CO 2 Behavior in a Highly Selective Ultramicroporous Framework: Insights from Single-Crystal X-ray Diffraction and Solid-State Nuclear Magnetic Resonance Spectroscopy

作者：Bligh Desveaux, Y. T. Angel Wong, Bryan E. G. Lucier, Victor V. Terskikh, Paul D. Boyle, Shan Jiang, Yining Huang · 发表于：The Journal of Physical Chemistry C · 年份：2019 · DOI：10.1021/acs.jpcc.9b03221 · 被引用次数：25 · 研究领域：Metal-Organic Frameworks: Synthesis and Applications、Advanced NMR Techniques and Applications、Covalent Organic Framework Applications

Metal–organic frameworks (MOFs) are a class of porous materials that have attracted much attention for gas adsorption applications. The ultramicroporous SIFSIX-3-Zn MOF, made up of zinc and pyrazine sheets pillared into a three-dimensional framework by hexafluorosilicate ions, has displayed remarkable carbon dioxide (CO 2 ) capture abilities. Even though the CO 2 adsorption capability of SIFSIX-3-Zn is known, a detailed experimental description of the CO 2 -loaded SIFSIX-3-Zn structure and the behavior of the adsorbed CO 2 guests is yet to be reported. In this work, CO 2 adsorption in SIFSIX-3-Zn is examined at the molecular level. Single-crystal X-ray diffraction (SCXRD) was employed to identify the CO 2 adsorption sites. The crystal structure of CO 2 -loaded MOF was subsequently compared to that of the as-made SIFSIX-3-Zn, which shows that the crystal symmetry of the MOF is guest-dependent, although the framework topology remains the same. 13 C, 19 F, 29 Si, and 67 Zn solid-state nuclear magnetic resonance (SSNMR) spectroscopy was also performed to investigate the as-made, activated, and CO 2 -loaded SIFSIX-3-Zn. The SSNMR results reveal new insights into the effect of guest inclusion on the structure of the three SIFISIX-3-Zn phases. We have also examined CO 2 dynamics in SIFSIX-3-Zn via variable-temperature 13 C SSNMR spectroscopy. Adsorbed CO 2 displays unusually hindered mobility, which is affected very little by temperature. This unique motional behavior is attributed ...