Rapid preparation of imide-based COF films through electropolymerization integrated with low-temperature annealing for high-performance electrochromic energy storage

Electrochromic energy-storage materials (EESMs) have received tremendous attention in the field of smart windows and visual energy-storage batteries. Covalent organic frameworks (COFs) are considered as superior candidates for high-performance EESMs owing to the designability of molecular structures, high electron-ion transport rates, and thermodynamically stable networks. In the present study, two triarylamine-based polyimide (TPI) COFs, DFPI and NTPI COF films were first built <i>via</i> a simple and efficient interfacial electropolymerization combined with low-temperature annealing technology. The electropolymerization mechanism of DFPI and NTPI COF films was elucidated in detail. TPPDA first undergoes an oxidative nucleophilic substitution reaction at the anode to produce an electrogenerated acid (EGA), followed by a polycondensation reaction between triphenylamine derivatives and anhydride catalyzed by EGA to form DFPI or NTPI COF films. Additionally, both the DFPI and NTPI COF films exhibited high-performance electrochromic energy-storage, including bipolar four color states (light red, colorless, yellow-green, and blue), high optical contrast (>70%), more than 1000 cycles, and high specific capacitance (80.9 and 72.2 mAh g^-1). This work enables the simple and rapid preparation of TPI COF films, which paves the way for the design and fabrication of TPI COF films for high-performance optoelectronics, electrochemical sensing, separation membranes, and EESMs.