Reversible Low-Temperature Metal Node Distortion during Atomic Layer Deposition of Al2O3 and TiO2 on UiO-66-NH2 Metal–Organic Framework Crystal Surfaces,ACS Applied Materials & Interfaces

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Reversible Low-Temperature Metal Node Distortion during Atomic Layer Deposition of Al2O3 and TiO2 on UiO-66-NH2 Metal–Organic Framework Crystal Surfaces
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2017-06-26 00:00:00 , DOI: 10.1021/acsami.7b05214
Paul C. Lemaire ₁ , Dennis T. Lee ₁ , Junjie Zhao ₁ , Gregory N. Parsons ₁

Affiliation

Metal–organic frameworks (MOFs) are chemically functionalized micro- and mesoporous materials with high surface areas and are attractive for multiple applications including filtration, gas storage, and catalysis. Postsynthetic modification (PSM), via solution or vapor-based techniques, is a way to impart additional complexity and functionality into these materials. There is a desire to shift toward vapor-phase methods in order to ensure more controlled modification and more efficient reagent and solvent removal from the modified MOF material. In this work we explore how the metal precursors titanium tetrachloride (TiCl₄) and trimethylaluminum (TMA), commonly used in atomic layer deposition, react with UiO-66-NH₂ MOF. Using in situ quartz crystal microbalance (QCM) and Fourier transform infrared spectroscopy (FTIR) at 150 and 250 °C, we find that the ALD precursors react with μ₃-OH hydroxyl and μ₃-O bridging oxygen groups on Zr₆ nodes, as well as oxygen from carboxylate linker groups. The reactions occur predominantly at the crystal surface at μ₃-OH hydroxyl sites, with TiCl₄ exhibiting greater diffusion into the MOF subsurface. FTIR analysis suggests that, at 150 °C, both TiCl₄ and TMA reversibly dehydroxylate the hydroxylated UiO-66-NH₂, which is accompanied by distortion of the zirconium metal clusters. Finally, we show that TiCl₄ is able to react with the dehydroxylated UiO-66-NH₂ structure, suggesting that TiCl₄ is also able to react directly with the bridging oxygens in the metal clusters or carboxylate groups on the organic ligand. A better understanding of chemical and thermally driven MOF dehydroxylation reactions can be important for improved postsynthetic modification of MOFs.

中文翻译：

UiO-66-NH ₂金属-有机骨架晶体表面上的Al ₂ O ₃和TiO ₂原子层沉积过程中的可逆低温金属节点畸变

金属有机骨架（MOF）是具有高表面积的化学功能化微孔和中孔材料，对于包括过滤，气体存储和催化在内的多种应用具有吸引力。通过溶液或基于蒸汽的技术进行后合成改性（PSM）是一种赋予这些材料更多复杂性和功能性的方法。为了确保更受控的改性以及从改性的MOF材料中更有效地去除试剂和溶剂，期望转向气相方法。在这项工作中，我们探索了常用于原子层沉积的金属前体四氯化钛（TiCl ₄）和三甲基铝（TMA）与UiO-66-NH _2的反应MOF。原位石英晶体微量天平使用（QCM），并在150和250傅里叶变换红外光谱（FTIR）℃，我们发现，对ALD前体与反应μ ₃ -OH的羟基和μ ₃上的Zr -O桥氧基₆个节点，以及来自羧酸酯连接基团的氧。该反应主要发生在在μ晶体表面₃ -OH羟基位点，用TiCl 4 ₄表现出更扩散到MOF地下。FTIR分析表明，在150°C下，TiCl ₄和TMA都可逆地使羟基化的UiO-66-NH ₂脱羟基，这伴随着锆金属簇的变形。最后，我们证明TiCl ₄能够与脱羟基的UiO-66-NH ₂结构反应，表明TiCl ₄也能够直接与金属簇中的桥连氧或有机配体上的羧酸酯基反应。更好地理解化学和热驱动的MOF脱羟基反应对于改进MOF的合成后修饰可能很重要。

更新日期：2017-06-28

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