Structure-activity relationship of ZIF-8@PAN derived N-doped carbon fibers in persulfate activation for tetracycline degradation: Integrated DFT and experimental investigations.

N-doped carbon materials serve as efficient metal-free catalysts for persulfate (PS) activation to degrade organic pollutants like tetracycline (TC). This study investigates the structure-activity relationship of hierarchical N-doped carbon fibers (NCNFs) derived from ZIF-8@PAN composites, focusing on their role in PS-mediated TC degradation. The NCNFs were synthesized through electrospinning of polyacrylonitrile (PAN) nanofibers incorporated with ZIF-8 nanoparticles, followed by controlled pyrolysis, which yielded a well-defined hierarchical pore structure with a high specific surface area (635.5 m2/g for NCNFs-900) and optimized nitrogen doping configurations. Extensive characterization via SEM, TEM, FT-IR, NMR, XRD, XPS, and Raman spectroscopy confirmed the morphological and structural evolution of the NCNFs and their precursors. The optimized NCNFs-900 demonstrated outstanding catalytic performance, achieving 91.2 % TC removal within 20 min under low catalyst loading, primarily due to the synergistic effects of high surface area and graphitic N content in enhancing PS activation. Mechanistic insights from EPR, quenching experiments, and electrochemical analyses revealed a predominantly surface-confined non-radical pathway, where reactive species are generated and consumed at the catalyst interface, thus minimizing diffusion limitations. Degradation pathways, proposed through LC-MS and DFT calculations, indicated three routes yielding low-toxicity intermediates. This work underscores the critical influence of material structure on catalytic activity and offers a design strategy for efficient carbon-based catalysts in advanced oxidation processes.