<p>Acid-modified LaMn_0.6Ni_0.4O₃ perovskite catalysts were prepared by an impregnation method and applied to the catalytic oxidation of toluene. The effects of hydrochloric acid, nitric acid, citric acid, and acetic acid modification on the physicochemical properties and catalytic performance were systematically investigated. Among all samples, the HCl-modified catalyst (HA-LaMn_0.6Ni_0.4O₃) exhibited the highest toluene oxidation activity. Characterization results demonstrated that acid modification significantly altered the crystal structure, surface morphology, and electronic states of the catalyst. For HA-LaMn_0.6Ni_0.4O₃, the specific surface area increased from 8.76 to 126.22 m²/g, the average crystallite size decreased to 15.83&#xa0;nm, and a well-developed mesoporous structure was formed, providing abundant exposed active sites. In addition, the ratios of Mn⁴⁺/Mn³⁺ and Ni³⁺/Ni²⁺ were markedly increased, leading to enhanced oxygen vacancy concentration and improved lattice oxygen mobility. Under simulated industrial conditions, the HA-LaMn_0.6Ni_0.4O₃ catalyst maintained approximately 70% toluene conversion after continuous operation for 35&#xa0;h, and elevated reaction temperatures further improved its adaptability to high toluene concentrations and high space velocities. These results demonstrate that surface acid modification is an effective strategy for enhancing the catalytic performance of Mn-based perovskite catalysts for toluene oxidation.</p> Graphical abstract <p></p>