Thermodynamic Evidence of Structural Transformations in CO2-Loaded Metal–Organic Framework Zn(MeIm)2 from Heat Capacity Measurements
| Autor: | Jason J. Calvin, Tomislav Friščić, Brian F. Woodfield, Matthew S. Dickson, Nancy L. Ross, Alexandra Navrotsky, Peter F. Rosen |
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| Rok vydání: | 2020 |
| Předmět: |
Thermodynamics
chemistry.chemical_element Sorption General Chemistry Zinc 010402 general chemistry 01 natural sciences Biochemistry Heat capacity Catalysis 0104 chemical sciences chemistry.chemical_compound Colloid and Surface Chemistry chemistry Molecular vibration Sodalite Metal-organic framework Anomaly (physics) |
| Zdroj: | Journal of the American Chemical Society. 142:4833-4841 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/jacs.9b13883 |
| Popis: | Metal-organic frameworks are a class of porous compounds with potential applications in molecular sieving, gas sequestration, and catalysis. One family of MOFs, zeolitic imidizolate frameworks (ZIFs), is of particular interest for carbon dioxide sequestration. We have previously reported the heat capacity of the sodalite topology of the zinc 2-methylimidazolate framework (ZIF-8), and in this Article we present the first low-temperature heat capacity measurements of ZIF-8 with various amounts of sorbed CO2. Molar heat capacities from 1.8 to 300 K are presented for samples containing up to 0.99 mol of CO2 per mol of ZIF-8. Samples with at least 0.56 mol of CO2 per mol of ZIF-8 display a large, broad anomaly from 70 to 220 K with a shoulder on the low-temperature side, suggesting sorption-induced structural transitions. We attribute the broad anomaly partially to a gate-opening transition, with the remainder resulting from CO2 rearrangement and/or lattice expansion. The measurements also reveal a subtle anomaly from 0 to 70 K in all samples that does not exist in the sorbate-free material, which likely reflects new vibrational modes resulting from sorbate/ZIF-8 interactions. These results provide the first thermodynamic evidence of structural transitions induced by CO2 sorption in the ZIF-8 framework. |
| Databáze: | OpenAIRE |
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