Assembling complex hierarchical structures facilely to improve the accessibility of catalytic sites inside bulk catalysts has long been desired but remains challenging. Herein, we fabricate the hierarchical polyoxometalate-based metal-organic framework ([email protected]) cuboctahedrons by solvent-assisted assembly, and propose a fractal growth mechanism. The great disparity in polarity of the dual solvents used endows them a different strength interaction with the POM. As a result, the polar enriched areas induced by the hydrophilic POM cause diffusion-limited aggregation along with the fractal growth. The obtained [email protected] fractal crystallites possess an ordered layered surface and mesopores developed from the fractal growth and microscopic separation of the system. The cuboctahedron morphology is directed by the anisotropy of the Keggin units. This is of great significance in constructing hierarchical structures via fractal growth caused by diffusion limit by choosing some solvents with proper polarity disparity, which can be extended to other systems.

长期以来一直期望容易地组装复杂的分级结构以提高本体催化剂内部催化位点的可及性，但是仍然具有挑战性。在本文中，我们通过溶剂辅助组装制造了基于多金属氧酸盐的金属-有机骨架（八面体）立方陶瓷，并提出了分形生长机制。所用双溶剂的极性差异极大，使它们与POM具有不同的强度相互作用。结果，由亲水性POM诱导的极性富集区域会导致扩散受限的聚集以及分形生长。所获得的[受电子邮件保护的]分形微晶具有有序的层状表面，并且通过分形生长和系统的微观分离而形成了中孔。立方八面体的形态由Keggin单元的各向异性决定。这对于通过选择某些具有适当极性差异的溶剂（可以扩展到其他系统），通过由扩散极限引起的分形增长来构建层次结构具有重要意义。