H 2 O-prompted CO 2 capture on metal silicates in situ generated from SBA-15.

A series of metal silicates, NaMSi 10 Ox (M = Cu, Mn and Ni), were prepared by in situ doping of metals into mesoporous SBA-15 under a hydrothermal process, displaying a continuous framework of SiO 4 structure with a narrow pore size distribution. These metal silicate materials were tested for CO 2 adsorption behavior in the absence and presence of water. The results exhibited that the effect of H 2 O on the CO 2 capture capability of metal silicates depends on the types of metal inserted into SBA-15. Compared to the dry condition, H 2 O addition enhances CO 2 uptake dramatically for NaCuSi 10 Ox by 25%, and slightly for NaNiSi 10 Ox (∼10%), whereas little effect is shown on NaMnSi 10 Ox. The metal silicate materials are stable after adsorption of CO 2 under wet conditions, which is benefited from their synthesis method, hydrothermal conditions. The improvement of CO 2 uptake on metal silicates by H 2 O is attributed to the competitive and synergistic adsorption mechanism on the basis of IR investigations, where initially adsorbed H 2 O acts as a promoter for further CO 2 capture through a hydration reaction, i.e. , formation of bicarbonate and carbonates on the surface of the samples. These observations provide new possibilities for the design and synthesis of porous metal silicate materials for CO 2 capture under practical conditions where moisture is present.