Identification of Nonequivalent Framework Oxygen Species in Metal鈥揙rganic Frameworks by 17O Solid-State NMR

详细信息    查看全文

• 作者：Peng He ; Jun Xu ; Victor V. Terskikh ; Andre Sutrisno ; Heng-Yong Nie ; Yining Huang
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：August 22, 2013
• 年：2013
• 卷：117
• 期：33
• 页码：16953-16960
• 全文大小：335K
• 年卷期：v.117,no.33(August 22, 2013)
• ISSN：1932-7455

文摘

Metal鈥搊rganic frameworks (MOFs) are a class of novel nanoporous materials with many potential applications. Structural characterization is important because understanding the relationship between the properties of these industrially relevant materials and their structures allows one to develop new applications and improve current performance. Oxygen is one of the most important elements in many MOFs and exists in various forms. Ideally, ¹⁷O solid-state NMR (SSNMR) should be an excellent tool for characterizing various oxygen species. However, the major obstacles that prevent applying ¹⁷O SSNMR to MOF characterization are the synthetic effort needed for ¹⁷O isotopic enrichment and the associated high cost. In this work, we successfully prepared several prototypical ¹⁷O-enriched MOFs, including Zr-UiO-66, MIL-53(Al), CPO-27-Mg (or Mg-MOF-74), and microporous 伪-Mg₃(HCOO)₆. Depending on the target MOF, different isotopic enrichment methods were used to effectively incorporate ¹⁷O from ¹⁷O-enriched H₂O. Using these ¹⁷O-enriched MOFs, we were able to acquire ¹⁷O SSNMR spectra at a magnetic field of 21.1 T. They provide distinct spectral signatures of various key oxygen species commonly seen in representative MOFs. We demonstrate that ¹⁷O SSNMR can be used to differentiate chemically and, under favorite circumstances, crystallographically nonequivalent oxygens and to follow the phase transitions. The synthetic approaches for preparation of ¹⁷O-enriched sample described in this paper are fairly simple and cost-effective.