Anionic silicate organic frameworks constructed from hexacoordinate silicon centres

Abstract

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.

An Olefin‐Linked Covalent Organic Framework as a Flexible Thin‐Film Electrode for a High‐Performance Micro‐Supercapacitor

“…Further calculation of solvent-accessible surface area (using ap robe radius of 1.84 )o ft he AAeclipsed layer stacking model gave av alue of 1388 m 2 g À1 . [17] This indicates that the measured surface area is quite close to the theoretical value,i mplying the presence of relatively ordered pore channels in g-C 34 N 6 -COF (Supporting Information, Figure S27). Aquenched solid density functional theory (QSDFT) cylindrical pore model was applied to evaluate the pore size distribution.…”

Donor–acceptor covalent organic frameworks for visible light induced free radical polymerization

“…In this work, two donor-acceptor COFs using electron deficient 4,4 0 ,4 00 -(1,3,5-triazine-2,4,6-triyl)trianiline and electron rich thiophene-based thieno [3,2- Covalent organic frameworks (COFs) have recently received increasing interest due to their intriguing properties such as low density, high porosity, good crystallinity and the possibility to introduce a range of organic functional moieties into chemically stable frameworks. [1][2][3][4][5] In terms of photochemistry, this combination of p-conjugated rigid architectures with high porosities and tailorable chemical functionalities in the COF backbones can enable: (a) rapid diffusion of charge carriers in the framework and to the surface, (b) immobilization of organic functionalities to enhance the life-time of excited species by preventing the formation of dimers, and (c) a high interface between the solid COF and reactants, electrolytes, sacricial donors and co-catalysts. In two-dimensional (2D) COFs, pfunctional organic building blocks can be organized in particular stacking patterns, thus that charge carriers can be transported in discrete and periodic columns.…”

Recent Trends in Covalent and Metal Organic Frameworks for Biomedical Applications

“…Common MOF families include zinc carboxylate-based MOFs, like MOF-5; copper (II) square paddle wheel, like HKUST-1; zirconium-based MOFs, like UiO-66; trivalent transition metal—carboxylate-based MOFs, like the MIL series, the subject of study as DDS; zeolite imidazolate frameworks, e.g., the ZIF series; and new frontiers like MOF-polymer blends [ 27 ]. In addition, anionic silicate organic frameworks (or Si-COFs), which are hexacoordinate silicate frameworks with metal counter-ions like lithium, sodium, and potassium, have been reported [ 51 , 52 ].…”