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 <i>organic</i> SBU in the formation of Mg₂H₆(H₃O)­(TTFTB)₃ (<b>MIT-25</b>), a mesoporous MOF with the new <b>ssp</b> 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