Iris-shaped Ru@MXene: one-pot molten salt etching-anchoring for enhanced PMS activation

The fabrication of efficient and stable catalysts for peroxymonosulfate (PMS) activation is critical for the remediation of tetracycline (TC), a refractory antibiotic pollutant. MXene-based materials have emerged as promising catalyst platforms, yet their conventional preparation relies on hazardous fluorine-based etchants and complex multi-step procedures. Here, we developed a facile, fluorine-free one-pot CaCl₂molten salt etching strategy. This method integrates MAX phase exfoliation with simultaneousin-situanchoring of Ru nanoparticles on MXene, yielding a Ru-Ca@Mo₂TiC₂MXene (Ru-Ca@MTC) composite. The chelation of dopamine and the intercalation of Ca²⁺synergistically regulated the material structure, endowing the Ru-Ca@MTC with an iris-like morphology, an expanded interlayer spacing, abundant oxygen vacancies, and uniformly distributed approximately 5 nm Ru active sites. The Ru-Ca@MTC/PMS system demonstrated excellent TC degradation performance, achieving 96% removal within 30 min, and maintained high catalytic activity over a wide pH range (2.74-10.76) with strong resistance to inorganic anions and actual water matrices. Mechanistic studies confirmed that TC degradation was dominated by¹O₂-based non-radical pathway, driven by Ruⁿ⁺/Ru⁽ⁿ⁺¹⁾⁺redox cycling and oxygen vacancy-induced PMS electron transfer. Seventeen degradation intermediates were identified, and toxicity assessments verified the significant reduction of TC toxicity after degradation. Additionally, Ru-Ca@MTC showed good reusability with 92.5% TC removal after five cycles. By enabling fluorine-free, one-pot synthesis of noble metal-loaded MXene catalysts, this work offers a simplified, safer, and scalable technical solution for the treatment of antibiotic-contaminated water.