Detecting Proton Transfer in CO2 Species Chemisorbed on Amine-Modified Mesoporous Silicas by Using 13C NMR Chemical Shift Anisotropy and Smart Control of Amine Surface Density(Article)

Chemistry - A European Journal

Journal Article

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 13C chemical shift anisotropy (CSA) tensors to proton transfer, is presented to unambiguously distinguish between ionic/charged and neutral CO2 species, formed upon adsorption of 13CO2 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. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

T. Čendak

L. Sequeira

M. Sardo

A. Valente

L. Mafra

Publication

Year of publication: 2018

Identifiers

ISSN: 09476539

Locators

DOI: 10.1002/chem.201800930

Alternative Titles