Activation of Carbonyl Groups in Polyimide-Based Covalent Organic Framework with Multiwalled Carbon Nanotubes toward Boosted Pseudocapacitance.

Abstract

Covalent organic frameworks (COFs) possessing a well-defined structure and abundant functional groups are prospective pseudocapacitive electrode materials. However, their intrinsic poor electrical conductivity and stacking problems usually impede the utilization of their active sites. Herein, we conduct an in situ growth of polyimide COFs (donated as NTDA COFs) enriched with carbonyl groups on multiwalled carbon nanotubes (MWCNTs). An impressive capacitance of 467 F g^-1 at 1 A g^-1 is achieved for the as-prepared NTDA/MWCNTs composite, significantly surpassing both the pure MWCNTs (60.3 F g^-1) and NTDA COFs (284.4 F g^-1). No decay of capacitance is observed after 10,000 cycles at 10 A g^-1. The assembled device NTDA/MWCNTs//activated carbon reaches a high energy density of 17 Wh kg^-1 at 750 W kg^-1 while keeping superior charging/discharging stability of 89.5% after cycling for 19,000 times at 10 A g^-1. In situ Fourier transform infrared (in situ FT-IR) tests together with the exploration of electrode kinetics show that the boosted capacitance of NTDA/MWCNTs is mainly donated by the redox reactions of carbonyl groups on NTDA COFs, which is largely activated by MWCNTs.