Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si-O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO building units. Clear evidence of the hexacoordinate environment around the silicon atoms is given by Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks-M[Si(CHO)], where M = Li, Na, K and CHO is 9,10-dimethylanthracene-2,3,6,7-tetraolate-crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with high surface area (up to 1,276 m g) was evidenced by gas-sorption measurements. The negatively charged backbone balanced with extra-framework cations and the permanent microporosity are characteristics that are shared with zeolites.
ChemShell is a scriptable computational chemistry environment with an emphasis on multiscale simulation of complex systems using combined quantum mechanical and molecular mechanical (QM/MM) methods. Motivated by a scientific need to efficiently and accurately model chemical reactions on surfaces and within microporous solids on massively parallel computing systems, we present a major redevelopment of the ChemShell code, which provides a modern platform for advanced QM/MM embedding models. The new version of ChemShell has been re-engineered from the ground up with a new QM/ MM driver module, an improved parallelization framework, new interfaces to high performance QM and MM programs, and a user interface written in the Python programming language. The redeveloped package is capable of performing QM/MM calculations on systems of significantly increased size, which we illustrate with benchmarks on zirconium dioxide nanoparticles of over 160000 atoms.
We report the first organically synthesized sp-sp hybridized porous carbon, OSPC-1. This new carbon shows electron conductivity, high porosity, the highest uptake of lithium ions of any carbon material to-date, and the ability to inhibit dangerous lithium dendrite formation. The new carbon exhibits exceptional potential as anode material for lithium-ion batteries (LIBs) with high capacity, excellent rate capability, long cycle life, and potential for improved safety performance.
Amorphous network materials are increasingly important with applications including as supercapacitors, battery anodes, and proton conduction membranes. Design of these materials is hampered by the amorphous nature of the structure and sensitivity to synthetic conditions. Here, we show that through artificial synthesis, fully mimicking the catalytic formation cycle and full synthetic conditions, we can generate structural models that can fully describe the physical properties of these amorphous network materials. This opens up pathways for rational design where complex structural influences, such as solvent and catalyst choice, can be taken into account.
Understanding the formation mechanism of ultra porous framework materials may lead to insights into strategies for the design and synthesis of novel ultra porous materials or for the increased surface area of known materials. Several potential formation mechanisms have been proposed based on experimental evidence. Here, we assess, via simulation of the network generation process, these mechanisms and have identified key processes by which network interpenetration is minimised and hence surface area is maximised.
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