Amino acids as highly efficient modulators for single crystals of zirconium and hafnium metal-organic frameworks
Amino acids as highly efficient modulators for single crystals of zirconium and hafnium metal-organic frameworks
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DOI：
10.1039/c5ta10401g
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发表时间：
2016-01-01
影响因子：
11.9
通讯作者：
Forgan, Ross S.
中科院分区：
文献类型：
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作者：
Marshall, Ross J.;Hobday, Claire L.;Forgan, Ross S.
锆和铪金属有机骨架（MOFs）的合成通常依赖于配位调制-在反应混合物中加入竞争性的单主题调制剂-以可重复地生成高结晶材料。通常，大量过量的单羧酸如甲酸、乙酸和苯甲酸被应用，但获得衍射质量的单晶，特别是UiO-66拓扑mof，仍然是麻烦的。在此，我们发现氨基酸，特别是l -脯氨酸，是UiO-66系列中Zr和Hf mof的高效调制剂，只需4个等量的氨基酸就可以获得无缺陷的大的、衍射质量的单晶。报道了五种晶体结构，包括以前无法以这种方式表征的mof，并利用分子动力学模拟来理解动态无序。此外，对一系列mof进行了深入的表征，从而可以比较Zr和Hf类似物的热稳定性和孔隙率。我们还表明，该协议可以扩展到微波合成，并且调制能力在一系列氨基酸之间变化很大。单晶的获得促进了我们对这些mof的机械性能的深入研究，我们期望我们的协议将能够发现新的Zr和Hf mof，并为其材料特性提供新的见解。
The synthesis of zirconium and hafnium metal-organic frameworks (MOFs) often relies on coordination modulation - the addition of competing monotopic modulators to reaction mixtures - to reproducibly generate highly crystalline material. Typically, large excesses of monocarboxylic acids such as formic, acetic and benzoic acid are applied, but access to diffraction quality single crystals, particularly of UiO-66 topology MOFs, remains troublesome. Herein, we show that amino acids, in particular L-proline, are highly efficient modulators of Zr and Hf MOFs of the UiO-66 series, with as little as four equivalents affording access to large, diffraction quality single crystals that are free of defects. Five crystal structures are reported, including MOFs which previously could not be characterised in this manner, with molecular dynamics simulations utilised to understand dynamic disorder. Additionally, a series of MOFs are characterised in depth, allowing a comparison of the thermal stabilities and porosities for Zr and Hf analogues. We also show that the protocol can be extended to microwave synthesis, and that modulating ability varies dramatically across a series of amino acids. Access to single crystals has facilitated our own in depth study of the mechanical properties of these MOFs, and we expect that our protocols will enable the discovery of new Zr and Hf MOFs as well as offer new insights into their materials properties.