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Elucidation of Surface Species through in Situ FTIR Spectroscopy of Carbon Dioxide Adsorption on Amine‐Grafted SBA‐15
Author(s) -
Foo Guo Shiou,
Lee Jason J.,
Chen ChiaHsin,
Hayes Sophia E.,
Sievers Carsten,
Jones Christopher W.
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201600809
Subject(s) - chemistry , fourier transform infrared spectroscopy , carbamic acid , adsorption , bicarbonate , amine gas treating , mesoporous material , infrared spectroscopy , inorganic chemistry , mesoporous silica , primary (astronomy) , nuclear chemistry , organic chemistry , catalysis , chemical engineering , physics , astronomy , engineering
Abstract The nature of the surface species formed through the adsorption of CO 2 on amine‐grafted mesoporous silica is investigated through in situ FTIR spectroscopy with the aid of 15 N dynamic nuclear polarization (DNP) and 13 C NMR spectroscopy. Primary, secondary, and tertiary amines are functionalized onto a mesoporous SBA‐15 silica. Both isotopically labeled 13 CO 2 and natural‐abundance CO 2 are used for accurate FTIR peak assignments, which are compared with assignments reported previously. The results support the formation of monomeric and dimeric carbamic acid species on secondary amines that are stabilized differently to the monocarbamic acid species on primary amines. Furthermore, the results from isotopically labelled 13 CO 2 experiments suggest the existence of two carbamate species on primary amines, whereas only one species is observed predominantly on secondary amines. The analysis of the IR peak intensities and frequencies indicate that the second carbamate species on primary amines is probably more asymmetric in nature and forms in a relatively smaller amount. Only the formation of bicarbonate ions at a low concentration is observed on tertiary amines; therefore, physisorbed water on the surface plays a role in the hydrolysis of CO 2 even if water is not added intentionally and dry gases are used. This suggests that a small amount of bicarbonate ions could be expected to form on primary and secondary amines, which are more hydrophilic than tertiary amines, and these low concentration species are difficult to observe on such samples.

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