Among the new types of entanglements in polymeric architectures the phenomenon of self-interpenetration has attracted attention in recent times. Two new three-dimensional networks that present this unusual topological feature have been obtained. The first species, [Ag(2-ethpyz)2][SbF6] 1 (2-ethpyz = 2-ethylpyrazine), contains four-connected silver centres that give [Ag4(2-ethpyz)4] squares linked into double-crankshaft ribbons. Each of these ribbons is joined to parallel identical motifs to form a three-dimensional four-connected binodal frame of (42,63,8)(42,6,82,9) topology, the same as that of coesite, a high-pressure polymorph of silica, exhibiting self-catenated 8-membered circuits. The second species, [Cu(bpe)2(SO4)]·5H2O 2 [bpe = 1,2-bis(4-pyridyl)ethane], is a nanoporous polymer based on copper(II) centres four-connected to pyridyl groups to give a [Cu(bpe)2] three-dimensional binodal network with the unprecedented (64,82)(6,85) topology, showing the unique feature that all the shortest circuits are self-catenated.