Cheng-Feng Du

A two-dimensionally microporous thiostannate with superior Cs+ and Sr2+ ion-exchange property

The removal of highly radioactive and long-lived 137Cs+ and 90Sr2+ from solution is of significance for radionuclide remediation. Herein we prepared a two-dimensionally microporous thiostannate, namely (Me2NH2)4/3(Me3NH)2/3Sn3S7·1.25H2O (FJSM-SnS), and systematically investigated its Cs+ and Sr2+ ion-exchange performance in different conditions. The structural stabilities and variation, ion-exchange kinetic and isothermal behavior, pH-dependent distribution coefficients (Kd), ion-exchange in simulated groundwater and ion-exchange applied to chromatography have been investigated. The results indicated that the maximum Cs+ and Sr2+ ion-exchange capacities of FJSM-SnS were 408.91 mg g−1 and 65.19 mg g−1, respectively. In particular, FJSM-SnS showed quick ion-exchange ability and wide pH resistance (0.7–12.7) which make it outstanding among the ion-exchangers. An ion-exchange chromatographic column was firstly studied for chalcogenido ion-exchange materials, that is, a column filled with 3.0 g FJSM-SnS could remove 96–99% of Cs+ ion and near 100% of Sr2+ ion at low ionic concentrations in 900 bed volumes solutions. Furthermore, the title material could be synthesized on a large scale by a facile, one-pot and economical solvothermal method. The relatively low cost but remarkable ion-exchange performance makes it promising for radionuclide remediation.

Syntheses, Crystal Structures, Ion-Exchange, and Photocatalytic Properties of Two Amine-Directed Ge-Sb-S Compounds.

Among numerous heterometallic chalcogenidoantimonates, relatively a few amine-directed Ge-Sb-S compounds have been synthesized. Presented here are the solvothermal syntheses, crystal structures, and ion-exchange, optical, and photocatalytic properties of two novel amine-directed Ge-Sb-S compounds, namely, [CH3NH3]20Ge10Sb28S72·7H2O (1) and [(CH3CH2CH2)2NH2]3Ge3Sb5S15·0.5(C2H5OH) (2). The structure of 1 features an unprecedented two-dimensional Ge-Sb-S double-layer composed of two twofold rotational symmetry-related thick [Ge8Sb28S72]n(28n-) single layers adhered via vertex-sharing [GeS4] tetrahedra. Compound 2 features a unique [Ge3Sb5S15]n(3n-) slab perforated with large elliptic-like windows. Remarkably, compound 1 exhibited excellent Cs(+) ion-exchange property despite the presence of excess competitive cations, such as Na(+), K(+), Mg(2+), and Ca(2+) ions. In addition, compound 1 displayed visible-light-driven photocatalytic activity for degradation of rhodamine B.

[AEPH2][GeSb2S6]·CH3OH: a thiogermanate–thioantimonate featuring an infinite ribbon-like structure with an unusual {GeSb3S11} unit and exhibiting the ability of photocatalytic degradation of organic dye

A new thiogermanate–thioantimonate, namely, [AEPH2][GeSb2S6]·CH3OH (1) (AEP = N-(2-aminoethyl)piperazine) has been solvothermally synthesized, whose structure features a one-dimensional anionic ribbon of [GeSb2S6]n2n− built of the firstly observed tetranuclear {GeSb3S11} cluster as secondary building unit. The photocatalytic study indicated that 1 was able to degrade Rhodamine B under visible irradiation.

Varied forms of lamellar [Sn3Se7]n2n− anion: the competitive and synergistic structure-directing effects of metal–amine complex and imidazolium cations

