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Understanding the Stability in Water of Mesoporous SBA-15 and MCM-41

2007; American Chemical Society; Volume: 111; Issue: 23 Linguagem: Inglês

10.1021/jp068526e

1932-7455

Anne Galarneau, M. Nader, Flavien Guenneau, Francesco Di Renzo, Antoine Gédeon,

Metal-Organic Frameworks: Synthesis and Applications

Surprisingly, SBA-15 mesoporous silicas are not as stable as expected in water, even at room temperature, despite their thick walls. The microporosity of SBA-15, synthesized at a temperature below 110 °C, is lost during water treatment, leading to a strong decrease in specific surface area and an increase in mesopore size. Only SBA-15s without microporosity, such as the ones synthesized at 130 °C, are stable under water treatment. Investigations by nitrogen adsorption isotherms and hyperpolarized 129Xe NMR spectroscopy have been performed in an effort to understand the silica dissolution/redeposition processes occurring during water treatment at room temperature and at the boiling point for three SBA-15s synthesized at different temperature levels: 60, 100, and 130 °C. The differences between the local curvatures of silica in the different structures explain the difference of behavior in water with respect to silica dissolution/redeposition. Similar experiments on MCM-41 lead to a totally different dissolution/redeposition process because of its thinner walls: decrease of pore size, surface area and pore volume.