chemistry and functional material. Here, new types of organic hybrid selenoarsenates [Mn(dien)2]2[AsII4Se6] (1, dien = diethylenetriamine) and [Mn(dien)2]2[Mn(AsIIISe3)2] (2) have been solvothermally synthesized by the reaction of K3AsO3, Se, and MnCl2·xH2O (x = 0, 2) in dien solution at 120 °C. 1 presents a hitherto unknown [AsII4Se6]4- anion with low-valent As2+ ion, which comprises a centrosymmetric six-membered [AsII4Se2] ring in chair-like conformation, while 2 contains a new type of heterometallic selenoarsenate(III) [Mn(AsIIISe3)2]4- constructed by the connection of one tetrahedral [MnSe4] and two rare noncondensed [AsIIISe3]3- anions. 1 and 2 were first combined with nickel nanoparticle (Ni) and the nickel foam (NF) for fabricating the 1/Ni/NF and 2/Ni/NF electrodes, which exhibited excellent oxygen evolution reaction electrocatalytic property with a low overpotential of 248 mV for 1 and 219 mV for 2 at 10 mA cm-2 in alkaline media.

Crystalline chalcogenidometalate-based compounds from uncommon reaction media

Chalcogenides are one of the most versatile inorganic materials families, further subdivided into a large variety of specific groups of compounds, ranging from neat binary or multinary solids and nanoparticles of the same formal compositions, both in crystalline or non-crystalline form, to complicated open-framework structures and cluster compounds, also including organ(ometall)ic derivates of the latter. The large variety regarding both the compositions and the structures is associated with an enormous variety of properties, ranging from simple or high-tech pigments through a multitude of opto-electronic devices and electrolytes to materials for ion separation or high-sophisticated catalysts. Naturally, this also goes hand in hand with a corrosponding breadth of synthesis strategies. Traditionally, chalcogenides have been accessed via high-temperature methods, which continuously have been replaced by lower-temperature approaches for economical and ecological reasons. Moreover, more recent methods also showed that new types of chalcogenide materials can be obtained under such milder conditions that are not accessible via traditional routes. To shed light onto one of the numerous families of chalcogenides, this feature article summarizes current achievements in the generation of multinary chalcogenidometallate-based clusters and networks via non-classical routes, using ionic liquids, surfactants, or hydrazine as reaction media at moderately elevated termperature.

Strong Photocurrent Response of Selenoarsenates With Different Transition Metal Complexes as Structure-Directing Agents

Four selenoarsenates with different transition-metal complexes [Co(tren)₂H]AsSe₄ [tren = tris(2-aminoethyl)amine] (1); [Ni₂(dien)₄](As₂Se₅) (dien = diethylenetriamine) (2); [Zn(tren)]₂(As₂Se₅) (3) and [Mn(tren)]₂(As₂Se₅) (4) were solvothermally synthesized in a mixed solvent of organic amine and alcohol solution. The compounds 1-4 have pyramidal/tetrahedral structures (AsSe₃/AsSe₄), and contain transition metal (Co²⁺, Ni²⁺, Zn²⁺ and Mn²⁺) complex that form distinct zero-dimensional (0-D) clusters. Arsenic atoms form a tetrahedron in compounds 1 and 2; 1 consists of discrete tetrahedral (AsSe₄) and transition metal complex [Co(tren)₂]²⁺; 2 is composed of an anion [As₂Se₅]^4- cluster and transition metal complex [Ni(dien)₂]²⁺. In compounds 3 and 4, arsenic atom forms a pyramidal AsSe₃ and the two pyramidal AsSe₃ share a corner connection to form a dimer [As₂Se₅]^4-; 3 is characterized as a cluster consisting of two unsaturated [Zn(tren)]²⁺ caiton linked by a dimer (As₂Se₅)^4- linkage; in 4, unsaturated [Mn(tren)]²⁺ caiton is linked to two trigonal-bipyramidal [Mn(tren)]Se via dimer (As₂Se₅)^4- to form [Mn(tren)]₄[As₄Se₁₀] cluster. To our knowledge, [Zn(tren)]₂(As₂Se₅) (3) is the first zinc selenoarsenate containing the (As₂Se₅)^4- anion type. Furthermore, the Mn²⁺ ions adopt a trigonal-biyramidal (five-coordinate) and octahedral (six-coordinate) environment. Adding K₂CO₃/Cs₂CO₃ to the synthesis system is necessary and may act as a mineralizer. Several properties of compounds 1-4 have been characterized in our studies, in particular their strong photocurrent response characteristics under visible light irradiation.

