Introduction of Functionality, Selection of Topology, and Enhancement of Gas Adsorption in Multivariate Metal–Organic Framework-177

Metal–organic framework-177
(MOF-177) is one of the most
porous materials whose structure is composed of octahedral Zn4O­(−COO)6 and triangular 1,3,5-benzenetribenzoate
(BTB) units to make a three-dimensional extended network based on
the qom topology. This topology violates a long-standing
thesis where highly symmetric building units are expected to yield
highly symmetric networks. In the case of octahedron and triangle
combinations, MOFs based on pyrite (pyr) and rutile (rtl) nets were expected instead of qom. In this
study, we have made 24 MOF-177 structures with different functional
groups on the triangular BTB linker, having one or more functionalities.
We find that the position of the functional groups on the BTB unit
allows the selection for a specific net (qom, pyr, and rtl), and that mixing of functionalities (-H,
-NH2, and -C4H4) is an important
strategy for the incorporation of a specific functionality (-NO2) into MOF-177 where otherwise incorporation of such functionality
would be difficult. Such mixing of functionalities to make multivariate
MOF-177 structures leads to enhancement of hydrogen uptake by 25%.