Proceedings of the National Academy of Sciences of the United States of America ( IF 11.1 ) Pub Date : 2021-03-09 , DOI: 10.1073/pnas.2008880118 Xiangwen Liu 1, 2 , See Wee Chee 1, 2, 3 , Sanoj Raj 4 , Michal Sawczyk 4 , Petr Král 4, 5, 6 , Utkur Mirsaidov 2, 3, 7, 8
Metal–organic frameworks (MOFs) are crystalline nanoporous materials with great potential for a wide range of industrial applications. Understanding the nucleation and early growth stages of these materials from a solution is critical for their design and synthesis. Despite their importance, the pathways through which MOFs nucleate are largely unknown. Using a combination of in situ liquid-phase and cryogenic transmission electron microscopy, we show that zeolitic imidazolate framework-8 MOF nanocrystals nucleate from precursor solution via three distinct steps: 1) liquid–liquid phase separation into solute-rich and solute-poor regions, followed by 2) direct condensation of the solute-rich region into an amorphous aggregate and 3) crystallization of the aggregate into a MOF. The three-step pathway for MOF nucleation shown here cannot be accounted for by conventional nucleation models and provides direct evidence for the nonclassical nucleation pathways in open-framework materials, suggesting that a solute-rich phase is a common precursor for crystallization from a solution.
中文翻译:
金属有机骨架纳米晶的三步成核 [化学]
金属有机框架(MOFs)是结晶纳米多孔材料,具有广泛的工业应用潜力。从溶液中了解这些材料的成核和早期生长阶段对于它们的设计和合成至关重要。尽管它们很重要,但 MOF 成核的途径在很大程度上是未知的。使用原位液相和低温透射电子显微镜的组合,我们表明沸石咪唑酯骨架-8 MOF 纳米晶体通过三个不同的步骤从前体溶液中成核:1) 液-液相分离成富溶质和贫溶质区域,然后是 2) 富溶质区域直接冷凝成无定形聚集体,3) 聚集体结晶成 MOF。