CUB-5: A Contoured Aliphatic Pore Environment in a Cubic Framework with Potential for Benzene Separation Applications

One
prominent aspect of metal organic frameworks (MOFs) is the
ability to tune the size, shape, and chemical characteristics of their
pores. MOF-5, with its open cubic connectivity of Zn4O
clusters joined by two-dimensional, terephthalate linkers, is the
archetypal example: both functionalized and elongated linkers produce
isoreticular frameworks that define pores with new shapes and chemical
environments. The recent scalable synthesis of cubane-1,4-dicarboxylic
acid (1,4-H2cdc) allows the first opportunity to explore
its application in leading reticular architectures. Herein we describe
the use of 1,4-H2cdc to construct [Zn4O­(1,4-cdc)3], referred to as CUB-5. Isoreticular with MOF-5, CUB-5 adopts
a cubic architecture but features aliphatic, rather than aromatic,
pore surfaces. Methine units point directly into the pores, delivering
new and unconventional adsorption locations. Our results show that
CUB-5 is capable of selectively adsorbing high amounts of benzene
at low partial pressures, promising for future investigations into
the industrial separation of benzene from gasoline using aliphatic
MOF materials. These results present an effective design strategy
for the generation of new MOF materials with aliphatic pore environments
and properties previously unattainable in conventional frameworks.