Premium
A Stand‐Alone Mesoporous Crystal Structure Model from in situ X‐ray Diffraction: Nitrogen Adsorption on 3 D Cagelike Mesoporous Silica SBA‐16
Author(s) -
Miyasaka Keiichi,
Hano Hiroko,
Kubota Yoshiki,
Lin Yangzheng,
Ryoo Ryong,
Takata Masaki,
Kitagawa Susumu,
Neimark Alexander V.,
Terasaki Osamu
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201201398
Subject(s) - mesoporous material , physisorption , materials science , mesoporous silica , porosity , adsorption , chemical engineering , desorption , microporous material , rietveld refinement , nitrogen , crystal structure , crystallography , composite material , chemistry , organic chemistry , engineering , catalysis
We present a modeling scheme to analyze cagelike silica mesoporous crystals based on in situ X‐ray diffraction (XRD) data collected during gas adsorption–desorption (physisorption) processes. Nitrogen physisorption on a silica mesoporous crystal of SBA‐16 was directly monitored by using synchrotron in situ powder XRD measurements conducted at SPring‐8. SBA‐16 is a well‐ordered mesoporous silica in which three‐dimensional interconnected cagelike primary mesopores are located at the body‐centered cubic lattice points. In addition, the surrounding silica matrix contains random microporous and mesoporous intrawall porosities that are significantly influential to the diffusion properties, and thus important to be quantified for this media. The in situ XRD data exhibits seven Bragg reflections throughout the measurements, and the present method allows one to obtain the maximal and stand‐alone information about the pore structure (for example, the mesopore size, the matrix density, the intrawall porosity, and pore surface roughness) together with the nitrogen film evolution in the primary mesopores and the intrawall pore‐filling in the silica matrix. We furthermore observe a macroscopic amount of nitrogen adsorbed assuming the density of the fluid, and confirm that the XRD “isotherm” recalculated from the analysis result is consistent with the conventional nitrogen isotherm on a semi‐quantitative level; however, these results suggest that the intrawall pores would have a greater contribution to the adsorption than considered based on the conventional isotherm analyses. The present method is readily extendable to any ordered mesopores wrapped by the wall matrix containing a certain intrawall porosity.