Microporous Metal–Organic Framework Stabilized by Balanced Multiple Host–Couteranion Hydrogen-Bonding Interactions for High-Density CO2 Capture at Ambient Conditions

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• 作者：Yingxiang Ye ; Shunshun Xiong ; Xiaonan Wu ; Liuqin Zhang ; Ziyin Li ; Lihua Wang ; Xiuling Ma ; Qian-Huo Chen ; Zhangjing Zhang ; Shengchang Xiang
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：January 4, 2016
• 年：2016
• 卷：55
• 期：1
• 页码：292-299
• 全文大小：590K
• ISSN：1520-510X

文摘

Microporous metal organic frameworks (MOFs) show promising application in several fields, but they often suffer from the weak robustness and stability after the removal of guest molecules. Here, three isostructural cationic metal–organic frameworks {[(Cu₄Cl)(cpt)₄(H₂O)₄]·3X·4DMAc·CH₃OH·5H₂O} (FJU-14, X = NO₃, ClO_4, BF₄; DMAc = N,N′-dimethylacetamide) containing two types of polyhedral nanocages, one octahedron, and another tetrahedron have been synthesized from bifunctional organic ligands 4-(4H-1,2,4-triazol-4-yl) benzoic acid (Hcpt) and various copper salts. The series of MOFs FJU-14 are demonstrated as the first examples of the isostructural MOFs whose robustness, thermal stability, and CO₂ capacity can be greatly improved via rational modulation of counteranions in the tetrahedral cages. The activated FJU-14-BF₄-a containing BF₄^– anion can take CO₂ of 95.8 cm³ cm^–3 at ambient conditions with an adsorption enthalpy only of 18.8 kJ mol^–1. The trapped CO₂ density of 0.955 g cm^–3 is the highest value among the reported MOFs. Dynamic fixed bed breakthrough experiments indicate that the separation of CO₂/N₂ mixture gases through a column packed with FJU-14-BF₄-a solid can be efficiently achieved. The improved robustness and thermal stability for FJU-14-BF₄-a can be attributed to the balanced multiple hydrogen-bonding interactions (MHBIs) between the BF₄^– counteranion and the cationic skeleton, while the high-density and low-enthalpy CO₂ capture on FJU-14-BF₄-a can be assigned to the multiple-point interactions between the adsorbate molecules and the framework as well as with its counteranions, as proved by single-crystal structures of the guest-free and CO₂-loaded FJU-14-BF₄-a samples.