Metal–organic materials that are constructed from polyhedral supermolecular building blocks, SBBs, can offer exquisite control over structure and afford useful features such as multiple cage types and relatively narrow pores. This contribution describes how a custom-designed porphyrin, tdcpp, self-assembles with M(II) (M = Zn, Cd) cations to generate the first examples of SBBs that are uniform polyhedra based upon a porphyrin molecular building block, MBB. The faces of tdcpp moieties link triangular M₂(CO₂)₃ or M(CO₂)₃ moieties to form small cubicuboctahedral SBBs that are in turn fused to adjacent SBBs at the opposite face of each tdcpp moiety. The resulting high symmetry augmented pcu topology networks, MMPF-4 (M = Zn) and MMPF-5 (M = Cd), exhibit two distinct polyhedral cages and are permanently microporous with selective CO₂ uptake.