Salionov Daniil, Semivrazhskaya Olesya O, Casati Nicola P M, Ranocchiari Marco, Bjelić Saša, Verel René, van Bokhoven Jeroen A, Sushkevich Vitaly L
Bioenergy and Catalysis Laboratory, Paul Scherrer Institute, 5232, Villigen PSI, Switzerland.
Laboratory for Organic Chemistry, ETH Zürich, Vladimir-Prelog-Weg 3, 8093, Zürich, Switzerland.
Nat Commun. 2022 Jun 29;13(1):3762. doi: 10.1038/s41467-022-31294-4.
The vast structural and chemical diversity of metal-organic frameworks (MOFs) provides the exciting possibility of material's design with tailored properties for gas separation, storage and catalysis. However, after more than twenty years after first reports introducing MOFs, the discovery and control of their synthesis remains extremely challenging due to the lack of understanding of mechanisms of their nucleation and growth. Progress in deciphering crystallization pathways depends on the possibility to follow conversion of initial reagents to products at the molecular level, which is a particular challenge under solvothermal conditions. The present work introduces a detailed molecular-level mechanism of the formation of MIL-53(Al), unraveled by combining in situ time-resolved high-resolution mass-spectrometry, magic angle spinning nuclear magnetic resonance spectroscopy and X-ray diffraction. In contrast to the general belief, the crystallization of MIL-53 occurs via a solid-solid transformation mechanism, associated with the spontaneous release of monomeric aluminum. The role of DMF hydrolysis products, formate and dimethylamine, is established. Our study emphasizes the complexity of MOF crystallization chemistry, which requires case-by-case investigation using a combination of advanced in situ methods for following the induction period, the nucleation and growth across the time domain.
金属有机框架材料（MOFs）在结构和化学性质上具有巨大的多样性，这为设计具有特定性能以用于气体分离、储存和催化的材料提供了令人兴奋的可能性。然而，自首次报道MOFs至今已有二十多年，但由于对其成核和生长机制缺乏了解，它们的合成发现和控制仍然极具挑战性。破解结晶途径的进展取决于在分子水平上追踪初始试剂向产物转化的可能性，而这在溶剂热条件下是一项特殊挑战。本工作介绍了通过结合原位时间分辨高分辨率质谱、魔角旋转核磁共振光谱和X射线衍射揭示的MIL-53(Al)形成的详细分子水平机制。与普遍看法相反，MIL-53的结晶是通过与单体铝的自发释放相关的固-固转变机制发生的。确定了N,N-二甲基甲酰胺（DMF）水解产物甲酸和二甲胺的作用。我们的研究强调了MOF结晶化学的复杂性，这需要使用先进的原位方法组合对诱导期、成核和整个时域内的生长进行逐案研究。
