constitutes an untapped resource. [5][6][7] In addition, tailoring molecules by adding redox-active functional groups can modulate both redox potentials and electrontransfer rates. [8,9] Thus, the vast array of organic molecules can construct a new class of electrodes, [10,11] if the main problems, such as excessive solubility, poor electronic conductivity, and vulnerability to chemical side reactions, can be solved. [5][6][7][8][9] A promising answer to these problems is the integration of small molecules into a crystalline network scaffold. [12,13] Covalent organic frameworks (COF) are well suited to form stable molecular crystals [14,15] ; Integration of organic building blocks via strong covalent bonds creates 2D structures, which are layered upon one another and held in place by π-π interactions. The resulting 3D structures inhibit the dissolution of the organic layers. Moreover, periodic mesopores are formed across the entire structure, providing effective ion-transport channels. [16][17][18] Typically, COF electrodes comprise redox functionality and linkage molecules, where the latter is responsible for the shape, mesopore size, π-conjugation, and stability of the COF. [13,19] Heteroatom-containing molecular linkers have been widely utilized to improve the wettability of COFs in electrolyte solutions. [20][21][22][23] β-Ketoenamine-linked COFs have been extensively used for capacitor and battery electrodes, and solid-state electrolytes. [24][25][26] However, a β-ketoenamine unit typically forms a nonconjugated in-plane structure of the COF, [26,27] the effect of which during electrochemical conditions has not yet been studied in depth. Imine linkage comprises partial π-conjugation over the 2D COF layer. [28,29] However, chemical instability of imine has been widely known, for example, hydrolysis in an acidic solution. [30] Therefore, the role of imine linkage remains to be explored in the nonaqueous solution-based electrochemical cells. Thiazole linkage has been recently developed to satisfy both chemical stability and the π-conjugated system. [31][32][33] Sulfur-containing thiazole, thiophene, and tetrathiafulvalene are a new class of moieties embedded into COFs and show excellent charge mobility and conductivity. [34][35][36][37] Thus, they have extended the applications of COFs to molecular electronics, and energy conversion and storage electrodes. [38][39][40][41][42][43] However, there is still a lack of study that proves true chemical and electrochemical stability of thiazole-linked COF under the battery operating conditions.Covalent organic frameworks (COFs) have been considered a potentially versatile electrode structure if they are made highly conductive and flexible to stabilize the redox functionality. Although conceptually plausible, COF-based electrodes have rarely satisfied high capacity, cyclability, and rate capability thus far. Incorporating thiazole moieties into the organic scaffold, it is able to fabricate π-conjugated and crystalline organic electrodes and demonstrate the fast two-elec...