Presented are the syntheses, characterizations and properties of a series of selenidostannate compounds directed by metal-amine complex (MAC) cations and/or [Bmmim](+) (Bmmim = 1-butyl-2,3-dimethylimidazolium). Mixtures of the ionic liquid (IL) (Bmmim)Cl and amines, such as ethylenediamine (en) and diethylenetriamine (dien), in various ratios were used to ionothermally/solvothermally prepare four selenidostannates, namely, [Mn(en)3]Sn3Se7 (1), [Mn(dien)2]Sn3Se7·H2O (2), (Bmmim)3[Mn(en)3]2[Sn9Se21]Cl (3) and (Bmmim)6[Mn(dien)2]2Sn15Se35 (4). Single-crystal X-ray diffraction analyses revealed that these compounds exhibit lamellar anionic [Sn3Se7]n(2n-) structures. [Sn3Se7]n(2n-) layers in all 1-4 possess a {6(3)} net, considering [Sn3Se10] semi-cube unit as a 3-connected node; however, diverse multi-membered rings exist there. In compounds 1 and 2, all the [Sn3Se10] units are 3-connected nodes interlinking with each other via edge-sharing two Se atoms to produce six-membered rings. However, in compound 3, the insertion of two [Sn3Se9] units into a six-membered ring results in a novel eight-membered heart-shaped ring, which has never been observed before in the family of chalcogenidostannates. More interestingly, the [Sn3Se7]n(2n-) layer in compound 4 consists of mixed six- and eight-membered rings. The phase composition is strongly dependent on the ratio of IL to MAC in the syntheses, e.g., 1 and 2 were obtained with IL:MAC ratios less than 3:1 and 4:1, while 3 and 4 were obtained when the ratios were increased to 4:1 and 5:1, respectively. The structural variation from 1 to 4 clearly indicates the competitive and synergistic effects between MAC and IL cation on the formation of lamellar selenidostannates. A synthetic approach via varying the ratio of IL to MAC cation as solvent and structure-directing agent will be attractive in the synthesis of novel chalcogenidometallates.

Microwave-assisted ionothermal synthesis of SnSex nanodots: a facile precursor approach towards SnSe2 nanodots/graphene nanocomposites

Presented here is a facile approach towards spherical SnSe2 nanodots/graphene nanocomposites via an ionic liquid media assembly process, which involved an easily scaled-up microwave-assisted ionothermal synthesis of SnSex nanodots (NDs) as precursors by the reaction of elementary tin and selenium in (Bmmim)Cl (Bmmim = 1-butyl-2,3-dimethyl imidazolium) followed by an assembly process under ambient conditions and subsequent thermal treatment. The regulation of the content of SnSe2 NDs could be conveniently achieved by varying the ratio of ND precursor to graphene oxide (GO). As evidenced by TG-MS and FTIR analysis, the assembly process could be attributed to the electrostatic interaction between the anionic GO and the positively charged SnSex NDs, which are fixed in the IL cation layer around the NDs as a medium. This conclusion was further confirmed by the TEM micrographs, which showed a constant particle size in the precursor and in the nanocomposites after thermal treatment. Lithium storage characterizations showed that the capacity of the as-prepared nanocomposite remained at 659 mA h g−1 after 30 cycles at a current density of 150 mA g−1, which is 1.5-times better than the theoretical capacity of SnSe2 (426 mA h g−1) and superior to the capacities of the previously reported SnSe2 nanoplate/graphene composite and many other tin selenide electrodes. Thus, the new approach represents a promising, simple, and scalable synthetic protocol for the fabrication of lamellar metal dichalcogenide (LMD) NDs/graphene nanocomposites.

From T2,2@Bmmim to Alkali@T2,2@Bmmim Ivory Ball-like Clusters: Ionothermal Syntheses, Precise Doping, and Photocatalytic Properties

Presented here are the syntheses, structures, and properties of an In-Sn-Se compound based on a ternary super-supertetrahedral T2,2 cluster nested by Bmmim cations and two of its alkali-doped quaternary analogues. By means of a one-pot ionothermal method, an alkali metal ion (Cs(+) or Rb(+)) could be precisely doped into the central cavity of the cluster, forming an alkali@T2,2@Bmmim quaternary cluster. Remarkably, the undoped compound exhibited excellent stability and visible light photodegradation ability over a wide range of pH, especially in acidic conditions.

