Department of Materials Science, Fudan University, Shanghai 200433, P.R. China.
Chemistry. 2012 May 29;18(22):6825-34. doi: 10.1002/chem.201102651. Epub 2012 Apr 11.
A new ammine dual-cation borohydride, LiMg(BH(4))(3)(NH(3))(2), has been successfully synthesized simply by ball-milling of Mg(BH(4))(2) and LiBH(4)·NH(3). Structure analysis of the synthesized LiMg(BH(4))(3)(NH(3))(2) revealed that it crystallized in the space group P6(3) (no. 173) with lattice parameters of a=b=8.0002(1) Å, c=8.4276(1) Å, α=β=90°, and γ=120° at 50 °C. A three-dimensional architecture is built up through corner-connecting BH(4) units. Strong N-H···H-B dihydrogen bonds exist between the NH(3) and BH(4) units, enabling LiMg(BH(4))(3)(NH(3))(2) to undergo dehydrogenation at a much lower temperature. Dehydrogenation studies have revealed that the LiMg(BH(4))(3)(NH(3))(2)/LiBH(4) composite is able to release over 8 wt% hydrogen below 200 °C, which is comparable to that released by Mg(BH(4))(3)(NH(3))(2). More importantly, it was found that release of the byproduct NH(3) in this system can be completely suppressed by adjusting the ratio of Mg(BH(4))(2) and LiBH(4)·NH(3). This chemical control route highlights a potential method for modifying the dehydrogenation properties of other ammine borohydride systems.
一种新型的氨合双阳离子硼氢化物 LiMg(BH(4))(3)(NH(3))(2)，通过简单的球磨 Mg(BH(4))(2)和 LiBH(4)·NH(3)成功合成。对合成的 LiMg(BH(4))(3)(NH(3))(2)的结构分析表明，它在空间群 P6(3)（No.173）中结晶，晶格参数为 a=b=8.0002(1) Å, c=8.4276(1) Å, α=β=90°，γ=120°，在 50°C 时。通过角连接 BH(4)单元构建了一个三维架构。NH(3)和 BH(4)单元之间存在强 N-H···H-B 氢键，使 LiMg(BH(4))(3)(NH(3))(2)能够在更低的温度下脱氢。脱氢研究表明，LiMg(BH(4))(3)(NH(3))(2)/LiBH(4)复合材料在低于 200°C 时能够释放超过 8wt%的氢气，与 Mg(BH(4))(3)(NH(3))(2)释放的氢气相当。更重要的是，发现通过调整 Mg(BH(4))(2)和 LiBH(4)·NH(3)的比例，可以完全抑制该体系中副产物 NH(3)的释放。这种化学控制途径突出了一种潜在的方法，可以用于修饰其他氨合硼氢化物体系的脱氢性能。
