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Abstract Carbon dioxide capture technologies are set to play a vital role in mitigating the current climate crisis. Solid‐state17O NMR spectroscopy can provide key mechanistic insights that are crucial to effective sorbent development. In this work, we present the fundamental aspects and complexities for the study of hydroxide‐based CO2capture systems by17O NMR. We perform static density functional theory (DFT) NMR calculations to assign peaks for general hydroxide CO2capture products, finding that17O NMR can readily distinguish bicarbonate, carbonate and water species. However, in application to CO2binding in two test case hydroxide‐functionalised metal‐organic frameworks (MOFs) – MFU‐4l and KHCO3‐cyclodextrin‐MOF, we find that a dynamic treatment is necessary to obtain agreement between computational and experimental spectra. We therefore introduce a workflow that leverages machine‐learning force fields to capture dynamics across multiple chemical exchange regimes, providing a significant improvement on static DFT predictions. In MFU‐4l, we parameterise a two‐component dynamic motion of the bicarbonate motif involving a rapid carbonyl seesaw motion and intermediate hydroxyl proton hopping. For KHCO3‐CD‐MOF, we combined experimental and modelling approaches to propose a new mixed carbonate‐bicarbonate binding mechanism and thus, we open new avenues for the study and modelling of hydroxide‐based CO2capture materials by17O NMR.
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Carbon Dioxide Capture at Nucleophilic Hydroxide Sites in Oxidation‐Resistant Cyclodextrin‐Based Metal–Organic Frameworks**
Abstract Carbon capture and sequestration (CCS) from industrial point sources and direct air capture are necessary to combat global climate change. A particular challenge faced by amine‐based sorbents—the current leading technology—is poor stability towards O2. Here, we demonstrate that CO2chemisorption in γ‐cylodextrin‐based metal–organic frameworks (CD‐MOFs) occurs via HCO3−formation at nucleophilic OH−sites within the framework pores, rather than via previously proposed pathways. The new framework KHCO3CD‐MOF possesses rapid and high‐capacity CO2uptake, good thermal, oxidative, and cycling stabilities, and selective CO2capture under mixed gas conditions. Because of its low cost and performance under realistic conditions, KHCO3CD‐MOF is a promising new platform for CCS. More broadly, our work demonstrates that the encapsulation of reactive OH−sites within a porous framework represents a potentially general strategy for the design of oxidation‐resistant adsorbents for CO2capture.
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- Award ID(s):
- 1719875
- PAR ID:
- 10446405
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Angewandte Chemie International Edition
- Volume:
- 61
- Issue:
- 30
- ISSN:
- 1433-7851
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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