Synthesis of High-Quality Mg-MOF-74 Thin Films via Vapor-Assisted Crystallization,ACS Applied Materials & Interfaces

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Synthesis of High-Quality Mg-MOF-74 Thin Films via Vapor-Assisted Crystallization
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2021-07-13 , DOI: 10.1021/acsami.1c12000
Ki-Joong Kim _{1,

2} , Jeffrey T Culp _{1,

2} , Paul R Ohodnicki ₁ , Praveen K Thallapally ₃ , Jinhui Tao ₃

Affiliation

The unique features of metal–organic frameworks (MOFs), such as their large surface areas and diversity of structures, make them suitable for a broad range of applications including storage, separation, and sensing of gases. Among all the MOFs, Mg-MOF-74 with the highest CO₂ uptake at 1 bar and 25 °C would be particularly beneficial for CO₂-related applications. One of the most critical enabling technologies for implementing Mg-MOF-74 is the preparation of dense and continuous films that would maximize the sorption behaviors. However, Mg-MOF-74 thin films present significant challenges in demonstrating large-scale coatings. Herein, we demonstrate for the first time high-quality Mg-MOF-74 films synthesized via a vapor-assisted crystallization (VAC) process. The VAC process described herein provides dense and highly crystalline layers of the Mg-MOF-74 thin film with a low coefficient of variation of film thickness below 7%. By minimizing the solvent use, the VAC process is also more environmentally friendly than conventional techniques. In this work, we first optimized a precursor solution for the VAC process and then investigated the effects of synthesis temperature, time, and droplet volume on the growth, crystallinity, and thickness of VAC Mg-MOF-74 films. The porosity of the MOF film was assessed by measuring the CO₂ uptake at room temperature and 1 bar. The obtained VAC Mg-MOF-74 films possess a well-defined microporosity, as deduced from CO₂ adsorption studies via quartz crystal microbalance (QCM) and comparison with bulk Mg-MOF-74 reference data. Furthermore, CO₂ cyclic adsorption–desorption experiments on the VAC Mg-MOF-74 films showed scaled uptakes to a wide range of CO₂ concentration without showing significant variations in the baseline. We specifically demonstrate how the film’s quality of the MOF affects adsorption behavior of CO₂ on VAC Mg-MOF-74 and drop-cast Mg-MOF-74 films.

中文翻译：

气相辅助结晶法合成高质量 Mg-MOF-74 薄膜

金属有机骨架 (MOF) 的独特特征，例如其大表面积和结构的多样性，使其适用于广泛的应用，包括气体的存储、分离和传感。在所有 MOF 中，在 1 bar 和 25 °C 下具有最高 CO ₂吸收的Mg-MOF-74将特别有利于 CO ₂相关应用。实施 Mg-MOF-74 的最关键的使能技术之一是制备致密且连续的薄膜，以最大限度地提高吸附行为。然而，Mg-MOF-74 薄膜在展示大规模涂层方面存在重大挑战。在此，我们首次展示了通过以下方式合成的高质量 Mg-MOF-74 薄膜蒸汽辅助结晶 (VAC) 工艺。本文所述的 VAC 工艺提供了致密且高度结晶的 Mg-MOF-74 薄膜层，其薄膜厚度变化系数低于 7%。通过最大限度地减少溶剂的使用，VAC 工艺也比传统技术更加环保。在这项工作中，我们首先优化了 VAC 工艺的前体溶液，然后研究了合成温度、时间和液滴体积对 VAC Mg-MOF-74 薄膜的生长、结晶度和厚度的影响。MOF 膜的孔隙率通过测量室温和 1 巴下的 CO ₂吸收来评估。将所获得的VAC的Mg-MOF-74膜具有良好定义的微孔，如从CO推导₂吸附研究通过石英晶体微量天平 (QCM) 并与块状 Mg-MOF-74 参考数据进行比较。此外，VAC Mg-MOF-74 薄膜上的CO ₂循环吸附-解吸实验表明，在很宽的CO ₂浓度范围内，CO _{2 的}吸收量按比例增加，而没有显示基线的显着变化。我们特别展示了 MOF 薄膜的质量如何影响VAC Mg-MOF-74 和滴铸 Mg-MOF-74 薄膜上的 CO ₂吸附行为。

更新日期：2021-07-28

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