Title
The impact of framework organic functional groups on the hydrophobicity and overall stability of mesoporous silica materialsThe impact of framework organic functional groups on the hydrophobicity and overall stability of mesoporous silica materials
Author
Faculty/Department
Faculty of Sciences. Chemistry
Research group
Laboratory of adsorption and catalysis
Publication type
article
Publication
Lausanne,
Subject
Physics
Chemistry
Source (journal)
Materials chemistry and physics. - Lausanne, 1983, currens
Volume/pages
132(2012):2/3, p. 1077-1088
ISSN
0254-0584
ISI
000301083800123
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
The hydrothermal, mechanical and chemical stability of various mesoporous materials have been studied in detail, using X-ray diffraction and nitrogen sorption. Pure siliceous nanoporous powders (MCM-41 and SBA-15) are evaluated against their hybrid counterparts; namely 2 types of periodic mesoporous organosilicas (benzene and ethane bridged PMOs) and an organosilane grafted MCM-41 material. In primary tests, the stability of the hybrid materials is found to be superior compared to that of the pure siliceous ones. The stability of the materials was correlated to their hydrophobicity via immersion calorimetry, applied for the first time in this context. Based on these results, a clear correlation between the hydrophobicity of a material and its stability has been revealed. In addition, with 29Si-MAS-NMR and vacuum experiments, the mechanism of the structural deterioration in the three different stability treatments could be unambiguously identified as the hydrolyzation of the siloxane bonds. The homogeneity of the hydrophobic groups throughout the entire network was found to be of great importance, irrespective of the hydrophobic nature at the surface as determined by calorimetric measurements. The results reveal that the most stable material can withstand (a) a pressure of 740 MPa during 5 min, (b) a 2 h stirring in a 2 M NaOH solution and (c) a 3 day steaming treatment at 393 K.
E-info
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