Methane storage in flexible metal-organic frameworks with intrinsic thermal management
Methane storage in flexible metal-organic frameworks with intrinsic thermal management
复制标题
DOI：
10.1038/nature15732
复制
发表时间：
2015-11-19
期刊：
影响因子：
64.8
通讯作者：
Long, Jeffrey R.
中科院分区：
文献类型：
--
作者：
Mason, Jarad A.;Oktawiec, Julia;Long, Jeffrey R.
作为一种更清洁、更便宜、全球分布更均匀的燃料，天然气作为运输部门的能源来源，与石油相比，具有相当大的环境、经济和政治优势（1,2）。尽管有这些优点，但它在环境温度和压力下的低体积能量密度带来了巨大的挑战，特别是对于轻型车辆来说，车内燃料存储空间很小(3)。在环境温度和中等压力下，吸附天然气系统具有在多孔材料中储存高密度甲烷（CH4，天然气的主要成分）的潜力(4)。尽管活性炭、沸石和金属有机框架已被广泛研究用于CH4储存（5-8），但在设计具有高容量的系统以及管理与吸附剂吸附和解吸气体相关的热波动方面存在实际挑战。在这里，我们在金属-有机框架中使用可逆相变来最大化CH4的可输送容量，同时在吸附和解吸过程中提供内部热管理。特别是，柔性化合物Fe（bdp）和Co(bdp) （bdp(2-) = 1,4-苯二吡啶酸酯）在特定的CH4压力下发生结构相变，导致吸附和解吸等温线具有明显的“阶梯”特征。这种行为使得比传统吸附剂更大的存储容量(9)，同时也减少了吸附过程中释放的热量和解吸过程中冷却的影响。与相变相关的压力和能量可以通过化学或机械压力的应用来调节。
As a cleaner, cheaper, and more globally evenly distributed fuel, natural gas has considerable environmental, economic, and political advantages over petroleum as a source of energy for the transportation sector(1,2). Despite these benefits, its low volumetric energy density at ambient temperature and pressure presents substantial challenges, particularly for light-duty vehicles with little space available for on-board fuel storage(3). Adsorbed natural gas systems have the potential to store high densities of methane (CH4, the principal component of natural gas) within a porous material at ambient temperature and moderate pressures(4). Although activated carbons, zeolites, and metal-organic frameworks have been investigated extensively for CH4 storage(5-8), there are practical challenges involved in designing systems with high capacities and in managing the thermal fluctuations associated with adsorbing and desorbing gas from the adsorbent. Here, we use a reversible phase transition in a metal-organic framework to maximize the deliverable capacity of CH4 while also providing internal heat management during adsorption and desorption. In particular, the flexible compounds Fe(bdp) and Co(bdp) (bdp(2-) = 1,4-benzenedipyrazolate) are shown to undergo a structural phase transition in response to specific CH4 pressures, resulting in adsorption and desorption isotherms that feature a sharp 'step'. Such behaviour enables greater storage capacities than have been achieved for classical adsorbents(9), while also reducing the amount of heat released during adsorption and the impact of cooling during desorption. The pressure and energy associated with the phase transition can be tuned either chemically or by application of mechanical pressure.