Cation-Induced Self-Assembly of α-MnO₂ Nanowires into High-Purity Self-Standing Three-Dimensional Network Aerogels for Catalytic Decomposition of Carcinogenic Formaldehyde at Ambient Temperature

Formaldehyde (HCHO), a ubiquitous gaseous pollutant in indoor environments, threatens human health under long-term exposure, necessitating its effective elimination. Due to its advantages in enhancing mass transfer and effectively exposing active sites, aerogels with a three-dimensional (3D) interconnected network structure are expected to achieve efficient and stable decomposition of HCHO at ambient temperature. However, how to realize the self-assembly of transition metal oxides to construct high-purity 3D network aerogels is still a huge challenge. Herein, the cation-induced self-assembly strategy was developed to construct high-purity self-standing 3D network manganese dioxide aerogels. The interaction between cations and the surface groups of nanowires is crucial for successful self-assembly, which leads to the cross-winding of nanowires with each other, forming a 3D-structured network. The K⁺-induced 3D-MnO₂ exhibited excellent catalytic performance for HCHO, which could continuously and steadily decompose HCHO into CO₂ and H₂O at ambient temperature. Thanks to the 3D interconnected network structure, on the one hand, it provides a large specific surface area and porosity, reducing mass transfer resistance and promoting the adsorption of HCHO and O₂ molecules. On the other hand, it is more important to fully expose the active sites, which can generate more surface active oxygen species and achieve effective recycling and regeneration. Importantly, 3D-MnO₂ has a strong ability to capture and activate water molecules in the atmosphere, which could be further involved in the replenishment of the consumed hydroxyl groups. This study proposes a strategy for self-assembly of transition metal oxides through cation-induction, which provides a new catalyst design approach for the room temperature decomposition of VOCs.