Two fully conjugated covalent organic frameworks as anode materials for lithium ion batteries

Abstract

Energy storage has attracted more and more attention for its close connection with our daily life. Since there are some unceasing issues about the eco-friendliness and sustainability of energy storage, eco-friendly storage materials are always what we highly desire. While covalent organic frameworks (COFs) promise numerous benefits in gas adsorption, catalysis and optoelectronic devices, synergistic combination of effective storage and eco-friendliness using COFs as storage materials has not been well studied. Herein, we present two fully conjugated porous COFs with high capability of selective gas adsorption and large capacity for Li ion storage. In the aspect of gas selective adsorption, their selectivity ratio for H₂ and CO₂ to N₂ reached ∼15 : 1 and 7 : 1, respectively. In Li ion storage, the COFs exhibited a high capacity (∼700 mA h g⁻¹) and a stable long life (500 cycles). Such good performance confirmed the high potential of COFs to be employed for eco-friendly energy storage. Importantly, using conjugated COFs not only avoids complex synthesis of classical conjugated polymers and multilayered or doped hybrids, but also translates their superb properties including structural diversity, flexibility, and high electrochemical activity into energy storage-related applications. The present work opens up a promising route for further utilization of COFs in energy-related fields such as electrode materials, supercapacitors, and Li–gas batteries.