Engineering carbonyl-rich conjugated microporous polymers with a pyrene-4,5,9,10-tetraone building block as highly efficient and stable electrodes for energy storage†

Abstract

As a solution to the environmental and energy crises, more safe and efficient energy storage technologies are extremely necessary. Conjugated microporous polymers (CMPs) bearing redox-active functional groups as well as nitrogen-rich moieties have received a lot of interest in energy conversion and storage applications. Herein, two novel redox-active pyrene-4,5,9,10-tetraone-based CMPs, BC-PT and TPA-PT, were successfully fabricated via Suzuki coupling of 2,7-dibromopyrene-4,5,9,10-tetraone (PT-2Br) with 3,3′,6,6′-tetrakis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9′-bicarbazole (BC-4BO) and N¹,N¹,N⁴,N⁴-tetrakis(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenyl)benzene-1,4-diamine (TPA-4BO), respectively. Their chemical composition, porosity parameters, morphological structures, and thermal behavior were investigated. In three-electrode supercapacitors, the electrochemical behavior showed that BC-PT CMP exhibited the top specific capacitance of 373 F g⁻¹ in aqueous KOH (1.0 M) at a current density of 1.0 A g⁻¹. It also possessed a great cyclability maintaining 94.37% of primary capacitance at 10 A g⁻¹ current density even after 5000 GCD cycles. A two-electrode supercapacitor with the BC-PT CMP displayed a superb electrochemical capacitance of 107 F g⁻¹ at 1.2 A g⁻¹, a greater retention of 97.69% over 5000 GCD cycles at 10 A g⁻¹, and a better energy density of 14.86 W h kg⁻¹. The excellent efficiency of BC-PT CMP compared to that of TPA-PT CMP can be explained in terms of high specific surface area (478 m² g⁻¹), large pore volume (0.44 cm³ g⁻¹), great planarity, and better conductivity. Accordingly, BC-PT CMP is a prospective candidate for storing energy. Besides the novelty of our synthesized polymers, they exhibited outstanding electrochemical characteristics, both in three-electrode and two-electrode systems, which were comparable to those of many other polymers.