A novel type of ionic covalent organic framework (ICOF), which contains sp(3) hybridized boron anionic centers and tunable countercations, was constructed by formation of spiroborate linkages. These ICOFs exhibit high BET surface areas up to 1259 m(2) g(-1) and adsorb a significant amount of H2 (up to 3.11 wt %, 77 K, 1 bar) and CH4 (up to 4.62 wt %, 273 K, 1 bar). Importantly, the materials show good thermal stabilities and excellent resistance to hydrolysis, remaining nearly intact when immersed in water or basic solution for two days. The presence of permanently immobilized ion centers in ICOFs enables the transportation of lithium ions with room-temperature lithium-ion conductivity of 3.05×10(-5) S cm(-1) and an average Li(+) transference number value of 0.80±0.02. Our approach thus provides a convenient route to highly stable COFs with ionic linkages, which can potentially serve as absorbents for alternative energy sources such as H2, CH4, and also as solid lithium electrolytes/separators for the next-generation lithium batteries.
Two novel porous 2D covalent organic frameworks (COFs) with periodically heterogeneous pore structures were successfully synthesized through desymmetrized vertex design strategy. Condensation of C(2v) symmetric 5-(4-formylphenyl)isophthalaldehyde or 5-((4-formylphenyl)ethylene)isophthalaldehyde with linear hydrazine linker under the solvothermal or microwave heating conditions yields crystalline 2D COFs, HP-COF-1 and HP-COF-2, with high specific surface areas and dual pore structures. PXRD patterns and computer modeling study, together with pore size distribution analysis confirm that each of the resulting COFs exhibits two distinctively different hexagonal pores. The structures were characterized by FT-IR, solid state (13)C NMR, gas adsorption, SEM, TEM, and theoretical simulations. Such rational design and synthetic strategy provide new possibilities for preparing highly ordered porous polymers with heterogeneous pore structures.
Covalent organic frameworks with high porosity and crystallinity have been synthesized, through macrocycle-to-framework strategy, using shape-persistent arylene-ethynylene macrocycles as the key components to control the topology and modulate the porosity.
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