The development of new vinylene-linked covalent organic frameworks (COFs) with special ionic structure and high stability is challenging. Herein, we report a facile, general method for constructing ionic vinylene-linked thiopyryliumbased COFs from 2,4,6-trimethylpyrylium tetrafluoroborate and other common reagents by means of acid-catalyzed Aldol condensation. Besides, pyrylium-, and pyridinium-based COFs also can be prepared from the same monomer under slightly different reaction conditions. The COFs exhibited uniform nanofibrous morphologies with excellent crystallinities, special ionic structures, well-defined nanochannels, and high specific surface areas.
First, a new covalent organic framework (HUT9) with disulfide bonds have been synthesized, which can be grown in situ on carbon nanotubes (CNT) as separator modification material for Li−S batteries. Experiments and DFT showed that disulfide bond could effectively capture soluble polysulfides (LiPSs) during discharge process, while promoting the conversion of LiPSs to Li 2 S/Li 2 S 2 and improve the utilization rate of sulfur. The polar groups of the covalent organic framework provide chemisorption, and an interwoven network of HUT9@CNT (physical constraints) cooperates to inhibit the transport of LiPSs. The modified battery has a capacity retention rate of 83% (decay rate of 0.032% per cycle) after 500 cycles at 1 C. Specifically, the battery with 2-HUT9@CNT modified separators (sulfur loading: 4 mg cm −2 , sulfur content: 80%, electrolyte/sulfur ratio: 10 mL g −1 ) can reach 3.4 mAh cm −2 area capacity after 50 cycles. This work enriched the COF material system and provided guidance for the application of organic materials in an energy storage system.
Considerable efforts have been made to design efficient thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs). However, the development of efficient red/near-infrared (NIR) TADF materials with emission...
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