An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Polyoxometalates (POMs) of Nb and Ta are greatly different from those of Mo, W, and V that have been studied extensively and developed well. The latter can be formed simply by acidification of their aqueous monomeric oxoanions and has found application areas from catalysis to magnetism, materials science, medicine, and nanotechnology. Even now the polyoxoniobate (PONb) chemistry has accelerated dramatically over the last 15 years, and a vast expansion of available PONbs has been reported. However, after nearly 200 years of POM research, Ta-based POM chemistry is still at its infant stage and only dominated by the isopolyoxotantalate ions (Ta6 and Ta10) and transition-metal-capped Ta6 species, along with two Ti-substituted polyoxotantalates [Ti2Ta8O28]8- and [Ti12Ta6O44]10- reported very recently. In this study, we discover two novel peroxotantalophosphate clusters [P4(TaO2)6O25]12- (1) and [P4(TaO2)6O24]10- (2) by incorporating phosphorus heteroatom into Ta-oxo framework, which represent the first two examples of heteropolytantalate. Interestingly, two P2Ta3 half-units are cis- and trans-condensed in 1 and 2, leading to "open" and "closed" configurations, respectively. These two chemically and structurally related clusters can be isolated in a controlled manner, and the yields are relatively high. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, 31P MAS NMR, FT-IR, TGA, and elemental analysis as well as by 31P NMR in solution. The results presented here provide a strategy to be applicable to other heteroatom-incorporated polyoxotantalates and further expand the phase space for polyoxotantalate chemistry.
A hexanuclear Cd II metal–organic framework ( 1 ) based on 4‐(1 H ‐pyrazole‐4‐carboxamido)benzoic acid (H 2 L) and featuring a three‐dimensional microporous framework was synthesized. Notably, 1 shows a unique fluorescence‐quenching response toward Fe 3+ ions with high selectivity and sensitivity (Stern–Volmer constant K SV = 2.07 × 10 4 m –1 ). The response is attributable to the coaction of absorption competition and energy‐transfer (ET) mechanism. Furthermore, spectral analysis indicates that the energy‐transfer mechanism makes the dominant contribution to the fluorescence quenching of 1 .
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
This study investigates the pore structure evolution of the reaction zones in wellbore cement samples exposed to a CO2-rich solution in equilibrium with 17 MPa supercritical CO2 over 14 days. Through advanced characterization methods of field emission SEM, QEMSCAN, and micro-CT, a new mechanism of CO2-cement reaction involving filling of nanopores in the interior of cement by gypsum was revealed. Gypsum was formed due to the liberation of SO42- from ettringite (AFt) and monosulfate (AFm) caused by a decrease in pH. Based on these experimental observations, a new CO2-cement reaction model that incorporates four distinct reaction zones is developed. This model provides a comprehensive framework for understanding the spatial and temporal distribution of minerals in cement due to high pressure CO2—cement reactions. This study demonstrates that the major damage induced by high pressure CO2 corrosion occurs in the most exterior region of the cement. The interior region of the cement maintains its integrity due to nanopore filling by gypsum.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
Abstract Niobium tungsten oxide is a potential replacement for graphite in fast‐charge lithium‐ion batteries due to its high rate performance and high stability. Herein, Nb 14 W 3 O 44 anode was synthesized by hydrothermal reaction of niobium oxalate and ammonium tungstate and sequent calcination of niobium tungsten oxide precursors. Compared with the traditional solid‐state method, the particle size and calcination time of Nb 14 W 3 O 44 obtained by the modified method are greatly reduced. Through orthogonal experiments, the optimal synthesis conditions were determined, and it was found that hydrothermal conditions have an important influence on the particle size of the final product, while the calcination temperature and time greatly affect the purity of the product and thus influence its specific capacity during cycles.
Two novel octamolybdate-based tricarbonyl metal derivatives have been successfully synthesized and characterized, which represent the first two examples of tricarbonyl metal groups attached to a new {Mo(8)O(30)} building block.
An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)