Alexander Rothenberger

Low trap-state density and long carrier diffusion in organolead trihalide perovskite single crystals

Large-crystal perovskite films The performance of organic-inorganic hybrid perovskite planar solar cells has steadily improved. One outstanding issue is that grain boundaries and defects in polycrystalline films degrade their output. Now, two studies report the growth of millimeter-scale single crystals. Nie et al. grew continuous, pinhole-free, thin iodochloride films with a hot-casting technique and report device efficiencies of 18%. Shi et al. used antisolvent vapor-assisted crystallization to grow millimeter-scale bromide and iodide cubic crystals with charge-carrier diffusion lengths exceeding 10 mm. Science, this issue p. 522, p. 519 Solution processing techniques enable the growth of high-quality, large-area perovskite crystals for solar cells. The fundamental properties and ultimate performance limits of organolead trihalide MAPbX3 (MA = CH3NH3+; X = Br– or I–) perovskites remain obscured by extensive disorder in polycrystalline MAPbX3 films. We report an antisolvent vapor-assisted crystallization approach that enables us to create sizable crack-free MAPbX3 single crystals with volumes exceeding 100 cubic millimeters. These large single crystals enabled a detailed characterization of their optical and charge transport characteristics. We observed exceptionally low trap-state densities on the order of 109 to 1010 per cubic centimeter in MAPbX3 single crystals (comparable to the best photovoltaic-quality silicon) and charge carrier diffusion lengths exceeding 10 micrometers. These results were validated with density functional theory calculations.

Ion-Exchangeable Cobalt Polysulfide Chalcogel

We present a promising approach in synthetic chalcogel chemistry that is extendable to a broad variety of inorganic spacers. Polychalcogenide aerogels with ion-exchange properties are demonstrated in cobalt polysulfide. The new materials show a broad range of pore sizes and high surface area of 483 m(2)/g.

Extraordinary Selectivity of CoMo3S13 Chalcogel for C2H6 and CO2 Adsorption

or metals, [ 5 ] has recently been expanded to include the emerging new chalcogenide materials called chalcogels. [ 6–10 ] Unlike the nanocrystalline chalcogenide aerogels reported by Brock et al., [ 6 , 11 , 12 ] the chalcogels feature random amorphous networks similar to those of silica. Because of the “soft” nature of electron-rich chalcogen atoms, the polarizability of the internal surface of chalcogels is much higher than those of metal oxides, porous carbons, and organic polymers and therefore provides an entirely new medium through which to study the diffusion and separation of gases. [ 13 ] Photocatalysis, catalysis, gas separation, and removal of heavy metals with chalcogels are just some of the proposed applications that make use of the unique electronic properties (tunable bandgaps and high surface polarizability) of such high surface area materials. [ 8 ]

Nanoporous amide networks based on tetraphenyladamantane for selective CO2 capture

Reduction of anthropogenic CO2 emissions and CO2 separation from post-combustion flue gases are among the imperative issues in the spotlight at present. Hence, it is highly desirable to develop efficient adsorbents for mitigating climate change with possible energy savings. Here, we report the design of a facile one pot catalyst-free synthetic protocol for the generation of three different nitrogen rich nanoporous amide networks (NANs) based on tetraphenyladamantane. Besides the porous architecture, CO2 capturing potential and high thermal stability, these NANs possess notable CO2/N2 selectivity with reasonable retention while increasing the temperature from 273 K to 298 K. The quantum chemical calculations also suggest that CO2 interacts mainly in the region of polar amide groups (–CONH–) present in NANs and this interaction is much stronger than that with N2 thus leading to better selectivity and affirming them as promising contenders for efficient gas separation.

KFeSbTe3: a quaternary chalcogenide aerogel for preferential adsorption of polarizable hydrocarbons and gases

The first telluride-based quaternary aerogel KFeSbTe3 is synthesized by a sol–gel metathesis reaction between Fe(OAc)2 and K3SbTe3 in dimethyl formamide. The aerogel has an exceptionally large surface area 652 m2 g−1 which is amongst the highest reported for chalcogenide-based aerogels. This predominantly mesoporous material shows preferential adsorption for toluene vapors over cyclohexane or cyclopentane and CO2 over CH4 or H2. The remarkably high adsorption capacity for toluene (9.31 mmol g−1) and high selectivity for gases (CO2/H2: 121 and CO2/CH4: 75) suggest a potential use of such materials in adsorption-based separation processes for the effective purification of hydrocarbons and gases.

