Multifunctional high-performance cement aerogels for CO₂ sequestration and thermal insulation

Aerogels are widely used as thermal insulation materials, but they suffer from low mechanical strength, poor fire resistance, and high carbon emissions. This paper presents an approach to fabricate cement aerogels with high mechanical performance and multifunctionality via in-situ cement hydration, freeze-casting, and freeze-drying. The fabricated aerogels feature a three-dimensional, porous, organic-inorganic hierarchical network of rigid calcium (aluminate) silicate hydrate dispersed and crosslinked with flexible polyvinyl alcohol via calcium/aluminum ion coordination bonds and hydrogen bonds. The resulting cement aerogels demonstrate multifunctional performance, combining high mechanical strength and toughness with thermal and environmental benefits. Specifically, they achieve a compressive strength of 80 MPa, a flexural strength of 8.9 MPa, and a toughness of 2260 kJ/m³, all while maintaining a low density of 0.465 g/cm³. Owing to their inorganic–organic hybrid porous architecture, the aerogels exhibit low thermal conductivity (0.051 W/(m·K)) and fire resistance. Their calcium-rich composition and porous hierarchical structure facilitate CO₂ uptake and in-situ mineralization into calcium carbonate. This results in a carbon capture capacity of 27.5 %, as quantified by thermogravimetric analysis based on CO₂-related mass loss after 28 days of curing under CO₂-rich conditions (30 °C, >95 % relative humidity). By integrating mechanical reinforcement, thermal insulation, and carbon sequestration into a lightweight and scalable cement aerogel, this work offers a compelling pathway toward sustainable construction and energy-efficient infrastructure.