Local structure changes of microporous titanosilicate ETS-10 upon acid treatment

In the present work, the local structure changes of microporous titanosilicate ETS-10 upon treatment with citric acid, phosphoric acid, and nitric acid were characterized using XRD, FTIR, Raman, XPS, DR-UV, Si-29 MAS NMR, and H-1-Si-29 CP MAS NMR techniques. The experimental results suggested that regardless of the nature of the acids, the replacement of alkali cations by protons altered the local structure of ETS-10 solid, including partial dissolution of the siliceous matrix and leaching of titanium species from the TiO6 chains. In the meantime, it was observed that the hexacoordinated Ti species of ETS-10 were changed to penta- and/or tetracoordinated ones, generating terminal TiOH groups, accounting for the observed enhancement of photodegradation activity of the acid-treated ETS-10 materials toward phenol compounds.