Understanding the Vibrational and Electronic Features of Ti(IV) Sites in Mesoporous Silicas by Integrated Ab Initio and Spectroscopic Investigations

Gloria Tabacchi, Enrica Gianotti, Ettore Fois, Gianmario Martra, Leonardo Marchese, Salvatore Coluccia, Aldo Gamba
  • The Journal of Physical Chemistry C, April 2007, American Chemical Society (ACS)
  • DOI: 10.1021/jp0665168

Titanium sites in mesoporous materials

What is it about?

Titanium-containing mesoporous silicas are technologically important materials, especially in the field of catalysis. Their amorphous silica matrix, however, makes it particularly difficult to link the appealing properties of these catalysts to the structure of the active site. This difficult problem might be solved by a combination of different experimental techniques with theoretical modeling.

Why is it important?

This integrated experimental and theoretical study explains the experimentally detected vibrational and optical properties of titanium-containing mesoporous silicas in terms of the microscopic structure of the catalytically active sites, i.e., the titanium centers. The most important general result of this study is that the chemical environment of the active site plays a key role in determining the observed properties. For example, contrary to what expected on the basis of previous literature, we found that the chemical environment of the hydroxyl group affects the -OH stretching frequency more than the type of tetrahedral cation (Ti or Si) to which the hydroxyl group is bonded. Similarly, the electronic excitation of the Ti sites are strictly dependent on the different local environment of the sites.

Perspectives

Gloria Tabacchi
university of insubria

This is a clear example of how integrated experimental and simulation approaches could be a successful strategy to correlate the observed properties of different types of Ti(IV) centers with the microscopic structure of the active site. A detailed knowledge of the structure of active sites is expecially important for materials like mesoporous silicas, for which structural data are particularly difficult to obtain because of their amorphous nature. For this reason, I think that this study is still timely and of interest for scientist working on mesoporous materials and on their many, diverse applications.

Read Publication

http://dx.doi.org/10.1021/jp0665168

The following have contributed to this page: Gloria Tabacchi