Mesoporous Alumina with Amidoxime Groups for CO₂ Sorption at Ambient and Elevated Temperatures

Development of various mesostructures with introduced basic species such as amine groups represents a viable strategy for enhancing adsorption of acidic molecules such as CO₂. To follow this strategy, mesoporous alumina-based materials with incorporated amidoxime functionality were prepared by evaporation induced self-assembly of commercial boehmite nanoparticles as an alumina precursor, (3-cyanopropyl)­triethoxysilane as an organosilica precursor, and Pluronic P123 triblock copolymer as a soft template under acidic conditions. In the next synthesis step, the resulting mesoporous materials with cyanopropyl groups were subjected to hydrothermal reaction with hydroxylamine hydrochloride at slightly basic conditions and 80 °C to convert cyanopropyl groups to amidoxime functionalities. The latter sorbents showed fairly high CO₂ uptake at ambient conditions (25 °C, 1.2 atm) and remarkably high sorption capacity (3.84 mmol/g) at 120 °C. Good thermal and chemical stabilities of these materials combined with high CO₂ uptake at elevated temperatures make them of potential interest for sorption of acidic gaseous molecules such as CO₂