A “Strongly” Self-Catenated Metal–Organic Framework with the Highest Topological Density among 3,4-Coordinated Nets

A new type of 3D “strongly” self-catenated metal–organic framework (SDU-9) has been constructed from [Cu2(COO)4] paddlewheel secondary building units and a tripodal carboxylate linker. SDU-9 ([Cu6(H2O)6L4]·24H2O, where [H3L = 4,4′,4″-(hydroxysilanetriyl)tris(triphenyl-4-carboxylic acid), represents a rare example of a highly symmetrical coordination network and extremely tight self-catenation. To the best of our knowledge, SDU-9 has the highest topological density among all known 3,4-coordinated nets.