The rare example of hybrid chalcogenoarsenates(III) incorporating trivalent vanadium complexes

A series of new hybrid vanadium chalcogenoarsenates(III) [VIII(en)2AsIIIS3] (1, en = ethylenediamine), [VIII(dap)2AsIIISe3] (2, dap = 1,2-diaminopropane), [VIII(teta)AsIIIQ3] {Q = S (3), Se (4), teta = triethylene-tetramine}, and [VIII2(en)6(μ2-O)][As2Se5] (5)...

Surfactant-assisted fabrication and supercapacitor performances of a 12-phosphomolybdate-pillared metal–organic framework containing a helix and its SWNT nanocomposites

By employing a surfactant-assisted hydrothermal method, a new POMOF with a multi-fold helix was obtained, and NiPMo12/SWNTs exhibits excellent electrochemical performance and good stability as an electrode material for supercapacitors.

Cs3CuAs4Q8 (Q = S, Se): unique two-dimensional layered inorganic thioarsenates with the lowest Cu-to-As ratio and remarkable photocurrent responses

Inorganic chalcogenides containing cations with lone-pair electrons have attracted considerable attention because of their potential applications in photocatalysis. In this research, two new copper thioarsenates with the lowest Cu-to-As ratio in the quaternary X/Cu/As/Q (X = inorganic cations; Q = chalcogen) system, namely Cs₃CuAs₄Q₈ (Q = S, Se), were obtained by a simple surfactant-thermal method at a low temperature. These two isostructural compounds belong to the monoclinic space group C2/c (no. 15) and are composed charge-balanced Cs⁺ cations and two-dimensional anionic [CuAs₄Q₈]^3- layers. Notably, photo-electrochemical measurements indicate that Cs₃CuAs₄Q₈ possesses a remarkable photocurrent response under simulated solar-light illumination. Further theoretical studies were performed to gain insights into the relationships between electronic structure and optical properties.

Two Organic Hybrid Manganese Selenoarsenates: The Discovery of One-Dimensional Low-Valent Selenoarsenate(II)

Two organic hybrid manganese selenoarsenates, [Mn(en)₃][MnAs^II₂Se₄] (1; en = ethanediamine) and {[Mn(atep)]₂[Mn(tepa)](As^VSe₄)₂} [2; atep = 4-(2-aminoethyl)triethylenetetramine], were made under mild solvothermal conditions. 1 is a new type of one-dimensional low-valent selenoarsenate(II) constructed by the linkages of tetrahedral [MnSe₄] units and two manners of bridging of [As^II₂Se₄]^4- anions. 2 comprises a neutral {[Mn(atep)]₂[Mn(tepa)](As^VSe₄)₂} molecule with a rare seven-coordinated manganese center, which represents the sole example of an organic hybrid selenoarsenate with the [Mn(tepa)]²⁺ complex as the bridging group. Both 1 and 2 exhibit special photocurrent responses upon visible-light illumination and magnetic properties.

