Mechanical properties of cubic zinc carboxylate IRMOF-1 metal-organic framework crystals
Mechanical properties of cubic zinc carboxylate IRMOF-1 metal-organic framework crystals
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DOI：
10.1103/physrevb.76.184106
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发表时间：
2007-11-01
影响因子：
3.7
通讯作者：
Allendorf, M. D.
中科院分区：
文献类型：
--
作者：
Bahr, D. F.;Reid, J. A.;Allendorf, M. D.
最近开发的一类被称为金属有机框架（MOFs）的纳米多孔材料由于其在传感，存储和化学分离方面的潜力而引起了相当大的兴趣。在许多应用中，了解其机械性能至关重要。我们报告使用两种不同的纳米压痕技术的IRMOF-1晶体的弹性模量的测量。从2.7 +/-1.0 GPa的平均单晶杨氏模量（E）计算的来自连续刚度测量的折合模量与从常规准静态测量获得的值非常一致。压痕后直接观察到永久变形而没有断裂。为了比较，我们进行了密度泛函理论（DFT）计算的弹性性质，使用局域密度近似（LDA）和广义梯度近似（GGA）。所得的E的良好收敛的DFT值（LDA-GGA平均值）为21.6 +/-0.3GPa，其中C（11）=0.28 +/-0.01GPa，C（12）=0.11 +/-0.01GPa，并且C（44）=0.03 +/-0.02GPa。通过DFT预测的高度各向异性弹性行为校正测量的模量，表明（100）面的有效模量为7.9 GPa。DFT预测在这里被期望是可靠的。因此，较低的测量杨氏模量最有可能是由于在这些框架材料中发生的无摩擦塑性变形期间的有趣行为。这种纳米多孔结构中的变形或屈曲可能导致我们在实验中可以应用的最低载荷下的结构变化。这似乎是MOFs的独特性质，其中塑性变形材料的弹性性质与更传统的纳米多孔金属、陶瓷和聚合物的弹性性质不同。
The recently developed class of nanoporous materials known as metal-organic frameworks (MOFs) is generating considerable interest because of their potential in sensing, storage, and chemical separations. In many applications, it is essential to understand their mechanical properties. We report the measurement of the elastic modulus of IRMOF-1 crystals using two different nanoindentation techniques. The reduced modulus from continuous stiffness measurements, calculated from the average single-crystal Young's modulus (E) of 2.7 +/- 1.0 GPa, is in good agreement with the value obtained from conventional quasistatic measurements. Permanent deformation without fracture has been observed directly after indentation. For comparison, we performed density functional theory (DFT) calculations of the elastic properties using both the local density approximation (LDA) and the generalized gradient approximation (GGA). The resulting, well-converged DFT value (LDA-GGA average) for E is 21.6 +/- 0.3 GPa, with C(11)=0.28 +/- 0.01 GPa, C(12)=0.11 +/- 0.01 GPa, and C(44)=0.03 +/- 0.02 GPa. Correcting the measured modulus for the highly anisotropic elastic behavior predicted by DFT suggests an effective modulus for the (100) face of 7.9 GPa. The DFT prediction is expected to be reliable here. Therefore, the lower measured Young's modulus is most likely due to an interesting behavior during fractureless plastic deformation that occurs in these framework materials. Deformation or buckling in this nanoporous structure likely leads to structural changes at the lowest loads we can apply in the experiment. This appears to be a unique property of MOFs, where the elastic properties of the plastically deformed materials behave differently than those for more traditional nanoporous metals, ceramics, and polymers.