Probing the nature and local structure of phosphonic acid groups functionalized in mesoporous silica SBA-15

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Title:	Probing the nature and local structure of phosphonic acid groups functionalized in mesoporous silica SBA-15
Authors:	蔡惠旭;Pan, Yu-Chi;Gavin Tsai, Hui-Hsu;Jiang, Jyh-Chiang;Kao, Chia-Chun;Sung, Tsai-Lung;Chiu, Po-Jui;Saikia, Diganta;Chang, Jen-Hsuan;Kao, Hsien-Ming
Contributors:	理學院化學學系
Keywords:	C: Nanops and Nanostructures;Condensed matter: structure, mechanical and thermal properties;Exact sciences and technology;Organic compounds;Physics;Structure of solids and liquids;crystallography;Structure of specific crystalline solids
Date:	2012-01-19
Issue Date:	2026-04-21 13:53:01 (UTC+8)
Publisher:	American Chemical Society;Columbus, OH: American Chemical Society
Abstract:	摘要： Well-ordered mesoporous silicas SBA-15 functionalized with variable contents of phosphonic acid groups (up to 25 mol % based on silica) have successfully synthesized via cocondensation of tetraethoxysilane (TEOS) and diethylphosphatoethyltriethoxysilane (PETES) using triblock copolymer Pluronic P123 as the structure-directing agent under acidic conditions. The status and local structures of the phosphonic functional groups are investigated by extensive multinuclear solid-state NMR studies. Solid-state 13C and 31P NMR results reveal that phosphonic ester moieties are obtained for the as-synthesized samples and for the samples subjected to template removal by concentrated H2SO4. The generation of phosphonic acid groups can be accomplished by dealkylation reaction via treating the template-extracted samples with concentrated HCl. Two distinct local environments for the phosphorus sites of phosphonic acid groups have been observed at 32 and 22 ppm in the 31P magic angle spinning (MAS) NMR spectra. The relative ratio between these two species is not sensitive to the loading of phosphonic acid groups incorporated, but it strongly depends on the moisture present in the materials. The PO3H2 groups forming the hydrogen bonds with the nearby Q3 Si–OH are the major species responsible for the 22 ppm peak based on the results of 1H → 31P → 29Si double cross-polarization NMR experiments and density functional theory calculations (DFT). Of particular interest is that 29Si{31P} rotational echo double resonance (REDOR) NMR experiments are utilized to measure 31P–29Si distances between the phosphorus site in the functional groups and the silicon sites in the silica framework. A 29Si–31P distance of 5.0 Å is obtained for the phosphorus site in the functional groups to the silicon site of the Q3 species for the as-synthesized sample. A reasonable fitting to the REDOR data for the acidified sample can also be achievable by assuming the presence of different structural units, whose 31P–29Si distance information is referred from the DFT results. The combination of REDOR and 1H → 31P → 29Si double cross-polarization NMR measurements and the DFT calculations allow one to gain deeper insights into the local environments of the organic groups functionalized in mesoporous silica materials. 其他題名： J. Phys. Chem. C 出版者： Columbus, OH: American Chemical Society 出版日期： 2012-01-19 出處： Journal of physical chemistry. C, 2012-01, Vol.116 (2), p.1658-1669 資源來源： American Chemical Society Journals 版權： Copyright © 2011 American Chemical Society 版權： 2015 INIST-CNRS 識別號： ISSN: 1932-7447 識別號： EISSN: 1932-7455 識別號： DOI: 10.1021/jp206017j
Appears in Collections:	[Department of Chemistry] journal & Dissertation

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