Insight into formaldehyde decomposition over MOFs-derived CeO2-MnOx bimetallic oxides

Abstract

The ubiquitous presence of formaldehyde as a pollutant has aroused significant environmental and health concerns. The design and performance of (OR: transition metal oxide) catalysts in the catalytic oxidation method continue to face a myriad of challenges. Herein, a series of CeO_2-x-MnO_x catalysts are synthesized using manganous nitrate impregnated Ce-metal–organic-frameworks as the precursor, followed by a traditional calcination step. Interestingly, we found that the gases released during the pyrolysis of metal–organic-frameworks significantly affect the valence states of Ce and Mn, which are key factors responsible for catalytic activity. Characterizations results show that the CeO_2-x-MnO_x-2.5 sample contains a large amount of Ce³⁺, a high Mn³⁺/Mn⁴⁺ ratio, and an abundance of reactive oxygen species on its surface. Density functional theory results demonstrate that oxygen vacancies not only effectively suppress charge loss of Mn and Ce atoms but also significantly enhance the adsorption strength of CeO_2-x-MnO_x-2.5 for both formaldehyde and O₂. These structural features jointly influence the adsorption as well as the rapid oxidation of formaldehyde molecules, leading to the excellent catalytic performance towards formaldehyde oxidation. This study provides a promising platform for designing straightforward, cost-effective, and highly efficient bimetallic catalysts suitable for low-temperature formaldehyde oxidation.