He Zhongjin, Zhang Kang, Jiang Jianwen
Department of Chemical and Biomolecular Engineering , National University of Singapore , 117576 , Singapore.
National Center for International Research on Deep Earth Drilling and Resource Development, Faculty of Engineering , China University of Geosciences , Wuhan , Hubei 430074 , China.
J Phys Chem Lett. 2019 Nov 21;10(22):7002-7008. doi: 10.1021/acs.jpclett.9b02808. Epub 2019 Nov 1.
The formation of CH hydrate in a mesoporous metal-organic framework MIL-101 is investigated by microsecond molecular dynamics simulations. CH hydrate is observed to form preferentially in the outer space of MIL-101 cavities rather than inside the cavities; only when the hydrate formation is nearly complete in the outer space can stable hydrate form in MIL-101 cavities. The underlying reason is revealed to be the easy dissociation of small hydrate clusters formed in the nanospace of the cavities, because of the diffusion of CH molecules out of the cavities into the outer space. Compared with dry MIL-101, the CH storage capacity of HO-saturated MIL-101 is drastically reduced as the cavities are occupied by HO. When oversaturated with HO, however, extra HO molecules in the outer space of the cavities can form considerable CH hydrate, significantly promoting CH storage capacity. This study provides important mechanistic insights into the formation mechanism and process of CH hydrate in MIL-101 and will facilitate the design of emerging materials for energy storage.
通过微秒级分子动力学模拟研究了介孔金属有机骨架材料MIL-101中CH水合物的形成过程。观察到CH水合物优先在MIL-101孔穴的外部空间形成，而非在孔穴内部；只有当外部空间的水合物形成接近完成时，MIL-101孔穴中才会形成稳定的水合物。其根本原因是由于CH分子从孔穴扩散到外部空间，使得在孔穴纳米空间中形成的小水合物簇易于解离。与干燥的MIL-101相比，由于孔穴被HO占据，HO饱和的MIL-101的CH储存容量大幅降低。然而，当HO过饱和时，孔穴外部空间中的额外HO分子可形成大量CH水合物，显著提高CH储存容量。该研究为MIL-101中CH水合物的形成机理和过程提供了重要的机理见解，并将有助于设计新型储能材料。
