Facile determination of the degree of modification of ordered mesoporous silica by liquid phase NMR

A new and facile analytical method to assess the amount of organic groups that are linked to the surface of ordered mesoporous silica (OMS) is proposed. The quantity of adsorbed compounds on OMS could also be studied as well as the amount of silanol groups within certain limits. A small amount of the OMS of interest is dissolved in a small volume of NaOD in D2O and a defined amount of a reference compound is added. Subsequently, the solution is analyzed by liquid phase NMR. The degree of modification can be inferred quantitatively from the H-1-spectrum. The high accuracy and the analysis time compared to solid-state H-1 and C-13 MAS NMR are the main benefits of this method. The findings are correlated with XRD, N-2-sorption, DRIFTS, TGA and MAS NMR data.