Unsaturated main-group compounds containing heteroleptic double bonds of bismuth remain exceedingly rare due to inherent pπ-pπ bond weakness. Here we report the synthesis and characterization of the first isolable silylidenebismuthane complexes, L(Me3Si)Si═Bi(SiMe3) and L(Me3Si)Si═Bi(SiiPr3) ((E)-1a,b) (L = PhC(NtBu)2), containing a neutral but strongly polarized silicon-bismuth double bond. The complexes were obtained as the E isomers in 55% and 60% yield through the salt metathesis reaction of LSiIICl with the corresponding potassium bis(silyl)bismuthanide complexes. Remarkably, LSiII-Bi(SiMe3)2 and LSiII-Bi(SiMe3)(SiiPr3) could not be observed but undergo a trimethylsilyl group migration from the BiIII atom to the SiII atom to form a Si═Bi moiety containing σ3λ4-coordinate SiII and σ2λ2-coordinate BiI atoms. The reactions of (E)-1a,b with [W(CO)5(thf)] cause the (E) → (Z) isomerization with respect to the silyl groups attached to furnish the corresponding terminal Bi→W(CO)5 complexes (Z)-2a,b, in which the Si═Bi π bonding interaction is significantly weakened. This and the nature of the Si═Bi bonds are corroborated by DFT calculations.

A novel solid polymer electrolyte based on chemically stable vinylene-linked covalent organic framework was developed, demonstrating enhanced Li + conductivity and improved battery performance.

Chemoselective reduction of nitroarenes to arylamines is a core technology for the synthesis of numerous chemicals. The technology, however, relies on applying precious noble metal catalysts. We present our findings on the development of robust nanoporous covalent triazine frameworks (CTFs) as metal-free catalysts for the green chemoselective reduction of nitroarenes. The turnover frequency is found to be 43.03 h-1, exceeding activities of the heteroatom-doped carbon nanomaterials by a factor of 30. The X-ray photoelectron spectroscopy and control experiments provide further insights into the nature of active species for prompt catalysis. This report confirms the importance of quaternary 'N' and 'F' atom functionalities to create active hydrogen species via charge delocalization as a critical step in improving the catalytic activity.

Tin nanoparticles are a promising candidate for Li-ion battery anodes to replace carbon materials due to their high theoretical Li-ion storage capacity (994 mAh/g), which is much higher than that of graphite (372 mAh/g). However, the poor cycling stability of tin emerged from large volume expansion, and contraction remains a challenging issue. To overcome these limitations, we designed Sn-containing silicon oxycarbonitride ceramic nanocomposites (Sn/SiOCN) by the chemical reaction of tin acetate with poly(vinyl)silazane Durazane 1800 in ice bath under argon, followed by the pyrolysis of as-obtained precursors at 1000 degrees C for 3 h under argon atmosphere. The Sn/SiOCH nanocomposites with different Sn contents are tested as anodes for lithium-ion batteries, delivering a high-discharge capacity of similar to 320 mAh/g at a current density of 2220 mA/g and extremely long cycling stability even at high charging rates (approximately 90% of the capacity is maintained after 1000 cycles). The outstanding electrochemical performance of Sn/SiOCH nanocomposites can be attributed to the improved charge transfer process due to the incorporation of metallic Sn nanoparticles into the amorphous SiOCN ceramic matrix, as revealed by electrochemical impedance spectroscopy (EIS) characterization. In situ XRD results confirm the formation of lithium-rich alloy phase Li7Sn2 during the lithiation process. (C) 2022 Elsevier Ltd. All rights reserved.

We report the synthesis of Ni/SiOCN ceramic nanocomposites with high surface area as catalysts for carbon dioxide and methane conversion.

Atomic layer deposition (ALD) of PO x on V 2 O 5 powder was applied as a tool to tailor active and selective sites of a bulk catalyst. ALD leads to homogeneous P deposition on the V 2 O 5 surface with linear increase of P content with each ALD cycle. The catalyst performance was evaluated and correlated to structural motifs identified by detailed characterization methods. The catalytic conversion of butane to maleic anhydride (MAN) was chosen as proof‐of‐concept reaction. The selectivity towards MAN increases with ALD cycle number from 1–3 ALD cycles and remains constant at higher ALD cycles. Restructuring of the catalyst surface is induced by steam during reaction conditions at elevated temperatures. Excessive P is migrating away from the catalyst surface to form various VOPO 4 polymorphs revealing partially but homogeneously covered V 2 O 5 by P. The formed VOPO 4 species barely contribute to the yield to MAN. Solid‐state 31 P‐NMR was used to identify fingerprints relevant for selectivity and activity. This work shows that synthesizing model catalysts by atomic layer deposition combined with detailed analytics can reveal property‐performance relationships.

