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Title: Mechanism of Preferential Adsorption of SO 2 into Two Microporous Paddle Wheel Frameworks M(bdc)(ted) 0.5

The adsorption of a corrosive gas, SO 2, into microporous pillared paddle-wheel frameworks M(bdc)(ted) 0.5 [M = Ni, , Zn; bdc = 1,4-benzenedicarboxylate; ted=triethylenediamine] is studied by volumetric adsorption measurements and a combination of in-situ infrared spectroscopy and ab initio density functional theory (DFT) calculations. The uptake of SO 2 in M(bdc)(ted) 0.5 at room temperature is quite significant, 9.966 mol kg -1(63.8%) at room temperature/1.132 bar, which represents the highest SO 2 uptake so far observed. Two different adsorption species are identified by infrared spectroscopy: one is typical physisorbed SO 2 species, characterized by a modest red shift of S-O stretching bands (36 cm -1 for νas and 7 cm -1 for νs); the other characterized by adsorption bands at 1242 and 1105cm -1 and by a much higher (~150°C) temperature to completely remove. Theoretical calculations including van der Waals interactions (based on vdW-DF) indicate that the adsorption geometry of SO 2 involves one molecule bonding of its sulfur atom to the oxygen atom of the paddle-wheel building unit and its two oxygen atoms to the C-H groups of the organic linkers by formation of hydrogen bonds. Such a configuration results in a large distortion of benzene rings, whichmore » is consistent with the experimentally observed shift of the ring deformation mode. The simulated frequency shift of the SO 2 stretching bands by vdW-DF is in excellent agreement with spectroscopically measured value of physisorbed SO 2. The IR absorptions at 1242 and 1105 cm -1 also suggest a stronger adsorption configuration, previously observed in SO 4-like species involving two oxygen atoms of the paddle wheel building units. The adsorption configurations of SO 2 into M(bdc)(ted) 0.5 derived by infrared spectroscopy and vdW-DF calculations provide the understanding necessary to develop industrial processes for SO 2 removal using microporous paddle-wheel frameworks materials.« less
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Publication Date:
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Report Number(s):
Journal ID: ISSN 0897-4756; KC0203020
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Resource Type:
Journal Article
Resource Relation:
Journal Name: Chemistry of Materials; Journal Volume: 25; Journal Issue: 23
American Chemical Society (ACS)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
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Country of Publication:
United States