Mechanism of Preferential Adsorption of SO₂ into Two Microporous Paddle Wheel Frameworks M(bdc)(ted)_0.5

Journal Article · Sun Dec 01 23:00:00 EST 2013 · Chemistry of Materials

DOI:https://doi.org/10.1021/cm401270b· OSTI ID:1130266

Tan, Kui; Canepa, Pieremanuele; Gong, Qihan; Liu, Jian; Johnson, Daniel H.; Dyevoich, Allison A.; Thallapally, Praveen K.; Thonhauser, Timo; Li, Jing; Chabal, Y. J.

The adsorption of a corrosive gas, SO₂, 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 SO₂ 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 SO₂ uptake so far observed. Two different adsorption species are identified by infrared spectroscopy: one is typical physisorbed SO₂ 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 SO₂ 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, which is consistent with the experimentally observed shift of the ring deformation mode. The simulated frequency shift of the SO₂ stretching bands by vdW-DF is in excellent agreement with spectroscopically measured value of physisorbed SO₂. The IR absorptions at 1242 and 1105 cm^-1 also suggest a stronger adsorption configuration, previously observed in SO₄-like species involving two oxygen atoms of the paddle wheel building units. The adsorption configurations of SO₂ into M(bdc)(ted)_0.5 derived by infrared spectroscopy and vdW-DF calculations provide the understanding necessary to develop industrial processes for SO₂ removal using microporous paddle-wheel frameworks materials.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1130266
• Report Number(s): PNNL-SA-93017; KC0203020
• Journal Information: Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 23 Vol. 25; ISSN 0897-4756
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English