A novel MOF-on-MOF-derived carbon-encapsulated CeO/Co/CoO humidity-resistant heterojunction with abundant oxygen vacancies for efficient ozone removal.

Ground-level ozone (O) can infiltrate indoor environments, severely impacting the environment and human health. Moisture-induced catalyst deactivation is a major challenge in catalytic ozone removal. MOF-template-derived heterojunctions supported by carbon materials can prevent chemisorption of water vapor at active sites. This paper presents a carbon-supported CeO/Co/CoO humidity-resistant heterojunction derived from a bimetallic-organic framework (Ce-BTC/Co-ZIF-67 precursor) via hydrothermal-carbonization. Instrumental characterization confirmed the successful construction of the heterojunction. The O removal efficiency was evaluated at the ppb level under different relative humidity conditions (RH = 0%, 50%, and 75%) at a weight hourly space velocity (WHSV) of 10,000 L g h and ambient temperature. The carbon-supported 20 wt% CeO/Co/CoO composite demonstrated 99 ± 0.2% O removal and a high reaction rate of 1.1 ± 0.06 μg.g.sec for 200 ppb O under an RH of 50% at ambient temperature. The O removal rate remained at approximately 92 ± 1.2%, even in harsh environments (75% RH), indicating excellent stability and strong moisture-resistance. Oxygen vacancies and defect structures are crucial for O adsorption and activation processes. The optimal catalyst exhibited greater electron mobility and redox ability than the pristine materials, as confirmed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) analyses. Furthermore, the as-synthesized catalyst is both recyclable and stable, making it suitable for practical applications. This research offers a new strategy for the fabrication of highly moisture-resistant MOF-derived heterojunctions, which will greatly facilitate the elimination of ground-level O in real indoor environments.