Synergistic Effects of Water and SO2 on Degradation of MIL-125 in the Presence of Acid Gases

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• 作者：William P. Mounfield III ; Chu Han ; Simon H. Pang ; Uma Tumuluri ; Yang Jiao ; Souryadeep Bhattacharyya ; Michael R. Dutzer ; Sankar Nair ; Zili Wu ; Ryan P. Lively ; David S. Sholl ; Krista S. Walton
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：December 8, 2016
• 年：2016
• 卷：120
• 期：48
• 页码：27230-27240
• 全文大小：708K
• ISSN：1932-7455

文摘

The behavior of metal–organic frameworks (MOFs) in the presence of acid gases may be decisive in their suitability for industrial applications. In this study, MIL-125 and MIL-125-NH₂ were investigated with SO₂ exposure in dry, humid, and aqueous environments. MIL-125 was found to be unstable in both humid and aqueous acidic environments, while MIL-125-NH₂ was stable under these exposure conditions, showing no change in textural properties or visual degradation, as observed through SEM. Both materials were stable in the presence of water and dry SO₂, suggesting that the reaction of these molecules to form an acidic species is likely a key factor in the degradation of MIL-125. In situ IR experiments confirmed the presence of sulfite species, supporting the hypothesis that the presence of an acidic sulfur species likely leads to the degradation of the MIL-125 structure. Computational investigation of several potential reaction mechanisms in MIL-125 indicated reactions involving the bisulfite ion are favored over reactions with water or SO₂. DFT simulations support the observation that MIL-125-NH₂ is stable in humid conditions, as all reactions are less favorable with the functionalized framework compared to the unfunctionalized framework. This combined experimental and computational study advances the fundamental understanding of MOF degradation mechanisms during acid gas exposure.