Activation of redox-active covalent organic frameworks enriched with imine and quinone sites towards high pseudocapacitance

Abstract

Redox-active covalent organic frameworks (COFs) can promisingly provide pseudocapacitance for supercapacitors. However, the intrinsic poor electrical conductivity and the stacking feature of COFs usually lead to a low utilization rate of the redox-active sites in their structural units. Herein, we prepare redox-active COFs enriched with imine and quinone groups from tetramino-benzoquinone (TABQ) and 2,5-dihydroxyterephthalaldehyde (Dha) monomers. The in-situ polymerization of these COFs on multi-walled carbon nanotubes (MWCNTs) results in the sufficient π–π interaction between the TABQ-Dha COF and the MWCNTs. The accelerated transport of electrons and activation of the redox-active groups of the TABQ-Dha COFs are then achieved with the assistance of MWCNTs to achieve a boosted capacitance of 398 F g−1 at 1 A g−1 as compared to the pristine TABQ-Dha COF (3 F g−1). In-situ FTIR and CV results reveal that the electrode reactions involve the redox-active transformation of imine and quinone groups in TABQ-Dha-MWCNTs which were activated to provide rich pseudocapacitance. Asymmetric supercapacitors (ASCs) assembled with graphene oxide (GO) supported TABQ (TABQ-GO) and TABQ-Dha-MWCNTs offers a high energy density of 12.8 Wh kg−1 at 750 W kg−1 and maintains a capacitance of 82.4 % after 20000 cycles at 5 A g−1, indicating its good potential towards practical application.