Compared to the microporous metal-organic frameworks, the presence of mesopores in hierarchically structured metal-organic frameworks markedly expands their use as hosts to accommodate larger bulky molecules, for anchoring molecular catalysts or for impregnation of catalyst precursors or voluminous drug molecules, allowing their free reaction or transformation without diffusion limitations in a confined space. While the fabrication of hierarchically structured MOFs is still a very challenging task because of the critical factors required to precisely control the pore sizes during the crystalline process, a few promising of synthetic methods have been reported including ligand extension method, soft-/hard-template method, stepwise ligand exchange, metal-ligand-fragment co-assembly, encapsulation and etching method, and modulate-induced defect formation strategy.<br/>For instance, by extending the ligands, the final cavities of some specific MOFs could reach widths in the mesopore range by increasing the length of organic linker. However, besides the elongated ligand needs multiple-step synthesis, pores of open MOFs built from this method are usually occupied by solvent molecules that must be removed to induce a permanent porosity and possibly induce the structural collapses. Another difficulty in the synthesis of a highly porous by ligand extension is that such products are often accompanied by framework interpenetration that drastically reduces the size of the pores. The work presented will discuss a novel template-free methodology, named as perturbation-assisted nanofusion synthesis, which can be used to fabricate hierarchically structured metal-organic frameworks at room temperature with grams product in hours.

Synthesis and applications of hierarchically structured metal–organic frameworks

255th National Meeting (2018)

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