Catalyst-free nitro-coupling synthesis of azo-linked conjugated microporous polymers with superior aqueous energy storage capability

Developing methods to construct conjugated microporous polymers (CMPs) with desirable structures is a crucial undertaking. However, obtaining azo-CMPs with extended azaacene cores is immensely challenging. Herein, we disclose the facile synthesis of diquinoxalino[2,3-a:2',3'-c]-phenazine-core CMP (3Qn-CMP; core diameter, similar to 1.6 nm) via the one-step hydrothermal homocoupling of nitro monomers in a mixture solution of N,N-dimethylformamide (or N,N-di-methylacetamide) and water (1:3, v/v). A 3Qn-CMP/rGO hybrid is readily prepared from CMP spheres (diameter, 0.5-1.5 mu m) anchored on reduced graphene oxide (rGO) nanosheets (similar to 3 layers) by synergizing the one-pot synthesis of (rGO) for intercalation and self-assembly. The highly porous hybrid features dual redox active sites with azo and imine linkages and efficient charge conduction. 3Qn-CMP and 3Qn-CMP/rGO exhibit outstanding energy storage capacity, current density tolerance (1-50 A g(-1)), and long-term cycling stability in aqueous acidic electrolytes. 3Qn-CMP and 3Qn-CMP/rGO also produce high specific capacitances of 615.4 and 847.8 F g(-1), respectively, at 1 A g(-1). Approximately 99.1% of this capacitance can be retained over 50,000 continuous charge/discharge cycles at 50 A g(-1). To the best of our knowledge, our hybrid outperforms most organic molecules or CMP-/rGO-based composites reported in the literature in terms of capacitance and cycling durability. This work provides a general strategy to access a new library of CMPs and hybrids with multilevel elaborate architectures tailored for target applications, such as electrochemical energy storage and catalysis.

Automated summary

The study presents a facile method for synthesizing CMPs, resulting in 3Qn-CMP and 3Qn-CMP/rGO hybrids with exceptional energy storage capacity and cycling stability. These materials feature dual redox active sites and efficient charge conduction, making them suitable for applications in electrochemical energy storage.