Apparent low surface areas in microporous SiO2-xerogels

Yulia Polevaya; Joshua Samuel; Michael Ottolenghi; David Avnir

doi:10.1007/BF00486712

Apparent low surface areas in microporous SiO₂-xerogels

Yulia Polevaya^*, Joshua Samuel, Michael Ottolenghi, David Avnir

^*Corresponding author for this work

Institute of Chemistry

Research output: Contribution to journal › Article › peer-review

27 Scopus citations

Abstract

Nitrogen adsorption at -195°C serves as routine method for the measurement of surface area of porous materials derived by sol-gel procedures. In a systematic study of the simultaneous effect of the pH and water-silane ratio of the starting solutions of preparation of SiO₂ xerogels on their surface areas, it was found that conditions of high acidity and low water/silane ratio result in microporous materials, the surface of which cannot be accessed by N₂ at -195°C, within a realistic time scale, but only by CO₂ at 0°C. In a typical result for TMOS/water/methanol = 1/2/3 at pH=1.0, the apparent N₂-area was zero, while the CO₂-area was 414 m²/gr. It is recommended to recheck apparent N₂-low surface areas of sol-gel materials by CO₂ adsorption. The behavior of pyrene-doped xerogels of this type is in agreement with the structural characterization by adsorption.

Original language	English
Pages (from-to)	65-70
Number of pages	6
Journal	Journal of Sol-Gel Science and Technology
Volume	5
Issue number	1
DOIs	https://doi.org/10.1007/BF00486712
State	Published - Jan 1995

Keywords

CO-adsorption
doped sol-gel
microporosity
pyrene
silica
TMOS

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title = "Apparent low surface areas in microporous SiO2-xerogels",

abstract = "Nitrogen adsorption at -195°C serves as routine method for the measurement of surface area of porous materials derived by sol-gel procedures. In a systematic study of the simultaneous effect of the pH and water-silane ratio of the starting solutions of preparation of SiO2 xerogels on their surface areas, it was found that conditions of high acidity and low water/silane ratio result in microporous materials, the surface of which cannot be accessed by N2 at -195°C, within a realistic time scale, but only by CO2 at 0°C. In a typical result for TMOS/water/methanol = 1/2/3 at pH=1.0, the apparent N2-area was zero, while the CO2-area was 414 m2/gr. It is recommended to recheck apparent N2-low surface areas of sol-gel materials by CO2 adsorption. The behavior of pyrene-doped xerogels of this type is in agreement with the structural characterization by adsorption.",

keywords = "CO-adsorption, doped sol-gel, microporosity, pyrene, silica, TMOS",

author = "Yulia Polevaya and Joshua Samuel and Michael Ottolenghi and David Avnir",

year = "1995",

month = jan,

doi = "10.1007/BF00486712",

language = "אנגלית",

volume = "5",

pages = "65--70",

journal = "Journal of Sol-Gel Science and Technology",

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publisher = "Springer Netherlands",

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T1 - Apparent low surface areas in microporous SiO2-xerogels

AU - Polevaya, Yulia

AU - Samuel, Joshua

AU - Ottolenghi, Michael

AU - Avnir, David

PY - 1995/1

Y1 - 1995/1

N2 - Nitrogen adsorption at -195°C serves as routine method for the measurement of surface area of porous materials derived by sol-gel procedures. In a systematic study of the simultaneous effect of the pH and water-silane ratio of the starting solutions of preparation of SiO2 xerogels on their surface areas, it was found that conditions of high acidity and low water/silane ratio result in microporous materials, the surface of which cannot be accessed by N2 at -195°C, within a realistic time scale, but only by CO2 at 0°C. In a typical result for TMOS/water/methanol = 1/2/3 at pH=1.0, the apparent N2-area was zero, while the CO2-area was 414 m2/gr. It is recommended to recheck apparent N2-low surface areas of sol-gel materials by CO2 adsorption. The behavior of pyrene-doped xerogels of this type is in agreement with the structural characterization by adsorption.

AB - Nitrogen adsorption at -195°C serves as routine method for the measurement of surface area of porous materials derived by sol-gel procedures. In a systematic study of the simultaneous effect of the pH and water-silane ratio of the starting solutions of preparation of SiO2 xerogels on their surface areas, it was found that conditions of high acidity and low water/silane ratio result in microporous materials, the surface of which cannot be accessed by N2 at -195°C, within a realistic time scale, but only by CO2 at 0°C. In a typical result for TMOS/water/methanol = 1/2/3 at pH=1.0, the apparent N2-area was zero, while the CO2-area was 414 m2/gr. It is recommended to recheck apparent N2-low surface areas of sol-gel materials by CO2 adsorption. The behavior of pyrene-doped xerogels of this type is in agreement with the structural characterization by adsorption.

KW - CO-adsorption

KW - doped sol-gel

KW - microporosity

KW - pyrene

KW - silica

KW - TMOS

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IS - 1

ER -

Apparent low surface areas in microporous SiO₂-xerogels

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Keywords

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