State of the art two-dimensional covalent organic frameworks: Prospects from rational design and reactions to applications for advanced energy storage technologies

In recent years, covalent organic frameworks (COFs) have attracted considerable attention due to their fantastic features and multiple potential applications in many areas. Aromatic subunits are linked by versatile linkages using the bottom-up strategy, endowing COFs with well-defined structures, precisely controlled pores, and versatile functional groups. So far, COFs have exhibited outstanding performances and great potentials in many applications. However, well-summarized reports about the recent advances of COFs, especially for energy-related research, are still lacking. Herein, we give a review of the state-of-the-art developments of COFs for energy storage, and especially focus on the two-dimensional (2D) COFs. First of all, various building blocks and linkages, as well as the synthetic strategies, are summarized and discussed in detail. Later, the up-to-date achievements of applying COFs for advanced energy storage technologies are presented. Lastly, the perspectives and critical challenges for COFs are proposed.