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Selectively Tuned Pore Condensation and Hysteresis Behavior in Mesoporous SBA-15 Silica: Correlating Material Synthesis to Advanced Gas Adsorption Analysis
journal contribution
posted on 2017-09-28, 00:00 authored by Rémy Guillet-Nicolas, François Bérubé, Matthias Thommes, Michael T. Janicke, Freddy KleitzRegarding the design
of SBA-15 silica, substantial efforts were
deployed in the past decade in order to understand the mechanism of
formation and the effects of the different synthesis conditions on
the structure and porosity of the resulting materials. However, better
insights into both the tailoring and the characterization of the pore
structure of such mesoporous materials are still needed in order to
enable the accurate control of adsorption and pore condensation properties
in SBA-15. For this, the influence of the synthesis parameters on
the properties of SBA-15 silica must be rationalized in terms of their
implications for pore architecture, i.e., pore structure and network
interconnectivity. Herein, it is demonstrated that pore condensation
and hysteresis behavior of inert gases in subcritical conditions confined
in ordered mesoporous SBA-15 silica can precisely be modulated as
a function of the synthesis parameters. Synthesis conditions were
found for generating SBA-15 samples that can be described entirely
as a pseudo one-dimensional (1-D) pore system (i.e., pore condensation
and hysteresis behavior are an intrinsic property of the liquid–vapor
transition in a finite volume, in agreement with the independent open
pore model). However, the data also revealed that distinct synthesis
conditions allow for the preparation of SBA-15 with pore condensation
properties affected by cooperative pore network effects, mimicking
the behavior observed for materials with a pristine three-dimensional (3-D) interconnected pore network topology, such
as KIT-6 silica. Therefore, this comprehensive study shows that SBA-15
should be best regarded as a family of solids with easily adjustable
porosity, ranging from corrugated and/or distorted pore systems to
highly interconnected networks of channels. The effect of each different
synthesis parameter on the final pore size of SBA-15 was carefully
monitored, and a threshold acid concentration range for optimal pore
size variation was found. In addition to substantial progress in the
SBA-15 synthesis, such in-depth characterization of a “model”
ordered mesoporous material coupled with advanced application of state-of-the-art
NLDFT methods is of prime importance both for the development of fundamental
research on the topic and for the applications requiring tailored
high surface area materials with selectively tuned pore structure.
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surface area materialsSBA -15 silicaSBA -15mesoporous SBA -15 silicathreshold acid concentration rangepore condensation propertiespore network topologySBA -15 samplessynthesis parameterspore network effectsNLDFTKIT -6 silicapore structurehysteresis behaviorSelectively Tuned Pore CondensationAdvanced Gas Adsorption Analysissynthesis conditionsSBA -15 synthesisMesoporous SBA -15 Silicapore size variationCorrelating Material Synthesis
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