Unusual Flexibility of Microporous Sulfides during Ion Exchange

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.

Three new Zn(ii) coordination polymers for highly selective and sensitive detection of Fe3+

In this work, three novel Zn(ii)-CPs with diverse structures and fascinating topologies can be highly selective and sensitive luminescent sensors for detection of Fe3+.

Stable 3D neutral gallium thioantimonate frameworks decorated with transition metal complexes for a tunable photocatalytic hydrogen evolution

Incorporating transition metal (TM) complexes into cluster-based chalcogenide frameworks is an effective synthetic strategy to induce structural diversity and control the optoelectronic properties, which may further improve their photocatalytic performance. However, limited studies have been conducted on frameworks constructed by TM complexes covalently bonded with supertetrahedral Tn clusters, let alone on their properties, especially photocatalytic H₂ activity. Herein, three new isostructural three-dimensional (3D) neutral inorganic-organic open frameworks of gallium thioantimonate comprised of thiogallate-based supertetrahedral T3 clusters that are covalently bonded with TM complexes ([TM(TEPA)]²⁺, TM = Mn/Ni/Fe, TEPA = tetraethylenepentamine) at the edges and are linked by single Sb³⁺ ions at the corner, namely, NCF-3-Mn/Ni/Fe have been solvothermally synthesized and structurally characterized, and display good thermal and chemical stability. Benefiting from an adjustable TM centre, the title compounds possess tunable photocatalytic H₂ evolution activity, among which NCF-3-Mn exhibits the highest photocatalytic activity probably due to its favourable band structure and enhanced carrier separation efficiency.

A novel copper-rich open-framework chalcogenide with chiral topology constructed from distinctive bimetallic [Cu5SnSe10] clusters

Reported here is the first chiral copper-rich open-framework chalcogenide with a quartz (qtz) topology built on distinctive [Cu₅SnSe₁₀] clusters connected by [SnSe₄] bridging units. Through in situ sulfur doping, sulfurized compounds could be obtained that exhibit improved photocatalytic performance. This work expands the family of COCs with new building blocks and topologies and demonstrates the significance of chalcogen doping in COCs.

Sodium-Stuffed Open-Framework Quaternary Chalcogenide Built with (Cu2Ga6S18)16- Ribbons Cross-Linked by Unusual Linear Cu(I) Pillars

A quaternary compound, Na₁₅Cu₃Ga₆S₁₈, the first member in the A-Cu-Ga-S (A = alkali metal) series, has been synthesized from a solid-state metathesis reaction between Na₆Ga₂S₆ and CuCl as well as from a combination of Na₂S, Ga, Cu, and S. The compound crystallizes in a monoclinic crystal system, space group C2/c, and represents a unique open-framework structure with channels filled with eight crystallographically distinct Na ions. The anionic framework is built up of infinite chains of corner-shared GaS₄ tetrahedra fused together by an edge-shared dimer of CuS₄ tetrahedra forming one-dimensional ribbons of (Cu₂Ga₆S₁₈)^16-, which are cross-linked by linearly coordinated S-Cu-S linkages resulting in a three-dimensional network with tunnels filled with Na atoms. Optical band gap measurements show that the compound has a direct band gap of 3.00 eV that is in good agreement with the theoretical band gap derived from density functional theory calculations. Band structure calculations further indicate that the states near the Fermi level are dominated by tetrahedral Cu⁺(d) and S(p) states resulting from the antibonding interactions, while s-d hybridization is prevalent in linear Cu⁺ coordination. Ionic conductivity measurements show that the compound has a room-temperature Na ion conductivity of 2.72 × 10^-5 mS/cm with an activation energy of 0.68 eV, which corroborates well the nudged elastic band calculations.

