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. Unlike the previously reported self-interpenetrated net, SDU-9 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 ...