Dry gel grafting of mesoporous silica: Application to amine-based CO2 adsorbents

A dry gel tumbling (DGT) method, which combines solution and gas phase grafting procedures, is presented as an energy- and cost-effective, and scalable route for the preparation of hybrid organosilica materials. For illustration, the preparation, characterization and performance of amine-grafted CO2 adsorbents (AGAs) is presented in detail. Materials prepared by DGT performed better compared to those derived from an optimized water-aided grafting procedure in toluene. Unusually high amine content (4.53 mmol/g), CO2 capacity (2.08 mmol/g) and amine efficiency (0.46) were obtained for this material. DGT offers maximum incorporation of organosilanes during grafting, i.e., an efficient and high yield reaction between the surface silanol groups and the alkoxyl groups of the silane, with grafting efficiencies >95% for propylamine-grafted adsorbents. The method was extended to the synthesis of hydrophobic AGAs, with increased resistance to leaching.