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Kinetic Influence of Siliceous Reactions on Structure Formation of Mesoporous Silica Formed via the Co-Structure Directing Agent Route

Lin, Ruiyu LU ; Carlström, Göran LU ; Dat Pham, Quoc; Anderson, Michael W.; Topgaard, Daniel LU ; Edler, Karen J. LU and Alfredsson, Viveka LU (2016) In Journal of Physical Chemistry C 120(7). p.3814-3821
Abstract

We investigate the mechanism responsible for the formation of mesoporous silica formed with the so-called costructure directing agent (CSDA) route. The synthesis relies on the interaction between silica source (tetraethylorthosilicate), cationic surfactant (C18H37N+(CH3)2(CH2)3N+(CH3)3Br2), and CSDA (carboxyethylsilanetriol), which results in a material functionalized with carboxylic groups. Depending on the concentration of HCl in the synthesis, the structure is defined by Fm3¯m (at high pH) and by Fd3¯m (at low pH), with a gradual transition in the intermediate pH range. Here, we aim at finding the origin for the... (More)

We investigate the mechanism responsible for the formation of mesoporous silica formed with the so-called costructure directing agent (CSDA) route. The synthesis relies on the interaction between silica source (tetraethylorthosilicate), cationic surfactant (C18H37N+(CH3)2(CH2)3N+(CH3)3Br2), and CSDA (carboxyethylsilanetriol), which results in a material functionalized with carboxylic groups. Depending on the concentration of HCl in the synthesis, the structure is defined by Fm3¯m (at high pH) and by Fd3¯m (at low pH), with a gradual transition in the intermediate pH range. Here, we aim at finding the origin for the structural change triggered by pH and investigate the effects of the hydrolysis of the silica source on the overall kinetics of the synthesis. A fast process results in Fm3¯m, regardless of pH, and a slow process results in Fd3¯m. The hydrolysis step is the important structural control parameter. We studied the cross-linking of silica and CSDA using 29Si NMR. The cross-linking is similar for the two structures, and possibly the Fd3¯m structure contains slightly more CSDA. 13C PT ssNMR was used to investigate the surfactant mobility/rigidity during the synthesis. The rigidity of the Fm3¯m is established much faster than that of the Fd3¯m.

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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Physical Chemistry C
volume
120
issue
7
pages
8 pages
publisher
The American Chemical Society
external identifiers
  • scopus:84959432922
  • wos:000371104400028
ISSN
1932-7447
DOI
10.1021/acs.jpcc.5b11348
language
English
LU publication?
yes
id
c0bea2e2-3aca-42c8-9de9-c4aa6d414873
date added to LUP
2016-07-14 12:45:57
date last changed
2017-01-01 08:30:29
@article{c0bea2e2-3aca-42c8-9de9-c4aa6d414873,
  abstract     = {<p>We investigate the mechanism responsible for the formation of mesoporous silica formed with the so-called costructure directing agent (CSDA) route. The synthesis relies on the interaction between silica source (tetraethylorthosilicate), cationic surfactant (C<sub>18</sub>H<sub>37</sub>N<sup>+</sup>(CH<sub>3</sub>)<sub>2</sub>(CH<sub>2</sub>)<sub>3</sub>N<sup>+</sup>(CH<sub>3</sub>)<sub>3</sub>Br<sub>2</sub>), and CSDA (carboxyethylsilanetriol), which results in a material functionalized with carboxylic groups. Depending on the concentration of HCl in the synthesis, the structure is defined by Fm3¯m (at high pH) and by Fd3¯m (at low pH), with a gradual transition in the intermediate pH range. Here, we aim at finding the origin for the structural change triggered by pH and investigate the effects of the hydrolysis of the silica source on the overall kinetics of the synthesis. A fast process results in Fm3¯m, regardless of pH, and a slow process results in Fd3¯m. The hydrolysis step is the important structural control parameter. We studied the cross-linking of silica and CSDA using <sup>29</sup>Si NMR. The cross-linking is similar for the two structures, and possibly the Fd3¯m structure contains slightly more CSDA. <sup>13</sup>C PT ssNMR was used to investigate the surfactant mobility/rigidity during the synthesis. The rigidity of the Fm3¯m is established much faster than that of the Fd3¯m.</p>},
  author       = {Lin, Ruiyu and Carlström, Göran and Dat Pham, Quoc and Anderson, Michael W. and Topgaard, Daniel and Edler, Karen J. and Alfredsson, Viveka},
  issn         = {1932-7447},
  language     = {eng},
  month        = {02},
  number       = {7},
  pages        = {3814--3821},
  publisher    = {The American Chemical Society},
  series       = {Journal of Physical Chemistry C},
  title        = {Kinetic Influence of Siliceous Reactions on Structure Formation of Mesoporous Silica Formed via the Co-Structure Directing Agent Route},
  url          = {http://dx.doi.org/10.1021/acs.jpcc.5b11348},
  volume       = {120},
  year         = {2016},
}