Cost-efficient and durable manganese-based catalysts are in great demand for the catalytic elimination of volatile organic compounds (VOCs), which are dominated not only by the nanostructures but also by the oxygen vacancies and Mn−O bond in the catalysts. Herein, a series of nanostructured Co−Fe-doped-δ-MnO 2 catalysts (Co−Fe-δ-MnO 2 ) with high dispersion were in situ fabricated by employing metal−organic-frameworks (MOFs) as reducing agents, dopants, and templates all at the same time. The as-obtained Co−Fe-δ-MnO 2 -20% catalyst exhibited robust durability and high catalytic activity (225 °C) for toluene combustion even in the presence of 5 vol % water vapor, which is 50 °C lower than that of pristine δ-MnO 2 . Various characterizations revealed that the homogeneously dispersed codoping of Co and Fe ions into δ-MnO 2 promotes the generation of oxygen vacancies and weakens the strength of the Mn−O bond, thus increasing the amount of adsorbed oxygen (O ads ) and improving the mobility of lattice oxygen (O latt ). Meanwhile, due to successfully inheriting the framework structures of MOFs, the obtained catalyst exhibited a high surface area and three-dimensional mesoporous structure, which contributes to diffusion and increases the number of active sites. Moreover, in situ DRIFTS results confirmed that the toluene degradation mechanism on the Co−Fe-δ-MnO 2 -20% follows the MVK mechanism and revealed that more O ads and high-mobility O latt induced by this novel method contribute to accumulating and mineralizing key intermediates (benzoate) and thus promote toluene oxidation. In conclusion, this work stimulates the opportunities to develop Co− Fe-δ-MnO 2 as a class of nonprecious-metal-based catalysts for controlling VOC emissions.
Catalytic
combustion has been known to be an effective technique
in volatile organic compound (VOC) abatement. Developing monolithic
catalysts with high activity at low temperatures is vital yet challenging
in industrial applications. Herein, monolithic MnO2-Ov/CF catalysts were fabricated via the in situ growth of K2CuFe(CN)6 (CuFePBA, a family of
metal–organic frames) over copper foam (CF) followed by a redox-etching
route. The as-synthesized monolith MnO2-Ov-0.04/CF
catalyst displays a superior low-temperature activity (T90% = 215 °C) and robust durability for toluene elimination even
in the presence of 5 vol % water. Experimental results reveal that
the CuFePBA template not only guides the in situ growth
of δ-MnO2 with high loading over CF but also acts
as a source of dopant to create more oxygen vacancies and weaken the
strength of the Mn–O bond, which considerably improves the
oxygen activation ability of δ-MnO2 and consequently
boosts the low-temperature catalytic activity of the monolith MnO2-Ov-0.04/CF toward toluene oxidation. In addition,
the reaction intermediate and proposed mechanism in the MnO2-Ov-0.04/CF mediated catalytic oxidation process were
investigated. This study provides new insights into the development
of highly active monolithic catalysts for the low-temperature oxidation
of VOCs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.