Revealing carbon capture chemistry with 17-oxygen NMR spectroscopy

Carbon dioxide capture is essential to achieve net-zero emissions. A hurdle to the design of improved capture materials is the lack of adequate tools to characterise how CO2 adsorbs. Solid-state nuclear magnetic resonance (NMR) spectroscopy is a promising probe of CO2 capture, but it remains challenging to distinguish different adsorption products. Here we perform a comprehensive computational investigation of 22 amine-functionalised metal-organic frameworks and discover that O-17 NMR is a powerful probe of CO2 capture chemistry that provides excellent differentiation of ammonium carbamate and carbamic acid species. The computational findings are supported by O-17 NMR experiments on a series of CO2-loaded frameworks that clearly identify ammonium carbamate chain formation and provide evidence for a mixed carbamic acid - ammonium carbamate adsorption mode. We further find that carbamic acid formation is more prevalent in this materials class than previously believed. Finally, we show that our methods are readily applicable to other adsorbents, and find support for ammonium carbamate formation in amine-grafted silicas. Our work paves the way for investigations of carbon capture chemistry that can enable materials design. A hurdle for designing improved capture materials is the lack of adequate tools to characterise how carbon dioxide adsorbs. Here the authors developed a method to understand how carbon dioxide is captured by materials. Their O-17 solid-state NMR spectroscopy reveals clear signatures for different capture products.

Automated summary

Carbon dioxide capture is essential for achieving net-zero emissions, but the lack of tools to characterize CO2 adsorption hinders the design of improved capture materials. In this study, the authors conducted computational investigations and performed experiments using O-17 solid-state NMR spectroscopy to successfully differentiate different CO2 capture products. Their findings pave the way for further research on carbon capture chemistry and materials design.