Systematic Design and Synthesis of Conjugated Microporous Polymers Containing Pyrene and Azobenzene Building Materials for High-Performance Energy Storage

Conjugated microporous polymers (CMPs), known for their high specific capacities, exceptional cycling stability, and outstanding rate performance, are being actively studied as advanced electrode materials for energy storage applications. The utilization of redox-active units in CMP materials in energy storage exhibits substantial promise. Nevertheless, the influence of the positioning of the redox-active region on the electrochemical behavior and battery performance remains a topic of uncertainty. Herein, we successfully created two CMPs using the Sonogashira-Hagihara coupling method, specifically by including redox-active azobenzene (Azo) moieties in the meta (m) and para (p) locations. These CMPs are named Py-mAzo-CMP and Py-pAzo-CMP. To produce them, we used precursor compounds (E)-1,2-bis(3-bromophenyl)diazene (mAzo-Br-2) and (E)-1,2-bis(4-bromophenyl)diazene (pAzo-Br-2), combined with tetraethynylpyrene (Py-T). Our primary focus was to investigate the impact of substituting the Azo unit at different positions. To assess the orientation of molecules and the pores of these Py-Azo-CMPs, we conducted a thorough analysis, including BET isotherm measurements and various spectroscopic and microscopic techniques. Our findings from TGA analysis indicated that these Py-Azo-CMPs exhibit a moderate thermal stability. One remarkable discovery was the excellent electrochemical performance of Py-pAzo-CMP, which displayed a capacitance of 142 F g(-1) (determined at 1 A g(-1)), showcasing its exceptional capacitive properties. Despite operating at a substantial current density of 10 A g(-1), both Py-mAzo and Py-pAzo-CMPs exhibited remarkable long-term stability, retaining over 92% of their capacity even after 5000 cycles. These results underscore the potential of Py-pAzo-CMP as a dependable and enduring choice for energy storage applications. Our findings highlight the significant promise of these Py-Azo-CMP materials and underscore their suitability for useful applications, including electrical energy storage (EES).