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. 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. 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. Although activated carbons, zeolites, and metal–organic frameworks have been investigated extensively for CH4 storage, 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) (bdp2-= 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, 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.
Nature (2015) doi:10.1038/nature15732
Received 28 April 2015 Accepted 04 September 2015 Published online 26 October 2015
http://www.nature.com/nature/journal/vaop/ncurrent/full/nature15732.html
作为一种清洁、廉价、储量丰富的燃料，天然气比石油具有更大的环境、经济和政治优势。不过，尽管如此，天然气在常温常压下较低的体积能量密度却是一个难以克服的缺点，尤其对于轻型汽车来说，没有富余的空间来储存大量的燃料。 Mason 等人开发了一种具有可逆相变性质的 MOF 材料，它可以最大化甲烷的可使用率，并且在吸附和解吸附过程中可以自发的进行热量控制。这种性质可以使材料具有比传统吸附剂更大的储存容量，同时降低了吸附和解吸附过程中热量带来的影响。（新材料在线）
