(425c) Addressing the Acid-Gas Stability and Material Evolution of MIL-101(Cr) Polyethyleneimine (PEI) Composites for Direct Air Capture (DAC) Under Different Conditions

The increase in concentration of carbon dioxide in the atmosphere above its preindustrial average level has been identified as one of the main contributors to climate change. At the start of the industrial era the CO₂ atmospheric concentration was as high as 280 ppm, and it has seen an increase up to 425 ppm at the start of the second quarter of 2024, which has triggered a series of climate effects that are not only detrimental for human activities but also for the survival of several animal and plant species. Carbon capture and sequestration (CCS) has been recognized as a necessary means to reduce this effect by either mitigating the CO₂ emissions to the atmosphere by capturing CO₂ at industrial sources or by attempting to reduce its concentration by capturing it from air (DAC). As one approach to achieve an efficient DAC of CO₂, material composites formed by a porous support as continuous phase and functionalized compounds such as amines as dispersed phase have been studied previously. An example of these materials is MIL-101(Cr) metal organic framework (MOF) impregnated with polyethyleneimine (PEI), which has shown a promising efficiency for direct air capture as well as good retainment of its capacity after adsorption/desorption cycling. However, it is not only important to study the performance of such materials for capturing CO₂, but it is also imperative to understand how these materials will be affected by contaminants found in air, such as SO₂, NO₂ and ground level O₃, which can vary in concentration depending on the season or the location where DAC modules are placed. Although some authors have reported the negative effect of exposure to acid gas species such as SO₂ and NO₂ over the CO₂ adsorption capacity of PEI supported on MIL-101(Cr, Mg), or strong interactions between SO₂ and amine groups on porous silica supported PEI, as an example, the information found on the literature about the effect of NO₂ over the stability of these materials and how their structure evolves as well as studies focusing on the influence of humidity and oxygen over the material stability during exposure to acid gases such as SO₂ and NO₂ is scarce. Moreover, data about the stability of these materials to ground level ozone (O₃) is non-existent. This work has focused on stability analysis of MOFs and MOF composites with promising performance for CO₂ DAC. Specifically, the goal is to study the effects of SO₂ and NO₂ through a design of experiments including factors such as humidity and the presence of oxygen the performance and structural stability of MIL-101(Cr)-PEI composites including a separate study focused on the effects of O₃ to understand material interactions with ground-level ozone. This presentation will discuss the influence that each individual acid gas species has over the stability of MIL-101(Cr)-PEI as well as the effects derived from having a combination of factors such as humidity, mixture of acid gas species and presence of oxygen.