trans-Bis(acetato-κO)bis­(2-amino­ethanol-κ2 N,O)nickel(II)

In the title compound, [Ni(CH3CO2)2(C2H7NO)2], the NiII cation, located on an inversion center, is N,O-chelated by two 2-amino­ethanol mol­ecules and further coordinated by two monodendate acetate anions in a slightly distorted octa­hedral geometry. The latter is stabilized by intra­molecular O—H⋯O hydrogen bonds involving the non-coordinated O atom of the acetate and the H atom of the hy­droxy group of the 2-amino­ethanol ligand. In the crystal, N—H⋯O hydrogen bonds link the mol­ecules into a three-dimensional supra­molecular framework that involves (a) the coordinated acetate O atom and one of the H atoms of the amino group and (b) the non-coordinated acetate O atom and the other H atom of the amino group

Ultramicroporous silicon nitride ceramics for CO2 capture

Carbon dioxide (CO2) capture is regarded as one of the biggest challenges of the 21st century; therefore, intense research effort has been dedicated in the area of developing new materials for efficient CO2 capture. Here, we report high CO2 capture capacity in the low region of applied CO2 pressures observed with ultramicroporous silicon nitride-based material. The latter is synthesized by a facile one-step NH3-assisted thermolysis of a polysilazane. Our newly developed material for CO2 capture has the following outstanding properties: (i) one of the highest CO2 capture capacities per surface area of micropores, with a CO2 uptake of 2.35 mmol g−1 at 273 K and 1 bar (ii) a low isosteric heat of adsorption (27.6 kJ mol−1), which is independent from the fractional surface coverage of CO2. Furthermore, we demonstrate that the pore size plays a crucial role in elevating the CO2 adsorption capacity, surpassing the effect of Brunauer–Emmett–Teller specific surface area

NH3-assisted synthesis of microporous silicon oxycarbonitride ceramics from preceramic polymers: a combined N2 and CO2 adsorption and small angle X-ray scattering study

We have developed a simple and general synthesis strategy to tune the chemical composition and pore size as well as the surface area of microporous ceramics. This method is based on modifying the structure of preceramic polymers through chemical reactions with NH3 at 300-800 degrees C, followed by thermolysis under an Ar atmosphere at 750 degrees C. Under these synthesis conditions polysiloxane (SPR-212a, Starfire (R) Systems) and polysilazane (HTT-1800, KiON Specialty Polymers) transform to microporous ceramics, while materials derived from polycarbosilane (SMP-10, Starfire (R) Systems) remain non-porous, as revealed by N-2 and CO2 adsorption isotherms. Small angle X-ray scattering (SAXS) characterization indicates that samples prepared from polycarbosilane possess latent pores (pore size < 0.35 nm) which are not accessible in the gas adsorption experiments. The microporous silicon oxycarbonitride (SiCNO) ceramics synthesized from polysilazane and polysiloxane by the above-mentioned route possess a surface area and micropore volume of as high as 250-300 m(2) g(-1) and 0.16 cm(3) g(-1), respectively, as determined by the N-2 adsorption method. The analysis of CO2 adsorption isotherms by the Dubinin-Astakhov equation confirms a narrow pore size distribution in the ceramics derived from polysilazane. Our synthesis strategy provides tools to engineer the microstructure, that is the chemical structure and porosity, of microporous SiCNO ceramics for potential applications in the fields of catalysis, gas adsorption and gas separation

Electrochemical study of NiO nanosheets: toward the understanding of capacity fading

NiO nanosheets are prepared by calcination of nickel hydroxide nanosheets, obtained by the hydrolysis of trans-bis(acetato-jO)bis(2-aminoethanol-j2 N,O)nickel(II) complex. BET analysis reveals the presence of a high specific surface area of 48 m2g-1 and a pore volume of 0.26 cm3g-1 after calcination at 400 �C. The two-dimensional NiO nanostructure undergoes a reversible lithium ion uptake and release revealing an initial unexpectedly high capacity of *1100 mAhg-1 at a cycling current of 400 mAg-1, exceeding the theoretical capacity of NiO (718 mAhg-1). We attribute this high storage capacity to the advantageous two-dimensional morphology of the sample, namely to the presence of agglomerates composed of NiO nanosheets, allowing a pronounced Li-ion storage through the insertion mechanism and by the formation of a polymer-like layer at the samples internal surfaces. However, after 20 cycles the recovered capacity diminishes rapidly due to the onset of Li-ion intercalation into NiO, which is found less reversible. In addition, an increase in the charge Transfer resistance and increase in the electrode polarization, measured by differential capacity, contribute to the analyzed capacity decay upon continuous cycling

In situ formation of tungsten oxycarbide, tungsten carbide and tungsten nitride nanoparticles in micro- and mesoporous polymer-derived ceramics

