An Advanced Dual‐Function MnO2‐Fabric Air Filter Combining Catalytic Oxidation of Formaldehyde and High‐Efficiency Fine Particulate Matter Removal

Abstract Comprehensive treatment of indoor contaminants such as volatile organic compounds (VOCs) and fine particulate matter (PM 2.5 ) using transition metal oxide catalysts or functional fibrous filters has gained substantial attention recently. However, coupling VOC oxidation catalysts into high‐performance filter systems remains a challenge. Herein, an overall solution to strongly bind manganese dioxide (MnO 2 ) nanocrystals onto polypropylene (PP) nonwoven fabrics is provided. For the first time, uniform heterogeneous nucleation and growth of MnO 2 onto PP nonwoven fabrics using intermediate inorganic nucleation films, including Al 2 O 3 , TiO 2 , and ZnO, formed conformally on the fabrics via atomic layer deposition (ALD) are demonstrated. How different ALD thin films influence the crystallinity, morphology, surface area, and surface oxygen species of the MnO 2 grown ALD‐coated PP fibers is further investigated. In addition to uniformity and integrity, ZnO thin films give rise to MnO 2 crystals with the largest fraction of available surface oxygen, enabling 99.5% catalytic oxidation of formaldehyde within 60 min. Moreover, the metal oxide filters provide excellent PM removal efficiencies ( e PM), achieving e PM 2.5 90% and e PM 10 98%, respectively, making the approach an outstanding method to produce fully dual‐functional filtration media.