Mg and P Codoped Chitosan-Based Composite Aerogel with Excellent Thermal Insulation, Flame Retardancy, and Formaldehyde Adsorption

Developing multifunctional materials that combine low thermal conductivity with high flame retardancy is key to meeting the demands of modern energy-efficient buildings. Chitosan (CS), with its natural biogenic properties and significant inherent flame retardancy, provides a unique design basis for high-performance thermal insulation and flame-retardant materials. In this work, we use an in situ coprecipitation strategy to load ammonium polyphosphate (APP) and magnesium phosphate compounds (main phase MgNH 4 PO 4 ·6H 2 O) onto the three-dimensional framework of CS, successfully constructing a Mg and P codoped chitosan-based composite aerogel (recorded as CS@APP@Mg–P aerogel) that synergistically enhances thermal insulation and flame retardancy. This material exhibits thermal insulation properties, with a thermal conductivity as low as 0.0251 W m –1 ·K –1, primarily attributed to the three-dimensional network structure and high porosity of the chitosan matrix. Its flame-retardant performance meets the UL-94 V-0 standard, with a peak heat release rate (pHRR) as low as 17.30 kW m –2, significantly outperforming similar composite materials. Additionally, the aerogel exhibits high adsorption capacity for formaldehyde (average adsorption rate >80%). The comprehensive performance mentioned above is attributed to the synergistic interaction among the CS matrix, APP flame retardant, and magnesium phosphate reinforcing phase (MgNH 4 PO 4 ·6H 2 O). This provides a strategy for developing biobased aerogels that integrate thermal insulation, flame retardancy, and formaldehyde adsorption, offering broad application prospects in energy-efficient buildings and indoor air purification.