Decoding the Role of Porosity and N,S-Doping in Covalent Triazine Framework-Derived Carbons and Their Carbon Nano-Onion Hybrids for Superior Supercapacitors

We report the first ionothermal synthesis of nitrogen- and sulfur-containing covalent triazine frameworks (CTFs) from NS (thiazolo[5,4-d]thiazole derivative), SS (thieno[2,3-b]thiophene derivative), and NSN (benzo[c][1,2,5]thiadiazole derivative) monomers and their hybrids with carbon nano-onions (CNOs). All materials were synthesized by pyrolysis at 700 °C. Comprehensive characterization by Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, and high-resolution transmission electron microscopy (HRTEM) shows that the materials consist of turbostratic, heteroatom-doped carbon frameworks in which CNOs introduce small graphitic crystallites and quasi-crystalline ordering. Triazine ring formation, and the presence of pyridinic/graphitic N together with C–S–C/C═S motifs confirm successful incorporation of heteroatoms into a π-conjugated carbon matrix, whereas HRTEM reveals concentric graphitic CNO shells intimately embedded in an amorphous-to-locally graphitic CTF phase, yielding strong interfacial contact and an interconnected porous architecture. The CTF-CNO hybrids show up to a 3-fold increase in specific capacitance relative to the corresponding pristine CTFs and retain high capacitance over a wide range of scan rates and current densities. NS-CTF-CNO combines a favorable balance of energy and power densities, low charge-transfer resistance, and a wide operational potential window, while NSN-CTF-CNO achieves the highest specific capacitance (1074 F g–1 at 10 mV s–1). These results establish a design strategy in which heteroatom-rich CTF frameworks are integrated with near-percolating CNO networks and tuned pore connectivity to optimize conductivity, ion transport, and fast, reversible charge storage in metal-free carbon electrodes.