Cross-linker-free fabrication of chitosan–MnO2 composite aerogels with synergistic adsorption-catalysis for high-efficiency room-temperature formaldehyde elimination

Abstract

Formaldehyde (HCHO) is a hazardous indoor air pollutant, yet conventional powdered adsorption materials suffer from aggregation and stability challenges. In this study, a chitosan–manganese dioxide (CS–MnO₂) composite aerogel was fabricated via a freeze-drying method without cross-linking agents to achieve synergistic adsorption and catalytic degradation of HCHO. The optimized CS–M2 aerogel leverages the structural stability of CS and the high surface activity of MnO₂, ensuring uniform MnO₂ dispersion and mitigating aggregation issues. The aerogel exhibits outstanding room-temperature performance, achieving an HCHO removal efficiency of 90.26% within 6 hours and an adsorption capacity of 38.99 mg g⁻¹, three times higher than that of pure CS. Kinetic analysis confirms a pseudo-second-order adsorption mechanism (R² = 0.994), supported by a hierarchical porous structure and excellent thermal stability (>250 °C), indicating potential flame-retardant properties. This work overcomes the trade-off between MnO₂ dispersion and reactivity through a green, scalable synthesis strategy, enabling persistent HCHO mineralization. The proposed approach advances the design of multifunctional aerogels for practical indoor air purification, effectively addressing environmental and health concerns.