Investigation of Missing-Cluster Defects in UiO-66 and Ferrocene Deposition into Defect-Induced Cavities
Investigation of Missing-Cluster Defects in UiO-66 and Ferrocene Deposition into Defect-Induced Cavities
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DOI：
10.1021/acs.iecr.8b03516
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发表时间：
2018-10-24
影响因子：
4.2
通讯作者：
Mu, Bin
中科院分区：
文献类型：
--
作者：
Shan, Bohan;McIntyre, Sean M.;Mu, Bin
深入理解金属有机骨架材料中的缺陷形成机理，对于合理设计材料结构至关重要。特别是，UiO-66框架中的缺陷已被证明对框架的功能和稳定性有重大影响。然而，合成条件对缺陷形成的影响是难以捉摸的，并且我们对UiO-66中的缺失配体和缺失簇缺陷的理解还远不清楚。在这项工作中，我们证明了缺失簇（MC）缺陷的形成是由于大量的部分去质子化的配体在合成溶液中。通过一系列控制缺陷形成的合成实验验证了所提出的机理。结果表明，MC缺陷的数量是敏感的去质子化试剂，合成温度，反应物浓度。在77 K下从N-2吸附等温线得到的孔径分布允许准确和方便地表征UiO-66中的缺陷。UiO-66骨架中缺陷的存在会导致其孔径分布与理论上完美的晶体结构所得结果存在显著偏差。由MC缺陷产生的额外空腔被证明允许沉积大的功能分子二茂铁（3.5埃× 4.5埃× 4.5埃）。通过将原始N-2-选择性框架调整为O-2-选择性框架，证明了成功的掺入。
Advancing our understanding of the defect formation mechanism in metal-organic frameworks (MOFs) is critical for the rational design of the material's structure. In particular, the defects in the UiO-66 framework have been shown to have a significant impact on the framework functionality and stability. However, the effects of synthesis conditions on defect formation are elusive and our understanding of missing-ligand and missing-cluster defects in UiO-66 is far from clear. In this work, we demonstrate that the formation of missing-cluster (MC) defects is due to the large number of partially deprotonated ligands in synthesis solution. The proposed mechanism is verified by a series of syntheses controlling the defect formation. The results show that the quantity of MC defects is sensitive to deprotonation reagents, synthesis temperature, and reactant concentration. The pore size distribution derived from the N-2 adsorption isotherm at 77 K allows accurate and convenient characterization of the defects in UiO-66. The existence of defects in the UiO-66 framework can cause significant deviations in its pore size distribution from the results derived from the theoretically perfect crystal structure. The extra cavities generated by MC defects are demonstrated to allow deposition of a large functional molecule, ferrocene (3.5 angstrom x 4.5 angstrom x 4.5 angstrom). The successful incorporation is proven by the tuning of the original N-2-selective framework to become an O-2-selective framework.