Template synthesis of hierarchical porous metal–organic frameworks with tunable porosity

Abstract

Hierarchical porous metal–organic frameworks (HP-MOFs) with tunable porosity are highly valuable for many applications. Here, we developed a versatile solvothermal method to synthesize various HP-MOFs, such as Cu–BTC and ZIF-8, by using an organic amine as the template. The resulting HP-MOF products were characterized by a complementary combination of X-ray powder diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption–desorption isotherms, pore size distributions analysis, thermogravimetric analysis, and density functional theory calculations. The results indicated that the obtained HP-MOF products had high thermal stability and contained multimodal hierarchically porous structures with mesopores or macropores interconnected with micropores. In addition, the porosities of the produced HP-MOFs could be easily tuned by controlling the amount of the template. The introduced organic amine served as the template to direct the formation of mesopores and macropores. Furthermore, the synthesis route is highly versatile as other organic amines (e.g., N,N-dimethylhexadecylamine and N,N-dimethyltetradecylamine) can also be used as templates to synthesize HP-MOFs. The method developed in this work may offer a new direction to synthesize various stable HP-MOFs with tunable porosities for a wide range of applications.