Porous adsorbents are a promising class of materials for the direct air capture of CO₂ (DAC). Practical implementation of adsorption-based DAC requires adsorbents that can be used for thousands of adsorption–desorption cycles without significant degradation. We examined the potential degradation of adsorbents by a mechanism that appears to have not been considered previously, namely, ozonolysis by trace levels of ozone from ambient air. We focused on amine-appended metal–organic frameworks, specifically amine-functionalized Mg₂(dobpdc), as a representative DAC adsorbent. Estimates based on the number of amine sites in these adsorbents and the ozone concentration in air suggest that degradation by ozone may be relevant over thousands of adsorption–desorption cycles if reactions with adsorbed ozone are fast. We used density functional theory calculations to estimate reaction rates for amine groups and carbon–carbon double bonds in amine-functionalized Mg₂(dobpdc).

中文翻译：

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通过臭氧分解直接捕获空气的吸附剂的长期降解评估


多孔吸附剂是一类很有前途的材料，可用于直接空气捕获 CO₂ （DAC）。基于吸附的 DAC 的实际实施要求吸附剂可用于数千次吸附-解吸循环而不会发生显著降解。我们研究了吸附剂通过一种以前似乎没有考虑过的机制的潜在降解，即通过环境空气中痕量臭氧的臭氧分解。我们专注于胺附加的金属有机框架，特别是胺官能化的 Mg₂ （dobpdc），作为代表性的 DAC 吸附剂。基于这些吸附剂中胺位的数量和空气中的臭氧浓度的估计表明，如果与吸附的臭氧反应很快，那么臭氧的降解可能在数千个吸附-解吸循环中相关。我们使用密度泛函理论计算来估计胺官能化 Mg₂ （dobpdc） 中胺基和碳-碳双键的反应速率。