Fully packed ultrasmall Au nanoclusters in covalent organic frameworks as positive electrodes for supercapacitors

Abstract

Supported metal nanoclusters have emerged as a highly promising class of materials with great potential across a wide range of applications including electrochemistry. However, the fully metal loading of supports with ultrasmall pore structures, such as covalent organic frameworks (COFs), which may yield new performances, remains a challenge. Learning from the synthetic strategy of atomically precise Au nanoclusters, herein, Au elements were first complexed with alkynyl-modified building blocks prior to the synthesis of COFs, and subsequent in situ reduction allowed the size-focused formation of Au nanoclusters within each pore. With a partially reduced Au content as high as ∼50.8 wt%, the Au nanocluster-filled COF composites surprisingly exhibited a remarkable decrease in resistance as low as 80.16 Ω compared to that of their parent COFs, i.e. 4341 Ω for the pristine COFs and 3328 Ω for the Au(I) complex-tethered COFs. This dramatic reduction in resistance opens up the possibility for the construction of supercapacitors. Furthermore, the composites showed an impressive specific capacitance of 241.4 F g⁻¹ at a current density of 0.1 A g⁻¹, together with excellent rate capability at a high scan rate of 200 mV s⁻¹. This work can be expanded to a general strategy for molecularly designing COFs with various metal NCs, potentially endowing the composites with novel application possibilities.