Amine-modified silica nanotubes and nanospheres: synthesis and CO2 sorption properties

Silica nanotubes (SNT) and silica nanospheres (SNS) were prepared in the presence of Pluronic F127 triblock copolymer. Post-synthesis grafting and co-condensation were used to introduce aminopropyl groups on the surface of SNT and SNS, respectively. Nitrogen adsorption was employed to evaluate the surface area and porosity of unmodified and modified SNT and SNS. These materials were tested for CO2 capture at ambient (25 degrees C) and elevated (120 degrees C) temperatures and showed high sorption uptakes (0.91-2.87 mmol g(-1)) at 120 degrees C. The CO2 uptakes obtained at 1.2 atm and 25 degrees C for SNT, SNS, and aminopropylmodified SNT and SNS are 2.81, 2.06, 2.35, and 1.54 mmol g(-1), respectively. The microporosity of the samples was shown to be beneficial for CO2 physisorption under ambient conditions, while basic amine groups were essential for enhancing CO2 chemisorption at elevated temperatures.