An ionothermally synthesized Mg-based coordination polymer as a precursor for preparing porous carbons

A new magnesium coordination polymer (Mg-CP), namely [Bmim]2[Mg6(NDC)5(HNDC)2(HCOO)2] (1, H2NDC = 1, 4-naphthalenedicarboxylic acid, [Bmim] = 1-butyl-3-methyl-imidazolium ion), has been ionothermally synthesized and structurally characterized. Single-crystal X-ray structural determination indicated that the title compound possessed an anionic three-dimensional (3D) framework constructed by the interconnections of unprecedented hexanuclear magnesium-carboxylate clusters as secondary building units (SBUs) via bridging NDC ligands. Compound 1 exhibited blue luminescence emission at 440 nm when excited at 360 nm. Significantly, the title non-porous Mg-CP could be utilized as a precursor for preparing porous carbons through thermal decomposition in optimized conditions. Different from the reported high decomposition temperature (>1000 °C) mostly based on porous Zn-CP precursors, the optimum decomposition temperature for 1 was only 700 °C, and the resulting porous carbons showed 465 cm3 g−1 adsorption volume for N2. The as-prepared carbon exhibited finely selective N2 adsorption ability over H2 and CO2. This work may provide a certain guiding significance for exploiting ionothermally synthesized Mg-CPs as a new type of precursor towards porous carbons.

Synthesizing 2D and 3D Selenidostannates in Ionic Liquids: The Synergistic Structure-Directing Effects of Ionic Liquids and Metal–Amine Complexes

Presented are the ionothermal syntheses, characterizations, and properties of a series of two- and three-dimensional selenidostannate compounds synergistically directed by metal-amine complex (MAC) cations and ionic liquids (ILs) of [Bmmim]Cl (Bmmim=1-butyl-2,3-dimethylimidazolium). Four selenidostannates, namely, 2D-(Bmmim)3 [Ni(en)3 ]2 [Sn9 Se21 ]Cl (1, en=ethylenediamine), 2D-(Bmmim)8 [Ni2 (teta)2 (μ-teta)]Sn18 Se42 (2, teta=triethylenetetramine), 2D-(Bmmim)4 [Ni(tepa)Cl]2 [Ni(tepa)Sn12 Se28 ] (3, tepa=tetraethylenepentamine), and 3D-(Bmmim)2 [Ni(1,2-pda)3 ]Sn8 Se18 (4, 1,2-pda=1,2-diaminopropane), were obtained. Single-crystal X-ray diffraction analyses revealed that compounds 1 and 2 possess a lamellar anionic [Sn3 Se7 ]n (2n-) structure comprising distinct eight-membered ring units, whereas 3 features a MAC-decorated anionic [Ni(tepa)Sn12 Se28 ]n (6n-) layered structure. In contrast to 1-3, compound 4 exhibits a 3D open framework of anionic [Sn4 Se9 ]n (2n-) . The structural variation from 1 to 4 clearly indicates that on the basis of the synergistic structure-directing ability of the MACs and ILs, variation of the organic polyamine ligand has a significant impact on the formation of selenidostannates.

Assembly and structural transformation of organic-decorated manganese selenidostannates

Presented here are three organic-decorated manganese selenidostannates with various structural dimensionalities (D), namely, 1D – SnSe3Mn(en)2 (en = ethylenediamine) (1), 2D – SnSe3Mn(en) (2) and 3D – MnSnSe4Mn(en)2 (3). 2 and 3 represent the first 2D and 3D organic-decorated Mn–Sn–Se compounds, respectively. A structural transformation was observed between 1 and 2.

Synthesis, Structure, Band Gap, and Near-Infrared Photosensitivity of a New Chalcogenide Crystal, (NH4)4Ag12Sn7Se22

A new chalcogenide crystal, (NH4)4Ag12Sn7Se22 (FJSM-STS), has been solvothermally synthesized. The crystal structure, which is composed of arrays of [Sn3Se9]n(6n-) chains interconnecting [SnAg6Se10]n(10n-) and [Ag3Se4]n(5n-) layers, is unprecedented among the reported A/Ag/Sn/Q (A = cation; Q = S, Se, and Te) compounds. Optical absorption together with theoretical calculations of the band structure indicate a direct band gap of 1.21 eV for FJSM-STS, which is close to the ideal band gap to maximize the photoconversion efficiency proposed by Shockley and Queisser. The toxic-metal-free crystal of FJSM-STS exhibits obvious photosensitivity in the near-infrared range. The variates of power and temperature on the photosensitivity have been studied.