Liu Yun, Kabbour Houria, Brown Craig M, Neumann Dan A, Ahn Channing C
NIST Center for Neutron Research, National Institute of Standards and Technology, Maryland, USA.
Langmuir. 2008 May 6;24(9):4772-7. doi: 10.1021/la703864a. Epub 2008 Mar 27.
Storing molecular hydrogen in porous media is one of the promising avenues for mobile hydrogen storage. In order to achieve technologically relevant levels of gravimetric density, the density of adsorbed H2 must be increased beyond levels attained for typical high surface area carbons. Here, we demonstrate a strong correlation between exposed and coordinatively unsaturated metal centers and enhanced hydrogen surface density in many framework structures. We show that the MOF-74 framework structure with open Zn(2+) sites displays the highest surface density for physisorbed hydrogen in framework structures. Isotherm and neutron scattering methods are used to elucidate the strength of the guest-host interactions and atomic-scale bonding of hydrogen in this material. As a metric with which to compare adsorption density with other materials, we define a surface packing density and model the strength of the H(2-)surface interaction required to decrease the H(2)-H(2) distance and to estimate the largest possible surface packing density based on surface physisorption methods.
在多孔介质中存储分子氢是移动氢存储的有前景的途径之一。为了达到技术上相关的重量密度水平，吸附氢的密度必须提高到超过典型高比表面积碳所达到的水平。在这里，我们证明了在许多骨架结构中，暴露的和配位不饱和的金属中心与增强的氢表面密度之间存在很强的相关性。我们表明，具有开放Zn(2+)位点的MOF-74骨架结构在骨架结构中显示出物理吸附氢的最高表面密度。等温线和中子散射方法用于阐明该材料中客体-主体相互作用的强度以及氢的原子尺度键合。作为与其他材料比较吸附密度的一个指标，我们定义了一个表面堆积密度，并对降低H(2)-H(2)距离所需的H(2)-表面相互作用强度进行建模，以及基于表面物理吸附方法估计最大可能的表面堆积密度。