We present a facile approach to design micro- and mesoporous ceramic nanocomposites, which avoids the sintering of nanoparticles even at high synthesis temperatures and in situ forms nanoparticles in high temperature stable porous silicon oxycarbonitride (SiOC(N)) matrices. Our case study includes the synthesis of micro- and mesoporous polymer nanocomposites (c-WO3−x/WO3×H2O/[–Si(O)CH2–]n) which contain cubic tungsten oxide and tungsten oxide monohydrate (c-WO3−x/WO3×H2O) nanowhiskers in highly micro- and mesoporous polycarbosilane–siloxane matrices. The thermolysis of c-WO3−x/WO3×H2O/[–Si(O)CH2–]n nanocomposites under a suitable atmosphere and temperature leads to the in situ formation of well-dispersed nanoparticles of cubic tungsten oxide (c-WO3−x), tungsten oxycarbide (W2CO), tungsten carbide (WC) and tungsten nitride (WN) in micro- and mesoporous matrices

Nanoporous Silicon Oxycarbonitride Ceramics Derived from Polysilazanes In situ Modified with Nickel Nanoparticles

Ni–polysilazane precursors were synthesized from polysilazane and trans- [bis(2-aminoetanol-N,O)diacetato-nickel(II)]. The Ni–polysilazane precursors are superparamagnetic indicating formation of nanosized nickel particles (2−3 nm) confirmed by HRTEM as well. The as-obtained Ni–polysilazane precursors were thermolized at 700 °C and transformed to ceramic nanocomposites, manifesting a nanoporous structure, revealing a BET surface area of 215 m2 g–1, a micropore surface area of 205 m2 g–1, and a micropore volume of 0.113 cm3 g–1. Although Si–C–N–(O) ceramics derived from the native polysilazane are nonporous, the pronounced development of porosity in the Ni/Si–C–N–(O) system was attributed to (i) the stabilizing effect of carbosilane bonds, which prohibit the formation of macropores during thermolysis; (ii) the reduced barrier for heterogeneous pore nucleation as a result of in situ created nickel nanoparticles; and (iii) the reduced viscous flow of the pores due to the presence of nickel nanoparticles and turbostratic carbon. The formation of turbostratic carbon is due to the reactions catalyzed by nickel nanoparticles that result in graphene stacking as inferred from the STA–MS studies

High-temperature stability and saturation magnetization of superparamagnetic nickel nanoparticles in microporous polysilazane-derived ceramics and their gas permeation properties

Superparamagnetic Ni nanoparticles with diameters of about 3 nm are formed in situ at room temperature in a polysilazane matrix, forming Ni/polysilazane nanocomposite, in the reaction between a polysilazane and trans-bis(aceto-kO) bis(2-aminoethanol-k2N,O)nickel(II). The thermolysis of the Ni/polysilazane nanocomposite at 700 °C in an argon atmosphere results in a microporous superparamagnetic Ni/silicon oxycarbonitride (Ni/SiCNO) ceramic nanocomposite. The growth of Ni nanoparticles in Ni/SiCNO ceramic nanocomposite is totally suppressed even after thermolysis at 700 °C, as confirmed by HRTEM and SQUID characterizations. The analysis of saturation magnetization of Ni nanoparticles in Ni/polysilazane and Ni/SiCNO nanocomposites indicates that the saturation magnetization of Ni nanoparticles is higher than expected values and infers that the surfaces of Ni nanoparticles are not oxidized. The microporous superparamagnetic Ni/SiCNO nanocomposite is shaped as a free-standing monolith and foam. In addition, Ni/SiCNO membranes are fabricated by the dip-coating of a tubular alumina substrate in a dispersion of Ni/polysilazane in THF followed by a thermolysis at 700 °C under an argon atmosphere. The gas separation performance of Ni/SiCNO membranes at 25 and 300 °C is assessed by the single gas permeance (pressure rise technique) using He, H2, CO2, N2, CH4, n-propene, n-propane, n-butene, n-butane, and SF6 as probe molecules. After hydrothermal treatment, the higher increase in the hydrogen permeance compared to the permeance of other gases as a function of temperature indicates that the hydrogen affinity of Ni nanoparticles influences the transport of hydrogen in the Ni/SiCNO membrane and Ni nanoparticles stabilize the structure against hydrothermal corrosion

Visible Light Photocatalysis with c-WO3–x/WO3×H2O Nanoheterostructures In Situ Formed in Mesoporous Polycarbosilane-Siloxane Polymer

In recent years, there have been significant efforts to find novel photocatalytic materials with improved properties. Thus, there is an active ongoing search for new materials that can operate at a broad range of wavelengths for photocatalytic reactions. Among photocatalytically active semiconductors, considerable attention has been given to tungsten oxide with a band gap of Eg ≈ 2.6 eV, which provides the opportunity to harvest visible light. In the present work, we report on a one-step synthesis of c-WO3–x/WO3×H2O nanowhiskers dispersed in a hydrolytically stable mesoporous polycarbosilane-siloxane ([−Si(O)CH2−]n) matrix. The as-synthesized nanocomposites possess high photocatalytic activity for the degradation of methylene blue (MB) under visible light irradiation. The enhanced photocatalytic activity is due to (i) the reduction in the electron–hole recombination rate because of the reduced dimensions of nanowhiskers, (ii) more efficient consumption of photogenerated electrons and holes as a result of the high surface-to-bulk-ratio of the nanowhiskers, and (iii) better electron–hole pair separation due to the formation of c-WO3–x/WO3×H2O nanoheterostructures