Screening New families of Metal Organic Frameworks for Hydrogen Storage

人类现在已经意识到，对石油的依赖不可能永远持续下去。人们正在疯狂地寻找可行的替代燃料，特别是用于汽车工业的燃料。氢气正在成为一个有前途的候选者，因为它可以从各种来源产生。作为一种清洁的燃烧替代品，氢气有潜力将我们的二氧化碳排放量大幅削减到2007年白色论文中建议的水平（到2050年减少60%），然而，要实用，任何新燃料都需要安全和紧凑。由于氢气在环境温度下是气体，因此需要在极高的压力下压缩或冷却至极低的温度，以提供足够的车辆行驶所需的供应。高压和低温都是不可接受的，尤其是出于安全考虑。为了避免这些问题，研究了化学品储存的方法。目前正在研究的领先者是微孔材料，它依赖于高表面积和强的氢结合亲和力。大规模合成和化学灵活性是其他重要的考虑因素，它们将基于有机间隔分子连接的金属离子的配位网络放在商店橱窗中。这些金属有机框架（MOFs）最近显示出基于锌簇/羧酸酯连接体的系统的氢吸收潜力，尽管在低温下表现出氢吸收值，接近美国能源部为车载氢存储设定的2010年目标。其结构基于通过二酚盐间隔基连接的锌（或铝）簇。这些系统具有氢吸收所需的所有属性，可以在多克规模上制备，并且易于进行化学改性，包括掺入在其他系统中显示的有利于氢吸收的碱金属离子。在我们的系统中的锌（和铝）簇也具有intruiging和潜在有用的构象，这创造了非常适合小分子捕获的内部口袋。

Mankind has now realised that its dependance on oil cannot last forever. Viable alternative fuels are frantically being sought, particularly for use in the automobile industry. Hydrogen is emerging as a promising candidate, as it can be generated from a variety of sources. As a clean burning substitute, hydrogen has the potential to dramatically cut our carbon dioxide emissions to the levels suggested in the 2007 White paper (60 % reduction by 2050), however to be practical any new fuel needs to be safe and compact. As hydrogen is a gas at ambient temperatures, it would need to be compressed under very high pressures or cooled to very low temperatures to provide sufficient supplies necessary for the running of vehicles. Neither high pressures nor low temperatures are acceptible, not least on safety grounds. In an attempt to circumvent these problems, methods of chemical storage are been investigated. Amongst the front runners currently under investigation are microporous materials, which relie on high surface area and strong hydrogen binding affinity. Large scale syntheses and chemical flexibility are other important considerations, which put coordination networks based on metal ions linked by organic spacer molecules in the shop window. These metal-organic frameworks (MOFs) have recently shown potential for hydrogen uptake with systems based on zinc clusters/carboxylate linkers exhibiting hydrogen absorption values, albeit at low temperatures, approaching the 2010 targets set by the US Department of Energy for on-board hydrogen storage.It is the intention here to evaluate a promising new familiy of MOFs, the structures of which are based on zinc (or aluminium) clusters linked by diphenolate spacers. These systems possess all the attributes necessary for hydrogen absorption, can be prepared on multi-gramme scale and are readily amenable to chemical modification, including the incorporation of alkali-metal ions shown in other systems to be beneficial to hydrogen uptake. The zinc (and aluminium) clusters in our systems also possess intruiging and potentially useful conformations, which create internal pockets that are well suited to small molecule capture.