The Organic Secondary Building Unit: Strong Intermolecular π Interactions Define Topology in MIT-25, a Mesoporous MOF with Proton-Replete Channels

The structure-directing role of the
inorganic secondary building
unit (SBU) is key for determining the topology of metal–organic
frameworks (MOFs). Here we show that organic building units relying
on strong π interactions that are energetically competitive
with the formation of common inorganic SBUs can also play a role in
defining the topology. We demonstrate the importance of the organic SBU in the formation of Mg2H6(H3O)­(TTFTB)3 (MIT-25), a mesoporous
MOF with the new ssp topology. A delocalized electronic
hole is critical in the stabilization of the TTF triad organic SBUs
and exemplifies a design principle for future MOF synthesis.