Detecting Proton Transfer in CO2 Species Chemisorbed on Amine-Modified Mesoporous Silicas by Using (CNMR)-C-13 Chemical Shift Anisotropy and Smart Control of Amine Surface Density
authors Cendak, T; Sequeira, L; Sardo, M; Valente, A; Pinto, ML; Mafra, L
nationality International
journal CHEMISTRY-A EUROPEAN JOURNAL
author keywords carbon dioxide fixation; density functional calculations; NMR spectroscopy; organic-inorganic hybrid composites; solid-state structures
keywords SOLID-STATE NMR; CARBON-DIOXIDE; OXIDE SURFACES; ADSORPTION; ADSORBENTS; COMPLEXES; CAPTURE; ACIDS; SPECTROSCOPY; ELEMENTS
abstract The wealth of site-selective structural information on CO2 speciation, obtained by spectroscopic techniques, is often hampered by the lack of easy-to-control synthetic routes. Herein, an alternative experimental protocol that relies on the high sensitivity of C-13 chemical shift anisotropy (CSA) tensors to proton transfer, is presented to unambiguously distinguish between ionic/charged and neutral CO2 species, formed upon adsorption of (CO2)-C-13 in amine-modified porous materials. Control of the surface amine spacing was achieved through the use of amine protecting groups during functionalisation prior to CO2 adsorption. This approach enabled the formation of either isolated or paired carbamate/carbamic acid species, providing a first experimental NMR proof towards the identification of both aggregation states. Computer modelling of surface CO2-amine adducts assisted the solid-state NMR assignments and validated various hydrogen-bond arrangements occurring upon formation of isolated/aggregated carbamic acid and alkylammonium carbamate ion species. This work extends the understanding of chemisorbed CO2 structures formed at pore surfaces and reveals structural insight about the protonation source responsible for the proton-transfer mechanism in such aggregates.
publisher WILEY-V C H VERLAG GMBH
issn 0947-6539
year published 2018
volume 24
issue 40
beginning page 10136
ending page 10145
digital object identifier (doi) 10.1002/chem.201800930
web of science category Chemistry, Multidisciplinary
subject category Chemistry
unique article identifier WOS:000439496600021
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journal impact factor 5.160
5 year journal impact factor 4.950
category normalized journal impact factor percentile 78.655
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