The cubchemioctahedral supermolecular building blocks, SBBS, of formula [M-6(bdc)(12)](12-) (M = Ni, Co) (as illustrated) have the requisite symmetry to be cross-linked by rigid tetracarboxylalo ligands in such a manner that 12-connected fcv nets with nanoscale features are generated. 3,5-H(4)ATC, L1, facilitates a structure with Ni that exhibits cavities with > 2 nm maximum dimensions, whereas H(4)BIPA-TC, L2, forms a net with Co or Ni that exhibits cavities with > 3 nm maximum dimensions.