Structure and crystallization of new chemically modified bioactive glasses based on the composition of ICIE16 were investigated. Solid-state NMR analysis was used to investigate the glass structure. For crystallization, non-isothermal heat treatment was conducted to calculate the crystallization activation energy (Ec) using Kissinger method. The structural analysis results indicate that BP1 glass has the most complicated structure among the synthesized glasses. NMR findings tell that phosphate groups are in QP0 and QP1 units while boron is bonded in B[3] and B[4] units. Moreover, BP1 also exhibited high tendency to volume crystallization (n ​= ​2.6; Ec: 390.4 ​kJ/mol) in comparison to ICIE16 glass which showed mostly surface crystallization (n ​= ​1.4; Ec: 275.7 ​kJ/mol). The phases that formed after crystallization are Na4Ca4Si6O18, Ca2SiO4 and Ca5(PO2)4 (SiO4)6. The experimental data indicate that BP1 glass has promising features of processing which may ease bone scaffolds (grafts) fabrication with valuable strength.

The first plasma-assisted immobilization of an organocatalyst, namely a bifunctional phosphonium salt in an amorphous hydrogenated carbon coating, is reported. This method makes the requirement for prefunctionalized supports redundant. The immobilized catalyst was characterized by solid-state C-13 and P-31 NMR spectroscopy, SEM, and energy-dispersive X-ray spectroscopy. The immobilized catalyst (1 mol %) was employed in the synthesis of cyclic carbonates from epoxides and CO2. Notably, the efficiency of the plasma-treated catalyst on SiO2 was higher than those of the SiO2 support impregnated with the catalyst and even the homogeneous counterpart. After optimization of the reaction conditions, 13 terminal and four internal epoxides were converted with CO2 to the respective cyclic carbonates in yields of up to 99 %. Furthermore, the possibility to recycle the immobilized catalyst was evaluated. Even though the catalyst could be reused, the yields gradually decreased from the third run. However, this is the first example of the recycling of a plasma-immobilized catalyst, which opens new possibilities in the recovery and reuse of catalysts.

An iridium dihydride pincer complex [IrH2 (POCOP)] is immobilized in a hydroxy-functionalized microporous polymer network using the concepts of surface organometallic chemistry. The introduction of this novel, truly innocent support with remote OH-groups enables the formation of isolated active metal sites embedded in a chemically robust and highly inert environment. The catalyst maintained high porosity and without prior activation exhibited efficacy in the gas phase hydrogenation of ethene and propene at room temperature and low pressure. The catalyst can be recycled for at least four times.

Pure and acceptor-doped CeO2 materials undergo different sequences of structural transformations during hydrogen treatment without crystalline hydride formation.

In this study the elemental compositions of melanoidin formed at 160 degrees C from D-glucose (Glc) and L-alanine (Ala) as well as from fructosylalanine - the corresponding Amadori rearrangement product - were compared. Specific chemical bonds were probed by FTIR spectroscopy. This approach tackles the different chemical pathways for melanoidin formation via the Amadori rearrangement in contrast to the reaction from Glc/Ala. Melanoidins formed from fructosylalanine contain about twice as much nitrogen and therefore amino acid as compared to melanoidin from Glc/Ala and exhibit higher absorption in the UV/Vis. Consequently, melanoidins formed from Glc/Ala contain more sugar degradation products with lower absorption due to a smaller size of the conjugated double bond network.

Potassium poly(heptazine imide) (PHI) is a photocatalytically active carbon nitride material that was recently prepared from substituted 1,2,4-triazoles. Here, we show that the more acidic precursors, such as commercially available 5-aminotetrazole, upon pyrolysis in LiCl/KCl salt melt yield PHI with the greatly improved structural order and thermodynamic stability. Tetra-zole-derived PHIs feature long-range crystallinities and unconventionally small layer stacking distances, leading to the altered electronic band structures as shown by Mott-Schottky analyses. Under the optimized synthesis conditions, visible-light driven hydrogen evolution rates reach twice the rate provided by the previous gold standard, mesoporous graphitic carbon nitride, which has a much higher surface area. More interestingly, the up to 0.7 V higher valence band potential of crystalline PHI compared with ordinary carbon nitrides makes it an efficient water oxidation photocatalyst, which works even in the absence of any metal-based co-catalysts under visible light. To our knowledge, this is the first case of metal-free oxygen liberation from water.

A freeze-casting route towards macroporous SiOC/SiO2 ceramic nanocomposites from preceramic polymers was developed. Amorphous SiOC/SiO2 monolith with pore channels aligned along the freezing direction were obtained from commercially available methyl-phenyl-vinyl-hydrogen polysiloxane (Silres® H62C) and amorphous silica derived from rice husk ash freeze-cast with water or tert-butyl alcohol, crosslinked and pyrolyzed at 1100°C in nitrogen. The influence of processing parameters such as solvent (tert-butyl alcohol or water), polymer to silica ratio (2:1, 1:1, 1:2), cooling rate (2, 4, 6°C/min) and pre-crosslinking of polysiloxane on the porosity and structure of the obtained ceramic nanocomposites were assessed by X-ray tomography, XRD, solid state NMR, scanning electron microscopy and mercury porosimetry. The microstructure of SiOC ceramics derived from the Silres H62C polysiloxane was studied as well.

