Zhou Wei, Wu Hui, Yildirim Taner
NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
J Am Chem Soc. 2008 Nov 19;130(46):15268-9. doi: 10.1021/ja807023q. Epub 2008 Oct 25.
Metal-organic frameworks (MOFs) with open metal sites exhibit a much stronger H2 binding strength than classical MOFs, due to the direct interaction between H2 and the coordinately unsaturated metal ions. Here we report a systematic study of the H2 adsorption on a series of isostructural MOFs, M2(dhtp) (M = Mg, Mn, Co, Ni, Zn). The experimental, initial isosteric heats of adsorption for H2 (Qst) of these MOFs range from 8.5 to 12.9 kJ/mol, with increasing Qst in the following order: Zn, Mn, Mg, Co, and Ni. The H2 binding energies derived from first-principles calculation follow the same trend as the experimental observation on Qst, confirming the electrostatic Coulomb attraction between the H2 and the open metals being the major interaction. We also found a strong correlation between the metal ion radius, the M-H2 distance, and the H2 binding strength, which provides a viable, empirical method to predict the relative H2 binding strength of different open metals.
具有开放金属位点的金属有机框架（MOF）由于H₂与配位不饱和金属离子之间的直接相互作用，表现出比传统MOF更强的H₂结合强度。在此，我们报告了对一系列同构MOF，即M₂(dhtp)（M = Mg、Mn、Co、Ni、Zn）上H₂吸附的系统研究。这些MOF的H₂实验初始等量吸附热（Qst）范围为8.5至12.9 kJ/mol，Qst按以下顺序增加：Zn、Mn、Mg、Co和Ni。第一性原理计算得出的H₂结合能与Qst的实验观测结果遵循相同趋势，证实H₂与开放金属之间的静电库仑吸引是主要相互作用。我们还发现金属离子半径、M - H₂距离和H₂结合强度之间存在强相关性，这提供了一种可行的经验方法来预测不同开放金属的相对H₂结合强度。
