Redox-Active Conjugated Microporous Polymers Featuring a Precise Pore Size for High-Performance Supercapacitor Energy Storage

Conjugated microporous polymers (CMPs) are popular for their unique characteristics, encompassing a substantial surface area, elevated porosity, highly adjustable physical and chemical properties, and an extensive π-conjugated framework. However, the synthesis of CMPs with a specific and narrow pore size distribution remains limited. In this study, we utilized a controlled Suzuki coupling reaction to prepare redox-active CMPs with a precise and narrow distribution of pore sizes for supercapacitor applications, addressing the limitations associated with their use. Two redox-active 9,9-bifluorenylidene (BF)-based CMPs, BF-Ph-DTDO and BF-DTDO CMPs, were synthesized via a one-pot Suzuki coupling polymerization reaction. The BF-Ph-DTDO CMP was synthesized using a combination of 3,3′,6,6′-tetrabromo-9,9′-bifluorenylidene (BF-4Br), 1,4-phenylenediboronic acid (Ph-2BOH), and 2,6-dibromobenzo[1,2-b:4,5-b’]dithiophene-4,8-dione (DTDO-2Br), whereas the BF-DTDO CMP was synthesized by combining 3,3′,6,6′-tetrakis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-9,9′-bifluorenylidene (BF-4BO) with DTDO-2Br. The BF-CMPs had a large surface area (336.22 m2 g–1) and outstanding thermal stabilities (Td10 at 658.29 °C and char yield at 79.51%). Interestingly, both CMPs demonstrated a specific and regulated pore size of 2.14 nm for the BF-Ph-DTDO CMP and 1.8 nm for the DTDO CMP. In addition, the pore size of the CMP frameworks significantly affected energy storage efficiency. The BF-Ph-DTDO CMP with the largest pore size attained a capacitance of 288.80 F g–1 in a three-electrode configuration at 0.5 A g–1 of current density, demonstrating remarkable 76.58% stability across 10,000 cycles. We also created a two-electrode symmetric supercapacitor device made of BF-Ph-DTDO CMP, which achieved a specific capacitance of 272.7 F g–1 at a current density of 0.4 A g–1, a peak energy density of 37.88 W h kg–1, , a power density of 462 W kg–1, and an operating voltage of 1.0 V. This research offers a promising approach for the development of electrochemical devices and next-generation supercapacitors.