Solid-state NMR Studies of Phenethyl Sulfonic Acid-functionalized MCM−41

다국어 초록 (Multilingual Abstract)

A sulfonic acid–water–silanol system in SO3H-functionalized MCM−41 was investigated using solid-state nuclear magnetic resonance techniques. The proton exchange rate between a water molecule and a silanol group in the S−PE−MCM−41 was determined by analyzing the 1D proton spectra, the proton EXSY spectrum, and 2H spin-lattice relaxation data under various hydration levels. Two kinds of water-bounding sites were found in the S−PE−MCM−41: weakly and strongly bound sites. Over several hours, water molecules bound to the weakly bound sites at the low hydration level migrated to the strongly bound sites. At high temperature, the S−PE−MCM−41 easily lost water molecules weakly bound to the silanol, while the strongly bound water molecules survived. Water molecules that participated in the hydration of the phenethyl sulfonate were involved in the hydrogenbonded silanol mechanism of proton conductivity. This phenomenon contributes higher proton conductivity to the S−PE−MCM−41 by the cooperation of sulfonyl and silanol groups in the proton transfer process, even at higher temperature.

참고문헌 (Reference)

1 Hwang, D. W., "Water Dynamics on the Surface of MCM−41 via 2H Double Quantum Filtered NMR and Relaxation Measurements" 105 : 5713-, 2001

2 Yoshida, K., "Thermodynamic, structural, and dynamic properties of supercooled water confined in mesoporous MCM−41 studied with calorimetric, neutron diffraction, and neutron spin echo measurements" 129 : 054702-, 2008

3 Holmberg, B. A., "Synthesis and proton conductivity of sulfonic acid functionalized zeolite BEA nanocrystals" 80 : 347-, 2005

4 Mikhailenko, S. D., "Solid electrolyte properties of sulfonic acid functionalized mesostructured porous silica" 52 : 29-37, 2002

5 "Silica Channel-Embedded High-Temperature Anhydrous Proton-Exchange Membrane Fuel Cells" 10 : 10352-, 2020

6 Batamack, P., "Proton NMR studies on concentrated aqueous sulfuric acid solutions and Nafion-H" 49 : 129-136, 1997

7 McKeen, J. C., "Proton Conductivity of Acid-Functionalized Zeolite Beta, MCM−41, and MCM-48: Effect of Acid Strength" 20 : 5122-, 2008

8 McKeen, J. C., "Proton Conductivity in Sulfonic Acid-Functionalized Zeolite Beta: Effect of Hydroxyl Group" 20 : 3791-, 2008

9 Marschall, R., "Ordered Functionalized Silica Materials with High Proton Conductivity" 19 : 6401-, 2007

10 Butler, L. G., "Nuclear quadrupole coupling constants and hydrogen bonding. Molecular orbital study of oxygen-17 and deuterium field gradients in formaldehydewater hydrogen bonding" 103 : 6541-, 1981

11 Takahara, S., "Neutron scattering study on dynamics of water molecules in MCM−41. 2. Determination of translational diffusion coefficient" 109 : 11231-11239, 2005

12 Takahara, S., "Neutron Scattering Study on Dynamics of Water Molecules in MCM−41" 103 : 5814-, 1999

13 Marschall, R., "Nanoparticles of Mesoporous SO3H-Functionalized Si-MCM−41 with Superior Proton Conductivity" 5 : 854-859, 2009

14 Kobe, J. M., "Deuterium NMR Characterization of Broested Acid Sites and Silanol Species in Zeolites" 99 : 5485-, 1995