Discerning molecular-level CO2 adsorption behavior in amine-modified sorbents within a controlled CO2/H2O environment towards direct air capture,Journal of Materials Chemistry A

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Discerning molecular-level CO2 adsorption behavior in amine-modified sorbents within a controlled CO2/H2O environment towards direct air capture
Journal of Materials Chemistry A ( IF 10.7 ) Pub Date : 2024-09-04 , DOI: 10.1039/d4ta05578k
Ah-Young Song _{1,

2} , John Young ₃ , Jieyu Wang ₁ , Sophia N. Fricke ₁ , Katia Piscina ₃ , Raynald Giovine ₄ , Susana Garcia ₃ , Mijndert van der Spek ₃ , Jeffrey A. Reimer _{1,

2}

Affiliation

Sorbents designed for direct air capture (DAC) play a crucial role in the pursuit of achieving net-zero carbon dioxide emissions. This study elucidates CO₂ adsorption from dilute, humidified CO₂ streams onto an amine-modified benchmark DAC adsorbent via solid-state NMR spectroscopy. Various NMR techniques, including 1D ¹H MAS, ¹³C MAS, 2D ¹H–¹³C HETCOR NMR, and ¹H R₂ and R_1ρ relaxometry reveal the impact of CO₂ partial pressure and H₂O on CO₂ adsorption behavior. We find that CO₂ concentration governs the stepwise formation of ammonium carbamate, carbamic acid, and physisorbed CO₂, where relative humidity (RH) at a desired low (<400 ppm) CO₂ loading affects total CO₂ uptake. The relaxation studies reveal the cooperative or competitive nature of H₂O–CO₂ sorption in CO₂-dilute humid gas, and in particular polymer swelling upon humidification. From those results, we demonstrate that the observed absorption capacity enhancement by humidity is caused by pore opening due to sorbent swelling, and not by bicarbonate formation. This NMR-discerned speciation provides insights into sorption behavior at different RHs in dilute CO₂ gas streams, simulating real-world atmospheric conditions, and governs the design of efficient and adaptable material-process combinations for solid sorbent DAC.

中文翻译：

在受控的 CO2/H2O 环境中识别胺改性吸附剂的分子级 CO2 吸附行为，以直接捕获空气

专为直接空气捕获 (DAC) 设计的吸附剂在实现二氧化碳净零排放方面发挥着至关重要的作用。本研究通过固态核磁共振波谱阐明了胺改性基准 DAC 吸附剂上稀释、加湿的 CO ₂流中的 CO ₂吸附。各种NMR技术，包括1D ¹ H MAS、 ¹³ C MAS、2D ¹ H– ¹³ C HETCOR NMR以及¹ H R ₂和R _1ρ弛豫测量揭示了CO ₂分压和H ₂ O对CO ₂吸附行为的影响。我们发现CO ₂浓度控制着氨基甲酸铵、氨基甲酸和物理吸附CO ₂的逐步形成，其中所需的低(<400 ppm) CO ₂负载下的相对湿度(RH)影响总CO ₂吸收。弛豫研究揭示了CO ₂稀湿气体中H ₂ O-CO ₂吸附的合作或竞争性质，特别是加湿时聚合物的膨胀。从这些结果中，我们证明观察到的湿度吸收能力增强是由吸附剂膨胀导致的孔张开引起的，而不是由碳酸氢盐的形成引起的。这种通过 NMR 识别的形态可以深入了解稀 CO ₂气流中不同相对湿度下的吸附行为，模拟真实的大气条件，并控制固体吸附剂 DAC 的高效且适应性强的材料工艺组合的设计。

更新日期：2024-09-05

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