Porous interpenetrating metal-organic frameworks with hierarchical nodes

We present the solvothermal syntheses, X-ray crystal structures, and gas sorption properties of a series of zinc-dicarboxylate-polypyridine where the dicarboxylate is 1,4-benzenedicarboxylate, 4,4′-biphenyldicarboxylate, or sulfone-4,4′-biphenyldicarboxylate and the polypyridine is bipyridine or 1,4-bis(4-pyridylethynyl)benzene. The structures consist of hierarchical two-, three-, and four-blade dimer or trimer nodes which generate the square or triangular topologies of the metal-carboxylate layers which are pillared by the bipyridine. Two-and 3-fold interpenetration of frameworks was observed depending on the length of both the carboxylate and the bipyridine. In all cases, the structure sustains a variable degree of space within the metal-organic frameworks where solvents are located. The solvents are easily lost and the structures display accessible voids where adsorption of other gases can be realized. The present set of compounds reveals a picture that does not conform to the current belief that interpenetration of lattices results in highly compact structures.