Characterisation of sol–gel derived titanium oxopolymers: first evidence of Ti–OH groups through 1H–17O CP NMR experiments

Abstract

Titanium oxo based xerogels obtained through hydrolysis of titanium tetrabutoxide in acidic conditions have been characterised through FTIR,¹⁷O MAS and ¹H–¹⁷O static CP NMR experiments. This latter technique allows the separation of the ¹⁷O NMR resonances corresponding to the protonated titanium oxo sites from those of the titanium oxo unprotonated sites, by varying the ¹Hto ¹⁷O contact time in a cross-polarisation sequence. These experiments clearly evidence the presence of Ti–OH groups. Their characteristic ¹⁷O NMR resonance, in titanium based xerogels, is located at about 200 ppm.