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 ¹⁷O 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 ¹⁷O 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.

二氧化碳捕获对于实现净零排放至关重要。设计改进的捕获材料的一个障碍是缺乏足够的工具来表征CO _{2 的}吸附方式。固态核磁共振（NMR）光谱是一种很有前景的CO ₂捕获探针，但区分不同的吸附产物仍然具有挑战性。在这里，我们对 22 种胺官能化金属有机骨架进行了全面的计算研究，发现¹⁷ O NMR 是 CO ₂捕获化学的强大探针，可以很好地区分氨基甲酸铵和氨基甲酸物种。计算结果得到了一系列 CO ₂负载框架上的¹⁷ O NMR 实验的支持，这些实验清楚地识别了氨基甲酸铵链的形成，并为混合氨基甲酸 - 氨基甲酸铵吸附模式提供了证据。我们进一步发现，在此类材料中，氨基甲酸的形成比之前认为的更为普遍。最后，我们表明我们的方法很容易适用于其他吸附剂，并为胺接枝二氧化硅中氨基甲酸铵的形成提供了支持。我们的工作为碳捕获化学研究铺平了道路，从而实现材料设计。