六核 Ce(IV)-O 团簇的溶解度和稳定性,Chemistry of Materials

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六核 Ce(IV)-O 团簇的溶解度和稳定性
Chemistry of Materials ( IF 7.2 ) Pub Date : 2023-07-17 , DOI: 10.1021/acs.chemmater.3c00636
Jonas Gosch ₁ , Erik Svensson Grape ₂ , Cesare Atzori ₃ , Felix Steinke ₁ , Kirill A. Lomachenko ₃ , A. Ken Inge ₂ , Norbert Stock _{1,

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Affiliation

稳定的分子簇对于多孔材料中的定向沉积很有意义。在这项工作中，我们报告发现了两个新的分子Ce-O簇，其组成为[Ce ₆ O ₄ (OH) ₄ (NO ₃ ) ₄ (DMF) ₄ (C ₇ H ₄ O ₂ X) ₈ ]·(DMF ) ₄ (H ₂ O) ₂ ( 1-X ) 和 [Ce ₆ O ₄ (OH) ₄ (H ₂ O) ₆ (NO ₃ ) ₆ (C ₇ H ₄O ₂ X) ₆ ] ( 2-X ) (X = -Cl、-CHO 和 -Br)。两种簇类型都包含相似的六核结构单元，晶体结构是根据单晶 X 射线衍射或 3D 电子衍射数据以及随后针对粉末 X 射线衍射 (PXRD) 数据的 Rietveld 精修确定的。晶体结构数据得到了铈离子周围局部结构结果的补充，这些结果是通过固态扩展 X 射线吸收精细结构 (EXAFS) 测量确定的。所有 Ce-O 团簇的组成均通过元素分析、核磁共振和红外光谱证实。Ce-O 团簇具有高度可溶性， 1-Cl和2-Cl的溶解度分别高达 101 和 136 g/L分别在有机溶剂中，这很大程度上取决于簇的类型和苯甲酸酯配体的官能化。此外，还确定了不同溶剂中溶解的簇的结构和组成完整性。1-Cl从二氯甲烷 (DCM) 中重结晶和拉曼光谱证实了溶液中两种簇类型的完整性。通过 EXAFS 测量对含有 4-氯苯甲酸酯的簇的 Ce K 边缘进行的进一步检查表明，溶解在 THF、DCM 和二恶烷中后，仅观察到1-Cl的铈环境发生微小变化，而2-Cl的结果表明溶解后部分降解。证明稳定性后，1-Cl的簇溶液用于浸渍介孔金属有机框架 Cr-MIL-101。通过 PXRD、电感耦合等离子体发射光谱、能量色散 X 射线光谱以及热重分析和 N ₂吸附测量进行的广泛表征，证实了 Ce-O 簇成功插入到框架的大介孔笼中。由于高表面积和潜在催化活性的结合，Cluster@MOF 材料在多相催化应用中可能受到高度关注。

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Solubility and Stability of Hexanuclear Ce(IV)–O Clusters

Stable molecular clusters are of interest for targeted deposition in porous materials. In this work, we report the discovery of two new molecular Ce–O clusters of composition [Ce₆O₄(OH)₄(NO₃)₄(DMF)₄(C₇H₄O₂X)₈]·(DMF)₄(H₂O)₂ (1-X) and [Ce₆O₄(OH)₄(H₂O)₆(NO₃)₆(C₇H₄O₂X)₆] (2-X) (X = −Cl, −CHO, and −Br). Both cluster types contain a similar hexanuclear building unit, and crystal structures were determined from single-crystal X-ray diffraction or 3D electron diffraction data and subsequent Rietveld refinements against powder X-ray diffraction (PXRD) data. The crystal structure data is complemented by results from the local structure around the cerium ions, determined by extended X-ray absorption fine structure (EXAFS) measurements in the solid state. The composition of all Ce–O clusters was confirmed by elemental analysis, NMR and IR spectroscopy. The Ce–O clusters are highly soluble, up to 101 and 136 g/L for 1-Cl and 2-Cl, respectively, in organic solvents, which strongly depends on the type of cluster and functionalization of the benzoate ligands. Moreover, the structural and compositional integrity of dissolved clusters in different solvents was established. Recrystallization of 1-Cl from dichloromethane (DCM) and Raman spectroscopy confirm the integrity of both cluster types in solution. Further examination by EXAFS measurements on the Ce K-edge of clusters containing 4-chlorobenzoate reveals that only minor changes in the cerium environment of 1-Cl are observed upon dissolution in THF, DCM, and dioxane, while the results for 2-Cl indicate a partial degradation upon dissolution. After proving the stability, a cluster solution of 1-Cl was used to impregnate the mesoporous metal–organic framework Cr-MIL-101. Extensive characterization by PXRD, inductively coupled plasma-optical emission spectroscopy, and energy-dispersive X-ray spectroscopy, as well as thermogravimetry and N₂-sorption measurements, confirm the successful insertion of Ce–O clusters into the large mesoporous cages of the framework. Due to the combination of high surface area and potential catalytic activity, the Cluster@MOF materials could be of high interest for application in heterogeneous catalysis.

更新日期：2023-07-17

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