Characterization of a New Porous Pt-Containing Metal-Organic Framework Containing Potentially Catalytically Active Sites: Local Electronic Structure at the Metal Centers

详细信息    查看全文

• 作者：Kai Chung Szeto ; Carmelo Prestipino ; Carlo Lamberti ; Adriano Zecchina ; Silvia Bordiga ; Morten Bj//pubs.acs.org/images/gifchars/oslash.gif" border="0">rgen ; Mats Tilset ; Karl Petter Lille
• 刊名：Chemistry of Materials
• 出版年：2007
• 出版时间：January 23, 2007
• 年：2007
• 卷：19
• 期：2
• 页码：211 - 220
• 全文大小：903K
• 年卷期：v.19,no.2(January 23, 2007)
• ISSN：1520-5002

文摘

A crystalline and thermally stable metal-organic framework (MOF) with Pt^II and Gd^III sites incorporatedin the structure has been recently reported. This material has been synthesized with the aim to developa heterogeneous Pt^II counterpart to homogeneous metal-organic complexes having C-H activatingproperties. The first account focused on the MOF synthesis and on structural and stability characterizationof the material. In the present work, a multitechnique approach has been adopted to investigate the effectof solvent removal and the reversibility of this process. Structural features have been investigated bymeans of powder X-ray diffraction and extended X-ray absorption fine structure spectroscopy at both Ptand Gd L₃-edges. Electronic properties have been studied with diffuse reflectance surface UV-vis andX-ray absorption near-edge spectroscopies. Finally, IR spectroscopy has been used to determine thevibration properties. Thermogravimetric methods have been used to quantify the water loss. X-rayabsorption spectroscopy has been used to compare the Pt environment in the periodic MOF structure, inrelated molecular complexes, and in the linkers. Our results demonstrate that the environment around Ptis more or less unaffected by the incorporation of the Pt centers in the molecular complexes into the 3Dextended framework of the Pt-Gd MOF. The principle of using known homogeneous complexes asbuilding blocks for the construction of single-site heterogeneous catalysts therefore seems applicable inthe present case. Removal of solvent water molecules from the internal voids of the as-prepared MOFpresents an opportunity to attain a porous material with accessible Pt^II sites. We observe that the structureundergoes a reversible loss of long-range order upon dehydration at ambient temperature. The environmentof Gd is somewhat perturbed in the dehydration/hydration process, while that of Pt is almost unaffected.When a total dehydration is achieved, the original structure is only partially recovered upon rehydration.