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Formaldehyde (HCHO) is carcinogenic and teratogenic, and is therefore a serious danger to human health. It also adversely affects air quality. Catalytic oxidation is an efficient technique for removing HCHO. The development of highly efficient and stable catalysts that can completely convert HCHO at low temperatures, even room temperature, is important. Supported Pt and Pd catalysts can completely convert HCHO at room temperature, but their industrial applications are limited because they are expensive. The catalytic activities in HCHO oxidation of transition-metal oxide catalysts such as manganese and cobalt oxides with unusual morphologies are better than those of traditional MnO2, Co3O4, or other metal oxides. This is attributed to their specific structures, high specific surface areas, and other factors such as active phase, reducibility, and amount of surface active oxygens. Such catalysts with various morphologies have great potential and can also be used as catalyst supports. The loading of relatively cheap Ag or Au on transition-metal oxides with special morphologies potentially improves the catalytic activity in HCHO removal at room temperature. The preparation and development of new nanocatalysts with various morphologies and structures is important for HCHO removal. In this paper, research progress on precious-metal and transition-metal oxide catalyst systems for HCHO oxidation is reviewed; topics such as oxidation properties, structure–activity relationships, and factors influencing the catalytic activity and reaction mechanism are discussed. Future prospects and directions for the development of such catalysts are also covered.

Three-dimensional (3D) ordered mesoporous MnO2 was prepared using KIT-6 mesoporous molecular sieves as a hard template. The material was used for catalytic oxidation of HCHO. The material has high surface areas and the mesoporous characteristics of the template, with cubic symmetry (ia3d). It consists of a β-MnO2 crystalline phase corresponding to pyrolusite, with a rutile structure. Transmission electron microscopy and X-ray photoelectron spectroscopy showed that the 3D-MnO2 catalyst has a large number of exposed Mn4+ ions on the (110) crystal plane surfaces, with a lattice spacing of 0.311 nm; this enhances oxidation of HCHO. Complete conversion of HCHO to CO2 and H2O was achieved at 130 °C on 3D-MnO2; the same conversions on α-MnO2 and β-MnO2 nanorods were obtained at 140 and 180 °C, respectively, under the same conditions. The specific mesoporous structure, high specific surface area, and large number of surface Mn4+ ions are responsible for the catalytic activity of 3D-MnO2 in HCHO oxidation.