The aim of this study was to identify specific chemical bonds and characteristic structures in melanoidins formed from d-glucose and l-alanine between 130 and 200 °C. The results might be used to control the type and amount of melanoidin produced during food processing. For this purpose, complementary techniques, such as FTIR, NMR, EPR, and MALDI-ToF, were employed. At 160 °C color, solubility and UV/Vis absorption change characteristically and consequently, structural transformations could be observed in FTIR and NMR spectra. For example, sharp signals of N-H, C-N, and C-H oscillations in the l-alanine spectrum are prone to inhomogeneous broadening in melanoidins prepared above 150 °C. These changes are caused due to formation of heterogeneous macromolecular structures and occur during condensation reactions that lead to an increasing loss of water from the melanoidins with increasing temperatures. Additionally, MALDI-ToF-MS indicates the polymerization of glyoxal/glyoxylic acid and EPR shows the formation of radical structures.

Max-Planck Institute of Colloids and Inter Research Campus Golm, 14424 Potsdam mpikg.mpg.de Institut de Chimie et des Procédés pour (ICPEES), ECPM, CNRS-Université de S Becquerel, 67087 Strasbourg, France Department of Chemistry, Technische Uni 10623 Berlin, Germany Department of Inorganic Chemistry, Fritz H Faradayweg 4-6, 14195 Berlin, Germany † Electronic supplementary information spectra, TGA-MS data, N2 sorption isoth temperature PL spectra, Mott–Schottky pl Cite this: J. Mater. Chem. A, 2017, 5, 8394

An organic semiconducting tetramer is converted by pyrolysis at 550 °C into a carbon nitride semiconductor with improved photocatalytic activity.

Characterization Hydrogen evolution reactions (HER). HER were performed using a side-irradiated closed steel reactor equipped with a Teflon inlet, thermocouple, pressure sensor, magnetic stirring and thermostat, and connected to a Schlenk manifold. In all the cases, Pt and triethanolamine (TEOA) were used as a co-catalyst for hydrogen generation and as a sacrificial holescavenger, respectively. In addition, being a good buffering agent, TEOA provides stable pH of 10.8 for the whole duration of the experiment. Pt was in-situ photo-deposited onto tested photocatalysts using hexachloroplatinic acid (H2PtCl6) as a precursor. During the experiment, the buildup of pressure was monitored as a function of the irradiation time. A 50 W white LED array was used as an energy efficient irradiation source. Hydrogen evolution set up and measurement procedure. All catalytic experiments were carried out under argon atmosphere. The double walled and thermostatically controlled reaction vessel was connected to a digital pressure sensor (Type-P30, DP = 0.1%, WIKA Alexander Wiegand SE & Co. KG, Germany) to monitor the pressure increase due to hydrogen evolution. 50 mg of sample were placed inside the reactor. Then the reactor was evacuated and refilled with argon for several times. H2O and TEOA were pre-treated before use. H2O was degassed first for 1 h under vacuum in an ultrasonic bath and followed by purging with argon for 1 h. TEOA at vigorously stirred in vacuum (0.05 torr) for 1 h and then purged for 1 h with argon. The solvent mixture (38 mL), composed of water and triethanolamine (TEOA) in the ratio of 9/1 (v/v) and 39.4 μL H2PtCl6 solution (corresponds to theoretical 3 wt. % of Pt loading onto the catalyst), were added, and the temperature was maintained at 25 °C by a thermostat. After stirring for 10 min to reach thermal equilibrium, the reaction was started by switching on 50 W white LED array (Bridgelux BXRA-50C5300, λ > 410 nm). The amount of evolved gas was continuously monitored by means of the time dependent pressure increase. The hydrogen evolution rate was calculated according to the Ideal Gas law:

Vanadium-containing Keggin-type heteropolyoxo molybdate ([PV2Mo10O40](5-)) was supported on silica SBA-15 (denoted as PV2Mo10-SBA-15). The structural evolution and catalytic activity of PV2Mo10-SBA-15 and a suitable reference V2Mo10Ox-SBA-15 were investigated under selective propene oxidation conditions by using insitu X-ray absorption spectroscopy. (31)PMAS NMR measurements of supported PV2Mo10-SBA-15 and reference H3PO4-SBA-15 were performed after the catalytic reaction. PV2Mo10-SBA-15 formed a mixture of mainly tetrahedral [MoOx] and [VOx] units during thermal treatment under propene oxidation conditions. Changes in the average local structure around V centers coincided with the changes in the average local structure around Mo centers and the onset of catalytic activity. In addition, mainly tetrahedral [MoOx] and [VOx] units seemed to be in close proximity and interacted under catalytic conditions. Conversely, in the reference material V2Mo10Ox-SBA-15 synthesized with individual V and Mo source precursors, Mo and V centers appeared to be more separated from each other. The structural environment of P in PV2Mo10-SBA-15 under catalytic conditions corresponded to a mixture of various species. P was connected to both the support material SBA-15 via POSi bonds and [MoOx] or [VOx] units. Apparently, the proximity of V and Mo in Keggin precursors was a prerequisite for obtaining (Mo,V) oxide species on the support material.