Further Investigation of the Effect of Framework Catenation on Hydrogen Uptake in Metal-Organic Frameworks
Further Investigation of the Effect of Framework Catenation on Hydrogen Uptake in Metal-Organic Frameworks
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DOI：
10.1021/ja803492q
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发表时间：
2008-11-26
影响因子：
15
通讯作者：
Zhou, Hong-Cai
中科院分区：
文献类型：
--
作者：
Ma, Shengqian;Eckert, Juergen;Zhou, Hong-Cai
研究了Pcn-6和Pcn-6‘的链状异构体对的吸氢性能(式均为Cu3(TATB)(2)，其中TATB代表4，4’，4‘-S-三嗪-2，4，6-三苯甲酸三酯，式为C24H12N3O6)。非弹性中子散射(INS)研究表明，吸附H-2的初始位置是两个异构体中相互作用能相当的桨轮单元的开放的铜中心。在H-2负载量较高时，H-2分子主要吸附在有机连接物上或其周围，连接的PCN-6中的相互作用比未连接的PCN-6‘中的相互作用强得多，导致具有连接的异构体中的吸氢量要高得多。在50bar压力下的吸氢测试表明，骨架链化有利于氢吸附的增强。例如，PCN-6在77K/50bar和298K/50bar时的过量吸氢量分别为72 mg/g(6.7wt%)和9.3 mg/g(0.92wt%)，而PCN-6‘在77K/50bar和298K/50bar时的过量吸氢量分别为42 mg/g(4.0wt%)和4.0 mg/g(0.40wt%)。重要的是，PCN-6在77K/50bar和298K/50bar下的总吸氢量分别为95 mg/g(8.7wt%)和15 mg/g(1.5wt%)(根据晶体密度估计，总体积值为53.0g/L)。值得注意的是，如果假定充电压力为1.5bar，PCN-6在77K时的预期可用容量高达75 mg/g(或41.9g/L)。
Hydrogen-sorption studies have been carried out for the catenation isomer pairs of PCN-6 and PCN-6' (both have the formula of Cu-3(TATB)(2), where TATB represents 4,4',4 ''-s-triazine-2,4,6-triyl-tribenzoate with a formula of C24H12N3O6). Inelastic neutron scattering (INS) studies reveal that the initial sites occupied by adsorbed H-2 are the open Cu centers of the paddlewheel units with comparable interaction energies in the two isomers. At high H-2 loadings, where the H-2 molecules adsorb mainly on or around the organic linkers, the interaction is found to be substantially stronger in catenated PCN-6 than in noncatenated PCN-6', leading to much higher H2 uptake in the isomer with catenation. Hydrogen sorption measurements at pressures up to 50 bar demonstrate that framework catenation can be favorable for the enhancement of hydrogen adsorption. For example, the excess hydrogen uptake of PCN-6 is 72 mg/g (6.7 wt %) at 77 K/50 bar or 9.3 mg/g (0.92 wt %) at 298 K/50 bar, respectively, and that for PCN-6' is 42 mg/g (4.0 wt %) at 77 K/50 bar or 4.0 mg/g (0.40 wt %) at 298 K/50 bar. Importantly, PCN-6 exhibits a total hydrogen uptake of 95 mg/g (8.7 wt %) (corresponding to a total volumetric value of 53.0 g/L, estimated based on crystallographic density) at 77 K/50 bar and 15 mg/g (1.5 wt %) at 298 K/50 bar. Significantly, the expected usable capacity of PCN-6 is as high as 75 mg/g (or 41.9 g/L) at 77 K, if a recharging pressure of 1.5 bar is assumed.