Metal-Organic Frameworks (MOFs) are a class of crystalline compounds whose scaffolding derives from metal clusters or ions that are interconnected by organic linkers. The high number of possible combinations of metals and ligands leads to high tunability of macroscopic properties and thus it is possible to employ MOFs in many fields of applications, including gas storage, gas separation, and catalysis [1,2]. During the design and development of a new MOF, it is extremely important to completely understand every macroscopic property of the compound and to relate it to its microscopic origin. Many techniques can be exploited and combined to characterize the structural and dynamic molecular properties of a MOF. Among them, Solid State Nuclear Magnetic Resonance (SSNMR) spectroscopy is certainly one of the most important because it can shed light on many aspects of the MOF at a molecular level, such as 3D structure, porosity [3], local dynamics [4], and host-guest interactions [5]. In this work, 1H, 13C, and 19F SSNMR spectroscopy has been employed to characterize two novel MOFs prepared with trifluoroterephthalic acid as the organic ligand: F3-UiO66(Ce) and F3-MIL140A(Ce). The former is characterized by a face-centered cubic topology in which hexanuclear clusters of CeIV are interconnected by ligands. In the latter, chain-like inorganic building units of CeIV are interconnected by ligands. SSNMR 1D and 2D correlation spectra have been used to obtain, also by comparison with powder X-ray diffraction results, a detailed characterization of the framework structure both in the presence and after removal of crystallization water. On the other hand, dynamic processes involving the fluorinated aromatic rings have been investigated through the analysis of variable-temperature 19F spin-lattice relaxation times. References: [1] Q. Qian et al., Chem. Rev. 2020, 120, 8161. [2] X. L. and H. T. Jian Cao, Curr. Med. Chem. 2020, 27, 5949. [3] N. Klein et al., Phys. Chem. Chem. Phys. 2010, 12, 11778. [4] X. Kong et al., J. Am. Chem. Soc. 2012, 134, 14341. [5] A. E. Khudozhitkov et al., J. Phys. Chem. C 2016, 120, 21704.
Structural properties of Fluorinated Metal Organic Frameworks (MOFs) by Solid State NMR
Lucia Calucci;
2022
Abstract
Metal-Organic Frameworks (MOFs) are a class of crystalline compounds whose scaffolding derives from metal clusters or ions that are interconnected by organic linkers. The high number of possible combinations of metals and ligands leads to high tunability of macroscopic properties and thus it is possible to employ MOFs in many fields of applications, including gas storage, gas separation, and catalysis [1,2]. During the design and development of a new MOF, it is extremely important to completely understand every macroscopic property of the compound and to relate it to its microscopic origin. Many techniques can be exploited and combined to characterize the structural and dynamic molecular properties of a MOF. Among them, Solid State Nuclear Magnetic Resonance (SSNMR) spectroscopy is certainly one of the most important because it can shed light on many aspects of the MOF at a molecular level, such as 3D structure, porosity [3], local dynamics [4], and host-guest interactions [5]. In this work, 1H, 13C, and 19F SSNMR spectroscopy has been employed to characterize two novel MOFs prepared with trifluoroterephthalic acid as the organic ligand: F3-UiO66(Ce) and F3-MIL140A(Ce). The former is characterized by a face-centered cubic topology in which hexanuclear clusters of CeIV are interconnected by ligands. In the latter, chain-like inorganic building units of CeIV are interconnected by ligands. SSNMR 1D and 2D correlation spectra have been used to obtain, also by comparison with powder X-ray diffraction results, a detailed characterization of the framework structure both in the presence and after removal of crystallization water. On the other hand, dynamic processes involving the fluorinated aromatic rings have been investigated through the analysis of variable-temperature 19F spin-lattice relaxation times. References: [1] Q. Qian et al., Chem. Rev. 2020, 120, 8161. [2] X. L. and H. T. Jian Cao, Curr. Med. Chem. 2020, 27, 5949. [3] N. Klein et al., Phys. Chem. Chem. Phys. 2010, 12, 11778. [4] X. Kong et al., J. Am. Chem. Soc. 2012, 134, 14341. [5] A. E. Khudozhitkov et al., J. Phys. Chem. C 2016, 120, 21704.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
