Imine-Linked π-Conjugated Covalent Organic Frameworks as an Efficient Electrode Material for Pseudocapacitive Energy Storage

Abstract

Covalent organic frameworks (COFs), having a very diverse structural makeup, flexibility, nanoscale porosity, and exceptionally high surface area, have recently attracted a huge amount of interest as the emerging materials for energy and environmental research. Herein, by employing the Schiff base reaction route, we planned and synthesized two imine-linked π-conjugated COFs (IC–COFs), i.e., TFPh-NDA and TFR-NDA, and explored them as electrode materials for asymmetric supercapacitor application. The TFPh-NDA and TFR-NDA IC-COFs possess high crystallinity and a large surface area with bimodal porosity. The imine-linked π-conjugated COFs showed a redox-active behavior and exhibited an outstanding gravimetric capacitance of 583 F·g–1 for TFPh-NDA and 362 F·g–1 for TFR-NDA in a three-electrode configuration. The TFPh-NDA IC-COF//activated carbon (AC)-based asymmetric supercapacitor devices (ASDs) exhibit a wide voltage window of 2.5 V (−1.0 to 1.5), indicating its potentiality in the supercapacitor market. The specific capacitance of the ASD was evaluated at different scan rates, with a maximum specific capacitance of 323.25 F·g–1 at 1 mV·s–1. Moreover, at a power density of 404.06 W·kg–1, the ASD has a maximum energy density of 280.58 W h·kg–1. The as-fabricated TFPh-NDA IC-COF//AC ASD exhibits an ultrastable capacitance retention of 98% of its initial capacitance even after 10,000 CV cycles. This discovery is an example of a prospective contender for applications involving capacitive storage.