The high-efficiency coupling of a Ni coordinated/uncoordinated pyridine N-COF self-supporting nanofilm as an asymmetric supercapacitor.

A large-area COF film with a pore size of 3.9 nm was prepared on a gas-liquid interface by the virtue of the limiting and guiding functions of sodium dodecylbenzene sulfonate, followed by modification by Ni ions with the reversible redox reaction of Ni(II/III), where Ni was evidently anchored on the N in BPY. The obtained COF and Ni-COF nanofilms could avoid the inevitable aggregation and stacking of bulk COF, which facilitated a high specific capacitance of 0.26 mF cm for the COF nanofilm and 0.38 mF cm for the Ni-COF nanofilm at 0.001 mA cm. Considering the pseudocapacitance and double-layer capacitance traits of Ni-COF and COF nanofilms, the asymmetric Ni-COF//COF film supercapacitor was assembled with a symmetric COF//COF film device as a control. The asymmetric Ni-COF//COF film supercapacitor could enhance the energy density of 273.9 mW h cm at 14.09 W cm from 85.2 mW h cm at 4.38 W cm for the symmetric COF//COF film device. This work provides a new perspective on the application of self-supporting COF nanofilms as film asymmetric supercapacitors.