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

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