Effects of the core of liquid-like SiO₂ nanoparticle organic hybrid materials on CO₂ capture

A series of specific liquid-like silicon dioxide (SiO₂) nanoparticle organic hybrid materials (NOHMs) were successfully prepared by employing different contents of SiO₂ as the core, 3-glycidoxypropyl trime thoxysilane (KH-560) or 3-(trihydroxysilyl)-1-propane sulfonic acid (SIT) as the corona and polyetheramine M-1000 (M-1000) as the canopy. These materials showed a solvent-free and liquid-like state at room temperature. The effect of the SiO₂ content in the NOHMs with different bonding types on the CO₂ capture capacity was investigated at 298 K and CO₂ pressures ranging from 1.0 to 2.5 MPa. It was demonstrated that the capacity of the sorbents improved with the decreasing of SiO₂ content. This result was due to the larger number of reactive groups and lower viscosity of the NOHMs. The reactive groups, such as secondary amine and ether groups, react with CO₂ molecules, while the lower viscosity creates larger molecular gap and weaker intermolecular forces, which facilitates the penetration of CO₂ molecules into the potential space between organic chains. In addition, the NOHMs synthesized via covalent bonds had a much better CO₂ capture capacity than the NOHMs with ionic bonds and the same content of SiO₂, owing to the protonation of the amine groups in the ionic bond-typed NOHMs, which renders them inactive for CO₂ uptake.