Solid amine adsorbents are promising for enclosed spaces because they combine high selectivity for CO2 with low regeneration energy. The challenge, the authors note, has been achieving fast kinetics, high capacity and long-term stability simultaneously. Polyethylenimine, a polymer densely packed with amine groups, tends to form entangled chains that block access to many of its own active sites, limiting both uptake rate and effective capacity.

The team addressed this by blending polyethylenimine with diethanolamine, aminoethylethanolamine and diethylenetriamine inside the foam’s pores. The amino alcohols weaken the polymer’s chain entanglement, making more amine sites accessible to incoming CO2 molecules. In addition, surface silanol (Si–OH) groups on the silica scaffold form hydrogen bonds with the amino alcohols, stabilizing them within the pores and improving cyclic durability.

The standout formulation combined polyethylenimine and diethanolamine in a 1:1 mass ratio. This hybrid achieved a CO2 uptake of 177 milligrams per gram of adsorbent, around 70 percent above the theoretical additive capacity of its two components, and showed no capacity decay after 60 adsorption–desorption cycles. Hybrid adsorbents across the series outperformed their single-amine counterparts in both uptake and kinetics.

To explain these gains, the researchers ran molecular dynamics simulations. The modeling attributes the improvements to increased free volume within the amine phase, percolated diffusion pathways that let CO2 move through the material, and hydrogen-bond-stabilized amine networks that hold the active chemistry in place over repeated cycles. These are model-based explanations consistent with the measured performance rather than direct observations of the material’s internal structure.

The results indicate that pore architecture and molecular blending can be engineered together rather than treated separately. The foam’s large pore volume supplies the loading headroom, while the amino alcohol additives unlock the polymer’s latent capacity by loosening its internal structure. The study reports laboratory-scale adsorption performance; long-term behavior in real indoor environments and performance at larger scales remain to be demonstrated.

Subject of Research: Hybrid amine adsorbents in mesoporous silica foam for room-temperature indoor carbon dioxide capture

Article Title: Amino alcohols and polyethyleneimine in mesoporous silica foam for indoor carbon dioxide capture

Article References: Lu, J., Shen, X., Lu, Y., Sun, X., Zhang, T., Chen, B., Wang, L., Lei, S., Yan, F., & Zhang, Z. (2026). Amino alcohols and polyethyleneimine in mesoporous silica foam for indoor carbon dioxide capture. Environmental Chemistry Letters. https://doi.org/10.1007/s10311-026-01932-0

Image Credits: AI Generated

DOI: 10.1007/s10311-026-01932-0

Keywords: carbon dioxide capture, mesoporous silica foam, polyethylenimine, diethanolamine, amino alcohols, solid amine adsorbents, indoor air quality, molecular dynamics simulations, adsorption kinetics, hydrogen bonding, Amino, alcohols