Mishra Rashmi, Bhawnani Rajan, Sartape Rohan, Chauhan Rohit, Thorat Amey S, Singh Meenesh R, Shah Jindal K
School of Chemical Engineering, Oklahoma State University, 420 Engineering North, Stillwater, Oklahoma 74078, United States.
Department of Chemical Engineering, University of Illinois at Chicago, 929 W. Taylor St., Chicago, Illinois 60607, United States.
J Phys Chem B. 2024 Oct 17;128(41):10214-10229. doi: 10.1021/acs.jpcb.4c04509. Epub 2024 Oct 9.
Recent research and reviews on CO capture methods, along with advancements in industry, have highlighted high costs and energy-intensive nature as the primary limitations of conventional direct air capture and storage (DACS) methods. In response to these challenges, deep eutectic solvents (DESs) have emerged as promising absorbents due to their scalability, selectivity, and lower environmental impact compared to other absorbents. However, the molecular origins of their enhanced thermal stability and selectivity for DAC applications have not been explored before. Therefore, the current study focuses on a comprehensive investigation into the molecular interactions within an alkaline DES composed of potassium hydroxide (KOH) and ethylene glycol (EG). Combining Fourier transform infrared (FT-IR) and quantum chemical calculations, the study reports structural changes and intermolecular interactions induced in EG upon addition of KOH and its implications on CO capture. Experimental and computational spectroscopic studies confirm the presence of noncovalent interactions (hydrogen bonds) within both EG and the KOH-EG system and point to the aggregation of ions at higher KOH concentrations. Additionally, molecular electrostatic potential (MESP) surface analysis, natural bond orbital (NBO) analysis, quantum theory of atoms-in-molecules (QTAIM) analysis, and reduced density gradient-noncovalent interaction (RDG-NCI) plot analysis elucidate changes in polarizability, charge distribution, hydrogen bond types, noncovalent interactions, and interaction strengths, respectively. Evaluation of explicit and hybrid models assesses their effectiveness in representing intermolecular interactions. This research enhances our understanding of molecular interactions in the KOH-EG system, which are essential for both the absorption and desorption of CO. The study also aids in predicting and selecting DES components, optimizing their ratios with salts, and fine-tuning the properties of similar solvents and salts for enhanced CO capture efficiency.
近期关于二氧化碳捕集方法的研究与综述，以及工业领域的进展，都凸显了高成本和能源密集型特性是传统直接空气捕集与封存（DACS）方法的主要局限。为应对这些挑战，与其他吸收剂相比，深共晶溶剂（DESs）因其可扩展性、选择性和较低的环境影响，已成为颇具前景的吸收剂。然而，此前尚未探究过它们在DAC应用中增强的热稳定性和选择性的分子根源。因此，当前的研究聚焦于对由氢氧化钾（KOH）和乙二醇（EG）组成的碱性DES内部分子相互作用的全面研究。结合傅里叶变换红外光谱（FT-IR）和量子化学计算，该研究报告了添加KOH后EG中诱导的结构变化和分子间相互作用及其对二氧化碳捕集的影响。实验和计算光谱研究证实了EG以及KOH-EG体系中存在非共价相互作用（氢键），并指出在较高KOH浓度下离子的聚集。此外，分子静电势（MESP）表面分析、自然键轨道（NBO）分析、分子中的原子量子理论（QTAIM）分析以及密度降低梯度-非共价相互作用（RDG-NCI）图分析分别阐明了极化率、电荷分布、氢键类型、非共价相互作用和相互作用强度的变化。对显式模型和混合模型的评估评估了它们在表示分子间相互作用方面的有效性。这项研究增进了我们对KOH-EG体系中分子相互作用的理解，这对于二氧化碳的吸收和解吸都至关重要。该研究还有助于预测和选择DES组分，优化它们与盐的比例，并微调类似溶剂和盐的性质以提高二氧化碳捕集效率。
