Rimsza Jessica M, Duwal Sakun, Root Harrison D
Geochemistry Department, Sandia National Laboratories, Albuquerque, New Mexico 87123, United States.
Dynamic Material Properties Department, Sandia National Laboratories, Albuquerque, New Mexico 87123, United States.
ACS Omega. 2024 Jun 19;9(26):29025-29034. doi: 10.1021/acsomega.4c04186. eCollection 2024 Jul 2.
Efficient carbon capture requires engineered porous systems that selectively capture CO and have low energy regeneration pathways. Porous liquids (PLs), solvent-based systems containing permanent porosity through the incorporation of a porous host, increase the CO adsorption capacity. A proposed mechanism of PL regeneration is the application of isostatic pressure in which the dissolved nanoporous host is compressed to alter the stability of gases in the internal pore. This regeneration mechanism relies on the flexibility of the porous host, which can be evaluated through molecular simulations. Here, the flexibility of porous organic cages (POCs) as representative porous hosts was evaluated, during which pore windows decreased by 10-40% at 6 GPa. POCs with sterically smaller functional groups, such as the 1,2-ethane in the CC1 POC resulted in greater imine cage flexibility relative to those with sterically larger functional groups, such as the cyclohexane in the CC3 POC that protected the imine cage from the application of pressure. Structural changes in the POC also caused CO adsorption to be thermodynamically unfavorable beginning at ∼2.2 GPa in the CC1 POC, ∼1.1 GPa in the CC3 POC, and ∼1.0 GPa in the CC13 POC, indicating that the CO would be expelled from the POC at or above these pressures. Energy barriers for CO desorption from inside the POC varied based on the geometry of the pore window and all the POCs had at least one pore window with a sufficiently low energy barrier to allow for CO desorption under ambient temperatures. The results identified that flexibility of the CC1, CC3, or CC13 POCs under compression can result in the expulsion of captured gas molecules.
高效的碳捕获需要经过设计的多孔系统，该系统能够选择性地捕获二氧化碳并具有低能量再生途径。多孔液体（PLs）是一种通过引入多孔主体而具有永久孔隙率的溶剂基体系，它能提高二氧化碳的吸附能力。一种提出的PL再生机制是施加等静压，在这种情况下，溶解的纳米多孔主体被压缩，以改变内部孔隙中气体的稳定性。这种再生机制依赖于多孔主体的柔韧性，而这可以通过分子模拟来评估。在此，对作为代表性多孔主体的多孔有机笼（POCs）的柔韧性进行了评估，在此过程中，在6吉帕的压力下，孔窗缩小了10%至40%。具有空间位阻较小的官能团（如CC1 POC中的1,2 - 乙烷）的POCs相对于具有空间位阻较大的官能团（如CC3 POC中的环己烷，它能保护亚胺笼免受压力影响）的POCs，其亚胺笼具有更大的柔韧性。POC的结构变化还导致在CC1 POC中约2.2吉帕、CC3 POC中约1.1吉帕以及CC13 POC中约1.0吉帕以上时，二氧化碳吸附在热力学上变得不利，这表明在这些压力及以上时，二氧化碳将从POC中被排出。从POC内部解吸二氧化碳的能垒因孔窗的几何形状而异，并且所有的POCs都至少有一个孔窗，其能垒足够低，以允许在环境温度下进行二氧化碳解吸。结果表明，CC1、CC3或CC13 POCs在压缩下的柔韧性会导致捕获的气体分子被排出。