Two-Step Reaction Mechanism of Roasting Spodumene with Potassium Sulfate

The conventional process of lithium extraction from α-spodumene (LiAlSi₂O₆) is energy-intensive and associated with high byproduct management cost. Here, we investigate an alternative process route that uses potassium sulfate (K₂SO₄) to extract lithium while producing leucite (KAlSi₂O₆), a slow release fertilizer. Presenting the first-ever in situ record of the reaction of α-spodumene with potassium sulfate, we use synchrotron X-ray diffraction (XRD) and differential scanning calorimetry (DSC) to document the reaction sequence during prograde heating. From 780 °C, we observe a broad endothermic DSC peak, abnormal expansion of the α-spodumene structure, and an increase in α-(Li, K)-spodumene peak intensity during heating with potassium sulfate, indicative of the exchange between lithium and potassium in the spodumene structure. When 11 ± 1% K occupancy in the M2 site of α-(Li, K)-spodumene is reached, the mechanism changes from ion exchange to a reconstructive transformation of α-(Li, K)-spodumene into leucite, evidenced by a decrease in α-spodumene and potassium sulfate abundance concurring with formation of leucite over a narrow temperature range between 850 and 890 °C. The increasing background intensity in synchrotron XRD above 870 °C suggests that a lithium sulfate-bearing melt starts to form once >90% of α-spodumene has been converted during the reaction. This fundamental understanding of the reaction between α-spodumene and potassium sulfate will enable future development of lithium extraction routes using additives to significantly decrease energy intensity and to produce marketable byproducts from α-spodumene.

Applying band gap engineering to tune the linear optical and nonlinear optical properties of noncentrosymmetric chalcogenides La4Ge3SexS12−x (x = 0, 2, 4, 6, 8, 10)

Band gap engineering was applied to tune the properties of a phase-matchable La4Ge3S12 by replacing S with Se, which uncovered five new compounds: La4Ge3SexS12−x (x = 2, 4, 6, 8, 10).

N, Baiyin M. Synthesis, crystal structure, photocatalysis, photocurrent response: one-dimensional K2HgSnSe4 and three-dimensional Na6Cu8Sn3Se13

Two novel selenidostannates were solvothermally synthesized and compound 2 displays a unique 3-D open frame structure.

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.

Cotemplating Assembly and Structural Variation of Three-Dimensional Open-Framework Sulfides

Open-framework sulfides (H₃O)KCu₆Ge₂S₈ (1) and (H₃O)RbCu₆Ge₂S₈ (2) were prepared by a cotemplating strategy. This shows that alkali-metal and protonated water cations act as cotemplates to direct the three-dimensional open-framework sulfides. These templates direct two types of one-dimensional channels that arrange parallelly, and different types of templates reside in different types of channels. By introduction of the Cs cation into the synthetic systems of 1 and 2, (H₃O)K_0.6Cs_0.4Cu₆Ge₂S₈ (3) and (H₃O)Rb_0.75Cs_0.25Cu₆Ge₂S₈ (4) were obtained. Compound 3 has a different anionic framework from those of 1 and 2, while 4 is isostructural with 1 and 2.

Size-Driven Stability of Lanthanide Thiophosphates Grown from an Iodide Flux

To determine the influence of the lanthanide size on the structures and properties of thiophosphates, a thiophosphate series containing different lanthanides was synthesized via high temperature flux crystal growth and their structures and physical properties analyzed and compared. Layered thiohypophosphates NaLnP₂S₆ (Ln = La, Ce, Pr) and thiopyrophosphates CsLnP₂S₇ (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Yb, Y) were grown out of an iodide flux using consistent reaction conditions across both series. Under the mildly reducing iodide flux reaction conditions, a rather rare example of phosphorus reduction from the +5 to the +4 oxidation state was observed. Both resultant structure types are based on lanthanide thiophosphate sheets with the alkali cations located between them. Magnetic susceptibility measurements were conducted and revealed Curie-Weiss behavior of the samples, with a Van Vleck contribution in the CsSmP₂S₇ sample. UV-vis data was found to be in good agreement with the literature, indicating little influence of the sulfide environment on the localized 4f orbitals.

Deep eutectic solvothermal synthesis of an open framework copper selenidogermanate with pH-resistant Cs+ ion exchange properties

Reported here is the deep eutectic solvothermal synthesis of an open framework copper selenidogermanate [NH₃CH₃]_0.75Cu_1.25GeSe₃ (CuGeSe-1), which shows a pH-resistant Cs⁺ ion exchange performance (q_m = 225.3 mg g⁻¹).