Metal-organic frameworks (MOFs) are hybrid porous materials composed of inorganic secondary-building units (SBUs) (metal ions or metal oxide clusters) and bridging organic multitopic linkers. The modular synthetic feasibility of utilizing various inorganic and organic building blocks, i.e. reticular chemistry, generates multitudes of diverse network topologies. For example, tetratropic linkers and Zr6 cuboctahedral SBUs can generate multiple network topologies such as csq, ftw, shp, sqc and scu under different synthetic conditions. NU-1000 is typically synthesized by adding the 1,3,6,8-tetrakis(p-benzoate)-pyrene (H4TBAPy) linker to a DMF solution of in-situ pre-formed Zr6 SBUs with benzoic acid modulators. The resulting framework consists of an 8-connected Zr6 SBU with mesoporous hexagonal channels and csq topology. NU-901, similarly contains 8-connected Zr6 SBUs with H4TBAPy linkers, yet it has microporous diamond-shaped channels with scu topology. However, solvothermal synthesis these materials often generate partial phase impurities containing a mixture of distinct network topologies. Given that topology affects the inclusion and diffusion of the substrate into the pores of a MOF, these phase impurities may significantly alter performance in gas separation and catalytic applications. Herein, we describe the synthesis of pure-phase NU-901, through the careful use of a specific zirconium salt and functionalized benzoic acid modulator, which allows us to tune the pore environment for enhanced carbon dioxide uptake.

Solvothermal synthesis of pure-phase NU-901: The effects of zirconium salt and carboxylic modulator components on MOF topology and phase purity

256th National Meeting (2018)

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