Activation\nof Carbonyl Groups in Polyimide-Based Covalent\nOrganic Framework with Multiwalled Carbon Nanotubes toward Boosted\nPseudocapacitance

Covalent organic frameworks (COFs) possessing a well-defined\nstructure\nand abundant functional groups are prospective pseudocapacitive electrode\nmaterials. However, their intrinsic poor electrical conductivity and\n stacking problems usually impede the utilization of their active\nsites. Herein, we conduct an <i>in situ</i> growth of polyimide\nCOFs (donated as NTDA COFs) enriched with carbonyl groups on multiwalled\ncarbon nanotubes (MWCNTs). An impressive capacitance of 467 F g<sup>–1</sup> at 1 A g<sup>–1</sup> is achieved for the\nas-prepared NTDA/MWCNTs composite, significantly surpassing both the\npure MWCNTs (60.3 F g<sup>–1</sup>) and NTDA COFs (284.4 F\ng<sup>–1</sup>). No decay of capacitance is observed after\n10,000 cycles at 10 A g<sup>–1</sup>. The assembled device\nNTDA/MWCNTs//activated carbon reaches a high energy density of 17\nWh kg<sup>–1</sup> at 750 W kg<sup>–1</sup> while keeping\nsuperior charging/discharging stability of 89.5% after cycling for\n19,000 times at 10 A g<sup>–1</sup>. <i>In situ</i> Fourier transform infrared (<i>in situ</i> FT-IR) tests\ntogether with the exploration of electrode kinetics show that the\nboosted capacitance of NTDA/MWCNTs is mainly donated by the redox\nreactions of carbonyl groups on NTDA COFs, which is largely activated\nby MWCNTs.