Brønsted acid sites in zeolites activate ozone to generate reactive oxygen species for CO oxidation

Low-temperature catalytic oxidation of carbon monoxide (CO) remains a significant challenge in environmental catalysis, especially under the conditions where water (H₂O) and sulfur dioxide (SO₂) are present. In this work, we demonstrate that Brønsted acid sites (BAS) in protonated zeolites can effectively activate ozone (O₃) to generate reactive oxygen species for efficient CO oxidation at temperatures below 150 °C. Systematic comparison among metal oxides, supported catalysts, and zeolites reveals that H-type beta zeolite (Hβ5, Si/Al = 5) exhibits the highest catalytic CO conversion, achieving >40% CO conversion at room temperature. Hβ5 shows higher resistance to deactivation in the presence of H₂O and SO₂ than Au and Pt-based catalysts. Kinetic studies reveal a linear correlation between CO conversion rates and the number of BASs, suggesting that BAS is an active site for this catalytic system. Modulation Excitation Diffuse Reflectance Infrared Fourier Transform Spectroscopy (ME-DRIFTS) and Density Functional Theory (DFT) calculations suggest that O₃ interacts directly with a BAS to form reactive oxygen species, which react with CO to give carbon dioxide (CO₂). Our findings provide new insight into non-transition-metal-based oxidation catalysis and offer a promising strategy for designing robust catalysts for industrial CO abatement under harsh flue gas environments.