Sulfur-Enriched Porphyrin-Based Covalent Organic Frameworks as Redox-Active Electrode for Aqueous Symmetric...

In this study, we report the design, synthesis and electrochemical evaluation of three porphyrin-based covalent organic frameworks (COFs), TTP-COF, BTP-COF, and TP-COF, integrating sulfur-rich π-conjugated aldehyde linkers (thieno[3,2-b]thiophene, bisthiophene and thiophene) with C₄-symmetric porphyrin knots via imine condensation. These frameworks exhibit enhanced electronic conductivity, efficient ion diffusion, and high structural stability. Among the tested materials, TTP-COF exhibited superior electrochemical performance in the three-electrode setup, delivering a high specific capacitance of 193.3 F g^-1. Furthermore, the symmetric supercapacitor (TTP-COF // TTP-COF) demonstrated a remarkable specific capacitance of 129.2 F g^-1, a high energy density of 35.2 Wh kg^-1, and outstanding cyclic stability, retaining its performance even after 25,000 charge-discharge cycles. Electrochemical studies revealed a dual charge storage mechanism involving both electric double-layer capacitance and pseudocapacitance, attributed to redox-active porphyrin units and sulfur-containing linkers. Nyquist analysis confirmed the lowest charge transfer resistance (R_ct = 0.18 Ω) for TTP-COF, highlighting its efficient charge transport characteristics. A symmetric supercapacitor device based on TTP-COF successfully powered white and red LEDs, validating its real-world applicability. This work underscores the potential of rationally engineered porphyrin-thiophene COFs as advanced materials for next-generation supercapacitor technologies.