期刊
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
卷 140, 期 28, 页码 8648-8651出版社
AMER CHEMICAL SOC
DOI: 10.1021/jacs.8b04520
关键词
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资金
- Center for Understanding and Control of Acid Gas-Induced Evolution of Materials for Energy (UNCAGE-ME), an Energy Frontier Research Center - U.S. Department of Energy (US DOE), Office of Science, Basic Energy Sciences (BES) [DE-SC0012577]
- NSF [DMR-1644779, CHE-1229170]
- State of Florida
- NIH [S10 OD018519]
- Taiwan Ministry of Education
- NATIONAL INSTITUTE OF GENERAL MEDICAL SCIENCES [P41GM122698] Funding Source: NIH RePORTER
- OFFICE OF THE DIRECTOR, NATIONAL INSTITUTES OF HEALTH [S10OD018519] Funding Source: NIH RePORTER
- Division Of Chemistry [1229170] Funding Source: National Science Foundation
We have identified a hydrated bicarbonate formed by chemisorption of O-13(2) on both dimethylaminopropylsilane (DMAPS) and aminopropylsilane (APS) pendant molecules grafted on SEA-15 mesoporous silica. The most commonly used sequence in solid-state NMR, C-13 CPMAS, failed to detect bicarbonate in these solid amine sorbent samples; here, we have employed a Bloch decay (pulse-acquire) sequence (with H-1 decoupling) to detect such species. The water that is present contributes to the dynamic motion of the bicarbonate product, thwarting CPMAS but enabling direct C-13 detection by shortening the spin lattice relaxation time. Since solid-state NMR plays a major role in characterizing chemisorption reactions, these new insights that allow for the routine detection of previously elusive bicarbonate species (which are also challenging to observe in IR spectroscopy) represent an important advance. We note that employing this straightforward NMR technique can reveal the presence of bicarbonate that has often otherwise been overlooked, as demonstrated in APS, that has been thought to only contain adsorbed CO(2)as carbamate and carbamic acid species. As in other systems (e.g., proteins), dynamic species that sample multiple environments tend to broaden as their motion is frozen out. Here, we show two distinct bicarbonate species upon freezing, and coupling to different protons is shown through preliminary C-13-H-1 HETCOR measurements. This work demonstrates that bicarbonates have likely been formed in the presence of water but have gone unobserved by NMR due to the nature of the experiments most routinely employed, a perspective that will transform the way the sorption community will view CO2 capture by amines.
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