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 (<b>SDU-9</b>) has been constructed from [Cu<sub>2</sub>(COO)<sub>4</sub>] paddlewheel secondary building units and a tripodal carboxylate linker. <b>SDU-9</b> ([Cu<sub>6</sub>(H<sub>2</sub>O)<sub>6</sub><b>L</b><sub>4</sub>]·24H<sub>2</sub>O, where [H<sub>3</sub><b>L</b> = 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, <b>SDU-9</b> has the highest topological density among all known 3,4-coordinated nets.