A Copper(I)-Thioarsenate(III) Inorganic Framework Directed by [Ni(en)3]2

One novel three-dimensional (3-D) copper(I)-thioarsenate(III) [Ni(en)₃]Cu₄As₄S₉ (1, en = ethylenediamine) has been solvothermally prepared with the utilization of the in situ formation of [Ni(en)₃]²⁺ complex as structure-directing agent (SDA). 1 contains cubane-like [Cu₈S₁₂]^16- clusters and rare tetrameric [As₄S₉]^6- units, which are interconnected to generate the first example of a 3-D anionic framework [Cu₄As₄S₉]_n^2n-, topologically identical to pyrite, and having large channels filled by [Ni(en)₃]²⁺ complex cations. 1 is a potential wide-band-gap semiconductor with an energy gap of 1.91 eV that exhibits selectively photocatalytic degradation of methylene blue under visible-light irradiation. The density functional theory calculation, photocurrent response, and magnetic properties of 1 were also investigated.

Two Series of Main-Group Heterometallic Selenides Synthesized in Two Different Types of Ionic Liquids

Imidazolium-based ionic liquids have been widely applied in the synthesis of organic hybrid chalcogenidometalates, while the other types of ionic liquids are rarely tried. Reported here is the first application of a pyridinium-based ionic liquid in the preparation of two main-group heterometallic selenides featuring isomorphic three-dimensional frameworks. Of particular interest is that three gallium-tin selenides possessing another type of three-dimensional framework have been prepared by replacing the pyridinium-based ionic liquid with imidalolium-based ionic liquids under the same reaction conditions.

AMnAs3S6 (A = Cs, Rb): Phase-Matchable Infrared Nonlinear Optical Functional Motif [As3S6]3- Obtained via Surfactant-Thermal Method

Exploration of a new nonlinear optical (NLO)-active functional motif is important in the rational design of promising infrared (IR) NLO materials. Compared with typical tetrahedral MQ₄ (M = IIB, III, IV metals; Q = S, Se) motifs, MQ₃ (M = As, Sb) pyramids favor high second-harmonic generation (SHG) efficiency while frequently hindering phase matching (PM) because of excessively large optical anisotropy. The surfactant-thermal method was first adopted to achieve PM in MQ₃-containing systems and synthesize mixed covalent-ionic IR NLO materials. Two new thioarsenates of AMnAs₃S₆ (A = Cs, Rb) exhibiting strong PM SHG efficiencies comparable to commercial AGS and laser-induced damage thresholds of one order higher than AGS were obtained. The [As₃S₆]^3- unit in their structures is an unprecedented NLO-active functional motif, which can be useful in designing new IR NLO compounds with large SHG efficiency. In addition, the surfactant-thermal method provides a new general strategy for synthesizing new IR NLO materials.

Host-Guest Thin Films by Confining Ultrafine Pt/C QDs into Metal-Organic Frameworks for Highly Efficient Hydrogen Evolution

Combining the features of host templates and guest species is an efficient strategy to optimize the photo/electrocatalytic performance. Herein, novel host-guest thin-film electrocatalysts are designed and developed with Pt doped carbon (Pt/C) confined into porphyrin-based metal-organic frameworks (MOFs). Porous MOF PCN-222 and PCN-221 thin films are used as the host templates and fabricated using vapor-assisted deposition method, and then the guest Pt/C quantum dots are encapsulated into the MOFs by loading the glucose mixed H₂ PtCl₆ and heating at 200 °C. Thanks to the confinement effect of MOF pores, the homogenous and ultrafine Pt/C nanowires (Pt/CNWs) and nanodots (Pt/CNDs) are confined in nanochannels of PCN-222 and nanocages of PCN-221 (Pt/CNW@PCN-222 and Pt/CND@PCN-221), respectively. The electrocatalytic study shows that the host-guest thin films have highly-efficient electrocatalytic hydrogen evolution performance under light irradiation. Furthermore, the time-resolved photoluminescent results reveal that Pt/CNW@PCN-222 has a faster charge transfer (441 ps) from PCN-222 to Pt/CNWs comparing to that (557 ps) of Pt/CND@PCN-221, indicating the guests with different shapes play an important role in the electrocatalytic performance. This work serves to present both the outstanding level of control in the precise synthesis and high potential for nanocomposite thin films in photo-electrocatalytic application.

