Kubas-Type Hydrogen Storage in V(III) Polymers Using Tri- and Tetradentate Bridging Ligands

详细信息    查看全文

• 作者：Tuan K. A. Hoang ; Ahmad Hamaed ; Golam Moula ; Ricardo Aroca ; Michel Trudeau ; David M. Antonelli
• 刊名：Journal of the American Chemical Society
• 出版年：2011
• 出版时间：April 6, 2011
• 年：2011
• 卷：133
• 期：13
• 页码：4955-4964
• 全文大小：1026K
• 年卷期：v.133,no.13(April 6, 2011)
• ISSN：1520-5126

文摘

Oxalic acid, oxamide, glycolic acid, and glycolamide were employed as 2-carbon linkers to synthesize a series of one-dimensional V(III) polymers from trismesityl vanadium(III)路THF containing a high concentration of low-valent metal sites that can be exploited for Kubas binding in hydrogen storage. Synthesized materials were characterized by powder X-ray diffraction (PXRD), nitrogen adsorption (BET), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR), Raman spectroscopy, thermogravimetric analysis, and elemental analysis. Because each of these organic linkers possesses a different number of protons and coordinating atoms, the products in each case were expected to have different stoichiometries with respect to the number of mesityl groups eliminated and also a different geometry about the V(III) centers. For example, the oxalate and glycolate polymers contained residual mesityl groups; however, these could be exchanged with hydride via hydrogenolysis. The highest adsorption capacity was recorded on the product of trismesityl vanadium(III)路THF with oxamide (3.49 wt % at 77 K and 85 bar). As suggested by the high enthalpy of adsorption (17.9 kJ/mol H₂), a substantial degree of performance of the vanadium metal centers was retained at room temperature (25%), corresponding to a gravimetric adsorption of 0.87 wt % at 85 bar, close to the performance of MOF-177 at this temperature and pressure. This is remarkable given the BET surface area of this material is only 9 m²/g. A calculation on the basis of thermogravimetric results provides 0.88 hydrogen molecule per vanadium center under these conditions. Raman studies with H₂ and D₂ showed the first unequivocal evidence for Kubas binding on a framework metal in an extended solid, and IR studies demonstrated H(D) exchange of the vanadium hydride with coordinated D₂. These spectroscopic observations are sufficient to assign the rising trends in isosteric heats of hydrogen adsorption observed previously by our group in several classes of materials containing low-valent transition metals to the Kubas interaction.