RESUMEN
Anionic covalent organic framework is an emerging class of functional materials in which included ionic species of the opposite charges play an important role in the ion conduction and selective gas adsorption. Herein, we reported a facile method to construct a series of germanate-based anionic COFs (Ge-COFs) by reticulating dianionic hexa-coordinated GeO6 nodes with anthracene building blocks adopting a hcb topology in an extended 2D framework. A systematic change of pore properties in Ge-COFs was observed through the incorporation of three different alkali metal cations: Li+, Na+, and K+. The intrinsically negatively charged backbone provides a host matrix with a homogeneous distribution of counter cations and poses variable and exciting features for gas adsorption and ionic conduction. Among the series, K+-based Ge-COF-K with a surface area of 1252 m2/g and pore volume of 0.84 cm3/g shows a maximum CO2 uptake of 126 cm3/g (247.4 mg/g) at 273 K and 1 bar, an IAST selectivity of 140 over N2. Ge-COF-K also exhibits a high SO2 kinetic breakthrough capacity of 154 mg/g at low ppm of SO2 concentration under ambient conditions among recently reported porous materials. Moreover, reasonably high lithium, sodium, and potassium ionic conductivities were observed with the values of 1.2 × 10-4, 3.4 × 10-5, and 2.2 × 10-5 S/cm for propylene carbonate infiltrated Ge-COF-Li, Ge-COF-Na, and Ge-COF-K at 100 °C, respectively.
RESUMEN
Anhydrous proton-conductive materials have attracted great attention in recent years. Doping imidazole as a proton carrier in porous materials, especially pure organic crystalline covalent organic frameworks (COFs), is a promising solution. However, the influence of the hydrogen donor ability of imine functional groups in COFs on the proton conduction has largely been unexplored. Herein, a series of iso-reticular thiophene-based COFs has been synthesized with a similar pore structure and surface area. Different amounts of imidazole were infiltrated to the COFs by vapor diffusion in a highly controlled manner. The introduction of thiophene rings increases the hydrogen bonding donation ability of the imine linker, which resulted in an enhanced proton conductivity of the imidazole-doped COFs by one order of magnitude. The formation of hydrogen bonding between the imine group and imidazole was demonstrated by Fourier transform infrared spectroscopy and density functional theory calculations.
RESUMEN
The metalloid-centered covalent organic framework has attracted great interest from both its structure and application. Heavier elements have seldomly been incorporated in the covalent organic frameworks, even if they exhibit special structural features and properties. Herein, we reported the first crystalline germanate covalent organic framework with hexacoordinated germanate linked by an anthracene linker. The existence of counterion lithium ions in the framework provides a high CO2 uptake of 88.5â cm3 g-1 at 273â K and a high CO2 /N2 selectivity of 101. A significantly improved lithium ion conductivity of 0.25â mS cm-1 at room temperature was observed due to the soft germanium center.