Nitrogen- and Sulfur-Rich Microporous Carbons Derived from Conjugated Microporous Polymers for CO₂ Uptake, Supercapacitor Energy Storage, and Electrochemical Hydrogen Production

In this work, we synthesized Py-DPABT CMP through Sonogashira-Hagihara cross-coupling reactions between N⁴,N⁷-bis(4-bromophenyl)-N⁴,N⁷-diphenylbenzo[c][1,2,5]thiadiazole-4,7-diamine (DPABT-Br₂) and 1,3,6,8-tetraethynylpyrene (Py-T). This Py-DPABT CMP was subsequently carbonized at 500 and 700 °C and transformed into a porous carbonaceous electrode precursor for supercapacitors (SCs), yielding Py-DPABT CMP-500 and Py-DPABT CMP-700 containing N and S heteroatoms. Using distinct analytical methods, we investigated the electrochemical characteristics, CO₂ uptake, configuration, porosity, thermal stability, and chemical structure of the Py-DPABT CMP before and after carbonization at 500 and 700 °C, respectively. After carbonization, the material (Py-DPABT CMP-500) achieved a BET surface area (SA_BET) of 423 m² g^-1 and the adsorption capacity of CO₂ reached 3.55 mmol g^-1 at 0 °C. Electrochemical evaluations revealed that Py-DPABT CMP-500 exhibited enhanced performance when utilized as supercapacitor electrodes, facilitated by heteroatoms. According to three-electrode analyses, Py-DPABT CMP-500 achieved specific capacitances up to 973 F g^-1 at 1 A g^-1. Additionally, they demonstrated exceptional durability, maintaining 98% of their capacity after 2000 cycles when tested at a current of 10 A g^-1. Furthermore, the capacitance of the symmetric coin cell Py-DPABT CMP-500 at 1 A g^-1 achieved 627 F g^-1. The hydrogen evolution reaction and performance of Py-DPABT CMP-500 were assessed in 1 M KOH electrolyte utilizing a three-electrode setup. The catalyst achieved a current density of 10 mA cm^-2 with an overpotential of 325 mV and exhibited a Tafel slope of 169 mV dec^-1. Additionally, it demonstrated a low charge transfer resistance (R_ct) of 88 Ω and a substantial double-layer capacitance (C_dl) of 72.8 mF cm^-2, highlighting its potential as an efficient electrocatalyst for HER applications. These findings underscore the potential practical applications of this electrode and investigate the synergistic effects of heteroatoms and the carbonization process in CMPs, enhancing their suitability for CO₂ uptake, supercapacitor, and HER.