高等学校化学学报

高等学校化学学报 ›› 2000, Vol. 21 ›› Issue (S1): 321.

• Chemistry in Materials Sciences • 上一篇    下一篇

NMR Study of Pore Surface and Size in a Mesoporous Material FSM-16

XIE Xiu-Lan1, HAYASHI Shigenobu2   

  1. 1. Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032, Marburg, Germany;
    2. National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
  • 出版日期:2000-12-31 发布日期:2000-12-31

NMR Study of Pore Surface and Size in a Mesoporous Material FSM-16

XIE Xiu-Lan1, HAYASHI Shigenobu2   

  1. 1. Fachbereich Chemie, Philipps-Universität Marburg, Hans-Meerwein-Strasse, 35032, Marburg, Germany;
    2. National Institute of Materials and Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
  • Online:2000-12-31 Published:2000-12-31

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摘要：

Surface structure, pore size distribution and pore wall thickness of a mesoporous material FSM-16 have been studied by X-ray powder diffraction (XRD), lH and 29Si MAS NMR and 1H liquid-state NMR, and by applying surface silylation as a probe. Concentrations of surface hydroxyl groups for FSM-16 are estimated from 29Si and 1H MAS NMR, which are about 3×l021 g-1, corresponding to approximately 3 nm-2. O2 molecules contribute to 29Si spin-lattice relaxation of Q2 and Q3 as well as Q4, suggesting thin wall thickness. 1H MAS NMR spectra indicate the presence of isolated and hydrogen-bonded hydroxyl groups. Both hydroxyl groups are silylated, where the silylated fraction is about 50%. The spatial distribution of surface hydroxyl groups is estimated from the line width in 1H static spectra. A rather homogeneous distribution is demonstrated in one of the samples. The sample with less homogeneous distribution has a larger affinity for moisture. Pore size and pore wall thickness were determined by 1H NMR measurements on water saturated FSM-16 samples, which are in good agreement with literature values obtained by N2 adsorption isotherms and transmission electron micrographs on a similar sample. In benzene saturated samples, a non-freezing surface layer of benzene is much thicker than that of water, which indicates a stronger interaction between benzene and the FSM-16 surface.

Abstract:

Surface structure, pore size distribution and pore wall thickness of a mesoporous material FSM-16 have been studied by X-ray powder diffraction (XRD), lH and 29Si MAS NMR and 1H liquid-state NMR, and by applying surface silylation as a probe. Concentrations of surface hydroxyl groups for FSM-16 are estimated from 29Si and 1H MAS NMR, which are about 3×l021 g-1, corresponding to approximately 3 nm-2. O2 molecules contribute to 29Si spin-lattice relaxation of Q2 and Q3 as well as Q4, suggesting thin wall thickness. 1H MAS NMR spectra indicate the presence of isolated and hydrogen-bonded hydroxyl groups. Both hydroxyl groups are silylated, where the silylated fraction is about 50%. The spatial distribution of surface hydroxyl groups is estimated from the line width in 1H static spectra. A rather homogeneous distribution is demonstrated in one of the samples. The sample with less homogeneous distribution has a larger affinity for moisture. Pore size and pore wall thickness were determined by 1H NMR measurements on water saturated FSM-16 samples, which are in good agreement with literature values obtained by N2 adsorption isotherms and transmission electron micrographs on a similar sample. In benzene saturated samples, a non-freezing surface layer of benzene is much thicker than that of water, which indicates a stronger interaction between benzene and the FSM-16 surface.

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