The synthesized mesoporous Al-MCM and Cr-doped Al-MCM material were characterized by UV, XRD and other techniques. Here in this study, moleculary-sesitive IR spectroscopy was used to determine the acid-base characteristics of these material using carbon monoxide and ammonia as probe molecules. Acid and basic sites were found to be present as determined by corresponding IR modes on surfaces. A simple organic aldehyde was used as a model compound to understand the reactivity of the nanoparticles towards catalytic degradation. It was observed that low temperature adsorption caused the aldehyde molecule to bind through H-bonding with surface –OH groups. In addition, a fraction of aldehyde adsorbed through Lewis acid sites- Cr (IV) and Al (III). The combination of both H-bonded and Lewis acid sites bound acetaldehyde underwent condensation reaction forming aldol which then dehydrated at elevated temperature forming 2-butenal. A fraction of adsorbed acetaldehyde underwent photodecomposition to CO<sub>2 </sub>during photooxidation at 273 K and 173 K This oxidation involves photoactive acetyl radical and Cr ion. The photochemical reaction produced a a variety of condensation products which were identified by using temperature programmed desorption.

Influence of acid-base behavior of MCM-41 mesoporous nanoparticles using <i>in situ</i> FT-IR spectroscopic study

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Influence of acid-base behavior of MCM-41 mesoporous nanoparticles using in situ FT-IR spectroscopic study