The solvothermal synthesis and characterization of quaternary arsenic chalcogenides CsTMAsQ3 (TM = Hg, Cd; Q = S, Se) using Cs+ as a structure directing agent: from 1D anionic chains to 2D anionic layers

Four new quaternary transition metal arsenic chalcogenide Cs-TM-As-Q compounds (TM = Hg, Cd; Q = S, Se) were synthesized using different mixed solvents. A 1,4-diaminobutane(1,4-dab)/water mixed solvent system was used to solvothermally synthesize the selenoarsenates CsTMAsSe₃ (TM = Hg (1), Cd (2)). In 1, the eight-membered ring anion chain consists of trigonal-planar [HgSe₃] and trigonal-pyramid [AsSe₃]. Compound 2 is similar to the eight-membered ring chain anion of compound 1, and [CdAsSe₃]^- further joins, through μ₃-Se and Cd, to form the layer anions [CdAsSe₃]^-. A 2-diaminopropane (1,2-dap) and water mixed solvent system was used to synthesize two thioarsenates, Cs₂TM₂As₂S₆ (TM = Cd (3), Hg (4)). Compounds 3, 4 and 2 are isostructural; the Cd and Hg atoms are four coordinated. Compounds 1-4 utilize Cs⁺ cations as a structural directing agent. Finally, the structural and optical properties of the novel series of arsenic chalcogenides were characterized.

Two dimensional ZIF-derived ultra-thin Cu-N/C nanosheets as high performance oxygen reduction electrocatalysts for high-performance Zn-air batteries

Bottom-up construction of transition copper-nitrogen-carbon (Cu-N-C) electrocatalysts with high-performance and long-term durability for the oxygen reduction reaction (ORR) still remains a great challenge. Herein, we propose a temperature-controlled synthesis strategy with confinement effect for fabrication of a novel two-dimensional dual-metal (Cu/Zn) zeolitic imidazolate framework material, which presents an ultrathin nanosheet morphology after high-temperature thermal treatment (denoted as Cu-N-UNS). By controlling the reaction temperature as well as regulating the ratio of metal ions and taking advantages of the confinement effect of surfactants, the rationally designed ultra-thin carbon layer not only prevents aggregation of transition Cu particles and avoids direct contact with reactants and electrolyte solutions to enhance the durability of electrocatalysts, but also shortens the electronic transmission path between the active transition metal species and carbon surface. Therefore, the electrocatalyst exhibits excellent electrocatalytic performance for the ORR (E1/2 ≈ 0.898 V), which is superior to those of state-of-the-art benchmark noble-metal electrocatalysts. Moreover, the even distribution of Cu-N-C and existence of N-Cu2+-Cu0 active sites make a great contribution to the electrocatalyst activity. Notably, the Cu-N-UNS used as air electrodes for Zn-air batteries also exhibits a high peak power density of ≈134.7 mW cm-2 at a current density of ≈231.9 mA cm-2 with remarkable durability.

Two amino acid-templated metal phosphates: surfactant-thermal synthesis, water stability, and proton conduction

Two new metal phosphates, namely, Zn(HPO₄)(C₆H₁₁NO₂) (1) and (C₅H₁₀NO₂)Ga₄(PO₄)₄F·3H₂O (2), were prepared under surfactant-thermal conditions. Single-crystal X-ray diffraction analyses reveal that compound 1 has a zigzag-chain structure decorated with homoproline and compound 2 has a three-dimensional zeolite-like structure templated by proline. Notably, compound 2 remains stable in both boiling water and aqueous solutions with a pH range of 2-12. It shows a proton conductivity of 8.89 × 10^-4 S cm^-1 at 85 °C and 95% relative humidity.