Ma Shengqian, Eckert Juergen, Forster Paul M, Yoon Ji Woong, Hwang Young Kyu, Chang Jong-San, Collier Christopher D, Parise John B, Zhou Hong-Cai
Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, USA.
J Am Chem Soc. 2008 Nov 26;130(47):15896-902. doi: 10.1021/ja803492q.
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 C(24)H(12)N(3)O(6)). 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 H(2) 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.
已对PCN - 6和PCN - 6'（二者化学式均为Cu(3)(TATB)(2)，其中TATB代表4,4',4'' - 均三嗪 - 2,4,6 - 三基 - 三苯甲酸酯，化学式为C(24)H(12)N(3)O(6)）的连锁异构体对进行了氢吸附研究。非弹性中子散射（INS）研究表明，吸附的H(2)最初占据的位点是桨轮单元中开放的Cu中心，这两种异构体中的相互作用能相当。在高H(2)负载量下，H(2)分子主要吸附在有机连接体上或其周围，结果发现连锁的PCN - 6中的相互作用比非连锁的PCN - 6'中的相互作用强得多，导致连锁异构体中的H(2)吸收量高得多。在高达50 bar的压力下进行的氢吸附测量表明，骨架连锁有利于增强氢吸附。例如，PCN - 6在77 K/50 bar时的过量氢吸收量分别为72 mg/g（6.7 wt%）或在298 K/50 bar时为9.3 mg/g（0.92 wt%），而PCN - 6'在77 K/50 bar时为42 mg/g（4.0 wt%）或在298 K/50 bar时为4.0 mg/g（0.40 wt%）。重要的是，PCN - 6在77 K/50 bar时的总氢吸收量为95 mg/g（8.7 wt%）（基于晶体密度估算，对应的总体积值为53.0 g/L），在298 K/50 bar时为15 mg/g（1.5 wt%）。值得注意的是，如果假设再充压压力为1.5 bar，PCN - 6在77 K时的预期可用容量高达75 mg/g（或41.9 g/L）。