Aluminosilicate Relatives: Chalcogenoaluminogermanates Rb3(AlQ2)3(GeQ2)7 (Q = S, Se)

The new compounds Rb(3)(AlQ(2))(3)(GeQ(2))(7) [Q = S (1), Se (2)] feature the 3D anionic open framework [(AlQ(2))(3)(GeQ(2))(7)](3-) in which aluminum and germanium share tetrahedral coordination sites. Rb ions are located in channels formed by the connection of 8, 10, and 16 (Ge/Al)S(4) tetrahedra. The isostructural sulfur and selenium derivatives crystallize in the space group P2(1)/c. 1: a = 6.7537(3) Å, b = 37.7825(19) Å, c = 6.7515(3) Å, and β = 90.655(4)°. 2: a = 7.0580(5) Å, b = 39.419(2) Å, c = 7.0412(4) Å, β = 90.360(5)°, and Z = 2 at 190(2) K. The band gaps of the congruently melting chalcogenogermanates are 3.1 eV (1) and 2.4 eV (2).

A recipe for new organometallic polymers and oligomers? Synthesis and structure of an oligo- and a polymeric arrangement of P–S anions

A route to organometallic polymers and oligomers is described using metal complexes with P/S-ligands as examples.

SOMC-Designed Silica Supported Tungsten Oxo Imidazolin-2-iminato Methyl Precatalyst for Olefin Metathesis Reactions

Synthesis, structure, and olefin metathesis activity of a surface complex [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4) (ImDipp = 1,3-bis(2,6-diisopropylphenyl)imidazolin-2-iminato) supported on silica by a surface organometallic chemistry (SOMC) approach are reported. The reaction of N-silylated 2-iminoimidazoline with tungsten(VI) oxytetrachloride generated the tungsten oxo imidazolin-2-iminato chloride complex [ImDippNW(═O)Cl3] (2). This was grafted on partially dehydroxylated silica pretreated at 700 °C (SiO2-700) to afford a well-defined monopodal surface complex [(≡Si-O-)W(═O)Cl2-ImDippN] (3). 3 underwent alkylation by ZnMe2 to produce [(≡Si-O-)W(═O)(CH3)2-ImDippN] (4). The alkylated surface complex was thoroughly characterized by solid-state NMR, elemental microanalysis, Raman, FT-IR spectroscopies, and XAS analysis. 4 proved to be an active precatalyst for self-metathesis of terminal olefins such as propylene and 1-hexene.

Structural diversity by mixing chalcogen atoms in the chalcophosphate system K/In/P/Q (Q = S, Se).

The new thiophosphate salt K(4)In(2)(PS(4))(2)(P(2)S(6)) (1), the selenophosphate salts K(5)In(3)(mu(3)-Se)(P(2)Se(6))(3) (2), K(4)In(4)(mu-Se)(2)(P(2)Se(6))(3) (3), and the mixed seleno-/thiophosphate salt K(4)In(4)(mu-Se)(P(2)S(2.36)Se(3.64))(3) (4) are described. For the first time, a structurally different outcome of a chalcophosphate reaction was observed when sulfur and selenium are mixed, for example, by the use of K(2)S/P(2)Se(5)/S/In instead of K(2)Se/P(2)Se(5)/Se/In or K(2)S/P(2)S(5)/S/In. In compounds 1-4 indium atoms exist in a variety coordination environments. While in 1, indium is octahedrally coordinated, in 2-4 tetrahedral, trigonal-bipyramidal, and octahedral coordination environments are found for indium atoms. This remarkable structural diversity possibly is a reason, why particularly indium chalcophosphate flux reactions often produce a large variety of compounds at intermediate temperatures. In the mixed seleno-/thiophosphate salt K(4)In(4)(mu-Se)(P(2)S(2.36)Se(3.64))(3) (4) most of the chalcogen sites around the tetrahedrally coordinated P atoms show mixed S/Se occupancy. There is, however, a preference for Se binding to In ions and S binding to potassium ions.

2D and 3D Silver(I)-Ethylenediamine Coordination Polymers with Ag–Ag Argentophilic Interactions

Two complexes of silver(I) salts with ethylenediamine (etda) as a ligand were prepared and characterized. The study of the crystal structures (of the 2-hydroxy-4-nitro-benzoate trihydrate (1) and nitrate (2)) has shown that the formation of 2D and 3D coordination polymer networks results from etda ligands bridging the silver atoms which are connected via Ag-Ag argentophilic interactions.