Tuning the Adsorption Properties of Isoreticular Pyrazolate-Based Metal鈥揙rganic Frameworks through Ligand Modification

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• 作者：Valentina Colombo ; Carmen Montoro ; Angelo Maspero ; Giovanni Palmisano ; Norberto Masciocchi ; Simona Galli ; Elisa Barea ; Jorge A. R. Navarro
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：August 1, 2012
• 年：2012
• 卷：134
• 期：30
• 页码：12830-12843
• 全文大小：693K
• 年卷期：v.134,no.30(August 1, 2012)
• ISSN：1520-5126

文摘

Two isoreticular series of pyrazolate-based 3D open metal鈥搊rganic frameworks, MBDP_X, adopting the NiBDP and ZnBDP structure types [H₂BDP = 1,4-bis(1H-pyrazol-4-yl)benzene], were synthesized with the new tagged organic linkers H₂BDP_X (X = 鈭扤O₂, 鈭扤H₂, 鈭扥H). All of the MBDP_X materials have been characterized through a combination of techniques. IR spectroscopy proved the effective presence of tags, while X-ray powder diffraction (XRPD) witnessed their isoreticular nature. Simultaneous TG/DSC analyses (STA) demonstrated their remarkable thermal stability, while variable-temperature XRPD experiments highlighted their high degree of flexibility related to guest-induced fit processes of the solvent molecules included in the channels. A structural isomer of the parent NiBDP was obtained with a sulfonate tagged ligand, H₂BDP_SO₃H. Structure solution from powder diffraction data collected at three different temperatures (room temperature, 90, and 250 掳C) allowed the determination of its structure and the comprehension of its solvent-related flexible behavior. Finally, the potential application of the tagged MOFs in selective adsorption processes for gas separation and purification purposes was investigated by conventional single component adsorption isotherms, as well as by advanced experiments of pulse gas chromatography and breakthrough curve measurements. Noteworthy, the results show that functionalization does not improve the adsorption selectivity (partition coefficients) for the resolution of gas mixtures characterized by similar high quadrupole moments (e.g., CO₂/C₂H₂); however, the resolution of gas mixtures containing molecules with highly differentiated polarities (i.e., N₂/CO₂ or CH₄/CO₂) is highly improved.