Probing Interactions of N-Donor Molecules with Open Metal Sites within Paramagnetic Cr-MIL-101: A Solid-State NMR Spectroscopic and Density Functional Theory Study.
Probing Interactions of N-Donor Molecules with Open Metal Sites within Paramagnetic Cr-MIL-101: A Solid-State NMR Spectroscopic and Density Functional Theory Study.
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DOI：
10.1021/jacs.7b10148
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发表时间：
2018-01
影响因子：
15
通讯作者：
T. Wittmann;Arobendo Mondal;C. B. L. Tschense;J. J. Wittmann-J.;Ottokar Klimm;Renée Siegel;B. Corzilius;Birgit Weber;M. Kaupp;J. Senker
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文献类型：
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作者：
T. Wittmann;Arobendo Mondal;C. B. L. Tschense;J. J. Wittmann-J.;Ottokar Klimm;Renée Siegel;B. Corzilius;Birgit Weber;M. Kaupp;J. Senker
理解主-客体相互作用是调节金属有机框架（MOFs）性质的关键要求之一。特别地，具有配位不饱和的刘易斯酸性金属位点的系统以高度选择性吸附过程为特征。这归因于与刘易斯碱性客体分子的强相互作用。在这里，我们表明，13 C MAS NMR光谱与国家的最先进的密度泛函理论（DFT）的计算相结合，可以解开水，2-氨基吡啶，3-氨基吡啶，二乙胺与开放的金属网站在铬MIL-101的相互作用。用超快魔角旋转获得的13 C MAS NMR谱很好地分辨，共振分布在1000 ppm以上。他们在开放的金属站点为每个客人提供清晰的签名。基于竞争实验，这导致以下结合偏好：水<二乙胺> 2-氨基吡啶< 3-氨基吡啶。利用自旋-晶格弛豫数据和~（13）C {1H} REDOR谱编辑得到的距离和关系进行了计算。实验数据被用来验证计算的Cr-MIL-101衍生物，其中包含Cr 3 O簇与磁耦合金属中心的NMR位移。虽然这两种方法提供了一个明确的分配和安排的客人在开放的金属网站，核磁共振数据提供额外的信息的客人和框架的动态。我们预计，我们的策略有可能探测吸附质混合物的结合情况在开放的金属网站的MOFs一般，从而访问微观相互作用机制，这是必不可少的衍生结构-性能关系的这一重要的材料类。
Understanding host-guest interactions is one of the key requirements for adjusting properties in metal-organic frameworks (MOFs). In particular, systems with coordinatively unsaturated Lewis acidic metal sites feature highly selective adsorption processes. This is attributed to strong interactions with Lewis basic guest molecules. Here we show that a combination of 13C MAS NMR spectroscopy with state-of-the-art density functional theory (DFT) calculations allows one to unravel the interactions of water, 2-aminopyridine, 3-aminopyridine, and diethylamine with the open metal sites in Cr-MIL-101. The 13C MAS NMR spectra, obtained with ultrafast magic-angle spinning, are well resolved, with resonances distributed over 1000 ppm. They present a clear signature for each guest at the open metal sites. Based on competition experiments this leads to the following binding preference: water < diethylamine ≈ 2-aminopyridine < 3-aminopyridine. Assignments were done by exploiting distance sum relations derived from spin-lattice relaxation data and 13C{1H} REDOR spectral editing. The experimental data were used to validate NMR shifts computed for the Cr-MIL-101 derivatives, which contain Cr3O clusters with magnetically coupled metal centers. While both approaches provide an unequivocal assignment and the arrangement of the guests at the open metal sites, the NMR data offer additional information about the guest and framework dynamics. We expect that our strategy has the potential for probing the binding situation of adsorbate mixtures at the open metal sites of MOFs in general and thus accesses the microscopic interaction mechanisms for this important material class, which is essential for deriving structure-property relationships.