期刊
CHEMISTRY-A EUROPEAN JOURNAL
卷 24, 期 40, 页码 10136-10145出版社
WILEY-V C H VERLAG GMBH
DOI: 10.1002/chem.201800930
关键词
carbon dioxide fixation; density functional calculations; NMR spectroscopy; organic-inorganic hybrid composites; solid-state structures
资金
- Fundacao para a Ciencia e a Tecnologia (FCT) [PTDC/QEQ-QAN/6373/2014, POCI-01-0247-FEDER-007678]
- FCT/MEC - FEDER under the PT2020 Partnership Agreement [POCI-01-0145-FEDER-0076791, UID/CTM/50011/2013, UID/MULTI/00612/2013, UID/ECI/04028/2013]
- Slovenian Research Agency [P1-0021]
- Investigador FCT program
- Portuguese NMR Network (RNRMN)
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.
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