Low field 1H NMR characterization of mesoporous silica MCM-41 and SBA-15 filled with different amount of water

• Low field 1H NMR characterization of MCM-41 and SBA-15 filled with water.
• The precision and potential of NMR method in determining pore size distributions.
• The T1/T2 ratio for water molecules was confirmed to be higher for SBA-15.
• The obtained value of T1/T2 is much higher than shown in earlier reports for water.
• Estimation of hydroxylation rate for mesopores partially covered by water molecules.

The low field 1H NMR characterization of pure mesoporous silica materials – MCM-41 and SBA-15 as a function of water content is presented. The values of surface relaxivities for both materials were estimated in order to compare pore size distributions obtained from relaxation spectra and N2 adsorption measurements. This comparison led to differentiation between contributions from ‘inner-bulk’ water molecules in pores and these from the surface. The T1/T2 ratio reflecting the strength of interaction between water molecules and the mesoporous silica surface was confirmed to be higher for SBA-15. Measurements for a mesopore surface partially covered by water provided quantitative information on the hydroxylation rate.

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