<p>A series of Cu_<i>x</i>Mn_5−<i>x</i>Ce₁₀ ternary composite oxides were rationally engineered via co-precipitationto activate peroxymonosulfate (PMS) for tetracycline (TC) degradation. Characterization confirms that Cu/Mn isomorphic incorporation into the CeO₂ lattice induces lattice distortion, forming a composite oxide with a high specific surface area (73.52 m²/g for optimal Cu₃Mn₂Ce₁₀). Systematic evaluation shows the optimal Cu₃Mn₂Ce₁₀/PMS system achieves exceptional performance, with a rate constant (<i>k</i> = 0.124&#xa0;min⁻¹ at 30&#xa0;°C) ~ 2.22-fold higher than its Cu-free counterpart. The apparent activation energy (<i>Eₐ</i> = 30.03&#xa0;kJ/mol) is significantly reduced. Mechanistic and transition-state thermodynamic analyses&#xa0;suggest a plausible associative inner-sphere pathway, wherein the porous architecture&#xa0;is proposed to assist in&#xa0;the pre-enrichment of TC, while surface-bound radical species (primarily SO₄⁻· and ·OH) are facilitated by&#xa0;the coupled Cu⁺/Cu²⁺, Mn⁴⁺/Mn³⁺ and Ce⁴⁺/Ce³⁺ redox cycles for subsequent degradation. This catalyst maintains &gt; 90% TC removal across a broad pH window (3–11) with robust structural stability. This work provides an efficient catalyst for antibiotic wastewater treatment and insights into multimetal synergy in advanced oxidation processes.</p>