Polyoxometalate-Based Metal Organic Frameworks (POMOFs): Structural Trends, Energetics, and High Electrocatalytic Efficiency for Hydrogen Evolution Reaction

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• 作者：Brigitte Nohra ; Hani El Moll ; L. Marleny Rodriguez Albelo ; Pierre Mialane ; J茅r么me Marrot ; Caroline Mellot-Draznieks ; Michael O鈥橩eeffe ; Rosa Ngo Biboum ; Jo毛l Lemaire ; Bineta Keita ; Louis Nadjo ; Anne Dolbecq
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：August 31, 2011
• 年：2011
• 卷：133
• 期：34
• 页码：13363-13374
• 全文大小：1199K
• 年卷期：v.133,no.34(August 31, 2011)
• ISSN：1520-5126

文摘

The grafting of the triangular 1,3,5-benzene tricarboxylate linkers (denoted trim) on tetrahedral 蔚-Keggin polyoxometalates (POMs) capped by Zn(II) ions, formed in situ under hydrothermal conditions, has generated three novel POM-based metal organic frameworks (POMOFs). (TBA)₃[PMo^V₈Mo^VI₄O₃₆(OH)₄Zn₄][C₆H₃(COO)₃]_4/3路6H₂O (蔚(trim)_4/3) is a 3D open-framework built of molecular Keggin units connected by trim linkers, with channels occupied by tetrabutylammonium (TBA) counterions. 蔚(trim)_4/3 is a novel (3,4)-connected net, named ofp for open-framework polyoxometalate, and computer simulations have been used to evaluate its relative stability in comparison with ctn- and bor-like polymorphs, showing the stability of this novel phase directly related to its greatest density. A computational study was also undertaken with the aim of locating TBA molecules, the positions of which could not be deduced from single crystal X-ray diffraction, and further rationalizes their structure directing role. In (TBA)₃[PMo^V₈Mo^VI₄O₃₇(OH)₃Zn₄][C₆H₃(COO)₃] (蔚₂(trim)₂), the building unit is not the molecular Keggin but a dimerized form of this POM. Their connection via trim linkers generates a 3D framework with channels filled by TBA cations. In (TBA)₃[PMo^V₈Mo^VI₄O₃₇(OH)₃Zn₄][C₆H₃(COO)₃]路8H₂O ([蔚(trim)]_鈭?/b>), zigzag chains are connected via the organic linkers, forming 2D grids. Modified electrodes were fabricated by direct adsorption of the POMOFs on glassy carbon or entrapment in carbon paste (CPE). A remarkable electrocatalytic hydrogen evolution reaction (HER) was detected with a yield greater than 95%, and a turnover number as high as 1.2 脳 10⁵ was obtained after 5 h. The reported POMOF-based electrodes are more active than platinum, with a roughly 260 mV anodic shift. Finally, the electrocatalytic activities of 蔚(trim)_4/3/CPE electrodes in various XCl (X = Li, Na, K, Cs) media have been studied. This allowed us to detect a cation effect and propose an electrocatalytic mechanistic pathway for the HER.