Metal–organic frameworks (MOFs) are crystalline, porous solids constructed from organic linkers and inorganic nodes that are promising for applications in chemical separations, gas storage, and catalysis, among many others. However, a major roadblock to the widespread implementation of MOFs, including highly tunable and hydrolytically stable Zr- and Hf-based frameworks, is their benchtop-scalable synthesis, as MOFs are typically prepared under highly dilute (≤0.01 M) solvothermal conditions. This necessitates the use of liters of organic solvent to prepare only a few grams of MOF. Herein, we demonstrate that Zr- and Hf-based frameworks (eight examples) can self-assemble at much higher reaction concentrations than are typically utilized, up to 1.00 M in many cases. Combining stoichiometric amounts of Zr or Hf precursors with organic linkers at high concentrations yields highly crystalline and porous MOFs, as confirmed by powder X-ray diffraction (PXRD) and 77 K N₂ surface area measurements. Furthermore, the use of well-defined pivalate-capped cluster precursors avoids the formation of ordered defects and impurities that arise from standard metal chloride salts. These clusters also introduce pivalate defects that increase the exterior hydrophobicity of several MOFs, as confirmed by water contact angle measurements. Overall, our findings challenge the standard assumption that MOFs must be prepared under highly dilute solvothermal conditions for optimal results, paving the way for their scalable and user-friendly synthesis in the laboratory.

中文翻译：

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锆基和铪基金属有机材料的高浓度自组装

金属有机框架（MOF）是由有机连接体和无机节点构成的结晶多孔固体，有望在化学分离、气体储存和催化等领域得到应用。然而，MOF（包括高度可调和水解稳定的基于 Zr 和 Hf 的框架）广泛应用的一个主要障碍是其台式可扩展合成，因为 MOF 通常是在高度稀释（≤0.01 M）的溶剂热条件下制备的。这需要使用数升有机溶剂来制备仅几克的 MOF。在此，我们证明基于 Zr 和 Hf 的框架（八个示例）可以在比通常使用的反应浓度高得多的反应浓度下自组装，在许多情况下高达 1.00 M。₂表面积测量。此外，使用明确的新戊酸封端簇前体可以避免标准金属氯化物盐产生的有序缺陷和杂质的形成。这些簇还引入了新戊酸缺陷，这些缺陷增加了几种 MOF 的外部疏水性，这一点已通过水接触角测量得到证实。总的来说，我们的研究结果挑战了 MOF 必须在高度稀释的溶剂热条件下制备才能获得最佳结果的标准假设，为在实验室中进行可扩展且用户友好的合成铺平了道路。