Effects of functionalization, catenation, and variation of the metal oxide and organic linking units on the low-pressure hydrogen adsorption properties of metal-organic frameworks
Effects of functionalization, catenation, and variation of the metal oxide and organic linking units on the low-pressure hydrogen adsorption properties of metal-organic frameworks
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DOI：
10.1021/ja056639q
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发表时间：
2006-02-01
影响因子：
15
通讯作者：
Yaghi, OM
中科院分区：
文献类型：
--
作者：
Rowsell, JLC;Yaghi, OM
氢吸附等温线的8个金属有机框架（MOFs），在77 K至1个大气压的压力下测量，已检查与它们的结构特征的相关性。所有材料显示出无滞后的近似I型等温线，并且在这些条件下任何材料都未达到饱和。在研究的六种等网格MOFs（IRMOFs）中，链状材料表现出最大的容量（以摩尔计），每个分子式单元高达9.8 H-2。将官能团（-Br、-NH 2、-C2 H4-）添加到IRMOF-1（MOF-5）的亚苯基连接上，或将它们替换为IRMOF-20中的噻吩并[3，2-B]噻吩部分，尽管所得材料的孔体积变化很大，但少量改变了吸附行为。与此相反，取代的金属氧化物单元与那些含有配位不饱和的金属网站导致更大的H2吸收。这些材料，MOF-74和HKUST-1，增强的亲和力，进一步证明了等量吸附热的计算，这是更大的覆盖范围内检查，相比那些代表性IRMOFs。结果表明，在低负载条件下，可以通过在金属氧化物单元上赋予更大的电荷梯度和调整连接度量来收缩孔尺寸来改善MOFs的H2吸附行为;然而，大的孔体积仍然是先决条件。
The dihydrogen adsorption isotherms of eight metal-organic frameworks (MOFs), measured at 77 K up to a pressure of 1 atm, have been examined for correlations with their structural features. All materials display approximately Type I isotherms with no hysteresis, and saturation was not reached for any of the materials under these conditions. Among the six isoreticular MOFs (IRMOFs) studied, the catenated materials exhibit the largest capacities on a molar basis, up to 9.8 H-2 per formula unit. The addition of functional groups (-Br, -NH2, -C2H4-) to the phenylene links of IRMOF-1 (MOF-5), or their replacement with thieno[3,2-b]thiophene moieties in IRMOF-20, altered the adsorption behavior by a minor amount despite large variations in the pore volumes of the resulting materials. In contrast, replacement of the metal oxide units with those containing coordinatively unsaturated metal sites resulted in greater H2 uptake. The enhanced affinities of these materials, MOF-74 and HKUST-1, were further demonstrated by calculation of the isosteric heats of adsorption, which were larger across much of the range of coverage examined, compared to those of representative IRMOFs. The results suggest that under low-loading conditions, the H2 adsorption behavior of MOFs can be improved by imparting larger charge gradients on the metal oxide units and adjusting the link metrics to constrict the pore dimensions; however, a large pore volume is still a prerequisite feature.