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

The low field H-1 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 N-2 adsorption measurements. This comparison led to differentiation between contributions from 'inner-bulk' water molecules in pores and these from the surface. The T-1/T-2 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. (C) 2016 Elsevier Inc. All rights reserved.