Development of Alumina⁻Mesoporous Organosilica Hybrid Materials for Carbon Dioxide Adsorption at 25 °C.

Two series of alumina (Al2O3)⁻mesoporous organosilica (Al⁻MO) hybrid materials were synthesized using the co-condensation method in the presence of Pluronic 123 triblock copolymer. The first series of Al⁻MO samples was prepared using aluminum nitrate nanahydrate (Al⁻NN) and aluminum isopropoxide (Al⁻IP) as alumina precursors, and organosilanes with three different bridging groups, namely tris[3-(trimethoxysilyl)propyl]isocyanurate, 1,4-bis(triethoxysilyl)benzene, and bis(triethoxysilyl)ethane. The second series was obtained using the aforementioned precursors in the presence of an amine-containing 3-aminopropyltriethoxysilane to introduce, also, hanging groups. The Al⁻IP-derived mesostructures in the first series showed the well-developed porosity and high specific surface area, as compared to the corresponding mesostructures prepared in the second series with 3-aminopropyltriethoxysilane. The materials obtained from Al⁻NN alumina precursor possessed enlarged mesopores in the range of 3⁻17 nm, whereas the materials synthesized from Al⁻IP alumina precursor displayed relatively low pore widths in the range of 5⁻7 nm. The Al⁻IP-derived materials showed high CO2 uptakes, due to the enhanced surface area and microporosity in comparison to those observed for the samples of the second series with AP hanging groups. The Al⁻NN- and Al⁻IP-derived samples exhibited the CO2 uptakes in the range of 0.73⁻1.72 and 1.66⁻2.64 mmol/g at 1 atm pressure whereas, at the same pressure, the Al⁻NN and Al⁻IP-derived samples with 3-aminopropyl hanging groups showed the CO2 uptakes in the range of 0.72⁻1.51 and 1.70⁻2.33 mmol/g, respectively. These data illustrate that Al⁻MO hybrid materials are potential adsorbents for large-scale CO2 capture at 25 °C.