Water-filled MCM-41 characterized by double-quantum-filtered H-2 NMR spectral analysis

The dynamics of water molecules confined in adsorbed layers of siliceous MC M-41 with a pore diameter of 2.8 nm is investigated at 230 K by deuteron nu clear magnetic resonance (NMR) relaxation studies including line shapes of the T-1 process and double quantum filtered (DQF) spectral analyses. H-2 DQ F NMR is a particularly sensitive tool for the determination of the adsorba te dynamics resulting from residual quadrupolar interaction due to the loca l order. The amount of monolayer water is determined. The monolayer water i s composed of two different water components characterized by water, with i sotropic reorientational motions, exchanging with water displaying a solidl ike spectrum with 4 kHz edge splitting. One may expect that the latter wate r is situated on surface sites in MCM-41. The restricted wobbling motion of the D-O bond is used to describe its dynamics which is one order of magnit ude slower than the isotropic reorientational motion. The order parameter, the motional correlation time, and the exchange rate thus determined provid e useful information on the structure and the adsorptive properties of the mesoporous system.